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Shrink fit into cast iron

Dave123

Aluminum
Joined
Jan 13, 2019
Resurrecting an and old crankshaft grinder. Turns out the support that holds the wheel and table gear shaft has cracked.
Being cast iron welding is not simple , so I am thinking of machining a new shaft support and boring the boss, then heat the boss and press the shaft support into place.
Would steel work OK for the shaft support tube or should I be looking at a piece of cast iron??

Dave Eddie
 

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What material is the shaft? Steel on steel is bad science, so if the shaft is steel, the housing should be cast iron or if steel, with a bronze bushing.

jack vines
 
Cast, bronze or steel ( as long as it gets lubrication) should all be fine. You're not going to run at 500 rpm so galling isn't likely if proper clearance is maintained. Make sure to keep that oil port operational and filled often. On a grinder good lubrication is the only chance at decent life for any component, I like to use light weight oil to essentially wash fines out of operational surfaces. Heavy lubricants can collect abrasive dust and become a lapping compound of a sort pretty quick.
 
Presumably. this is a low speed (manual), situation. in which case steel on steel isn't going to be a problem. If you want to do a weld repair to keep things original, use a 55% to 98% nickel rod (or Inconel 82 wire, if you're rich :D) with a bit of pre-heating (200°C/400°F). The resulting weld will be easily machinable.
 
Eddie, Though welding is possible as discussed above, it is not worth the trouble. I would just do as you suggest in your post. Originally, it looks like the entire length of shaft served as a bearing and was oiled the entire length by the oil port. So, I’d be inclined to bronze sleeve the assembly by simply Loctiting in a full length or segmented bearing. Some sort of felt wiper and cap or rubber seal to reduce grit ingress at the outboard end seems like a good idea. There plenty of meat to inset it if necessary to maintain clearance. Oil it often as it probably was intended to clean itself by oozing oil.

Denis
 
Thanks for the input, I have opted for the steel shrink fit into cast. You are correct in that this is a support for the rack and pinion gear shaft which is turned via the hand wheel, so no high speed involved.
So far the repair looks to be fine.

Dave
 








 
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