Wednesday, August 19, 2020

A Minor Shop Update

I haven't updated this in a while, but my two valves are at the last two stages of fabrication.  To get to this stage from completing my test valve over two weeks ago, I needed to make two valve cages out of a bronze rod that I have and cut two new valves from drill rod (a piece of oil-hardening tool steel).  Shouldn't have taken as long as it did.

One valve standing up, one lying down in front of it, and two bars that work the chuck on my Sherline lathe in the background.  The cages are just sitting there, not bonded in any way - they slide on the valve stem.

There's a few steps left.  First, I have to put the valves into the stack up of pieces that make up the valve block assembly, put aside to wait for this back in July. 

See that hole on the right side of the block, top slice?  Once those are in place, that hole gets redrilled through the valve cage.  The slice on the bottom has the drill hole on the opposite side, for the exhaust pipe.  (Top valve is intake bottom is exhaust, BTW).  Then each valve will be spun against its cage with some lapping compound to make the valve fit that valve cage perfectly - they're literally made for each other.  

That uses the extra 1/4" diameter steel past the valve to twist the valve and push lightly into the bronze valve cage.  Some guys twist those valves in their fingers using the 1/4" stem as a handle; others have used a portable drill to power it.  

Once that's complete, I'll put the valve back in the lathe, cut off the excess material and then finish cut it to final length.  Then do the other valve.  The valve block will be put back together with gaskets between the slices. 

This has been a very slow stage, and that's primarily due to the small parts - the valve stems are 3/32" (0.094") diameter and everything has to be made precisely.  See the hole through the valve stems, near the small diameter ends?  That hole is 0.040" diameter, the smallest drill bit I have (#60).  Because of the sizes, none of the work holding accessories that I have will work.  I needed a piece that would hold the valve close to the top of the jaws in my vise, but it had to be thinner than the 3/32 stem.  It took over an hour to round up something of the right size in my scrap pile and cut it to size.  For most of what I work on, I can use a standard thickness parallel but those are too thick to hold the valve stem.  


  1. I don't know how you can even see those parts well, let alone make them and install them. I am seriously impressed.

    1. One word: OptiVISORs. Really, more than that: magnifiers.

      My usual way of setting up parts in the mill vise so I know where zero is won't work with these parts, so I painted the ends blue and scratched a line on them. Then I had to put the center drill on that line, while the thing was in the vise. It took a flashlight (the two 100 watt bulbs put just no light onto the piece) and a 10x magnifier to sorta see it, but I wasn't at all comfortable until it was drilled and I could verify the hole was in the right place.

    2. Wow. I probably would have drilled the #60 crosshole first, given the strong possibility of ruining all the other work...

    3. Wow. I probably would have drilled the #60 crosshole first, given the strong possibility of ruining all the other work...

      The test valve I did first is the first time I've ever made a valve. Since I don't know what I'm doing, I've been following a tutorial I found online and that guy drilled the hole after shaping the back side of the valve and the stem completely. Because drilling virtually always leaves a bur I have to put it back in the lathe and hold sandpaper on the stem to de-bur it. Then abrasive from the paper gets in the hold and clogs it up, so I have to poke that out. It's tedious.

    4. I am in awe of what you are managing to do with pieces barely big enough to be seen. I wonder if it's even necessary to lap the valve face in, at this size.