Bolt fit/interference fit/light drive fit

Jesse Jenks · Post by **Jesse Jenks** » Sat Feb 18, 2012 10:31 am

Thanks Ken,
So that's for a close tolerance fit where you might have to bang the bolt in
with a 14 ounce hammer. A light drive fit is defined in the Standard
Aircraft Handbook as a .0015 max clearance between bolt and hole, where the
bolt will move when a hammer handle is held against the head and pressed
with the weight of the body. This seems to contradict what I read earlier
that up to .006 is acceptable, but sounds more reasonable anyway.
So if most of my 1/4 bolts mic out at .247-.248, what size reamer should I
get to end up with a "light drive fit". I would think getting 2 more at .247
and .248 would be pretty good, along with the ones I already have at .2495,
or should I go slightly undersize, say .2465 and .2475? I found in the
archives a link to KBC tools, which has a nearly infinite range of sizes for
about $15.00 (US) each.
Jesse

Exactly. An interference fit means that the hole should be smaller than
the bolt and the bolt has to be pushed or lightly tapped in.
Ken

I am confused about the meaning of "interference fit". When reading about
close tolerance bolts and reamers designed for them, I saw where a .5 to
1.5 thou interference fit was specified. Does that mean the hole is
supposed to be that much smaller than the bolt, or the other way round?
Jesse

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Ken · Post by **Ken** » Sat Feb 18, 2012 10:31 am

Six thou is probably fine for something that has several bolts and is
not cyclically loaded or that is clamped tight. The strut only has one
bolt and the load cycles when you land so a snug fit is preferable. If
it takes a bit of thumb pressure to insert the bolt I'd be very happy
myself. I'd also be happy as long as there was no obvious loose play. I
would not particulary want to have to hammer the bolts in. That only
works once anyway and it is a safe bet your bolts will be removed a few
times. So if I were purchasing another reamer I'd likely try a .2475.
Just as bolts have tolerances, so do reamers. Affordable reamer are
probably something like +/- .0005 as a wild guess. Some folks like the
adjustable reamers but I'm not enthralled by them. Besides there are
lots of ways to make a hole a bit larger if you need to.

I'm hesitant to mention this but if you think you won't need your .2495
anymore, you could try making it smaller by rubbing a small grinding
stone along the edges. Angled to as to keep the edge sharp. And tested
on scrap a couple of times...

Ken

Jesse Jenks wrote:

Thanks Ken,
So that's for a close tolerance fit where you might have to bang the bolt in
with a 14 ounce hammer. A light drive fit is defined in the Standard
Aircraft Handbook as a .0015 max clearance between bolt and hole, where the
bolt will move when a hammer handle is held against the head and pressed
with the weight of the body. This seems to contradict what I read earlier
that up to .006 is acceptable, but sounds more reasonable anyway.
So if most of my 1/4 bolts mic out at .247-.248, what size reamer should I
get to end up with a "light drive fit". I would think getting 2 more at .247
and .248 would be pretty good, along with the ones I already have at .2495,
or should I go slightly undersize, say .2465 and .2475? I found in the
archives a link to KBC tools, which has a nearly infinite range of sizes for
about $15.00 (US) each.
Jesse

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Wayne G. O'Shea · Post by **Wayne G. O'Shea** » Sat Feb 18, 2012 10:32 am

Jesse...I've read thru most of these now on the bolt fit. I am assuming you
are talking the main spar strut attach fitting that uses 3 bolts?? as I know
you aren't doing the wing strut yet. Put all three bolts in and see if you
can detect any movement of the fittings. Coat the suckers (fittings and
bolts) with what ever product you are using for corrosion proofing between
the seams, tighten them down properly and carry on!

