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anticgov

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I have 4 pistons that need the wrist pins honed out to 19mm. They are currently at 17mm. All the local machine shops I've contacted either can't do it or are under contract and can't accept any other work. If this is something you can do please contact me with a price. Thank you
 
19 mm works out to 0.748 so you would probably have to bore or ream them then lap to size- costly job for just 4 pieces
-Mark
 
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What is your budget for this? Wrist pins are usually fitted to very close tolerances in the ten-thousandths of an inch range so
it's a job that would take some time to do well
 
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@anticgov do you need new circlip grooves as well?

It's interesting just to think about how to fixture/secure a piston—perhaps with a domed crown and curved skirt—for accurate boring on a mill table or in a lathe chuck. Anyone want to weigh in on how they'd clamp it without distorting the piston or marring its surfaces? 6 jaw chuck on a rotary table? Custom clamping nest?
 
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Good questions Allen, I hadn't even gotten that far yet
 
Rest the piston on a Tee slot with soda can shims, and clamp to the interior? (I'm not an engine guy :) )
 
Sorry to be so vague, it's really a simple process if you have the correct equipment. There is a YouTube video of a guy explaining how it's done. Fiatnutz is the creator and the title is piston pin bore enlargement 17mm to 18mm. As for price I'm finding that this job costs $15-$25 a piston. Allen looks like there is two options, c clips or floating and I was considering floating to be the better route. Thank you for your responses. It's been a nightmare trying to get my samurai back on the road after a friend dropped a washer down the intake completely destroying cylinder number 4 pistons.
 
Thanks for the video reference!

Between the "alignment pin that we had to make" and "this is a long and drawn-out process," $25/piston sounds optimistic. Hope you can find an automotive specialty machine shop familiar with the process.

I wonder what "hone" refers to here... enlarging a hole by 2mm sounds like it'd take forever with a hone alone.
 
It is easy if you have the equipment. But the equipment is not normally found in a normal commercial machine shop, but rather in a high performance engine rebuild shop. Back in the day (about 45 years ago) when I ran an engine build shop, we used to do this kind of stuff all the time. We had the equipment to do it.

One of the keys to hanging onto a piston is a piston vice.
1664993548283.png


And an old one
1664993630154.png


Then you need a Sunnen rod hone
1664993838088.png
 
Jim is dead on correct. Shops specializing in motorcycle engine rebuilding should have the tools he's referencing.
Curious; where did you get the pistons? If U.S. made, the manufacturer might do the job. Or possibly exchange them for correct ones.
 
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