[How do I?] Calculate Bore Id To Get An Exact Bushing Id After Press Fit

If this was a drill bushing that was slipping one of my senior journeyman showed me to press fit was to prick the wall of the reamed hole with a center punch in about three places. It will not move once pressed in place.

Good luck
 
Here is the Engineering Info from Boston Gear. Hope this helps.
 

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TommyD said:
Maybe turn the bushing to size, knurl the od and bore the id close to finished dia, maybe .010 over. Smear the knurl with JB Weld and press in. After the JB hardens, I think it's somewhere near 17 hours, bore the id to size.​
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I think if you knurled it then the pores might be closed up on the OD.
 
thanks for all the info everyone, especially the Boston Gear and Oilube references. Boston Gear recommends a max of 0.0055 press fit in soft metals for the size of the housing I'll be working with and Oilube lists a max press fit of 0.0045, although mentions that press fits at the upper limits of the recommended range require a lot of force to push in. The close in ratio for that wall thickness bushing is ~80% which will give me a good idea of what to aim for as well. Pressing a cold bushing into a hot pulley should also help, as long as I can do it quickly.

I do get the recommendation to buy the right size, but from all the searching I've done (and I've done a lot) to get the right bore size without a subsequent boring operation (or even with) will be $20+ for 2 bushings inc. postage, which just isn't going to happen right now, especially if I have 2 on my bench that cost me a buck on closeout :)
 
Bob Korves said:
I think if you knurled it then the pores might be closed up on the OD.
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My thought process was that the OP was interested in the ID only to be functional. Not much pressure is required to knurl soft materials.
 
TommyD said:
My thought process was that the OP was interested in the ID only to be functional. Not much pressure is required to knurl soft materials.
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My thought process was that the bushings would be oiled from the OD through a direct or wick oiler. Of course, both of us are guessing. Matt does need to make sure oil can somehow get into the bushings to replenish them.
 
Sorry, forgot that bit :) The bushing set up is 2 separate bushings at either end of the pulley with a reservoir between them and an oiling point by a set screw in the valley of one of the Vs of the step pulley. So technically it doesn't matter what I do to the OD of the bushing, but I'd like to keep the no. of manipulations of bushing and pulley to a minimum to reduce the chance of introducing errors. I'm pretty sure the non-concentricity before was caused by a previous owner making the bushing OD undersize and then gluing it in. you can see what's left of the glue (or loctite) and it's definitely not evenly distributed. I'm pretty sure I can do a better job than that :D
 
I don't know how much pressure Zamak will take before cracking but it isn't a lot. I dropped a Zamak nut on the floor and promptly broke it in two pieces so it can't be that tough. I'm thinking if I had to do this I would at least consider finding a bushing with the desired ID and turning the OD to what I need for a line-to-line fit at most or perhaps turn it a few tenths undersize and use LocTite.
 
yeah, that's a worry for sure and not much I can do about with the materials at hand. The max press fit for soft materials (presumably aluminium) is 50% more than what I'm shooting for, so hopefully that's enough of a margin do deal with zamac. Or there'll be a new project post of "how do I make my own 4 step geared pulley" :)
 
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