Cheers,
Wayne

----- Original Message -----
From: "Ken" <klehman@albedo.net>
To: <rebel-builders@dcsol.com>
Sent: Wednesday, May 18, 2005 2:39 PM
Subject: Re: Bolt fit/interference fit/light drive fit

Six thou is probably fine for something that has several bolts and is
not cyclically loaded or that is clamped tight. The strut only has one
bolt and the load cycles when you land so a snug fit is preferable. If
it takes a bit of thumb pressure to insert the bolt I'd be very happy
myself. I'd also be happy as long as there was no obvious loose play. I
would not particulary want to have to hammer the bolts in. That only
works once anyway and it is a safe bet your bolts will be removed a few
times. So if I were purchasing another reamer I'd likely try a .2475.
Just as bolts have tolerances, so do reamers. Affordable reamer are
probably something like +/- .0005 as a wild guess. Some folks like the
adjustable reamers but I'm not enthralled by them. Besides there are
lots of ways to make a hole a bit larger if you need to.

I'm hesitant to mention this but if you think you won't need your .2495
anymore, you could try making it smaller by rubbing a small grinding
stone along the edges. Angled to as to keep the edge sharp. And tested
on scrap a couple of times...

Ken

Jesse Jenks wrote:

Thanks Ken,
So that's for a close tolerance fit where you might have to bang the bolt

in

with a 14 ounce hammer. A light drive fit is defined in the Standard
Aircraft Handbook as a .0015 max clearance between bolt and hole, where

the

bolt will move when a hammer handle is held against the head and pressed
with the weight of the body. This seems to contradict what I read earlier
that up to .006 is acceptable, but sounds more reasonable anyway.
So if most of my 1/4 bolts mic out at .247-.248, what size reamer should

I

get to end up with a "light drive fit". I would think getting 2 more at

.247

and .248 would be pretty good, along with the ones I already have at

.2495,

or should I go slightly undersize, say .2465 and .2475? I found in the
archives a link to KBC tools, which has a nearly infinite range of sizes

for

about $15.00 (US) each.
Jesse

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Jesse Jenks · Post by **Jesse Jenks** » Sat Feb 18, 2012 10:32 am

Hi Wayne,
Actually 4 bolts, but yes it's the main spar strut attachment fittings. I'm
pretty sure there won't be any movement at the fitting. I got some AN-174
bolts and that helped in three locations, but one in the middle is still
pretty sloppy. I got a reply from Robin today saying it's OK to drill the
one hole (maybe it's OK to drill them all out, but I only asked for one)
out to 5/16. Not sure if I need to/want to. Like you say, with epoxy primer
in the hole it should be fine, and the other 3 fit well. Not tight, but no
play. I have some undersize reamers coming for future use.
Thanks for the reply.
Jesse
As a side note to the reply from Ken below, I did try sharpening a .2495
reamer down a couple thou since I got 6 of them on ebay. I was able to go
down to .247 and keep a sharp edge, but now it chatters like crazy, and
doesn't make a smooth hole. I guess they are pretty finicky little things.

From: "Wayne G. O'Shea" <oifa@irishfield.on.ca>
Reply-To: <rebel-builders@dcsol.com>
To: <rebel-builders@dcsol.com>
Subject: Re: Bolt fit/interference fit/light drive fit
Date: Tue, 24 May 2005 19:33:42 -0400

Jesse...I've read thru most of these now on the bolt fit. I am assuming you
are talking the main spar strut attach fitting that uses 3 bolts?? as I
know
you aren't doing the wing strut yet. Put all three bolts in and see if you
can detect any movement of the fittings. Coat the suckers (fittings and
bolts) with what ever product you are using for corrosion proofing between
the seams, tighten them down properly and carry on!

