[How do I?] Making a bronze bushing

T. J.

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I could use some advice on making this part. I'm restoring a Marvel #2 power hacksaw (restoration thread here if you're interested). I need to make a bronze bushing with a 1.125" OD, 1.000" ID, and 7.5" long. The length and wall thickness (1/16") have me worried. I don't know if I can bore that length accurately from one end. If I have to bore it from both ends, then I'll have to worry about crushing the thin walled part in the chuck when I swap ends. I also have a question about materials. McMaster-Carr has 932 bearing bronze and "easier to machine" 936 bearing bronze. Is the 936 enough better to justify the additional cost? Any pointers would be appreciated!
 

markba633csi

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You might want to buy the bushing already made- check out Bunting bushings catalog- Zoro carries them
Does the bushing need to be one single piece or could it be two separate pieces? Might be cheaper if you can do the latter
Mark
 

T. J.

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Thanks Mark. I checked out Bunting's website. It doesn't look like they have one long enough. It does need to be a single piece.
 

benmychree

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I would seriously doubt that it needs to be full length in one piece, generally, things like that are not made like that, two bushings with a length of 2 or 2 1/2" long would likely be adequate for the job.
 

brino

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machPete99

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Also see what McMaster Carr has for bushings. They will also have the raw stock.
 

T Bredehoft

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I would expect one bushing one inch long on each end would do the job, (not knowing what the job is).
 

Superburban

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If this is the location for the bushing, no reason you cannot do two 3.25", or even four 1.875" bushings.

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T. J.

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Well, its a bit more complicated than that. The shaft you see there runs inside the bushing in question. Since I have the machine totally disassembled, I can’t really take a photo to illustrate the situation, but here’s a diagram. The bushing has a shaft running on the inside and the saw frame assembly pivots on the OD. So yes, it does need to be one piece.
 

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MontanaLon

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Start with a 1" ID tube with 1/8" wall thickness. Run a 1" drill through it to make sure the shaft will go through. Then put a bull nose center in the tail stock and put it in the 3j and turn down the outside diameter to 1.125. No need for it to be super tight tolerance as it isn't a critical tolerance application.

Use HSS cutter and take light passes. It will hold up because the thickness in the 3j never changes and then part it off.
 

derf

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Looks to me that you could do it with 3 separate bushings. One short one in the middle, and 2 longer ones on each end.
 

mksj

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It would seem that the bearing material could be divided into sections, in ether case very thin walled and will be hard to get uniformity. I would go with what MontanaLon indicated, McMasterCarr sells 13" section of 1" ID 1.25" OD bearing bronze, I would slide it onto a 1" drill rod clamp down on the bronze with the chuck and use a live center on the 1" internal rod at the other end. Ideally you would want to use a 4J independent of set-true type of chuck to zero out any runout. I turn bronze with sharp ground edge carbide inserts, the same that I use for aluminum, take light cuts per pass. I mostly use 932 bronze, but 936 may be a better choice being easier to machine and higher yield strength, downside is it is much more expensive. I would go with 932. You would need to ream the tube first with a thousandth over to 1.001" if your shaft is 1.000". The ID spec. on the 932 tubing is -0.019" to -0.202", so could be a real PTA to bore true if significantly under and you would need some external support if removing any significant amount of material, but a 7" depth is going to be tricky and brass/bronze can be grabby/chatter cutting. If you need to center bore, I would start with thicker wall tubing. If it needed centrer boring/reaming then would use a stead rest to maintain alignment.

I still do not follow why you could not press in some thin wall oil embedded bushings for each casting pivot, if you could get by with four or five 1.5" section pressed into each casting, it would be $10-15 for the set and a lot less difficulty.

One of my first projects was a bronze vintage roulette wheel shaft that was not running true. It was fairly thin wall and the end thread for the spinner was mangled. I started by re-cutting the base , truing up the shaft and re-cutting the 1" thread to 15/16" and fabricating a new threaded insert for the spinner. Overall length was ~8", it cleaned up well, I took ight passes with very sharp carbide inserts. Ran true when the owner installed it.
20161231_090940.jpg
 

T. J.

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I guess I am leaning more toward making it one piece since that is how the original part was made. Also, if multiple bushings were used, then the original method of delivering oil to the crankshaft wouldn't work. I think I'll try making it in one piece and if it's a complete failure, I'll use separate bushings.
 

epanzella

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If you have to turn it around to finish boring, make a plug to go into the part already bored to prevent crush.
 

Tinkertoy1941

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Something to think about!
Buy brass material of sufficient oversize for both OD & ID
Drill and ream the ID to get the size required
Make a CRS arbor to slip fit in the reamed brass sleeve
Loctite or superglue the bushing to the arbor
Use the arbor to hold the bushing and machine the OD
Warm the brass bushing to remove from arbor from bushing
This way you could make the bushing as long as required with out worry of crushing the bushing
 
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