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Post by miniburrell on Mar 17, 2009 12:11:18 GMT
Hi all
can any one help me, i am building a 10V and currently making part of the piston,
i am cutting a 5BA thread and it keeps going crockedso when i screw the rod into the piston its not at 90 degree`s,
what am i doing wrong
MB
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Post by baggo on Mar 17, 2009 13:15:36 GMT
Hi Mb,
Is it the piston rod you are threading? If so, the way I do it is to hold the rod in the lathe chuck and then thread it with a die in a tailstock die holder. This ensures the thread will be true on the rod. Also, tap the piston with that held in the chuck and a tap in the tailstock chuck.
Make the piston oversize and then finish to size after it's threaded onto the piston rod. Hold the rod in an accurate chuck or better still, a collet. That way everything should run true.
John
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jasonb
Elder Statesman
Posts: 1,209
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Post by jasonb on Mar 17, 2009 16:05:33 GMT
Also put a chamfer on teh end of the piston rod, this will help the die start.
Screw the central screw of your die holder in to expand the die for teh first cut then adjust until you get a good fit in the piston and use cutting fluid if you don't have anything then a drop of oil will help.
Jason
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Post by petercolman on Mar 20, 2009 20:01:31 GMT
I would also make the rod with a shoulder for the piston to screw up to then counterbore the piston so the run out on the thread was not giving trouble. I this way even poor threads come up square when the piston bottoms out on the shoulder.
Peter
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Post by Shawki Shlemon on Mar 21, 2009 9:14:23 GMT
If piston is CI , I do exactly as baggo describes but if piston is gunmetal , i silver solder the SS rod to the piston which is roughly machined and finish it in the lathe using collet to hold it in central .
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