Cast iron Wall Thickness

I plan to make some press fit bushings into an ally block that will run a steel shaft - hand turned and rarely used. The original drawing calls for steel bushings but I rather fancied making them out of meehanite - if only 'cos the only cast I've turned is skimming my faceplate. However the dimension (which can be altered) calls for an ID of 24mm and OD 29mm i.e wall thickness 2.5mm over a 15mm length with a 3mm flange at one end.

Is a cast material likely to crack while being bored out to that wall thickness? And presumably better to bore out before turning down externally?

thanks,

pgk

pgk, Go for it, that is about the size I have used for pistons for hot air engines, and I'v been able to get the skirt thickness down to a little over 1 mm. Did break one when I took one of the grooves on the outside a bit deep.

I'd turn the inside nearly to size, then take the outside to size, then finish the inside. Turning the outside (I find) can close up the bore a thou or two, so if you leave .005" you'll have a little meat to work with getting it to size.

Others may disagree, that's OK, I just do it my way. This is the power end of a stove top Stirling Engine, piston is a bit of window weight cast iron 30 mm diameter, the cylinder is a bit of the tube from inside a car shock absorber.

Ian S C

I doubt if you will have that problem with any continuously cast iron such as meehanite. Wall thickness and cracking is more of a problem with castings especially if they have been cooled quickly. It can leave a lot of stress. Obviously hit hard enough it will crack rather than bend.

John

-

This should be OK if you press the liner in with a spigotted bar with the spigot loose enough to allow for liner contraction. Colin

Should not be a problem I have done 3" long, 1.25" dia, 1/16" wall thickness lineres for IC engines without problems

Excellent, thanks all - pgk