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

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

Kyle Boatright wrote:

A 1/8" dimple die won't fit in a #40 hole, which is roughly 3/32.

--------------------------------------------

Dear Kyle (and the Group),

I believe my cited comment had to do with using poppers. The 100
degree dimpling sets use a steel mandrel -- typically, a finishing nail
with the point clipped off -- that you replace periodically as the work
progresses.

When using thin/soft metal, using the popper-type dimpling dies tends
to enlarge the hole. Come back to set (pull) the rivets and they're
liable to pull right through the hole, leading to the Conventional
Wisdom that countersunk-head poppers don't work. They do -- at least
for aluminum poppers -- but only if the hole is the proper size.

Start with a pilot hole that is smaller than the intended rivet size --
and select a pulling mandrel to fit. Anything that fits will work. (I
think I used 4d finishing nails.) Just make sure your puller can grip
the shank and that the head of the nail is large enough to not pull
through the die. A pneumatic puller will give you more uniform
results. You will need to ream/drill the hole to size prior to setting
the rivet but the result is a tight, symmetrical dimple.

If you have a lathe, dimpling dies for poppers are easy to make.
(Hint: For the male die, grind the angle into your tool bit. For the
female, simply grind a drill bit to 100 degrees. They may be used
as-made but will last longer if case-hardened.) 100 degree dimple die
sets for poppers are also available from AirParts, ATS and so on.

-R.S.Hoover

Thanks. Hopefully there is more dimpling to do where I can try starting
with a smaller hole.

Mike


"Drew Dalgleish" wrote in message
...
Hi Mike
It may be an issue with the 6061 skins cuz I found the same problem
when I was building my rebel. I used the cheap dimpler that has a nail
through the centre or the same dies that I welded to a pair of vice
grips. Drilling 3/32" then dimpling then opening up the holes to #30
worked for me.

I am using cleco brand and, yes, I am using the copper ones. The dimple
dies are the "springback" ones from US Tool. The skins are 6061 if that
makes a difference.

Mike
MU-2


"Kyle Boatright" wrote in message
...

"Mike Rapoport" wrote in message
k.net...
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.

Never had that problem and I did a bunch of drilling and dimpling on the
RV-6. Are you drilling #30 to start with and using quality dimple dies?
I
hate to ask, but are you using the copper colored clecos, or have you
accidentally dipped into the silver ones?

Another option is that your cleco's are worn out. Any chance of that?

KB

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.

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.

--
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