The Murphy Builders Site

Posted: **Fri Feb 17, 2012 5:18 pm**

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Date: Fri, 26 Mar 1999 15:35:00 -0700 (MST)
From: Neil F Humphrey <neil@uwyo.edu>
Subject: another question on epoxy etc.
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By the time you have drilled through several layers of material, and used
the resulting holes for drill guides for other holes, I sometimes find
that the resulting bolt holes are a couple of thousandths oversize. This
isn't a problem for rivets, but there is sometimes a barely perceptible
slop on the inserted bolts. Anybody else worried about this enought to do
something about it? Is the epoxy chromate strong enough as a gap filler
to fill a couple of thousandths of an inch... anybody out there with
thoughts? since I am sure others have worried about this.

Neil Humphrey
#371

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Posted: **Fri Feb 17, 2012 5:18 pm**

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To: <murphy-rebel@dcsol.com> (Murphy Rebel)
From: Bob Patterson <bob.patterson@canrem.com>
Subject: Re: another question on epoxy etc.
Message-Id: <E10QwJK-0003hl-00@mail4.toronto.istar.net>
Date: Sat, 27 Mar 1999 11:51:51 -0500

Several thou. of slop sounds serious to me - it might be better to ream
to allow the next size larger bolt !

Any slop can cause greatly increased wear rates, and create major
safety problems quickly. I have seen flutter problems on gliders caused
by barely perceptible movement on control surface attachments !

Useing Epoxy on bolts is not a good idea, in any case, as the adhesive
effect will make it difficult or impossible to remove the bolt -
which you will want to do for service !!

Best to talk to Kerry, at Murphy, about these sorts of problems -
a little time on questions now could save a lot of grief later !!

.....bobp

-----------------------------orig.----------------------------------
At 03:35 PM 3/26/99 -0700, you wrote:

By the time you have drilled through several layers of material, and used
the resulting holes for drill guides for other holes, I sometimes find
that the resulting bolt holes are a couple of thousandths oversize. This
isn't a problem for rivets, but there is sometimes a barely perceptible
slop on the inserted bolts. Anybody else worried about this enought to do
something about it? Is the epoxy chromate strong enough as a gap filler
to fill a couple of thousandths of an inch... anybody out there with
thoughts? since I am sure others have worried about this.

Neil Humphrey
#371

Posted: **Fri Feb 17, 2012 5:18 pm**

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Date: Sun, 28 Mar 1999 13:25:32 -0700 (MST)
From: Neil F Humphrey <neil@uwyo.edu>
Subject: Re: another question on epoxy etc.
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Thanks for the comments, but I guess I didn't make myself clear. My
handbook of standard aircraft practise says that for a 1/4 inch bolt, the
hole can be up to 6 thousands oversize! In addition if you micrometer the
AN bolts you will find they have considerable slop, and average about 4
thousands undersize. As a result, a hole that is to be drilled to
1/4inch, micrometers at (say) .251 thousands... and the bolt that goes in
it is 4 thou under.. hence 5 thou of slop even in a close tolerance 1/4
inch hole. And my query was whether others had worried about this..
But I expect I am just being overly anal,... since the only solution is to
go to close tolerance bolts and reamed holes.
Oh, well, I will just go back to deburring.

Neil Humphrey

On Sat, 27 Mar 1999, Bob Patterson wrote:

Several thou. of slop sounds serious to me - it might be better to ream
to allow the next size larger bolt !

Any slop can cause greatly increased wear rates, and create major
safety problems quickly. I have seen flutter problems on gliders caused
by barely perceptible movement on control surface attachments !

Useing Epoxy on bolts is not a good idea, in any case, as the adhesive
effect will make it difficult or impossible to remove the bolt -
which you will want to do for service !!

Best to talk to Kerry, at Murphy, about these sorts of problems -
a little time on questions now could save a lot of grief later !!

.....bobp

-----------------------------orig.----------------------------------
At 03:35 PM 3/26/99 -0700, you wrote:
By the time you have drilled through several layers of material, and used
the resulting holes for drill guides for other holes, I sometimes find
that the resulting bolt holes are a couple of thousandths oversize. This
isn't a problem for rivets, but there is sometimes a barely perceptible
slop on the inserted bolts. Anybody else worried about this enought to

do

something about it? Is the epoxy chromate strong enough as a gap filler
to fill a couple of thousandths of an inch... anybody out there with
thoughts? since I am sure others have worried about this.

Neil Humphrey
#371

Posted: **Fri Feb 17, 2012 5:18 pm**

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To: <murphy-rebel@dcsol.com> (Murphy Rebel)
From: Bob Patterson <bob.patterson@canrem.com>
Subject: Re: another question on epoxy etc.
Message-Id: <E10RNQG-0006zq-00@mail4.toronto.istar.net>
Date: Sun, 28 Mar 1999 16:48:49 -0500

Sorry Neil !!

I DID take you to mean that you were several thou BEYOND the normal
tolerances ....

I do know of builders who have epoxy chromated (lightly) bolts
before inserting. They let it harden BEFORE use. The idea was to give
added protection, in case cad plating were scraped during installation.
Shouldn't present problems - but I think you ARE probably worrying a
bit too much. Still, much better that way than not worrying enough !!
;-) :-)

....bobp

-----------------------------orig.---------------------------------
At 01:25 PM 3/28/99 -0700, you wrote:

Thanks for the comments, but I guess I didn't make myself clear. My
handbook of standard aircraft practise says that for a 1/4 inch bolt, the
hole can be up to 6 thousands oversize! In addition if you micrometer the
AN bolts you will find they have considerable slop, and average about 4
thousands undersize. As a result, a hole that is to be drilled to
1/4inch, micrometers at (say) .251 thousands... and the bolt that goes in
it is 4 thou under.. hence 5 thou of slop even in a close tolerance 1/4
inch hole. And my query was whether others had worried about this..
But I expect I am just being overly anal,... since the only solution is to
go to close tolerance bolts and reamed holes.
Oh, well, I will just go back to deburring.

Neil Humphrey

On Sat, 27 Mar 1999, Bob Patterson wrote:

Several thou. of slop sounds serious to me - it might be better to ream
to allow the next size larger bolt !

Any slop can cause greatly increased wear rates, and create major
safety problems quickly. I have seen flutter problems on gliders caused
by barely perceptible movement on control surface attachments !

Useing Epoxy on bolts is not a good idea, in any case, as the

adhesive

effect will make it difficult or impossible to remove the bolt -
which you will want to do for service !!

Best to talk to Kerry, at Murphy, about these sorts of problems -
a little time on questions now could save a lot of grief later !!

.....bobp

-----------------------------orig.----------------------------------
At 03:35 PM 3/26/99 -0700, you wrote:
By the time you have drilled through several layers of material, and

used

the resulting holes for drill guides for other holes, I sometimes find
that the resulting bolt holes are a couple of thousandths oversize.

This

isn't a problem for rivets, but there is sometimes a barely perceptible
slop on the inserted bolts. Anybody else worried about this enought to

do

something about it? Is the epoxy chromate strong enough as a gap filler
to fill a couple of thousandths of an inch... anybody out there with
thoughts? since I am sure others have worried about this.

Neil Humphrey
#371