Pressing brass bushings

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EOsteam
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Joined: Thu Jan 31, 2013 1:33 am
Location: Pendleton, Oregon

Pressing brass bushings

Post by EOsteam »

I have to press some bronze bushings into the link girder castings for the support and articulation of the links and the reverse links. The bronze bushings are 1/2" OD and 3/8" ID. If I use the standard sizing for the bushings they will get a .0005" interference fit. Is it better to press the bushings and then bore for the ID size or size the ID and then press? I continue to generate questions as I build. I am one of those who is building his dream engine (4-8-4 daylight) all the while learning how to machine. I am only going to build this one engine so I didn't want to construct an engine with which I wasn't in love and possibly suffer burnout. So far, even with the inevitable boos boos, it's still a joy! Thanks again for all the help I have received on this board. You are all a treasure!
Harper
Rich_Carlstedt
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Re: Pressing brass bushings

Post by Rich_Carlstedt »

If they are bronze you do it one way, and if they are oillite ( lube impregnated ) you do it another way.

Bronze , insert and bore after

Oillite, do not bore , you size the hole to give you the finished bore
say the bushing is +.003 on OD and + .001 on ID and you want to use a shaft on size but have .0005 running clearance
SO that size says you want .0005 above your shaft and subtract it to get bore
Example
Lets say you have a .499 shaft with above specs
so your desired ID of the bushing is .4995 and you know the bushing is .501 ID so that means your hole needs to be
.0015 less on than the OD of the bushing . So the hole is bored to .0015 smallerr than the bushing OD ...For oillite !
Rich
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Bill Shields
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Re: Pressing brass bushings

Post by Bill Shields »

Or put the bushings with a light slip fit and loctite
Too many things going on to bother listing them.
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liveaboard
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Re: Pressing brass bushings

Post by liveaboard »

I've done it both ways.
Sizing first is easier because you do the work on the lathe. But you need to get those measurements just right, and it's difficult to measure the bores accurately unless you have an expensive internal micrometer.

Honing or boring after pressing is less prone to error on size, but more prone to alignment error.

On balance, I prefer to bore the bushing to size before pressing. My experience is that on pressing, the bore will shrink equal to the amount of interference between the parts; although I have no doubt there is some slight difference that is beyond my pay grade.
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