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Re: tap-n-die sets

To: "Palmer, Lew (UCI)" <>
Subject: Re: tap-n-die sets
From: "W. Ray Gibbons" <>
Date: Fri, 2 Jun 1995 18:50:40 -0400 (EDT)
On Fri, 2 Jun 1995, Palmer, Lew (UCI) wrote (to me, privately):

> You're right. Most LBCs after the mid-50's used UNF threads. That was not 
> this issue I was trying to point out. My issue was with someone saying that 
> a 10-32 tap was appropriate for any LBC. To my knowledge, no LBC ever used a 
> 10-32 thread. This size was 2BA on all British cars, regardless of age. UNF 

Well, I was the turkey who said it.  And it appears that you are right, I
am wrong, wrong, wrong.  I was relying on Lindsay Porter's book on
Sprite/Midget restoration.  I can't find it right now, but I have just
looked up the section on screw threads in his book on MGB restoration.  He
talks out of both sides of his mouth.  On the one hand, he says:  "A
popular screw size in the MGB is 2BA (British Association), but that size
is fully compatible with the American No. 10-32 screw."  That is what I
remember his saying in the Sprite/Midget book, and I took that to mean 
that the two were identical.  But in the MGB book, he goes on to compare 
them, and I see that: 

2BA: diameter = .185, TPI = 31.358
10-32  d = .190, TPI = 32

So they are different.  The fact is, however, that I used new 10-32 screws
extensively in the bugeye.  The eye cannot detect the difference so they 
can be used freely when one is replacing both the screw and its nut.  It 
is more problematic if one is replacing just one or the other.  

I am trying to think whether there were any cases where I had captive
nuts, so I would be screwing a 10-32 screw into a 2BA nut.  There must
have been some; the only ones that come to mind are for the door check
straps, and the nuts that hold the fuse block to the fender, and probably
the nuts that hold the tail light base to the body.  I don't remember any
problems whatever.  In practice, they *did* seem fully compatible.  Over
the length of the usual nut, I suspect they should be extremely close. 

Most of the time, of course, I cleaned paint out of the threads with a
10-32 tap, and after that, there would not be any interference.  Anyhow,
you were correct and I should not have disagreed with you unless I was
sure of my facts. 

So, Will Zehring, delete my recommendation for 10-32 taps, or if you use
them, know that it isn't really right.  For 1/4 on up, the UNF
and UNC recommendations are still OK. 

   Ray Gibbons  Dept. of Molecular Physiology & Biophysics
                Univ. of Vermont College of Medicine, Burlington, VT
        (802) 656-8910

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