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Dimple Dies

Jarrett

Member
Hello all! Just finished my vertical stabilizer last week and I am now moving forward with both the rudder and horizontal stabilizer. Today I was looking over my vertical stabilizer and I noticed that there was a very small gap between the manufactured heads and the dimpled portion of the skin denoted by the slight shadow under the heads.
https://photos.app.goo.gl/kJoRtW5ZXgd4W93r6
https://photos.app.goo.gl/SY3f6gkt1NVSyvE57
My first thought was that the manufactured head was not perfectly flush with the skin (maybe a riveting mistake), so I put the flat end of a ruler over top of the rivets and saw that the rivets were indeed flush. I then took a look at my practice project and realized that these rivets did not have this same shadow under the rivets. This is when I realized that on the practice project I used Brown dimple dies and on my V-Stab I used Cleaveland dies. I then went ahead and did a controlled test. I took a piece of scrap and dimpled two #40 holes using both dies.
https://photos.app.goo.gl/o1TpuWdVoYzg93pz7
Notice how with the die on the left there is the slight gap, and on the right there is none, which is what I had suspected. I have had a great experience with both companies, so I'm not trying to start any wars :) Is this gap normal for those that have used the Cleaveland Dies? Once the plane is painted these gaps won't be visible so it's not the end of the world, but as I am ready to dimple the rudder skins I want to know if I should change back to the other dies, or be worried at all? Thanks!
 
I've used both...

I started my build with dimple dies from Brown, so most of my HS & VS were done with those. I bought some Cleaveland dies also, and I can't honestly say that I've noticed much of a difference through the rest of my build to date.

Generally I prefer the Cleaveland dies, but at the end of the day if the parts nest & the rivet goes in OK I don't get too worried. If the rivet heads aren't totally flush for me I usually put it down to my riveting technique (perhaps not quite enough pressure on the gun) rather than the dimple. I assume that you had whatever tool you used to dimple set properly, or if you used a C-frame that you gave it a solid whack.

Did you perhaps use a sub-structure die on the skin? That might explain the slight gap.
 
Hey Geoff, for the skin I just used the standard 3/32 dimple dies. I've been doing a little bit of digging around and I've found that some builders have similar results.
http://wolfcry.net/rv-14/blog#gallery-14
Initially I thought it was my riveting technique, but even before riveting when the rivet is placed in the hole there is a tiny gap. All of the parts fit together nicely and the rivets are flush, so I think I'll just have to live with it (won't notice it after paint). I'm using a DRDT-2 for my riveting (which I love), and have been very careful not to under-dimple. Thanks!
 
Something is not right. Not sure what. Almost looks like -4 dies and -3 rivets? Wish you were closer so I could be more help.
 
For you, with your method, the Brown dies look much better. I would recommend using them. As your project gets further along try the test again. It would be interesting to see if the results are the same.
Nice work, you have a good eye for detail!
 
Might you be using a substrate die?

Cleaveland sells a substrate did which I use all of the time. It is to be used to dimple substrate structures like ribs or nested skin overlaps. Looks like you could be using that by mistake. It will leave a slightly larger dimple to allow cleaner nesting. Just a thought. There is a part number etched on the die. Check it out.
 
Dies

Check the side of the dies for size. Should be engraved 426-3
It's possible you have Cleveland Tank or Substructure dies. They wll be stamped "426-3T" or "426-3SS". Could also be dies mixed up.
 
Hello everyone, thanks for the input! For the skins I used the standard CAT 426-3 and I used the CAT 426-3s (reduced diameter) only for the ribs/spars as per instructions. I'm dimpling the rudder skins today, so I think I'm going to go ahead and use the Brown dies for now. I'll maybe do one or two holes with the Cleaveland dies to get another side-by-side comparison. Thanks!
 