Cheers,
Wayne

----- Original Message -----
From: "Ken" <klehman@albedo.net>
To: <rebel-builders@dcsol.com>
Sent: Wednesday, May 18, 2005 2:39 PM
Subject: Re: Bolt fit/interference fit/light drive fit

Six thou is probably fine for something that has several bolts and is
not cyclically loaded or that is clamped tight. The strut only has one
bolt and the load cycles when you land so a snug fit is preferable. If
it takes a bit of thumb pressure to insert the bolt I'd be very happy
myself. I'd also be happy as long as there was no obvious loose play. I
would not particulary want to have to hammer the bolts in. That only
works once anyway and it is a safe bet your bolts will be removed a few
times. So if I were purchasing another reamer I'd likely try a .2475.
Just as bolts have tolerances, so do reamers. Affordable reamer are
probably something like +/- .0005 as a wild guess. Some folks like the
adjustable reamers but I'm not enthralled by them. Besides there are
lots of ways to make a hole a bit larger if you need to.

I'm hesitant to mention this but if you think you won't need your .2495
anymore, you could try making it smaller by rubbing a small grinding
stone along the edges. Angled to as to keep the edge sharp. And tested
on scrap a couple of times...

Ken

Jesse Jenks wrote:

Thanks Ken,
So that's for a close tolerance fit where you might have to bang the
bolt
in
with a 14 ounce hammer. A light drive fit is defined in the Standard
Aircraft Handbook as a .0015 max clearance between bolt and hole, where
the
bolt will move when a hammer handle is held against the head and
pressed
with the weight of the body. This seems to contradict what I read
earlier
that up to .006 is acceptable, but sounds more reasonable anyway.
So if most of my 1/4 bolts mic out at .247-.248, what size reamer
should
I
get to end up with a "light drive fit". I would think getting 2 more at
.247
and .248 would be pretty good, along with the ones I already have at
.2495,
or should I go slightly undersize, say .2465 and .2475? I found in the
archives a link to KBC tools, which has a nearly infinite range of
sizes
for
about $15.00 (US) each.
Jesse

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Wayne G. O'Shea · Post by **Wayne G. O'Shea** » Sat Feb 18, 2012 10:32 am

Hey, been awhile since I bolted the internals of a wing together and the
mind is still reeling in that Lake Trout! The 4th bolts just for pucker
factor anyhow LOL!

Wayne

----- Original Message -----
From: "Jesse Jenks" <jessejenks@hotmail.com>
To: <rebel-builders@dcsol.com>
Sent: Tuesday, May 24, 2005 10:39 PM
Subject: Re: Bolt fit/interference fit/light drive fit

Hi Wayne,
Actually 4 bolts, but yes it's the main spar strut attachment fittings.

I'm

pretty sure there won't be any movement at the fitting. I got some AN-174
bolts and that helped in three locations, but one in the middle is still
pretty sloppy. I got a reply from Robin today saying it's OK to drill the
one hole (maybe it's OK to drill them all out, but I only asked for one)
out to 5/16. Not sure if I need to/want to. Like you say, with epoxy

primer

in the hole it should be fine, and the other 3 fit well. Not tight, but no
play. I have some undersize reamers coming for future use.
Thanks for the reply.
Jesse
As a side note to the reply from Ken below, I did try sharpening a .2495
reamer down a couple thou since I got 6 of them on ebay. I was able to go
down to .247 and keep a sharp edge, but now it chatters like crazy, and
doesn't make a smooth hole. I guess they are pretty finicky little things.

From: "Wayne G. O'Shea" <oifa@irishfield.on.ca>
Reply-To: <rebel-builders@dcsol.com>
To: <rebel-builders@dcsol.com>
Subject: Re: Bolt fit/interference fit/light drive fit
Date: Tue, 24 May 2005 19:33:42 -0400

Jesse...I've read thru most of these now on the bolt fit. I am assuming

you

are talking the main spar strut attach fitting that uses 3 bolts?? as I
know
you aren't doing the wing strut yet. Put all three bolts in and see if

you

can detect any movement of the fittings. Coat the suckers (fittings and
bolts) with what ever product you are using for corrosion proofing

between

the seams, tighten them down properly and carry on!

