Today's shop time

First order of the day was the cam fork - a straight forward milling job to get to size:

And after sawing off from the parent stock, drilling and tapping and a quick rub over emery:

Then I made the cam roller:

This is the second one I made; the first one went on a flying trip while I was trying to clean up burrs - I just heard it hit a wall and something metallic; didn't even see where it went... At least the shop monster got a bit to eat

A little M2 bolt followed to act as roller pin - just some brass threaded rod turned down, threaded, and the head section filed to a hex while on the lathe:

Then I had to re-make the cam roller again

- I made the original one 3/16" and when I started putting things together, it looked way too small. Misread the print; it was supposed to be 5/16"! Parting off on the lathe no longer intimidates me like it used to, but on these smallish bits I always end up with quite a big burr that have to be removed from the parted face afterward. I tried something different for this one: before drilling the center hole, I parted it to just under the drill size, then center drilled and drilled the hole to size. Works a treat; I ended up with the roller sitting on the drill and only a very light burr:

The finished fork with the roller installed on it:

While posting, I happened to notice this photo was the 2000th one taken with my current digital camera - and I've only had it for about a year. A quick calculation, and it has paid for exactly half of it's purchase price in saving on having 35mm film developed!
The valve plate needs a 0.28mm slot cut in it, and Phil very kindly describes making a small slitting saw for the job. I deviated slightly from his design, but used the same principle. First some 12mm silver steel turned down on the lathe; the section closest to the chuck I just cut using successive parting cuts with the rear toolpost, and then slowly and lightly faced the front section down to obtain the correct width. A very sharp HSS toolbit made this a no-brainer though I was a bit apprehensive of machining to such a thin width initially:

Then some delicate-but-rough-looking milling on the rotary table followed. The first person to spot the boo-boo I made has a choice of one of two prizes:

The prizes to choose from are a) an under-water hair dryer or b) a steam loco catching kit consisting of a bag of charcoal and a bear trap

- UK members don't qualify for option b though, as it would just get used to heat shops

Fortunately, my mill can run in reverse....
I very gently filed cutting clearance behind the teeth, and then hardened the cutting teeth by heating red hot with a blowtorch and dunking vertically in oil.
For this cutter, I didn't bother to temper afterwards; it did not come out quite as well as I would have liked, so will most likely be a single-use one for brass only.
I then started work on the valve plate. Some brass, carefully milled down to size:

And then used the cutter made earlier to slit the top - worked a treat

:

After using a bigger slitting saw to separate the valve plate from it's parent stock, it was just clamped by the protrusion in the middle, and milled down to the correct thickness of 0.3mm:

A bit of clean-up, and careful flat-lapping of the face (to remove toolmarks and get it really flat and smooth) followed - and that's the valve plate done:

I noticed something interesting while doing the flat-lapping. Normally I can see the lapping starting to take effect very slightly on the outside edges first, but on this one, it started in the middle and took quite a bit of lapping to reach the outside edges... I think while milling the bottom flat, the milling cutter bent the thin outside edges slightly down. Just a tiny detail to consider in future....
At this point my woes really started... I had the bit of 0.1mm feeler gauge to make the valve spring plate from. Mark-out went easy and a pair of tin-snips made short work of trimming it down. Then I had to consider drilling a 2mm hole in it to fit on the valve pushrod. Thin plate and drills don't go well, so I sandwiched it between some aluminium scraps clamped with a toolmaker's vise:

Drilling went well, but I could feel that this feeler gauge plate was something different; it was tough to get through with the drill...
When I tried bending it, this happened:

- this steel plate does not like bending...
That was the only bit of 0.1mm plate I had... The off-cuts are too small to use, but I used the busted bit to do an experiment; I tried bending it around some 1mm rod, and that went OK:

Except, when I tried the minutest adjustment after the original bend, it promptly snapped again.
I tried bending it while heated red-hot with the pencil torch; same result. I had a closer look at the feeler gauge set this came from, and it's made by Gedore in South Africa - pretty good quality kit - hence good quality, but frustrating, steel in this case. I thought it was a cheapy set of imports; what a waste of good tooling. At that point I decided to call it a day and have a good sleep over what to do next for the valve plate spring. Besides, it had started raining here and rain is best appreciated sitting on the stoep (porch) with a very cold beer in hand.
Regards, Arnold