Hello everyone, thanks for the input! For the skins I used the standard CAT 426-3 and I used the CAT 426-3s (reduced diameter) only for the ribs/spars as per instructions. I'm dimpling the rudder skins today, so I think I'm going to go ahead and use the Brown dies for now. I'll maybe do one or two holes with the Cleaveland dies to get another side-by-side comparison. Thanks!

What type of device are you using to form the dimples. When I see dimples like yours it?s usually the device that?s the problem rather than the dimple dies.
 
Early in my building I noted the same gap and cheated by spinning a deburring tip in there lightly a couple of times and the rivets were perfectly flush. I used Avery dies.

The only time you will notice is before paint or during polishing the skin. The little gaps will wick in black goo in the polishing process and it must come out or leave streaks in when buffed.
 
Check that the dies are not the Tank or Substructure dyes that are made by Cleaveland. This are oversized and may create the problem that you are seing
 
Rudder Dimpling Complete

So I went ahead and dimpled my rudder skins with the Brown dies and I am very happy with how they turned out! When rivets are placed in everything fits together nice and snug. I did get the chance to do one dimple with the Cleaveland dies and this is how it turned out.
https://photos.app.goo.gl/TSEC7d3zgoA3bjKdA
On the left is the Cleaveland die and on the right is the Brown die. For these dimples I used the DRDT-2, and the results are same as when I dimple with my TACTO hand squeezer. Moving forward I will be using the brown dies on the skins and Cleaveland dies on ribs (substructure). I'm not exactly sure why the Cleaveland dies are producing this gap... Some builders have experienced these results in the past, so maybe it's just how they're manufactured? In the end, once it's all painted I won't notice these gaps on the vertical stabilizer, so I think I'll have to relax (I've started dreaming about the build :)) Thanks everyone!
 
It almost looks like you have a tank die vs the standard die. Give a shout to Cleaveland tool and they may be able to help you out.
Regardless, I'm sure the brown dimples will work just fine for you.
 
I see you linked my question so my .02 is this. The cleveland dies have a slightly different angle/shape to them which creates this gap/appearance which could be considered a con.

The pro side to this is when comparing two large sheets that are side by side, one using cleveland dies and another brand the skin deformation around the holes is much lower using the cleveland dies.

I used the DRDT-2 during my build but also tried the C-Frame and had almost the same results with the cleveland dies.

My plan was always to polish the plane so I was shooting for smooth skins without deformation around the rivets. If your planning to paint that may not be an issue for you.

I'd suggest on the thicker skins, setup the DRDT with a fairly tight preload and give each hole a double pull on the handle.

Good luck on the build, I've got 65hrs on mine and she hasn't fallen out of the sky yet...

Walking around at Oshkosh the past few years and looking at other RV's its a 50-50 mix with planes having the gap and not.
 
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I've used only the Cleaveland dies and I have no gaps. I don't see on all your samples the "coin" impression around the dimple. When I dimple I get a definite impression of the die, using a DRTD2. Is it possible the height of the brown die is slightly higher so you are getting more driving pressure with it?

Are you dimpling with the plastic on? I don't.

Also it is possible that the method for dimpling the rib isn't getting a deep enough dimple there. It is possible to setup the squeezer so it isn't generating enough pressure, esp if it is pneumatic. It will act right but takes more fiddling than the DRDT2.
 
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I've used only the Cleaveland dies and I have no gaps. I don't see on all your samples the "coin" impression around the dimple. When I dimple I get a definite impression of the die, using a DRTD2. Is it possible the height of the brown die is slightly higher so you are getting more driving pressure with it?

Are you dimpling with the plastic on? I don't.

Also it is possible that the method for dimpling the rib isn't getting a deep enough dimple there. It is possible to setup the squeezer so it isn't generating enough pressure, esp if it is pneumatic. It will act right but takes more fiddling than the DRDT2.

+++!

I've been invited to 'review' several new builder's workmanship over the years. The #1 issue I find is improper dimpling. I get explanations from builders, such as ?I used my expensive ?hydro-dynamic electoflux confabulator?, so they must be right!?

Wrong.

