Many years ago a four-way tool post project was purchased for the South Bend lathe, a kit from Metal Lathe Accessories, which is seemingly no longer in business. (Though possibly their web address has changed.) The kit, MLA-16 Quick Change Toolposts, has two large cast iron blocks, which will be machined to square blocks, one with slots on all four slides and screws for tool holding. The second will be machined for boring bars.
Besides the cast iron blocks, the kit came with detailed plans and instructions. The first step is squaring up the two cast iron blocks and that is my morning goal. A boss is present on both blocks, where the eventual through hole will be drilled for the screw holding the block to the South Bend cross slide. This boss will be aligned perpendicular to the spindle axis, while held in the four jaw chuck. The block will then be faced up to, but not including, the boss. With one flat face in hand the remaining five faces will be cut parallel and perpendicular to one another.
There is a chance the shaper might be used for some of this work.
The block of cast iron was held in the four jaw chuck and reasonably centered on the boss. The boss was faced as seen in the first photo below. Then the remainder of the block was faced in 0.010" increments, removing about 1/8" in order to completely face the part as seen in the second photo. The finish is quite poor, so some web searching was done for recommendations which include, carbide (not the HSS used), minimal rounding of the cutter point with slow feed, and slow speed < 100 rpm.
A different lathe tool was located, a brazed carbide tool. The tool was honed on a stone. It is a 3/8" tool so it was supported by the red labeled ring on the South Bend tool post. The finish seen in the picture below shows the significantly improved cutting with this tool, though only 0.005" per pass with a very slow hand feed rate. The feel is even more indicative of a smoother finish.
The garage is finally warm enough to return to this project, early March and supposed to be 70° tomorrow! The boss around the toolpost was reduced until the diameter was 1". The work done above never approached the center of the work piece, so I never noticed just how far off center the cutting tool was! Turns out the tool is not 3/8", so a shim was quickly fashioned from aluminum. Much better cutting!
The light that was recently installed for this lathe is in the wrong position and needs to be moved. That will be fixed prior to further work on this toolpost. Should be a simple and quick task to accomplish.
With the top completed the block of iron was flipped over in the four jaw chuck to face the opposite side. The block was quite close to centered so cutting commenced. Deeper cuts were made on this face, 0.015", though I was dissuaded from going even deeper due to the intense chatter as the corners were cut. A single slow pass at reduced depth of cut gave a reasonable finish.
With this side flattened thought was given to the desired final height of the tool post. The block is almost 2 1/2" in height and according to the plans for a South Bend 9" lathe it needs to be closer to 1 5/8". Removing almost an inch via facing sounds pretty tedious, but with the four sides in their current state, using the band saw vise might be precarious.
The plan is to square up the four remaining faces, maybe with the shaper, and then move to the bandsaw with parallel faces which the vise can more firmly hold. The shaper is at least temporarily not a possibility. The block sitting in the vise is too tall for the tooling. The block could be mounted directly to the base (?), but I don't have any appropriate way of clamping it. Maybe an angle plate mounted to the shaper with the block clamped to the angle plate.
The remaining four sides were cleaned up with the casting held in the four jaw chuck. Between 1/8" and 3/16" was removed (0.020" DOC) from each side to flatten the side. The process worked reasonably well as all opposite faces are close to parallel with no more than 0.010" difference between corners, though often much less. The faces have not been checked for perpendicularity as a decent square is not kept in the garage. The two photos below show the process, using wood blocks when gripping the unfinished and often curved sides, as well as the finished product.
The rags seen in the photo above were not very helpful in keeping the dust off of the lathe. Significant work was required to get the chips off the rag and the machinery still had a lot of dust to remove.
The casting is not very square. A setup on the shaper table is needed. The three T-slots are 2 1/4" apart and the T-slot is 3/8" to 5/8". Before purchasing an angle plate that is larger than the one used on the Sherline mill, I will attempt to use a set of 1-2-3 blocks. For them to be used T-nuts and screws need to be made to hold the 1-2-3 blocks to the shaper's table. Large C-clamps will hold the casting to the 1-2-3 blocks.
Discovered this morning that some round steel bar needs to be purchased. The only size available in my storage is 1/2". The nut that fits into the T-slot will be made from 1/4" X 5/8" steel bar. Two pieces were cut from stock, each about 5/8" long. These were deburred and set in the vise on a parallel. A 3/8" end mill was used to remove about 0.030" from one 1/4" side of both.
The steel was turned 90° and both set square, relative to the cut sides, at either end of the vise. The exposed sides were cut with the same end mill about 0.1" at a time and with a 0.005" DOC. The size of the nut was reduced to a 0.60" square. The nuts were then set on parallels with the large flat side up and the thickness was reduced to 0.220".
