Robert
There is a slight, I repeat slight difference between the 2 thread
standards. It has to do with the angle of the thread and the depth of the
thread. You need a machinist handbook to read all the specs and see the
differences. I guarantee you that if you run a SAE tap through a UNF nut
you will get a pile of metal shavings.
Here is an easy way to see the difference; grab any UNF bolt and
find 2 SAE equivalent bolts, hold the SAE bolts together at the threads then
hold them up against a light and look at the thread mesh. Now do the same
the same with the UNF and SAE threads together, you will see more light
through the threads. That is the minor difference in the 2 thread
standards.
Can you use a SAE bolt in a UNF nut - YES. I'm just pointing out
that if you use a SAE tap to chase a UNF nut the UNF bolt will feel loose.
I don't believe there is any kind of safety issue here or any torque loading
problem. I simply prefer to chase any UNF thread with a UNF bolt or a UNF
tap and not a SAE tap.
Ron Fraser
-----Original Message-----
From: owner-tigers@autox.team.net [mailto:owner-tigers@autox.team.net] On
Behalf Of Robert Dobrowski
Sent: Tuesday, June 14, 2005 10:18 PM
To: rfraser@bluefrog.biz
Cc: lgooch@satx.rr.com; tigers@autox.team.net
Subject: Re: Front crossmember
I don't understand your statement that SAE threads are different from UNF.
Reading through my SAE handbook it specifically calls out the use of UNF
threads on SAE fasteners.
On Tue, 14 Jun 2005 00:28:28 -0400 " Ron Fraser" <rfraser@bluefrog.biz>
writes:
> There is a slight difference between UNF threads and SAE fine
threads
> and your 1/2" - 20 tap has now change the threads to SAE
> fine. The
> UNF bolt will now feel loose in those threads. Since you changed
> to an
> SAE bolt, there is no problem as long as you stay with the SAE bolt.
>
> I do not have a set of UNF tap and die so I use UNF bolts as
> taps.
> I just use a Dremel tool to cut flutes down the length of the bolt
> threads
> and then run that bolt through to clean the threads. You really
> should use
> UNF bolts in the cleaned threads, but I have also used the UNF bolt
> tap to
> clean the threads and then used SAE bolts.
>
> Ron Fraser
>
>
>
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