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Back To dimples again!!!

vluvelin

Well Known Member
Was not happy with my dimples with DRDT-2 and (dies from popular store 426-3 )
1) fit of rivet in dimple is not complete
2) dimple not crisp not well defined
3) nesting
Many people suggested C-frame makes it much better tried that no difference in results (for me).

NOTEs
1) Dies are not defective purchased 6 sets in total during 2 years period.
2) Reason for this post is to understand if
I have no knowledge in the subject ( most likely)
or
developer of this dies didn't spend enough time to tune them
or
because they try 1 size fit all solution


Please review and comment. I am new guy in aviation and hold only home school diplomas in everything I do. So please don’t shoot!!!

Here is dimple I managed to get using DRDT-2 and Modified dies
Material .032
DRDT2 preload material thickness - 1.25 turns
Drill bit used #40 Double margin
Hole final size Original dies 2.65mm -.104 Modified dies 2.70mm -.106
sorry fill better in metric

Rivets_Fit.jpg


ModOr_1.jpg


ModOr_3.jpg


ModOr_REAR_view.jpg


ModOr_4.jpg


ModOr_Side_view.jpg



Modified dimple rivet fit
MO_Rivet-fit2_Small.jpg


Modified not deburred
Mo_Bot_No_Debure_Small_Pic.jpg


Mo_Bot_Not_Debure_Small.jpg
 
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Wow. You are DEDICATED to your new craft, sir! All I did was go look at the planes at the airfield and my dimples looked like they did so I went with it. :D :p
 
1. You don't say how you "modified" the dimple dies, please elaborate.
2. The modified die holes look much bigger than the .001" difference in your opening post. Did you measure them with a digital caliper?
3. The photos are great. What kind of 24x graduated magnifier did you use?

I used the Cleaveland dimple dies with a pneumatic squeezer and with a C frame. Used the latter with two heavy hits with a dead blow hammer and am quite happy with the results.

Using the same dimple dies for a skin and a rib, the two parts will never nest perfectly, but after setting the rivet they will be "close enough".
 
Might want to try some different dies. Could you possibly borrow some to test out?? The DDRT takes all the guesswork out of it.
 
I'm a broken record on my allegiance to the c-frame - used it on every dimple that I could fit. I also own a DRDT that was only used during my practice kits. I was never satisfied with the results. I will say, that it must have been user error, as so many people are happy with it. I just got tired of messing with it when my c-frame results were so nice. One thing I've seen routinely - now that I somewhat know what I'm looking at - is underdimpling. I've seen videos of folks hitting the c-frame with barely any force and you glance down the rivet line and see all kinds of light bending around the rivets. I used a metal claw hammer - smaller one (not sure of the weight; not at home right now), and gave 3, not so gentle smacks for each hole. You can hear, and even feel, when the dimple is fully formed. Doesn't take long to get the feel and get into the groove with excellent results. I really like this video from Mike at Cleaveland

https://m.youtube.com/watch?v=Qo9QCMaNSoA

Oh yeah - I also only used Cleaveland's dies.
 
+1 on retry with different dimple dies. For absolute best results, make sure that they are 'spring back' style dies (though you can get decent dimples with standard dies).

The topside views of all the images have the look of an underdimpled operation, but the bottom views all look like you got a nice crisp dimple. That's why I'd try a different set of dies.

And FWIW, more expensive stuff has to work better, because you paid more for it, right? ;-) You can get perfect dimples with a C-frame & a heavy mallet (and good dies).

Charlie

edit: Jon posted while I was typing; good info from him. I used a fat rubber mallet instead of a hammer or dead-blow. One medium whack to start, then a serious whack like driving a 20d framing nail. (You really can't hit it too hard, using a soft face mallet.)
 
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I can second the Cleaveland die suggestion. I was surprised at how much difference they made over the other set I had been using. I used a C-frame with a 2# dead blow mallet, 2-3 good hard whacks.
 