The centers of both nuts were marked out and punched. Holes were drilled through both, beginning with a spud drill, using the spud center to first locate the punch mark. The holes were drilled through with a #18 drill followed by an I drill. The nuts were moved to the vise and tapped 5/16"-24. After a bit of clean-up the nuts are seen below, before and after tapping. They thread smoothly on the one 5/16"-24 bolt I found and exhibit very little play.
To complete this side project two threaded rods needed to be prepped. A 6" length of 3/8" steel hex was held in the three jaw chuck in the South Bend lathe. The end was center drilled. I had forgotten that sometime last year the drill chuck and its Morse adapter had gotten stuck in the tailstock. The chuck can be removed from its taper, but the other end of the taper has resisted all of my persuasive entreaties. A tailstock center had been fashioned for the drill chuck and used once or twice. This tailstock center was pushed into the drilled end of the rod with about 5" exposed.
The rod was reduced to about 0.330" when significant vibration was noticed at the tailstock end. No amount of tightening of the tailstock center made a difference. Finally, the culprit was discovered, the tip of the tailstock center had broken off in the center drilled hole! (Shown in the first photo below.) A side project within a side project was spawned. The tailstock center must not have been hardened when made last year. The center was moved to the Sherline lathe. The headstock was rotated 30° and the tip was reformed. The tip was filed round as shown in the photo below. The part was hardened, heated to bright orange for about one minute, then quenched in oil. A file skipped off the steel tip.
The end of the rod was redrilled and the improved tailstock center was put back in place leading to much nicer cutting. The rod was reduced to 0.312", actually 0.308" near the headstock and 0.315" near the tailstock. A bit of filing reduced the tailstock end appropriately. The rod was then moved to the vise where about 1" was exposed above the vise jaws. This was threaded with a 5/16"-24 die. The rod was pulled up out of the vise jaws another inch and the threading continued until 4 1/2" of rod was threaded. Cutting fluid was liberally applied throughout the threading process. The out-of-focus threaded rod is shown below.
The rod was then cut from the remaining hex stock and sawed a second time cutting it in half. This yielded two 2 1/4" lengths of threaded rod. The rods held in a three jaw chuck had their ends chamfered with a file. The rods slipped easily through the holes in the 1-2-3 block and into the slots on the shaper table. They are shown below, sans nuts.
The nuts fit the rods, though not as smoothly as the purchased screw. The nuts were glued to the rods with red LocTite. Two more nuts were needed and these were made from 1/2" steel hex. A 1" length was cut from stock, faced and center drilled. After drilling with a #18 drill and an I drill the piece was tapped 5/16"-24. The part was returned to the lathe, where the end was chamfered. A 0.25" length was parted off. The new end was chamfered and a second 0.25" nut was parted off. Both nuts needed some clean-up before the second photo below. The set of parts was then tried out on the shaper, seen in the third photo.
While looking for my two large C-clamps an angle plate was discovered! The new T-bolts fit it well, so it was used instead of 1-2-3 blocks. The angle plate was set on the shaper table and the casting was clamped upside-down to the angle plate with an adjustable parallel beneath. This set the top face square to the table and perpendicular to one side. The bottom was then set up for cutting. The setup is shown in the two photos below.
The stroke length was adjusted with the screw on the top back end of the ram and the large knob on the front of the shaper. The knob changes the stroke length about 1/4" per revolution. The screw on the ram's top adjusts the stroke starting point. These parts of the shaper are pictured below.
The pulleys were set for the slowest cutting speed and this is where I began. The cross movement was set at about 0.005" per pass. The depth of cut was set at 0.010". Cutting proceeded smoothly, but sloooow! A single pass across the 3" block took sixteen minutes. The pulley belt was moved to the next set of pulleys doubling the speed. The depth of cut was increased to 0.015" and then to 0.020" with little change in cutting ease. A short video of the shaper action is below. After an hour about 3/32" of material had been removed. Almost an inch remains. Accomplishing this with the shaper is not going to work in my lifetime.
Numerous issues were discovered as the shaper work proceeded. Drops of oil flew out the back every so often, their source undiscovered. The screw that is turned by a small lever and moves the shaper table toward the cutting tool, just visible in the bottom of the video, would stop functioning every so often. Instead of advancing 0.005" it would just oscillate. A bit of pressure with the fingers kept it moving forward. After three or four passes significant heat was coming from the motor/pulleys. There is also a pronounced rattle coming from inside the cabinet. That and the vibration of the machine is most likely responsible for the poor finish the machine always provides. It is past time for a rebuild.
