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Lathe counter-shaft repair advice

crazycuda

Plastic
Joined
Jan 12, 2018
Location
USA
Got a 14 1/2 that needs counter shaft work, making a new shaft is not going to be an issue but I am undecided what is going to be the best way to repair the worn out iron bearings. I am tossing up between going with a bronze bushing (660)with oil grooves or going with needle bearings. My concern is since I'm using a 1045 shaft will it hold up to the needle bearings or will they tear up the shaft and I'll be redoing it again in a few years.
I already checked around for the later set up off a 16" (since my parts are stamped 14 1/2-16 and pn's show interchanges) but for the shaft cradle and pulley I may as well go buy a parts machine. So that option got ruled out.
Any thoughts or advice would be appreciated
 
1045 will be torn up with a needle bearing. In that case I would use 8620 with HT. My choice for repair would be bushings either bronze or iron. The tricky bit is bushing alignment. You should use a pilot reamer to be certain.
 
I'm thinking you should be able to purchase a hardened thin-wall sleeve (inner race) for that bearing to run on. Sounds like you are making the shaft so you could incorporate the design change no?
 
Why not just keep it simple and use plain bearings? Needle bearings don't offer any huge advantage, and may be big problems down the line, or perhaps even sooner. Someone mentioned alignment of the bores, needle bearings sure won't like any misalignment. Bronze will be the most forgiving, and kept lubed, they'll last for decades.
 
The issue I hit against using an inner race is the pulleys. If I cut down the shaft to fit an inner race or hardened sleeve I would have to sleeve from the main 3 groove pulley in just past where the needle bearing would run on one end. Since the pulley is pressed on as well as held in by a taper pin think that might open up a can of worms. I am limited to opening the bore in the casting to 1.65 and still have enough meat to cut back in the felt oilier groove.
I've thought about going with a hardened/chromed shaft but the thought of having to drill it for the taper pin as well as the collar lock set screw and inner pulley set screws has me totally cringing, Plus the price jump. Now I got myself over thinking how forgiving are the needle bearings if the casting flexes with heating and cooling as well as load.
 
It's a repair i'm planning to do twice. One to an up coming build of a 16, and once that machine is operational, i plan to return to the 16 that i currently run to address things i need a lathe or mill to do.

I find that both have excessive wear for that pulley/shaft assembly, but with the pockets filled with oil, the weight of pulley/shaft assembly is such that they dont bang around or vibrate under power. With that in mind, i was thinking making bronze bushings with about .0015 to .002 clearance to each shaft journal.

My plan is to straighten up each shaft journal first, either with lathe, or cylindrical grinder, rather than make new shaft.

Then bore the two saddles. Make the bushings press fit, with id's to whatever the size of shaft is cleaned up with oil clearane figured in. Working off existing holes i was thinking i wouldn't need to line bore, or ream from one to the other, so long as I'm fairly concentric in making bushings, but i haven't crossed that bridge with it either.

The thing i don't like about needle bearings, is if they get dents in races from the needles, be it wear, getting banged, shock or hard load or whatever. Then you get vibration. If that doesn't happen, they work great and make for easy replacement in the future.
 
If there's not enough meat in the casting to do it right with the later design automotive wheel bearing-style bearings that SBL used, it's probably safer to run with bronze as you were planning. As long as you have a good lube schedule, they'll be fine. The countershaft bearings aren't all that heavily loaded if your belts (motor drive v-belts or cone pulley flat belt) aren't set too tight. As long as the oil flows, the bronze will last longer than you or I will. :)
 
Thanks to everyone for there input. I ixnayed the the needle bearing idea because of possible alignment issues (thermo shift) and having to go with a hardened shaft (which jumps the price of the repair in parts a bunch). I have to try and keep this project on a tight budget as the further I go down the rabbit hole in finding things that need to be replaced.
 








 
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