Cheers,
Wayne

----- Original Message -----
From: "Ken" <klehman@albedo.net>
To: <rebel-builders@dcsol.com>
Sent: Wednesday, May 18, 2005 2:39 PM
Subject: Re: Bolt fit/interference fit/light drive fit

Six thou is probably fine for something that has several bolts and is
not cyclically loaded or that is clamped tight. The strut only has one
bolt and the load cycles when you land so a snug fit is preferable. If
it takes a bit of thumb pressure to insert the bolt I'd be very happy
myself. I'd also be happy as long as there was no obvious loose play.

I

would not particulary want to have to hammer the bolts in. That only
works once anyway and it is a safe bet your bolts will be removed a

few

times. So if I were purchasing another reamer I'd likely try a .2475.
Just as bolts have tolerances, so do reamers. Affordable reamer are
probably something like +/- .0005 as a wild guess. Some folks like the
adjustable reamers but I'm not enthralled by them. Besides there are
lots of ways to make a hole a bit larger if you need to.

I'm hesitant to mention this but if you think you won't need your

.2495

anymore, you could try making it smaller by rubbing a small grinding
stone along the edges. Angled to as to keep the edge sharp. And tested
on scrap a couple of times...

Ken

Jesse Jenks wrote:

bolt
in

where

the
pressed
earlier
should
I

at

.247
.2495,

the

sizes
for

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Jesse Jenks · Post by **Jesse Jenks** » Sat Feb 18, 2012 10:32 am

Roger that,
If I could only get THAT hole to pucker! Anyone know how to scare aluminum?
Jesse

Hey, been awhile since I bolted the internals of a wing together and the
mind is still reeling in that Lake Trout! The 4th bolts just for pucker
factor anyhow LOL!

Wayne

----- Original Message -----
From: "Jesse Jenks" <jessejenks@hotmail.com>
To: <rebel-builders@dcsol.com>
Sent: Tuesday, May 24, 2005 10:39 PM
Subject: Re: Bolt fit/interference fit/light drive fit

Hi Wayne,
Actually 4 bolts, but yes it's the main spar strut attachment fittings.
I'm
pretty sure there won't be any movement at the fitting. I got some
AN-174
bolts and that helped in three locations, but one in the middle is still
pretty sloppy. I got a reply from Robin today saying it's OK to drill
the
one hole (maybe it's OK to drill them all out, but I only asked for
one)
out to 5/16. Not sure if I need to/want to. Like you say, with epoxy
primer
in the hole it should be fine, and the other 3 fit well. Not tight, but
no
play. I have some undersize reamers coming for future use.
Thanks for the reply.
Jesse
As a side note to the reply from Ken below, I did try sharpening a .2495
reamer down a couple thou since I got 6 of them on ebay. I was able to
go
down to .247 and keep a sharp edge, but now it chatters like crazy, and
doesn't make a smooth hole. I guess they are pretty finicky little
things.

From: "Wayne G. O'Shea" <oifa@irishfield.on.ca>
Reply-To: <rebel-builders@dcsol.com>
To: <rebel-builders@dcsol.com>
Subject: Re: Bolt fit/interference fit/light drive fit
Date: Tue, 24 May 2005 19:33:42 -0400

Jesse...I've read thru most of these now on the bolt fit. I am assuming
you
are talking the main spar strut attach fitting that uses 3 bolts?? as I
know
you aren't doing the wing strut yet. Put all three bolts in and see if
you
can detect any movement of the fittings. Coat the suckers (fittings and
bolts) with what ever product you are using for corrosion proofing
between
the seams, tighten them down properly and carry on!

Cheers,
Wayne

----- Original Message -----
From: "Ken" <klehman@albedo.net>
To: <rebel-builders@dcsol.com>
Sent: Wednesday, May 18, 2005 2:39 PM
Subject: Re: Bolt fit/interference fit/light drive fit

is
one
If
happy
play.
I
few
.2475.
the
.2495
tested
the
bolt
in
Standard
where
the pressed earlier should
I
more
at
.247
at
.2495,
the
sizes
for

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