The horizontal band saw was used to remove most of the material about 1/2". The cast iron block was then returned to the shaper with the same face on the angle plate. As expected the band saw left a crooked face with the high point the back corner in this setup. The cut block is sitting on the bandsaw in the first photo below. The second photo shows the block back in the shaper after one pass cut into only the corner. The shaper continued cutting for an hour with constant babysitting before the face was flat, a rough flat. This is documented in the last two photos. The block is now 1 3/4" thick and needs to be 1 5/8".
Two things concern me about squaring up this block. First it needs to be done in the lathe as the shaper is just too slow. Time on the shaper might be worth it if the finish were better. Setup on the lathe leading to getting right angles out is the challenge. The other issue is the opposite faces on the sides. Similar amounts need to be removed from opposite faces or the current center of the block, which will be drilled and bored for the mounting screw, will no longer remain the center.
The first face cut was the bottom. About an eighth of an inch was removed to reduce the height to 1 5/8", with the last slow cut removing 0.005". The finish was decent and improved by first sanding with a green 3M pad followed by a gray pad. (The first is equivalent to "0" steel wool and the second to "00".) The width of the block in one direction was measured at 3 3/16", so 7/32" was removed from each of the opposite sides. Again a final light slow cut followed by brief sanding produced a decent finish as seen in the photo below.
Oy!! Made a mistake and recut two sides already cut. I now have a block that is too small in one direction. The cut was made without looking for the marks purposefully made on the two sides that needed to be cut! Unfortunately, this is not the first time I have pulled this kind of stunt. This block just became the toolholder for two boring tools.
The second cast iron block that came with the kit was faced on the bottom and top. The inner section or boss for the eventual through hole was left about 1/16" high of the face, after facing it until it was 1" in diameter. Over 1/2" was cut off of the back with the bandsaw. The back was then faced parallel with the front.
With two parallel faces the sides were sawn off, again with the bandsaw, about 1/4" was removed on all four sides. These cuts were very crooked; I am not the best with the horizontal bandsaw. All four sides were then faced until flat, perpendicular to top and bottom, and parallel to the opposite face. The 2 3/4" square block and an intermediate cut are shown below. A shim was used when gripping the block by the boss.
Slotting on the South Bend lathe was begun this morning. The vertical milling attachment was easily attached in place of the compound. It was adjusted until a dial gauge showed less than 0.001" drift over an inch (front to back), meaning it was square to the axis of the spindle. The block was mounted on two small parallels and a scrap of aluminum was used between the block and the screws to hold the block tightly in place. The photo below shows the setup.
A 3/8" two flute end mill was held in a collet and a first pass was made. All went well so the passes were increased to 0.015" depth of cut. At 0.020" there was much more vibration. The end mill cut the slot easily. Cutting had begun approximately 1/16" above the desired lower bound of 0.700", the needed height of the block to set a 3/8" tool bit on center. The slot was cut to 0.375" depth. The casting was lowered in 0.015" increments to raise the top of the slot 1/16". The bottom of the slot was then widened so the bottom of the slot is 0.700" above the bottom of the block. The second photo below shows the completed slot after deburring.
While measuring the bottom of the slot it was discovered that one end of the slot was about 0.005" lower than the other. An important measurement was not made during setup, the angle of the milling attachment relative to the top of the bed. This will be fixed before cutting the other three slots.
After adjusting the angle of the milling attachment, the drift was less than 0.002" per inch. This was about as good as I could get it. The milling continued around all of the remaining three sides. Getting all corners within a few thou of 0.700". The corners will be labeled with the height and some shim stock will be located to make sure all tools will be located on center.
The block of cast iron was returned to the four jaw chuck and centered. The center hole was drilled up to 5/8" and then bored. The final bore diameter was 0.788". The second block for the boring tools will need to be bored to the same diameter. A photo of the slotted and bored casting is shown below.
Needing to remove some Sharpie marks, I grabbed xylene as it was close. The Sharpie marks were not removed. The black carbon, already wiped off, continued to blacken the paper towel soaked with xylene. Xylene is a good solvent to remove the black carbon, which gets on everything, when machining cast iron.
The second block of cast iron was also bored on center to 0.788" after drilling to 5/8".
Holes, you can never have enough holes! The square tool holder for four tools needs sixteen holes to hold the tools. These were marked out, 3/16" in from the edge with five evenly spaced holes per side. The marks were punched, center drilled and drilled, #7, on the large drill press in the garage. The holes were then tapped 1/4"-20 by hand and chamfered. The burrs on the inside of the slot were removed by filing. The photo below shows the block just after completing threading. Nothing will get done for the next week as I am off to a Florida beach, Perdido Key!
In the bits of time during packing for the trip the casting was given a final finish. Five sides, skipped the bottom as I was afraid of losing its flatness, were filed with a coarse bastard file and then with a smooth file. The filing was followed by sanding with a green pad, then a gray pad. The finished product was wiped down with xylene and is shown below.
