Jack...
My horde of extras has saved me a lot of money. Some of the smaller pieces are almost embarrassingly small from having things whittled from them. I don't throw dollars into the woods either....LOL.
The past week has been a bit of a grind. The rib has gotten less sore, but only because I haven't given in to it. Teeth are now fully ground and my reflexes are quite highly honed to any movement near the damned thing. I still managed to get a few things done, but this morning was the first time back turning the dials on the mill. Most of my time has been spent cleaning up solder spots, fine tuning some of the hand filed stuff and cussing the cat. He likes it when I'm doing bench work and tends to land in my lap at the most inopportune moments.
Today I tackled a small conundrum. The arms need two small but accurately placed holes in each of the small webs at the big ends. The snarl comes when you realize there are no straight edges to clamp in the vice. Add to that the fact the the hand shaping was done to visual standards rather than to specific measurements and you've got to think out of the box, down the block and around the corner to find your solution. Ok.... so maybe not quite that far, but I've still got to drill the holes and they have to be uniformly located to match up to studs and against a solid edge.. So what's an overbeard, nearly no haired, former leaping gnome to do?
Two points in the making of the arms were rock solid.... the two pivots. Everything I did to the arms was based on them, so we know they are indexable. That is where it begins. I drilled holes to fit 3/16 dowel pins in a small chunk of aluminum, on the same centers as the original tooling plate.
I touched off the bottom edge of the stanchion to establish my cut line and then removed it so nothing untoward happened to it. I then made a light cut and replaced the arm to check the fit. With one minor move of the X axis, the fit was nice and snug without needing any significant force to seat the dowel pin in the head hole. If you've noticed the small notch on the bottom side, you'll have to forgive me for taking you along on the second run through of this process....(grin).
Here you'll see the slot I added to give the drill bit access to the brass part when the drilling begins. The part was simply too narrow to allow drilling guide holes, so the open galley was Hobson's Choice.
The addition of a hold down was not a choice but a requirement. There isn't a lot of meat holding the base of the stanchions so some support in the way of a 6-32 screw will help ward off the gremlins from attacking during a delicate bit of drilling.
The extra metal on the "big end" will have to go if I'm to be able to access the part with a center drill. I do not drill holes without having center drilled them, even in nice open easy work spots. I'm certainly not going to miss doing it in a tight spot like this. I've got one shot at getting it right, so I'm giving things a lot of ounces of prevention here. My handy dandy carbide tipped arbor saw made quick and clean work of the task.
Here is the jig after both sides were cut and the excess metal removed. The reason for needing both sides may not be obvious. The two cylinders are of different diameters. This is because they combine to form a compound system where the larger cylinder accepts expanded steam from the smaller high pressure cylinder. Expanded steam requires more room so the low pressure cylinder has a larger bore and therefore a larger outer diameter.
The arms were cut to fit the larger diameter for convenience, knowing that a modification would be needed. A .060 rim was then cut and soldered to the bases of two of the arms. This gives the holes in the heads the same elevation so they accept the 3/16 shaft without binding. Two different diameters means I had to cut two different sized arcs in the jig.
This little jig will serve double duty as I continue to hand fit the stanchions. It will give me a good reference for keeping things square as I continue to remove tool marks and head for the final polishing phase. I like it when one tool can do more than one thing..... a bit of
efficiency laziness never hurt anyone....LOL.
This project didn't make any major advances in the engines, but it does give me a chance to share jig making with the new guys. There are many ways to skin a cat and setting up a jig is one of them. Don't let yourself get stymied by a vise and clamps when a part is not an easy set up. Look at it and see if you can secure it with something that is easier to tie down.... and then make your own jig.
Steve
