dimpling

"Bruce E Butts" wrote in message
...

Mike,
Veeduber recommends that one drill with a #40, deburr and then dimple
with the 1/8" dimple dies. I have done some like that and some using
the #30 drill first. Sometimes I have to 'open up' the hole a bit with
a reamer when trying to put in the rivet when I use the #40 bit first.
Veeduber's advise was in reference to using blind rivets iirc.

The springback dimple dies are meant for dimpling fuel tank skins so
that smearing sealant will not make the rivet stand proud of the dimple
so I think they may be a few thousandths oversize.

Hope this helps and remember all advice is worth what you paid for it!
Bruce

Be careful using a 1/8" dimple die in a #40 hole. The aluminum can develop
radial cracks around the hole as the dimple die is forced into the smaller
hole. Check on scrap, first, obviously, but I suspect it is a function of
thickness as well as material (e.g., 6061...).

Michael Pilla

Mike, Don't drill #40 then dimple with 1/8" die. If you look at the
finished dimple under high power magnification (ie; jewelers loupe), you
will find the metal has cracked around the edges of the hole due to
distortion. Not good. Definitely drill #30 for your 1/8" dimple. Also,
dimpling the hole definitely makes it bigger. Try putting the undrilled end
of a number drill in the hole before and after dimpling. You will find the
hole grows by a drill size or two. The Cleveland tank dies I used stretched
the hole about .0045 larger and I had trouble making 3/32" rivets hold
properly. Look at the geometry of the die on a cross section and picture
what the hole will do if you push the cone deeper into the hole. For my two
cents, I'll stick with standard or springback dimple dies from now on. As to
your problem, my guess is either your drill bit could be dulled or you're
not staying straight with the hole when drilling. Also, be careful how much
deburring you do on a hole after drilling. Too many turns and the hole gets
bigger. YMMV. Good luck and keep driving those rivets. Bill Korff

"Bruce E Butts" wrote in message
...

Mike,
Veeduber recommends that one drill with a #40, deburr and then dimple with
the 1/8" dimple dies. I have done some like that and some using the #30
drill first. Sometimes I have to 'open up' the hole a bit with a reamer
when trying to put in the rivet when I use the #40 bit first. Veeduber's
advise was in reference to using blind rivets iirc.

The springback dimple dies are meant for dimpling fuel tank skins so that
smearing sealant will not make the rivet stand proud of the dimple so I
think they may be a few thousandths oversize.

Hope this helps and remember all advice is worth what you paid for it!
Bruce

The objective is to end up with a hole which after dimpling is #30,
i.e. 0.1285. Others have noted that dimpling enlarges the hole. So,
MY strategy is what you alluded to earlier - drill slightly undersize.
Big enough to admit the cleco, but smaller than you want the hole to
end up after dimpling.

My procedure for flush riveted skins is to drill #40 and cleco with
3/32", take everything apart, deburr, put it back together, drill (or
ream - its a little marginal, but you can ream to #32 from a #40 pilot
hole, and it leaves less of a burr - notice I'm NOT deburring a second
time) with #32, take it apart, dimple, cleco with 1/8, rivet. I'm an
inexperienced builder, so this anal retentive procedure makes up for my
lack of skills and confidence.

I also have a punch that simultaneously punches and dimples. You can
get them from Aircraft Spruce and others, but be aware that the
American made punch costs more than a whole ChinCom Roper-Whitney
knockoff punch set. And they are not actually that useful - you can't
use them for matched hole tooling for instance.

In article .com,
"flybynightkarmarepair" wrote:

The objective is to end up with a hole which after dimpling is #30,
i.e. 0.1285. Others have noted that dimpling enlarges the hole. So,
MY strategy is what you alluded to earlier - drill slightly undersize.
Big enough to admit the cleco, but smaller than you want the hole to
end up after dimpling.

My procedure for flush riveted skins is to drill #40 and cleco with
3/32", take everything apart, deburr, put it back together, drill (or
ream - its a little marginal, but you can ream to #32 from a #40 pilot
hole, and it leaves less of a burr - notice I'm NOT deburring a second
time) with #32, take it apart, dimple, cleco with 1/8, rivet. I'm an
inexperienced builder, so this anal retentive procedure makes up for my
lack of skills and confidence.

I also have a punch that simultaneously punches and dimples. You can
get them from Aircraft Spruce and others, but be aware that the
American made punch costs more than a whole ChinCom Roper-Whitney
knockoff punch set. And they are not actually that useful - you can't
use them for matched hole tooling for instance.

I would suggest looking at the hole with a 10X magnifier and look for
small cracks. The best dimpled holes are those that are drilled,
deburred, then dimpled with a good set of dies and somethhing to hold
the dies. The combination punch/dimpler leaves a fair number of stress
raisers in the hole and can be susceptible to fatigue.

--
Remve "_" from email to reply to me personally.

Whatcha need to do is take a little scrap of aluminum with the correct
size hole in it. When you put the cleco through your part, you put the
scap on the end of the cleco and that will "clamp" the parts to your cleco.

John

John T wrote:

Whatcha need to do is take a little scrap of aluminum with the correct
size hole in it. When you put the cleco through your part, you put the
scap on the end of the cleco and that will "clamp" the parts to your cleco.

John


Doesn't help if he's closing a part or has a bunch of holes that need
clecos. If he really needs to do as you suggest washers are cheap and
smaller than you the scrap you suggest. I can't imagine a situation
where one would need to use a back up if one is using proper proceedure
and good tools.

Dan, U.S. Air Force, retired

Using the scrap backup is an accepted practice for holes that have been
dimpled, but are too big to hold the correct cleco due to the deforming
of the hole from dimpled. If its something that needs a blind rivet,
then of course, this won't work.

John

Unfortunately the areas with the flush rivets (leading edges of flaps and
ailerons) have no access to insert or remove the scrap or washers after
riveting.

Mike


"John T" wrote in message
...
Whatcha need to do is take a little scrap of aluminum with the correct
size hole in it. When you put the cleco through your part, you put the
scap on the end of the cleco and that will "clamp" the parts to your
cleco.

John

In article t,
"Mike Rapoport" wrote:

When I dimple holes in thin sheet they get larger to the point where the
clecos won't hold. Should I drill holes that are to be dimpled for 1/8
rivets a little smaller (like #31 or #32)? What are others doing?

Mike
Murphy Moose.

Assuming you aren't overdimpling, which isn't a given, I'd check the
pre-dimpled hole size. I mean really check it, with a comparator if
possible, or a set of gauge pins at least. You're never going to get a
round hole with a drill bit, and it's common to get them oversized, as
well.

If dimpling adds to the hole diameter, you obviously don't want to start
with a hole that's already too big.

A drill chuck that runs out, a bent drill, or holding the drill at some
angle other than perpendicular to the workpiece will make an oversize
hole.

The closest approximation to a round, correctly sized hole, I believe,
is to punch it and then ream it. For newer Van's customers, the punching
is done. Throw out those silly drill bits and get a couple of reamers.