Just returned from Florida (gratuitous beach shot below) and discovered an oops! A counterbore needs to be bored in the bottoms of both tool holders, 5/16" deep and 2" diameter. Boring was tackled this morning. The slotted block was centered in the four jaw chuck. The boring bar was shortened and a stop was set at 5/16". The hole was bored in 0.02" increments to 2" using a hole gauge to measure progress. The edge was lightly chamfered with a round file. The first metalworking photo shows the boring and the second the finished counterbore.
The second cast iron block was bored similarly. Screws, 1/4"-20 X 1" SHCS, were ordered this morning from Bolt Depot, so much cheaper than the same screws from Menards even with shipping included.
After a few minutes of figuring out how the post assembly works, time was spent on planning its construction. The photo below shows the post assembly overview from the plans. The mounting screw that is attached to the tee nut is lifted as the handle turns, locking the assembly to the compound.
A tee nut needs to be prepared, a simple process and I've made one before. The post will be made from a 2 3/8" piece of 2" diameter steel rod. The base of this post fits in the recesses bored yesterday. The post diameter is 0.749", a sliding fit in the center holes of the two tool holders. The top 3/4" is threaded 3/4"-16. These threads will need to be cut on the lathe. The post also needs to be drilled through 3/8" to fit the mounting screw.
The ball cap nut is the complex part of this assembly. The 1 1/4" ball has a 1" flat on the bottom. It is drilled through 19/32" to fit the mounting screw head. The bottom 5/8" or so are drilled and threaded 3/4"-16. A handle needs to be made that will screw into the side of this ball at a 10° angle.
Work this morning will begin with the post, if I can locate a piece of 2" round stock. My lucky day! An 8" length of 2" steel round was quickly located, even though it was hiding in the back of the steel stock. A 2 1/2" length was cut off with the horizontal band saw. This was held in the 3-jaw chuck and faced. The first 1/2" was cleaned of scale giving and easy fit in the two counterbores. The part was reversed in the 3-jaw chuck and center drilled. The part was then held at the exposed end with a live tailstock center and 2" was reduced to 0.750". The first photo below shows this reduction in progress. A lengthy process as only 0.015" was removed per pass—any more and significant chatter developed.
The test fit reminded me that the bores were 0.788"! Forgot that small detail after a week in Florida. The shaft needs to be expanded or an insert needs to be made for both bores—the former was chosen. A 2" length of 1" steel round was held in the 3-jaw chuck and faced. The rod was center drilled and drilled up to 5/8". It was bored to 0.747", too small for a force fit. Another 0.001" was removed giving a nice sliding fit on the shaft! The ID is now 0.751"!
Mistakes compounding mistakes. The shaft was enlarged slightly by knurling. The first photo below shows the knurling in progress, a bump knurler on the QCTP. The second photo shows the knurled rod adjacent to the too large tube. The knurled rod would not slide into the tube, so at least this went well. The length of the rod and tube were too long for my largest vise to effect a press fit. The tube was heated with a propane torch until it was a uniform brown color. The knurled shaft dropped right into the tube. The third photo shows the conjoined tube and rod, though it was still hot and the tightness of the fit had not been checked. The last photo shows the expanded shaft, still hot, but also tight.
You might think I was high during this work! Florida has legalized cannabis and one restaurant had mocktails spiked with THC. I did not partake. Had enough in my youth.
The shaft needs to be reduced so it is a sliding fit in the two bores, about 0.783". This should be easier to pull off, but with my record who knows! This reduction in diameter went well. The shaft was reduced to 0.785", an easy sliding fit in both cast iron blocks. The first 3/4" needs to be threaded, so was further reduced to 0.750", revealing the nice knurl. Don't know how this will affect threading, but should be fun. The knurl was hit with a file to remove some of the bumpiness, seen below.
The reduced end of this shaft needs to be threaded. I have only cut threads with the South Bend lathe once before and need to refamiliarize myself with the process. A 1936 book from the South Bend Lathe Co. lays out the process.
One problem: I don't have wires for measuring thread depth. Neither do I have a 3/4"-16 nut. Best wire size is 0.57735 X Pitch = 0.03608", though as high as 0.056" can be used. Pitch diameter = Measured + 0.866025 X P - 3 X wire size. A pitch diameter of 0.7094" is the target.
The thread relief was cut with a parting blade at the beginning of the non-reduced section. The reduced section was "painted" with a blue Sharpie. The gears were set to produce a 16 TPI thread. The compound was set at 29°. The cross slide moved the tool to just touching after aligning the thread cutting tool with the fishtail. The carriage was moved after pulling back on the cross slide. Moving it back to the previous setting and advancing the compound 0.001" set up the first pass. The feed screw was engaged and threading lever flipped when the threading dial crossed a line. The lathe was stopped and the pitch was verified with a thread gauge.
