Chris's Build of a Stanley 735 Engine

[crueby]

Gotcha - for my case with the internal threads done first, I measured the ID and calculated in the depth of cut that I had used, it got me very close to the OD for the caps.

[mklotz]

A very nice treatise on the three wire method is here...

https://littlemachineshop.com/images/gallery/instructions/ThreeWireMethod.pdf

If the math scares you, the 3WIRE.ZIP archive on my page will be useful.  It calculates the best wire size and measurement over wires when using the three wire method to check the pitch diameter of a thread.

A piece of styrofoam (e.g. packing material) works well to hold the wires while making measurements.  Lay a cloth under the workpiece to catch dropped wires; they're very hard to find amongst the swarf.

[crueby]

Thanks Marv, will give it a look!

[crueby]

This morning got the base caps shaped and threaded. The end of the thread was undercut so they would screw down flat to the cylinder end. These caps will have holes in the center for the piston rods and glands, but I will drill those with the caps in place on the cylinders and the cylinders held on the arbor, to ensure they are aligned to the bore as screwed in.
Here are the parts so far, with the base caps in place, and the top caps ready for the next bit of shaping. All four caps need to hace the outside faces recessed to form ribs, which I assume they used to help screw them into place and out again.

Very pleased with how the threading worked out, that was one of the new skills I had to learn on this project (thats one of the fun things in this hobby, always new stuff to learn).
 

[Mcgyver]

man, you sure squeeze a lot out of that little machine, kudos!  Nice progress on the engine

[cnr6400]

Looking great Chris! 

[Brian Rupnow]

Looking really great Chris. Threading with a lathe is one of those things I CAN do, but it makes me quiver all over. I put all of the appropriate change gears on my lathe and did cut a 3/4" coarse thread that would accept a 3/4" standard nut. Having actually threaded something, I put it up on my shelf of "Look what Brian can do stuff", removed all the change gears, and I've never threaded anything again. Something I didn't know when I bought my second lathe, was that if you buy a gear head lathe, you don't have to mess with change gears. I had looked at a gear-head lathe at the company that sells them and decided that it was too noisy. I am a master of finding things out after the fact, but in this case it didn't hurt me. All of the threading I have to do can be done with taps and dies.----Brian

[crueby]

Looking really great Chris. Threading with a lathe is one of those things I CAN do, but it makes me quiver all over. I put all of the appropriate change gears on my lathe and did cut a 3/4" coarse thread that would accept a 3/4" standard nut. Having actually threaded something, I put it up on my shelf of "Look what Brian can do stuff", removed all the change gears, and I've never threaded anything again. Something I didn't know when I bought my second lathe, was that if you buy a gear head lathe, you don't have to mess with change gears. I had looked at a gear-head lathe at the company that sells them and decided that it was too noisy. I am a master of finding things out after the fact, but in this case it didn't hurt me. All of the threading I have to do can be done with taps and dies.----Brian

This did work, but as you say not something I want to do every day. The way Sherline did the gear holders is not quite secure enough, found that after every pass I had to tap the one lever back into place to keep it from slipping too far out and skipping teeth, which throws everything off. But, unless they make a 26.25x0.9mm tap/die set for a few dollars (doubt they do at all), this was the way to go! Hand turning the spindle gets old quick...

[crueby]

This afternoon got started on the top end caps again - undercut the end of the threads so the cap will fit down all the way, drilled the end shallow for a row of 4-40 screws, and parted them off from the bar. The screws were used to hold the part to a scrap bit of bras bar stock so I could hold it in the 3-jaw without marring the threads. This let me mill out the recess in the top, forming the ridges which are used to install/remove the caps. The screws are in line with the ridge, so they didnt break through.


One down, one to go...

[Don1966]

Very intuitive Dog and some amazing machining.........


 
Don

[crueby]

Very intuitive Dog and some amazing machining.........


 
Don

Thanks Don, though as you will see in the next post, I did not need to make the little holder for the top caps... Not much time wasted fortunately...

[crueby]

With the two top caps shaped, next moved on to the base caps, which differ in that they have a center boss for the piston rod and gland, plus they have four ribs rather than two. When setting them up, I realized that drilling the holes in the inside for the screws was a waste of time - the rim above the threads gives a place to grip in the chuck without marring the threads.   

The layout for these was easy - worked out to 8 turns on the rotary table for the inner edge of the slot, then 10 turns to the start of the next slot. So, cutting these went pretty quickly, started each slot down to depth along the inside, then several passes on each to widen them out to size. So, here are the bottom caps shaped and screwed onto the cylinders:


as well as the top caps:

I've got a pair of smooth flat-ended jewelry pliers that fit the slots nicely, makes an easy way to screw them on and off as needed. In final assembly, will add some thread sealant goop for a gas tight fit.
Next up? I am thinking going back to the cylinder blocks, doing a little more filing/sanding, and get started on the holes for the valve sleeves. These sleeves hold the piston valves. Or is it spool valves? Two names for the same thing? 

[zeeprogrammer]

Two names for the same thing? 

Why not? I know of several names that you go by. 

[cnr6400]

I think the naming convention is spools in hydraulic valves, piston valves for steam. Also pi$$ed-on valves for the leaky ones I have made before I learned the tricks about PTFE rings on piston valves, and radii at window corners in port openings on sleeves for piston valves.    

[crueby]

Two names for the same thing? 

Why not? I know of several names that you go by. 

Oh, there have been lots of names over the years!  Some could even be mentioned here.   
My answer to 'do that, it will build character' is always that I dont need character, I am one!