When To Say Bushing Needs Replacing??

[Kroll]

Afternoon guys,well this afternoon I clean up the feedshaft for my Colchester lathe went to slide it through the tailend bushing of the bed.About mid way I stop and could move the shaft around pretty easy so I remove it and took some readings of the OD of the shaft which was .748 then measure the bronze bushing which was .754 Guys does this sound like the bushing needs to be replace?How big is to big,or how wore out does the bushing have to be before you would replace it?Removing the bushing looks like it will be a pretty good project,but if it needs to be done how should I go about doing it?Getting closer to finishing I hope----kroll

 

[Bob Korves]

It is no doubt .750" nominal, and may have been near that size when new. I suppose the lead screw might have been around .750" when new as well, with the bushing sized to clear it by a thou or so. Measure the shaft carefully where it fits in the bushing. Make the bearing a bit smaller on the I.D. and large enough to press it in to the bed on the O.D. The bushing I.D. will shrink because of the press fit and should be reamed to the proper clearance after installation, guessing about .001" clearance, but maybe others here know the factory specs.

 

[mattthemuppet2]

that would be a bear to replace - how do you get it perfectly in line after you install it? Another option if the existing bushing is in good condition (not bell mouthed, gouged etc) would be to turn the leadscrew end down and fit a collar over the end of it, then turn that down to the existing ID of the bushing.

 

[Kernbigo]

no

 

[Andre]

As long as the bore is fairly well machined and clean, if you turn your bearing with an ever so slight taper (taper it with a file) it should press in pretty straight if you're careful. Using a small square before pressing it in can really help. Or turn it ever so slightly undersize an use locktite

I would think .006 would be more than adequate for a leadscrew support bearing.

 

[joshua43214]

Making a tool to press out the old bush and press in a new one is a quick and easy job.
It is just a cup with a hole in the bottom to receive the old bush, and pin to press the new bush in.
A bolt passes through the pin and the cup and is used to apply pressure.
If the old one does not want to start moving, just put it under pressure and strike the tool with a mallet to get it going.
If you add a smaller diameter to the pin that fits inside the new bush, it will help guide it square into the hole.
This is a fairly easy tool to make, and is good practice for machining to size and making square shoulders.

I would make the new bush 0.001" oversized on the ID, and bore and ream to final size on the ID. After installation, you can ream again by hand (unless you are brave enough to ream with a power drill). reaming to size before installation will make it easier to ream to size after installation.
Don't Loctite the new bush, you are only going to ruin someones day in the future (it might be your day that gets ruined). Press fit is correct.

It will make replacing the bush about 5 minutes worth of work and will do it painlessly and precisely.
Making the new bush the right size will be the hardest part of the job, not getting in or out.
When I was a mechanic, replacing bushings was a pretty common thing. I mostly just used a pair of sockets that fit right and a long bolt. It helps to have hundreds of sockets though...
I have an expensive bushing puller set for larger sizes, but never needed one for smaller sizes.
It will take less time to make the tool than to drive to HF, save your money.

here is a pic I found on Google of a fairly typical shop made tool

 

[4GSR]

I'd leave it alone. I've seen them worn much more than that and told to leave them alone when I wanted to replace them. All its doing is providing support for the lead screw or feed rod, or both. Just keeps them from flopping around!

 

[schor]

I agree with Joshua, get a new bushing. Here's a vid I made on how to remove one.

 

[4GSR]

View attachment 118906

One thing I would do if I was you, remove those ball type oilers. Traditionally, they never get any oil, and its evidence of that in the wear in the bushings. (Still wouldn't replace the bushings). But do replace with regular Gits oil cups. You can get them from McMaster-Carr. I usually keep a few around for my rebuilds as I see fit. KEn

 

[Kroll]

Good morning guys and thanks for the opinions and the links and the video( I also watch the x axis video Steve provided,on my to do list) and think I will also install the oil cups that ken suggested,good ideal.Looking at the pic that joshua provided makes it look doable for someone like me.But if just being about .006 out I was more concern about the extra noise that it would make by bouncing around.Sounds like its not that much,but I am going to order the bushings and have them on hand for that just in case moment,so going to move on to the lead screw.I am getting excited,thanks guys for the help---kroll