I'm a broken record on my allegiance to the c-frame - used it on every dimple that I could fit. I also own a DRDT that was only used during my practice kits. I was never satisfied with the results. I will say, that it must have been user error, as so many people are happy with it. I just got tired of messing with it when my c-frame results were so nice. One thing I've seen routinely - now that I somewhat know what I'm looking at - is underdimpling. I've seen videos of folks hitting the c-frame with barely any force and you glance down the rivet line and see all kinds of light bending around the rivets. I used a metal claw hammer - smaller one (not sure of the weight; not at home right now), and gave 3, not so gentle smacks for each hole. You can hear, and even feel, when the dimple is fully formed. Doesn't take long to get the feel and get into the groove with excellent results. I really like this video from Mike at Cleaveland

https://m.youtube.com/watch?v=Qo9QCMaNSoA

Oh yeah - I also only used Cleaveland's dies.

Could you please post high res picture of your dimple Cleveland 426-3 and C-farme?
 
+1 on retry with different dimple dies. For absolute best results, make sure that they are 'spring back' style dies (though you can get decent dimples with standard dies).

The topside views of all the images have the look of an underdimpled operation, but the bottom views all look like you got a nice crisp dimple. That's why I'd try a different set of dies.

And FWIW, more expensive stuff has to work better, because you paid more for it, right? ;-) You can get perfect dimples with a C-frame & a heavy mallet (and good dies).

Charlie

edit: Jon posted while I was typing; good info from him. I used a fat rubber mallet instead of a hammer or dead-blow. One medium whack to start, then a serious whack like driving a 20d framing nail. (You really can't hit it too hard, using a soft face mallet.)


The dimples used Non modified and modified from same store and they are not chip ones 39.00$

reflection test was done and results are better then on this video on both modified and non modified sets 1.25 turn preload
 
Just a thought...

How much are you deburring? It is very easy to over-do it and deform the dimpled hole. Again....just a thought
 
I can second the Cleaveland die suggestion. I was surprised at how much difference they made over the other set I had been using. I used a C-frame with a 2# dead blow mallet, 2-3 good hard whacks.

in what units you measure mallet whacks.????
I tried C-Frame not much better then DRDT results
Can you Post High res picture of dimples your C frma + Cleveland 426-3
 
How much are you deburring? It is very easy to over-do it and deform the dimpled hole. Again....just a thought

you can see pictures and measurement above there is picture of NOT deburred bottom skin other pictures are deburred skin
 
Dies

I've had good luck with the old avery dies, hard plastic mallet and 1 good whack. No complaints from any of my rivets or tech advisors.
 
Take a quick look at this recent thread about the same issue: http://www.vansairforce.com/community/showthread.php?t=152064

Post #20 in the thread says that he showed the dimples to a very experienced A&P/Builder and that he saw no cause for concern with them.

My dimples and rivets look the same way, using Cleaveland dies, on both a DRDT-2 and a C-Frame. I'm pretty sure the gap under the edge of the rivet head is because the dies have a slightly round edge right there. I did try an older set of dies I am borrowing from a finished builder (not sure where he got them) and the gap does not exist when I use them.

I emailed Van's about this since I already have finished parts with this small gap under the edge of the rivet head and based on what I described was told that the dies are working the way they should. Personally, I'm not going to worry about it because I'm sure primer & paint will fill in those gaps.
 
in what units you measure mallet whacks.????
On a scale of "Corrective discipline applied to kindergartener" to "break a CRT face with a cinderblock", I used a force of "dimple sheet aluminum with a dead blow mallet".
 
Take a quick look at this recent thread about the same issue: http://www.vansairforce.com/community/showthread.php?t=152064

Post #20 in the thread says that he showed the dimples to a very experienced A&P/Builder and that he saw no cause for concern with them.

My dimples and rivets look the same way, using Cleaveland dies, on both a DRDT-2 and a C-Frame. I'm pretty sure the gap under the edge of the rivet head is because the dies have a slightly round edge right there. I did try an older set of dies I am borrowing from a finished builder (not sure where he got them) and the gap does not exist when I use them.

I emailed Van's about this since I already have finished parts with this small gap under the edge of the rivet head and based on what I described was told that the dies are working the way they should. Personally, I'm not going to worry about it because I'm sure primer & paint will fill in those gaps.

I read all of this and see all i could on youtube but not satisfied with what i see
some while back everybody was sure the earth is flat and every one you ask was assuring you it is flat but not everybody was satisfied with this answer!!!
 
On a scale of "Corrective discipline applied to kindergartener" to "break a CRT face with a cinderblock", I used a force of "dimple sheet aluminum with a dead blow mallet".