The first pass was a 0.005" DOC and ensuing passes were smaller, eventually settling on 0.002" per pass. At about 0.035" depth a purchased nut was tried. It only got a quarter turn before locking up. An additional 0.010" were cut and the fit checked. It was quite tight, but could be turned on by hand about halfway. Another 0.002" was cut and the nut fit very nicely. The threads were cleaned up with a 3-corner file and a chamfer was cut on the end of the screw. The first photo below shows the threads and the second the threaded nut.
What was not discussed above was the two hours of labor prior to cutting threads. The cross slide handle fell off. The nut could not be located. Much chip sweeping of the garage floor around the lathe and still no nut. I decided to make a nut and sought my home made wrench to remove the similar nut on the compound rest. The missing nut was stuck on the end of the wrench!! It must have fallen off previously and I struggled to get it back on, so left the repair for another day. Gotta love a 70 year old brain.
I had been having trouble with the cross slide, 0.1" of runout, so decided this was the chance to repair it. The compound was removed and with some effort the taper cutting attachment was removed as well. Removing the cross slide revealed the new nut installed when the lathe was reconditioned, not the problem. The problem was a combination of factors, but the biggest was the loose nut that surrounds the end of the cross slide screw and sits behind the numbered dial. All was cleaned and oiled. The nut was tightened with a spanner wrench. The dial installed and the handle put back on. A gap remained between the nut and the slide casting of about 0.009" as measured with feeler gauges. I have no shim stock so resorted to a 'budgie job' to get the machine running. Aluminum foil was folded until it was the appropriate thickness. A U-shaped curve was cut out and this slipped over the cross slide screw in the gap. All parts were returned and the cross slide now works well with about 0.020" of runout, not bad for a seventy-one year old lathe.
The photo shows the foil sitting behind the nut, actually a screw that fits over the cross slide screw. The not so missing nut can also be seen in the handle.
The plan for the clamping handle is shown below. Consideration needs to be given on how best to hold the part during the multiple machining operations, so the different bores run true.
I don't have any steel round between 1" and 1 1/2", so the latter will be used. A 2" length will be held in the lathe and about 1" will be reduced to 1 1/4". The blank will be drilled through 19/32" and the first 3/4" opened for threading. The threaded section needs to be bored to 0.689". Threading will be followed by making the ball. The ball turning will be done using the "Lathe Cutting Round Grooves" calculation tool from the list above. Parting off should release the ball. Adding the handle will be considered later—holding the part via the screwed in shaft should make this straightforward.
A 2.25" length of 1 5/8" steel rod was cut off with the bandsaw. This was held in the South Bend lathe chuck and faced. 1 1/4" was reduced to 1 1/4", the desired diameter of the ball handle. This stage of machining is shown below. The part was center drilled and drilled 1 1/4" deep up to 3/8". This hole was opened to 11/16" for a depth of 3/4". This part of the hole measured 0.684", slightly less than the needed 0.689", but close enough. A second photo shows the part at this stage.
The back of the hole was bored to 19/32". Cutting a thread relief groove was the next challenge. A tool was ground to cut this groove and is seen below. The tool was made from 3/16" HSS and was shimmed to sit on center. A lot of cutting fluid was applied and the tool was slowly advanced into the steel after positioning it at the back of the area opened for threading. After 0.050" the tool was retracted ending the squealing from the chatter. Not a bad groove from the looks of it.
Threading was a bust. A small threading tool was held in a QCTP holder and shimmed. It was centered and multiple attempts were made to produce a thread (16 TPI). The tool was difficult to keep from shifting in the holder. When that problem was solved, the QCTP started turning! I struggled to get the required rigidity and after realizing I had cut multiple threads, the work was abandoned. Some new ideas are needed. Either a better thread cutting tool is needed or a tap needs to be purchased. Taps were purchased, but won't arrive for five days…
The hole for the cap screw head was bored to 0.40" this morning. After quickly accomplishing this time was taken to clean the lathe. The black carbon from cutting cast iron had turned the machine gray. Rags soaked with xylene easily cleaned the lathe of carbon and years of accumulated gunk. The photo below shows the cleaned lathe and cabinet.
This morning was spent making the T-nut for the tool holder. A cut off scrap of the cast iron (don't know if this is appropriate for a T-nut) was marked out for a slightly oversized square of iron, seen below. The piece was cut out with the horizontal bandsaw. The shaper was used to first square the piece up and reduce it to 15/32" X 1 1/4" X 1 1/4" also shown below.
