Subject: drills for reamers?

From: [email-masked]
Date: 6 Jul 1996 20:56:08 GMT

Hi!

Are there any rules for figuring which is the largest drill one should use before reaming a hole?

Say, for example, that I want a 1/2" reamed hole.
I should buy a 1/2" reamer, but which is the largest drill I should use before starting the reamer?

Thanks in advance.

eduardo haddad filho
[email-masked]

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From: FabNet <[email-masked]>
Date: Sat, 06 Jul 1996 20:33:53 -0500

> I should buy a 1/2" reamer, but which is the largest drill I should use before starting the reamer?

Now it's been 12 years since I studied this but best I can remember.
Typically you want to take off very little material with you reamer.
About .001-.006
You want to put as little strain on your reamer as possible, creating less
twist in your reamer, giving you a more accurate hole.
If I were drilling a 1/2" hole. I would:
Drill a 1/4" pilot hole
Then a 7/16" pilot
Then .496 or closest you have
Then ream that hole to .500
This would make a good accurate straight hole.

Hope this helped
Andy

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From: [email-masked] (Russ Kepler)
Date: Sun, 7 Jul 1996 01:24:52 GMT

>I should buy a 1/2" reamer, but which is the largest drill I should use before starting the reamer?

I try to get within .010" for a larger reamer, and .005 for something
in the .125" range.  You really don't want to take too much off with 
a reamer.
-- 
Russ Kepler, at home	[email-masked]

                    Please Don't Feed the Engineers

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From: [email-masked] (Errol Groff )
Date: Sat, 6 Jul 1996 22:29:51

>[email-masked]

A good rule of thumb is: under 1/2" drill 1/64" smaller than your finish size 
and over 1/2" drill 1/32" under finish size.

Hope this helps.  

Errol Groff