Dimples must be crisp. Under dimpling produces waviness in the skin and the rivets improperly nest. If you look down a row of dimples, the light reflection in the skin must be flat.

When I demonstrate how to adjust their dimpler, or how hard to whack with a c-frame dimpler, the light bulb comes on. It's about seeing the halo around the dimples... No halo means it's a problem.

The difference between manufacturer's dimple dies has not been an issue for me, but they could be contributing.

Try again. Whack harder or adjust your dimpler in or out. Get the halos and you should be good.

V
 
Under dimpling

+++!

I've been invited to 'review' several new builder's workmanship over the years. The #1 issue I find is improper dimpling. I get explanations from builders, such as “I used my expensive “hydro-dynamic electoflux confabulator”, so they must be right!”

Wrong.

Dimples must be crisp. Under dimpling produces waviness in the skin and the rivets improperly nest. If you look down a row of dimples, the light reflection in the skin must be flat.

When I demonstrate how to adjust their dimpler, or how hard to whack with a c-frame dimpler, the light bulb comes on. It's about seeing the halo around the dimples... No halo means it's a problem.

The difference between manufacturer's dimple dies has not been an issue for me, but they could be contributing.

Try again. Whack harder or adjust your dimpler in or out. Get the halos and you should be good.

V

Finally. Thank you for bringing this up.
I get asked as well and underdimpling is often the issue. If someone asks, I help.
If they don't, oh well. I've seen entire airplanes underdimpled.
Burnish doughnut is good. Distorted pillow is not.
:eek:
 
+++!

I've been invited to 'review' several new builder's workmanship over the years. The #1 issue I find is improper dimpling. I get explanations from builders, such as ?I used my expensive ?hydro-dynamic electoflux confabulator?, so they must be right!?

Wrong.

Dimples must be crisp. Under dimpling produces waviness in the skin and the rivets improperly nest. If you look down a row of dimples, the light reflection in the skin must be flat.

When I demonstrate how to adjust their dimpler, or how hard to whack with a c-frame dimpler, the light bulb comes on. It's about seeing the halo around the dimples... No halo means it's a problem.

The difference between manufacturer's dimple dies has not been an issue for me, but they could be contributing.

Try again. Whack harder or adjust your dimpler in or out. Get the halos and you should be good.

V

On the DRDT-2 you feel a definite end-point, slight "pop" perhaps when the dimple is fully formed. If you don't feel that, it's usually not a great dimple - easy to fix though, just hit it again to feel the end point.
 
Your problem is the DRDT-2...not the dimple dies. What you require is dimples with well defined angular shoulders...not rounded shoulders.

There are two ways to form dimples. Firstly you can do it with a device that applies a static pressure (like the DRDT-2) and secondly you can do it with a device that applies a dynamic pressure (like a C-throat). The first is a squeeze, the second is an impact. Only the impact will give you truly well defined angles at the shoulders as opposed to curves.

If you want show quality deep seated rivets you need to use a C-throat and preferably give each dimple 2 impacts.

I know the DRDT devices are popular...they?re easy to use, convenient, and quiet...unfortunately they just don?t produce high quality dimples.

Get hold of a C-throat from someone or go over to someone?s place that has one and do some dimples to compare....you?ll see the difference immediately.
 
Bob, I imagine a couple hundred people are going to disagree after I do. But to each their own. The speed and excellent results I get from the DRDT-2 make me wonder how anyone does it different. I don't think my shoulder would take a few hundred double whacks a few afternoons in a row. I also doubt that many production aircraft are built with hand-dimpling processes.
 
Get hold of a C-throat from someone or go over to someone?s place that has one and do some dimples to compare....you?ll see the difference immediately.

Plus 1 to this, use a steel hammer and your Cleaveland dies, yes it's noisy and slower but... best in show dimples!
Russell
 
Plus 1 to this, use a steel hammer and your Cleaveland dies, yes it's noisy and slower but... best in show dimples!
Russell

I agree. The C-Frame a big @ss hammer with one firm solid whack and you will have perfect dimple everytime. It took me a bit of time and practice to figure this out. Don't be afraid of hitting it too hard.
 