The shaper was also used to cut out the corners to produce the T. Lines were scribed where the corners need to be cut. The depth was read off of the dial for lowering the tool. The width was measured by running the tool to the line and noting the setting on the cross feed dial. Returning to this position on each pass was simple. The depth of cut was 0.015" and went 0.25" deep. The cross feed went 0.19" into the stock. The work was repeated on two edges. The nicely fitting T-nut is seen in the compound rest in the second photo below.
The center of the nut was laid out and punched. The part was center drilled and then drilled up to 5/16". The hole was tapped 3/8"-16 and deburred to produce the completed T-nut.
The taps arrived and were immediately put to work. The handle nut was still in the 3 jaw chuck, so the tapered tap was pressed between the hole and a center held in the tailstock. The tap was turned until one or two threads were cut. The part was moved to the vise and threading continued until the tap bottomed out. A 1/2" wrench was used to turn the tap, not ideal as it is too short for the work, but I don't have a tap handle large enough for this tap. (Sounds like another project!) The tapered tap was followed by the plug tap and the bottoming tap. The shaft fits nicely in the nut, seen in the two photos below.
Time for ball making. The original idea, seen below, was to hold the part between the chuck and a tailstock center. The part does not sit sufficiently concentric when held by threads, so this approach was abandoned.
The second approach was simply holding the part in the 3 jaw chuck. The above ball cutting tool was utilized to get a rough idea of depths of cut as a parting tool is moved from one end to the other. A 1/16" parting tool was utilized and the step sizes were also 1/16". The tool output was adapted to the starting position, which is 1/4" from the bottom of a complete ball with diameter 1 1/4".
After completing all of the cuts but one, filing work was done on the outer end and a bit on the inner and still attached end. Filing was done initially with a coarse bastard cut file. The last cut was made, parting off the ball, which didn't roll too far. The ball was screwed to the tool holder shaft and filing continued.
The coarse filing was continued until all but one line was removed. This line was from a parting tool cut that went off line when the parting tool shifted in its holder! A feature added to break up the monotony of a perfect ball. Filing shifted to a fine file and then gray and green Scotch Brite pads were used to produce a decent finish.
All that remains is making the handle and attaching it to the ball. A 3/8"-16 socket head cap screw also needs to be purchased. The exposed handle shaft is 1 1/2" long and the ball is to be made 3/4" diameter. 3/8" stainless steel rod and 3/4" brass round stock were found in the stockpile, so those are the materials to be used.
A 1" length of the 3/4" brass round bar was cut and faced in the Sherline lathe. The faced end was drilled, #3 drill, and threaded 1/4"-28. This half of the ball was turned with the ball forming tool. A 2" length of 3/8" stainless steel was cut and faced. The end was turned down to 0.25" and threaded with a 1/4"-28 die. This screw was screwed into the half ball and held in the chuck. The opposite end was then rounded. It is not a ball, but an elongated ball as the brass was not faced close enough to 3/4". The ball was sanded to 1000 grit. The opposite end of the handle's shaft was reduced to 0.25" for a length of 0.15".
After some failed attempts to hold the nut at a 10° angle, the setup shown below was utilized. A spotting drill started the hole, followed by a 0.25" drill, followed by a 1/4" end mill to produce a flat bottomed hole 0.150" deep.
The handle shaft did not fit tightly in the hole in the nut as expected, so it was punched in multiple locations. These punch marks tightened the fit, but not enough. The turned down length of the handle was moved to the South Bend lathe and knurled as seen in the photo below. This knurl took some effort to press into the hole, but was still not sufficient to hold the shaft tightly. Some JB Weld was located and mixed. This epoxy was placed in the hole in the nut and the handle pressed into place. Meanwhile, the opposite end was treated with red Loctite and the brass ball screwed on. The JB Weld needs to dry overnight. The second photo shows the glued brass ball with the shaft pressed in place, before it was discovered that the shaft was not held tight enough. The third photo shows the part after applying JB Weld.
Hmmm! The setup did not work when attempting to tighten the undrilled block for boring bars. The block could not be tightened with all of the parts put in place. This was after shortening the 3" purchased screw by 0.25". The problem is the central shaft. The threads are not long enough by about one or two threads. The block for the four cutting tools could be tightened sufficiently, though with a lot of pressure on the handle, causing the JB Weld to break loose. Probably not JB's fault as the epoxy has to be at least 20 years old.
The nut works to tighten the block in place by pulling up on the shaft. This shaft in turn presses against the bottom of the screw head. The screw pulled up drags the T-nut along, tightening it in the T-slot.
It is not clear to me how to fix this issue. The disk at the bottom of the shaft could be thinned, but it only sticks out about 1/16", and needs to stick out some. The threads on the central shaft could be extended, but the thread relief prevents that from working. I might need to remake the central shaft. I will give it some thought before proceeding. So close to completion!
