S50 cylinder machining setup

Hi,

I'm making a Stuart S50 and I've faced the ends of the cylinder and bored it out on the lathe. Now I need to machine the portface parallel with the bore. Is there anything wrong with this setup?

The rod is an HSS tool blank and I've set the unmachined mounting face vertical with a square. I was going to cut towards the vice jaws to minimise the risk of the cylinder moving in the vice. I can't think of any other way of holding it. Or should I do it on the lathe like Tubal Cain did?

Any comments welcome.

Gary

Gary, I would do the same setup EXCEPT I would not use the bar. Your setup assumes the tops of the vice jaws are parallel to the milling table. Are they ? I would guess the vice's fixed jaw is just as perpendicular to the milling table. I would set the casting at the midpoint of the jaws to minimise any twisting effect of the clamping force out of line with the vice screw. Set the casting as low as you can place it with allowance for the cut. I would put a piece of paper between the moveable jaw and the casting face. I never learned the use of paper in the "real" world, rather I learned it in ME. It does work. Also, watch carefully as you cut. You should notice a better finish cutting one direction versus the other. I would take all the finish cuts in one direction only.

I would bolt it to an angle plate rather than use the vice.

Gary, you could even bolt it between two angle plates to give a more ridgid mounting, or two 123 blocks. My vice is fairly rubbish, so I have to find other ways of doing things. Ian S C

Thanks for the suggestions guys.

Bruce - good point about the vice jaws. I've not checked them so if I end up using this method I'll put a DTI on them first. I knew about putting it in the centre to minimise twisting forces but had just clamped it quickly for a photo so might have forgotten to move it into the centre before cutting. What is the benefit of putting paper next to the jaw? I would have done all the cuts in the same direction.

Chris & Ian - I'll have to think about this. I presume you mean with the end flange against the plate/s and a bolt running through the bore or perhaps on either side. In that case how would I ensure the bore is parallel to the table?

Doh! Thinking this through as I type and I've just realised that of course the bore is perpendicular to the end face so that ensures it is parallel to the table. I started off using the tool blank through the bore so I had a reference to set the amount of metal to remove. But maybe there is another way. I didn't like the idea of scribing around the casting as Tubal Cain suggests. He was doing it on a lathe only.

I'm not really as thick as this sounds, it's just that experience is incredibly useful when workholding.

Gary

Hi Michael,

Thanks for your input. I can feel the purchase of another angle plate at Harrogate coming on only have one at the moment.

I'm loosely following the Tubal Cain write-up serialised in ME from August 1992 and trying to figure out which bits are better done on the milling machine. I assume he did the bore first because it was easier to measure an exact amount from the edge of the bore to the portface (which he did with a height gauge) rather than trying to bore to an exact diameter with the edge of the bore ending up a specified distance from the portface. More difficult to describe than to do.

Gary

I took a skim across the top of my vice jaws, and the step. Together with adjusting the vice gibs, I can machine things parallel to reasonable accuracy, only clamping to the table for critical jobs.

Neil

In the end thanks to Ian's suggestion I used this setup:-

The front clamps were left out of the picture for clarity. It might not be ideal but it seemed to work. Then I used the same arrangement for the mounting face which is facing forward in this picture.

Gary