Mild steel & cast iron

Hello

Anybody have any Advice on wear, regarding running Cast iron against none hardened mild steel, say as a bearing surface, not running at any speed like a shaft , just say, cast iron rubbing against the mild steel

I need to make a clamp to hold a mild steel square Bar/shaft, the clamp will move along the bar/shaft and clamp it at different positions .

thanks

lee

Hi there, Lee,

Many of the old lathes used a mild steel mandrel running directly in cast iron. Given proper lubrication, they ran for decades (some are still running). The cast iron contains graphite which has lubricating qualities but oil is still necessary.

If your clamping relies on flexing the cast iron one side of the 'bearing', then the fit needs to be very close - if you try to flex the cast iron too much, it'll crack. That's the failure mode of many of the older lathe head-stocks.

I suggest that one ingredient for your scheme to be successful is that you take precautions to exclude dirt and grit from getting into the clearance (small though it may be) between your cast iron and mild steel parts.

Best regards,

Swarf, Mostly!

Thanks for your reply/advice

I did think it would be alright, but sometimes I start to question my own knowledge and experience,I rather not be saying to myself, why in the hell did I do that ! , I should of known better, So I post on here get second opinions and advice

I do have a block of bronze , but like to keep it for special occasions/projects

Thanks

lee

As a sliding component, the cast iron on mild steel would be quite OK, but the cast iron is best not used as a clamp. Maybe make the clamp from steel, with a cast iron insert for the sliding surface. Ian S C

Simple screw to close up the slit style clamp sounds risky with cast iron onto a square bar. Look to be too many opportunities for monster stress risers leading to cracking if the fit isn't just so. Side screw, with handle if need be, and soft pad against one side of the bar looks to be a safe way.

Alignment can be an issue too. Every simple slide on a square bar thing I've seen has been intrinsically less than precise when it comes to retaining alignment through moving and clamping. Given the choice, on round shafts at least, I like the screw clamped floating collars in a bore at 90° to the shaft system which is strong when clamped and has minimal effect on alignment. If you needed reliable alignment its possible that something similar with simple 45° angles on the collars would work across the corner on the square bar. Take out the corners of the slider so the bar is pushed onto the flats when the screw pulles the collars up together as though it were on a Vee block and it ought to be decently precise.

Clive

Swarth, Ian, and Clive,

Only just caught your post, Many thanks for your advice, they are most appreciated, something for me to think on

Thanks

Lee

Could you perhaps put up a photo of a sketch of the shaft and clamp that you propose to make, maybe this type of sketch. It was going to go in this post but never mind, this sketch was done for another web site.  One or two dimensions are helpful, the key dimension on the reamer is its diameter, in this case the diameter of the crankshaft that was being fitted,.375" in that case.    Ian S C

Edited By Ian S C on 11/05/2014 11:48:25

Ian sc is spot on with his idea. cast iron is best for surface sliding but would make a poor clamp