Decided to remake the central shaft, though slightly differently. Instead of making it from one piece of steel the bottom disk will be made separately as a press fit onto the shaft. The shaft needs to be a slip fit in the toolholder blocks and the press fit in the disk, so will require some care in its production. The disk was made first from a 2" round steel bar held in the three jaw chuck. One end was faced and a hole was drilled and bored to 0.784" for a 1/2" depth. The disk was cut off with the bandsaw at 1/2", held in the chuck on parallels, and turned down to 0.35" thickness.
A 2 1/2" length of 1" steel (12L14) rod was cut off with the bandsaw. The end was faced. The diameter was reduced to 0.785" for 0.375". This will fit the disk made above.
The part was turned in the chuck to complete the opposite end. This end was turned down to 0.75" for a length of 0.87". It was then threaded 3/4"-16. The threading did not proceed well with movement of the QCTP. (I have a difficult time getting it tight enough to not move!) In any event some threads were cut and the nut fits reasonably well. The part was then drilled to 3/8" to fit the central screw.
The force fit end of the part was held in the three jaw chuck with the outer end supported by a live center in the tailstock. The central portion of the shaft was reduced to 0.785" for a sliding fit in the two tool holders. The vise was used to press the shaft into the disk—care being taken to start the shaft perpendicular to the disk. Again the disk does not fit the depression in the tool holder when the shaft is inserted. The depression is not centered with respect to the central hole. The disk was reduced until a fit was found. The assembly was put together sans the handle. The nut was carefully tightened with a spanner. Success! the tool holder is held quite tightly. Now I need to figure out how best to attach the handle.
Tightening the two blocks on the shaft was not repeatable. After a bit of studying the design and playing I guessed that the disk at the end of the shaft was turning around over the top of the cross slide. A sheet of gasket material was cut into the shape of a donut fitting the bottom of the disk. The gasket was glued on with spray contact adhesive. This worked and the whole can be tightened to the cross slide, though using a spanner to tighten the ball nut.
The gasket material was applied to the first disk/shaft made, not the two piece version. The threads are better on the first, so its modification was explored first.
The block for boring bars was tightened into place and aligned with the spindle at 1/2" from the edge. The 1/2" drill chuck was held in the spindle and after center drilling a hole was drilled through with a 1/8" drill. This hole was opened in small increments to minimize pressure on the block to avoid turning it. The hole was reamed 3/8".
The block was loosened and turned 180°. The same process was repeated on the opposite side, though drilling with the 1/8" drill was stopped part way through when the block was noticed to no longer be square! The block was tightened more carefully and some consideration was given on how best to straighten the hole. A center cutting end mill was chosen, 3/8". The drill chuck in the spindle was swapped for a collet and the end mill was slowly fed into the block of cast iron. The end mill was limited to a little over an inch of drilling. At this point it was replaced with a 3/8" drill and the hole was completed. The hole was opened in small increments and reamed to 1/2". The hole seems to be square via measuring its distance from the edge at both ends.
The last thing needed to turn this block into a boring bar holder is tapped holes. The holes were marked out 1/2" from the edge. The first hole on each side was located 7/16" from the edge and successive holes were spaced 1/2" apart. The last of the four marked hole locations fell 7/16" from the far edge. After marking out and punching all eight holes the block was moved back to the garage, where the holes were drilled, first with a center drill and then with a #7 drill. In line with all of the other issues this project has presented, the center drill snapped off in the second hole! That hole was not finished. The other seven holes were tapped 1/4"-20. A bit of reaming cleaned up the holes for the boring bars.
Quite the journey, though not quite finished as the handle still is not attached to the ball nut. The photos below display all of the parts at this stage, a good place to take a break from this project and consider some others that have been waiting in the wings.
An attempt was made to salvage the nut and handle this morning. The hole in the nut was milled a bit deeper back in the Sherline mill. The hole is somewhat mangled after all of the attempts to make the handle fit. In any event the handle had the reduced portion removed and a new reduced portion was made to fit the hole. This work on the handle required a bit of ingenuity as the ball on the end makes work holding difficult. The jaws in the two South Bend fitting chucks were too deep and the ball did not sit behind them and allow the shaft to be gripped. An old four jaw chuck from an friend and co-worker came to the rescue. This chuck was held in the much larger four jaw, chuck in a chuck. The handle was held by the shaft with the ball sitting behind the jaws of this smaller chuck. The small chuck's jaws were adjusted to get the handle running true.
