Recently retired, I leased some space and bought some machine tools. My friend showed up asking me to repair or fabricate a new part for a cylinder on his mini excavator. Doesn't look like rocket science, but wanted to check on what kind of steel I should be using for this sleeve and any other wise words you might offer. First post, so apologies if I'm in the wrong place. He's buying a new cylinder, but wants these sleeves built so he can weld them on. Asked ChatGPT and got an earful about ID hardening, bushings, etc. Is any of that relevant?
Its obviously not a big production machine. Keep it over greased, loctite in place and may work for years. Would have to see the entire unit. Should or could work. Simon C
Do the pins run straight in the tube or are hardened bushings pressed in? If the latter, 1045 or 4140 would be OK. 4140 is stronger but will need preheat for welding, and will be tougher to machine if your lathe is a small "hobby" size. Bearing in mind the relatively small size of the part, distortion may be an issue during welding. You might consider welding then boring to finish size later.
No bushings. Lathe is 16" Precision Mathews, also large PM mill. Thought about distortion, welding happening elsewhere, but I can bore it out if it distorts, as you suggest. ChatGPT suggested a tight tolerance, like a thou, which seems odd. Don't I need some room for the grease? Sounds like 4140 is the way to go.
I’ve used DOM tubing, 4140, and some unknowns with success. Sounds like you have the machines to pick your material. As far as dimensions, when cutting a pin bore I shoot for .002”-.004” over pin diameter. In that particular application I would try to find a hardened bushing/bearing for the pin and press fit it into the rod eye.
Thank you. Those tolerances sound more reasonable. The current part (unknown material) is elongated in the rod travel direction by 0.020" which sounds like some significant loads, so I was thinking more beef would be better. But it could be wear instead of distortion (I'll go back and check that). I'm going to guess that a combination DOM sleeve with hardened bushing will not be (too much?) weaker than without the bushing.
I don’t think that would be weaker with a thicker wall DOM and bushing. That’s a pretty small machine, what is the pin diameter?
30mm