# Press Fit



## Maris Dislers (Nov 23, 2018)

Hi Gang,

I built a small diesel engine that has a 3mm pressed-in crankpin. Didn't get the fit right and it came loose. No big deal - just make another hole in crankweb and try again. How much smaller should that hole be than the actual pin size? For folk who think in inches, think about fit for a .125 inch pin. Pin is a cut down needle roller, going into steel cranbkweb.


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## vidio1 (Nov 24, 2018)

duplicate


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## vidio1 (Nov 24, 2018)

https://www.engineersedge.com/general_tolerances.htm


There are countless resources on the web........


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## goldstar31 (Nov 24, 2018)

I'd consider silver soldering if there is sufficient clearance for the solder to 'wick'. File a minute channel for it to happen.

Norm


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## tornitore45 (Nov 25, 2018)

When silver brazing requires to keep parts precisely located I reduce the diameter about 0.006" (or whatever your alloy suggest) for let's say 3/4 of the length. It is better to have 3/4 of the length fully vetted than a spotty weak braze.


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## Richard Carlstedt (Nov 25, 2018)

For a 3mm pin, you should look for .005 to .01 mm press normally
You don't say what the material is ? The above is for steel.
You should consider heating the crank to 150 -200 C to make the fit easier and stronger.
(Shrink fits are 2 x stronger)  
Your hole growth will be about .002mm per 100 C if i did it right
Rich


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