C-frame

Count me in. Need a poll. C-frame and a 2lb dead blow. Harbor Fright lifetime warranty. I blew up four of them.:D
 
Your problem is the DRDT-2...not the dimple dies. What you require is dimples with well defined angular shoulders...not rounded shoulders.

There are two ways to form dimples. Firstly you can do it with a device that applies a static pressure (like the DRDT-2) and secondly you can do it with a device that applies a dynamic pressure (like a C-throat). The first is a squeeze, the second is an impact. Only the impact will give you truly well defined angles at the shoulders as opposed to curves.

If you want show quality deep seated rivets you need to use a C-throat and preferably give each dimple 2 impacts.

I know the DRDT devices are popular...they’re easy to use, convenient, and quiet...unfortunately they just don’t produce high quality dimples.

Get hold of a C-throat from someone or go over to someone’s place that has one and do some dimples to compare....you’ll see the difference immediately.

I think I disagree with the assertion that the DRDT-2 creates inferior dimples due to some inherent flaw. My DRDT-2 creates excellent dimples. The trick for me was making sure to set it up right so that it compresses properly. When I received mine (purchased from another builder), it made rounded dimples, but after adjustment, which I only ever had to do once, it is great. The ram guide and the lower die holder have to be aligned well, and the ram has to be set to go over center properly. It can take some effort to move the handle with the ram set up right, but it works great. I can apply more force with the DRDT-2 than with my pneumatic squeezer and it makes better dimples.
 
Bob, I imagine a couple hundred people are going to disagree after I do. But to each their own. The speed and excellent results I get from the DRDT-2 make me wonder how anyone does it different. I don't think my shoulder would take a few hundred double whacks a few afternoons in a row.

Dudley, the problem with this type of thread is that often the opinions simply come down to defence of choice. Another problem is that people give opinions when they have no relativity because they have only used one technique.

This thread was started by a builder who is using a DRDT-2 and is unhappy with the quality of his dimples. It?s a very common occurrence...just look back through the archives.

I?m a TC so I see many RV projects and some of the builders are using a DRDT and most are happy with the tool and with the quality of the dimples that it produces. But mostly they just don?t know anything different. They just don?t know what they don?t know. Quite often they?re satisfied with dimples that I personally would not tolerate. But it?s not an issue of safety...it?s just a matter of how fussy one is.

I?ve used a C-Frame, a pneumatic squeezer, and a DRDT, and there is no question in my mind that the C-Frame produces a dimple with better definition thus ensuring a more deep seated rivet. This is particularly true in thicker aluminium gauges.

Finally, there are a couple of different issues being discussed here and the two are being confused. One revolves around convenience, and the other centres on quality. No doubt the DRDT is very convenient...but it is the C-Frame that produces the better quality.

I also doubt that many production aircraft are built with hand-dimpling processes.

Maybe, but I doubt that many production aircraft are built with DRDTs either. ;)
 
I suppose DRDT vs C-Arm could be a primer war... I agree do what works...

I had a tour at the GenDynamics Fort Worth jet factory when my HS friend and college roommate went to work there; amazing place (1986). I wish I could go back now and see how they do all the things I do on a build. I took the Boeing tour and while it was amazing we were a long way from the work. In 86 I got to walk the shop floor for a day; so cool. I'd like to see how the factory deburrs, for example. Thread creep......
 
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?The thread was started by a builder who is using a DRDT-2 and is unhappy with the quality of his dimples?...using the Cleavland dies. Maybe it?s a combination of the Cleaveland dies and the DRDT-2 because the OP clearly stated he doesn?t have the problem with the Brown dies and the DRDT-2. I used both a DRDT-2 and C-frame, as well as Cleaveland and other brands of dies and had the same issue as the OP with the Cleaveland dies. My .02 keep the DRDT-2 if you are satisfied with the results...ditch the Cleaveland dies since they are not working well for you. There are only a few dimple aficionados that will scrutinize your dimples under a magnifying glass, but what is important is how they look to you not them.

