Turning a cylindrical bar into a semi circular cross section bar?

I do like JasonB’s solution as getting the upright, well upright was a concern of mine. My only worry is whether the 5/8” cylindrical bar will fit in my tool post.

must check that today

Edited By Paul McDonough on 05/03/2023 09:40:53

Fingers crossed though as you are likely to need to do other milling with the lathe a simple clamp bar may be a worthwhile investment in time and material, I still have and use the ones I made for my little Unimat 3 which must be about 40yrs old.

You mentioned about making a vee block from the offcut from the base, having sawn a similar bit off it is rather small and would be hard to hold for making into a Vee block. Luckily you don't need a vee block and have all that is needed.

After facing the ends of the supplied stock set it up in the 4-jaw using some lathe tools as packing (remove before switching on) and set it lengthways so that the lathe axis is on the point where the cylinder pivot goes. You can then face back to produce the flat surface and then drill and tap the pivot hole, it is important to get this perpendicular to the face for a good seal and doing it all at one setting will ensure it is. Guide the tap with the tailstock chuck so it does not wander and give a wonky thread.

If you have a bench drill you can take the chuck off the lathe and move it with the work still in place to that to drill the steam passage

If you don't and have to drill on the lathe then just move the work in the 4-jaw

It looks like the bore is offset in the stock so you can then use the 4-jaw to hold your work and set it to run true to a marked ctr position and spot drill, drill and bore or ream the hole.

Depending on what you have to make and finish the hole I would consider making it a through hole so any lapping will be easier and then just turn and loctite in a stepped cap to close off the cylinder.

Ah yes I spotted this challenge for later!

Again thank you for your encouraging how to do it pictures, it is much more than I expected

Well yes but if the design had specified a bit of angle instead of half round, the OP would probably be running the engine in by now. Easy for me to say after 40 years in engineering design, not so easy for a beginner to see.

Martin

It did fit in my tool post and this process has now been completed, thank you for your help