This next project was undertaken as I needed something simple and metallic to tackle. A kit was purchased from Hemingway Kits in the UK. This kit is for making a rule holder and scriber. This page covers the rule holder. A photo of the rule holder as seen in the plans is shown below.
The first task is converting the one metric part of the plan, a screw and its accompanying nuts, into thread sizes I have tooling for. The plans call for an M5 thread, internal and external. The M5 seems closest to a #10 coarse thread, so where the plans call for M5, 4.134 mm, 5.126 mm, and 5.2 mm substitute #10-32, 0.149", 0.190", and 0.199".
Squaring up the two ends of the provided 1" X 1" X 2" block of mild steel was next. The steel block was clamped to the angle plate with two machinist's clamps with one square end at the top. The block was held vertically by checking with a square. The top was milled flat with a fly cutter in 0.003" increments. The block was flipped end for end and the same machining was used to square up the opposite end as well as remove about 1/16" of excess material. This milling left the block 2.033" long.
Reducing the height by 0.080" for 1.5" was done on the shaper. The machine was set to cut 0.005" wide and 0.010" deep. This left a rough finish, which was cleaned up a little by taking a last pass without changing the depth, a spring pass. The first photo below shows the second pass in progress and the second photo shows the completed reduction.
The reduced end of the block was marked for the drill hole per the plans. The part was held in the four jaw chuck with a scrap of aluminum in the reduced section. After aligning it was centered drilled and then drilled through with a #8 drill, 0.199", clearing chips every 3/16-1/4". The hole was then opened up with a 3/8" drill to a depth of 1 3/16". The pictures below show the part in the chuck and after cleanup.
A 5/16" X 1 7/16" slot was marked out on the rule holding block. The slot was cut with a 5/32" end mill as the 3/16" and 1/4" end mills were all in bad shape. It was cut in 0.010" depth increments and then widened to the scribed lines. The slot measures 0.310" wide. It was cut to a depth of 0.140". The resulting slot is seen in the photo below.
Two sets of end mills were ordered from Shars this morning, one two flute and the other four. Amazingly, using regular shipping they arrived the following afternoon!
The second part to be made is the sliding nut. This begins with a 3/8" shaft of CRS. The steel was mounted in the lathe and faced. The rod was drilled 1/8" for a depth of 5/8". The shaft was transferred to the mill, where it was flattened on one side to 1/16" depth and for a length of 5/8". Returning the part to the lathe, it was parted off at 1/2". A bit of cleanup with a file produced the not yet complete part seen below.
A piece of steel was cut from the provided stock and squared up to 1/2" X 3/16" X 5/16". The 5/16" dimension was adjusted by a thousandth to a sliding fit in the slot. Two 1/16" holes were drilled through the block 5/16" apart. The block was clamped to the semi-cylinder and aligned as best as possible by eye and touch. One hole was transfered to the cylinder, a 1/16" pin inserted, the part reclamped, and the second hole was transfered. Two pins were slipped into the two holes, each about 1/4" long. The two parts were soldered together and cleaned up with a file. The photo shows the part at this point. The pins can only be seen upon close inspection.
The sliding nut was held vertically in the mill vise, redrilled with a #25 drill, 0.149". The nut was then tapped 10-24. After chamfering the ends of the threaded hole the nut was tried in the slot. It got stuck about 3/4 of the way in as the two parts were not perfectly aligned when soldering. A bit of milling and filing later, the nut slides easily but with little play. The photo below shows the almost finished sliding nut in the slot. The nut was finished by filing a slight angle on one end of the rectangular portion for holding the rule. The second photo shows a rule trapped between the sliding nut and the holder's similar 7° angled edge.
Spent the morning in the 80+° garage making the screw. I will blame the many errors on the heat. A 2 1/2" length of 5/16" rod was cut off with a hacksaw and the rod was moved to a collet. The end was faced and 1 1/8" were reduced to 0.190" for 1 1/8" using tailstock support. A 10-24 die was started in the tailstock die holder and finished using a die wrench. The part was removed from the collet and moved to a smaller collet holding the just threaded end. Numerous issues plagued reducing and threading this end beginning with the center drill breaking off. Eventually, 1/2" of the end was threaded 8-32 instead of the planned 10-32. The photo below shows the part threaded into the moving nut. All is well in the end.
The final part was made next. The screw handle was to be made from the 5/8" stock included in the kit. When looking for some 1/2" stock in the scrap bin, I stumbled across a 1" length of 1/2" aluminum rod that had a knurl on one end. Anything that saves me from knurling is greatly appreciated, so this became the handle nut. The aluminum scrap is seen below with its less than perfect knurling.
The scrap was cut off at a little over 1/2" with a hacksaw. The knurled end was put into the three jaw chuck and faced. The diameter was reduced to 3/8" for 1/4". A stop was put behind the part using a collet to hold a 3/16" piece of scrap (scrap for scrap). The handle was then drilled with a center drill and then with a #29 drill. The part was tapped 8-32. The screw handle is shown below.
The body of the rule holder was sanded up to 400 grit. No effort was made to get rid of the original slightly pitted finish or to remove the machining marks, just enough to brighten it up a bit. All parts except the aluminum screw handle were wiped with 3-in-1 oil as the sliding nut was already showing some rust. The screw handle was glued to the screw with Locktite. The two photos below show the completed rule holder with and without a rule.