The above attempt failed as the hole is not a uniform diameter, discovered when trying to fit the newly machined handle. The outer part of the hole is wider than the inner by 0.005" or so! Probably butchered by the spanner when cranking it hard to tighten the nut on the shaft. Maybe threads will be tried, though only 3 or 4 will fit in the hole. Threads were tried. The reduced end on the shaft was removed and 0.18" were reduced to 0.312". The end was threaded with a die. The ball was threaded with a tap, 5/16"-24, though few threads were cut and doing so at an angle was challenging. The shaft would not thread into the hole, the threads in the hole were to few to hold more than one thread from the ball.
One last task, prior to redesigning the handle, was height checking the tools clamped in the tool holder. The tool holder was assembled on the post using a purchased nut. Minimal tightening was required to lock the tool holder in place. Inserting and tightening a 3/8" tool was followed by putting a collet in the spindle and a tailstock center in the collet. The tool was significantly above center, which the photo below attempts to show. It is a almost an 1/8" high, a combination of the disk sticking out of the tool block and the added gasket material. The tool holder will be remilled after carefully measuring the height difference. Measuring was accomplished by setting the dial gauge to 0.000 when sitting on the tool tip. The gauge was moved to the center of the spindle and then to the top of the 0.374" tailstock center in the collet. The height difference was 0.072". That difference subtracted from 0.187" gives the excess height of the tool tip, 0.115".
The boring tools will also need to be checked for appropriate height. If the bars are above the correct height, which I suspect will be the case the bottom of the tool holder will need to be pared down.
The block was set up in the vertical milling attachment. 0.100" was removed from the bottom of each slot in 0.01" passes. The back of the slots was not touched. The first photo below shows the roughed second slot. The slots were then finished with the removal of another 0.015". The second photo shows the tool tip now on spindle center.
Returned to the handle this morning. I was frustrated by the minimal clearance for a handle inserted in the ball, so decided to design something simpler with room for the handle. The design below was settled on after considering a few others. There is plenty of room for affixing the handle and the handle will sit above the screws holding the tools in place.
A failed ball handle blank was used to make this handle. Its 1 5/8" large diameter was reduced to 1 1/2" followed by a bit of sanding with green and gray Scotch pads. Corners were chamfered. This part is shown below
The hole was opened to 11/16" by drilling 3/4" deep". The smaller hole was opened to 5/8" through. The smaller end of the blank was mostly cut off with a hacksaw, leaving over 1/8" of reduced diameter. This smaller end was further reduced to 1" after facing to 1/8". The end with the larger diameter hole was threaded 3/4"-16 with taps. The part is shown below.
The shaft for the handle was quickly made from a 3" length of 3/8" drill rod. One end was faced and reduced to 0.25" for a length of 1/2". This end was threaded, 1/4"-28 with a die after chamfering the end. The opposite end was chamfered and threaded 3/8"-24. These latter threads were slightly crooked, but this should be hidden inside the handle's ball.
A brass ball, not quite round, was located in the scrap bin. Decided to use smaller threads, so the 3/8" threaded end of the shaft was reduced to 0.25" and threaded 1/4"-28. The ball was set in the vise on the milling table and first drilled with a spotting drill. This was followed by drilling with a #3 drill. The drill went catty whumpus, but the hole was threaded anyway. What's a crooked ball between friends, anyway? The two screws on the shaft were treated with thread locker followed by screwing the nut and the ball in place. The photo below shows the result, but hides the cock-eyed aspect of the ball.
The height of the boring tools also needed to be checked. The same process from above was followed. This indicated that a boring tool in the boring block was 0.046" high. The block was held in the four jaw chuck and the center hole was centered with the aid of a dial indicator. The bore for the disk was then deepened by 0.046". Setting the boring tool block in place with a center in the spindle shows the boring tool now on center.
Back after a weekend in St. Louis with the oldest grandson—loads of fun. It is now June and time to finish this project. The new handle was installed on the post, but did not go sufficiently deep, catching on the head of the SHCS. The handle was held in the four jaw chuck and dialed in with a dial indicator. The top was opened by 1/32" with a boring bar in the boring holder. This boring operation is shown below.
The handle sticking out gave me some worries. A lot of testing was done before the actual cutting began. I stood off to the side during the cuts. Luckily, no problems arose.
Testing the handle a second time showed the SCHS now fit in its provided opening, but the threads were insufficiently deep. The handle was rechucked and recentered. An 11/16" drill was used to drill about 1/8" deeper. The threads were extended into this newly opened bore with a bottoming tap. The handle now went on smoothly and hit the top of the boring block. Unfortunately, I was unable to put enough pressure on the handle to lock the block in place, still able to turn it by hand, though with a lot of force!!! The same was true of the four-way tool holder. A long wrench on a nut does the trick, but this tightening could not be repeated with the shorter handle.
The project will be shelved for now. Maybe after a period of reflection, I will return with fresh ideas.