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Re: Machine shops and costs of machining...Please Help

To: "Randall Young" <ryoung@navcomtech.com>
Subject: Re: Machine shops and costs of machining...Please Help
From: mporter@zianet.com
Date: Fri, 11 Jul 2003 21:01:15 -0600
Cc: triumphs@autox.team.net
References: <NCBBKDNEEKEOHAOIIOIIKEHKFLAA.ryoung@navcomtech.com>
Randall Young writes: 

> That's absurd !

I agree. Prices may be higher in CA, but a 7-journal crank shouldn't cost 
more than about $80-90 to grind to the next undersize. 

Here's the other silliness--sending it off to have the scroll ground off. 
That can be done at the same time as grinding the journals to size. Might 
take one additional set-up to get the correct radius on the sides of the 
crank grinding wheel, but I doubt even that would be required. 

As for more grinding required after nitriding (more likely Tufftriding, 
these days), the journals will grow, and they will be somewhat discolored. 
Tufftriding may cause a journal to grow by about 0.001", I think, so the 
simplest procedure is to grind slightly undersize, maybe 0.0005" (based on 
the recommendations of the nitrider for that journal size), nitride, then 
polish the crank to the standard dimension. That still leaves a few 
thousandths of harder material, and cleans up the discoloration and the few 
iron nitride nodules that are formed on the surface. 

That said, it is possible that the $220 crank grinding fee included the cost 
of nitriding and polishing afterwards. But the only way to know for sure 
would be to have the surface hardness of the crank checked. A shop doing 
nitriding could likely do that. 

Cheers.

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