There are three variables here:
Dimple dies, the DRDT-2 and builder technique.

They are interconnected and not independent. If the Cleaveland dies are a different thickness, even by a few mils, the DRDT-2 would need to be adjusted to make good dimples. A c-frame does not have this issue, but technique is more important. I would get an experienced builder involved pronto, and get the diagnosis within 5 minutes.

V
 
I set up DRDT-2 per instructions and cannot tell a difference between dimples done with it versus the C-frame. I tried every technique when I did the training class at Synergy back in 2016, and have used the C-frame with a hammer from time to time (I have both).

Physics alone would suggest that any perceived superiority of one device over another is erroneous. The die will do what it is designed to do if the proper force is applied to properly prepared material - velocity is the only difference in techniques and count me "dubious" as to whether that has anything to do with it.
 
Physics alone would suggest that any perceived superiority of one device over another is erroneous. The die will do what it is designed to do if the proper force is applied to properly prepared material - velocity is the only difference in techniques and count me "dubious" as to whether that has anything to do with it.

I agree. Also beatings things with a hammer seems an imprecise method; although many Ferrari's were built this way.
 
Physics alone would suggest that any perceived superiority of one device over another is erroneous. The die will do what it is designed to do if the proper force is applied to properly prepared material - velocity is the only difference in techniques and count me "dubious" as to whether that has anything to do with it.

I did a rough estimation of a #8 screw dimple with a 2lb hammer and a 5 lb hammer. I ignored the mass of the set holder since it's (sort of) 0 due to the spring. I also ignored the flat area of the die since it has almost no effect on the dimple. I used the area of the dimple itself (0.340" diam; 0.050" depth)

Swinging the hammer at 5 m/s (which is a pretty good whack but very doable), you get ~2400 psi out of the 2 lb and ~6000 psi out of the 5 lb. #40 and #30 will be even higher.

Your average pneumatic squeezer is rated for 3000 psi. I don't know what the drdt2 is rated at, maybe half that?


That said, I tested the c-frame vs my pneumatic with a 1-1/2" yoke when dimpling the tank and couldn't tell the difference. And i've used the c-frame, a 3000 psi pneumatic, a 6000 psi pneumatic (gator jaws) to dimple #30 and #40 and they all look exactly the same to me.
 
I did a rough estimation of a #8 screw dimple with a 2lb hammer and a 5 lb hammer. I ignored the mass of the set holder since it's (sort of) 0 due to the spring. I also ignored the flat area of the die since it has almost no effect on the dimple. I used the area of the dimple itself (0.340" diam; 0.050" depth)

Swinging the hammer at 5 m/s (which is a pretty good whack but very doable), you get ~2400 psi out of the 2 lb and ~6000 psi out of the 5 lb. #40 and #30 will be even higher.

Your average pneumatic squeezer is rated for 3000 psi. I don't know what the drdt2 is rated at, maybe half that?


That said, I tested the c-frame vs my pneumatic with a 1-1/2" yoke when dimpling the tank and couldn't tell the difference. And i've used the c-frame, a 3000 psi pneumatic, a 6000 psi pneumatic (gator jaws) to dimple #30 and #40 and they all look exactly the same to me.

I'm no engineer, but my point is this: It takes a certain amount of force to permanently deform the metal from it's pre-dimple shape to the post-dimple shape. Under-dimpling results from inadequate force - we all agree on that. BUT once adequate force has been applied to create a permanent properly formed dimple, in the proper shape the die is designed to create, more force will not improve the quality of the dimple. I would hazard a guess (admittedly a GUESS) that more force than required is more likely to deform the material beyond the "ideal dimple" shape, if the die allows enough compression travel between die halves. If the die limits the travel, then no amount of force (unless enough is applied to deform the die) will change the shape of the dimple.
 
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