I tryed C frame with Cleveland dies different variation on wacks to the point of skin starting to deform and becoming concave
don't see improvement in crispiness
 
Could you please post high res picture of your dimple Cleveland 426-3 and C-farme?

I'm not at home right now, but found a few from the very beginning of my build in my log. The first two are the rudder (back riveted); the third is the vertical (gun). The pics aren't the best, but the dimple/rivet/skin is almost perfectly in plane. Again, this is from a few forceful wacks and Cleaveland dies.

998B42A1-DEE8-4F32-861E-F15F6AFA3E37.jpg


49D77D4E-57C5-465D-ABAD-8282C194B302.jpg


574C04D5-D7D8-49D9-9AAE-9B5CC7DDFD2E.jpg
 
There is expensive vs. cheap, and there is [whichever] good vs. defective.

There is structurally fine, and there is 'looks perfect' (in addition to structurally fine). No question to me that what's shown in the pics is safe.

Perhaps the photos over-emphasize potential issues. I took a zoomed pic of one of mine (most say my riveting is quite good) and the pic over-emphasizes the edge of the dimple next to the rivet head. Have you laid a straightedge across the driven rivet heads? For 'looks perfect': On a flat skin surface, with the straightedge along the rivet heads and 'back lit', you should see minimal light between skin & straightedge, and have a hard time picking out where the rivets are located. It should be somewhat difficult (not impossible, but difficult) to catch a fingernail on the rivet head.

There's a milspec for minimum/maximum hole size for each rivet size, & IIRC, using a #40 drill, light debur with a 3 flute debur tool and dimpling will take the hole out to the max in the spec, and if you're even slightly aggressive with the debur operation, it will go over the max diameter. It wouldn't surprise me if half the -3 rivets flying in RV's were driven in holes that are bigger than the milspec max.

FWIW,

Charlie
 
rv7charlie;you should see minimal light between skin & straightedge said:
i clearly understand what you are saying
this is exactly what I trying to do

I want to understand why those dimples that cost 40$ not made to dimple like modified one ???
is this because i have no education and missing something
or
because they didn't spend enough time to make it this way
or
because each skin thickness require different dies to be made and they try to 1 fit all approach???
 
In the rest of the message, I (and others) was trying to say that you may just have a defective die. Even Lear Jets have warranty claims. I've got an A/N nut that the manufacturer failed to thread. Stuff happens.

Have you borrowed someone's known-good set of dies, and tested them on some scrap to compare?

Charlie
 
In the rest of the message, I (and others) was trying to say that you may just have a defective die. Even Lear Jets have warranty claims. I've got an A/N nut that the manufacturer failed to thread. Stuff happens.

Have you borrowed someone's known-good set of dies, and tested them on some scrap to compare?

Charlie

this is ruled out
first set of dies purchased 2 years ago second set purchased last year in October used them to replace skin on wing purchased for experiment 4 more sets from same store ( with good reputation here advised by many)

there is very little variation in dimensions only 1 set had 4.8mm at the top of the head of mail die others 4.7mm

6 sets in 2 years span can not possible be bad
 
I'm not at home right now, but found a few from the very beginning of my build in my log. The first two are the rudder (back riveted); the third is the vertical (gun). The pics aren't the best, but the dimple/rivet/skin is almost perfectly in plane. Again, this is from a few forceful wacks and Cleaveland dies.

998B42A1-DEE8-4F32-861E-F15F6AFA3E37.jpg


49D77D4E-57C5-465D-ABAD-8282C194B302.jpg


574C04D5-D7D8-49D9-9AAE-9B5CC7DDFD2E.jpg


Yes looks nice!
if you can snap high resolution one from dimple both sides of skin
 
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I'm a broken record on my allegiance to the c-frame - used it on every dimple that I could fit. I also own a DRDT that was only used during my practice kits. I was never satisfied with the results.

+1 for this. The DRDT uses static pressure to make an impression. As a result the DRDT does not produce enough pressure to produce a really crisp dimple profile, especially in .032 aluminium. The C frame uses dynamic pressure and therefore produces a much more defined profile.

I used a C frame and 2 solid whacks with a heavy computhane hammer....perfect dimples with well seated rivets. You can actually feel when the dimple is fully formed....you can feel it "bottoming out".

I used the C frame for all external skins where I obviously wanted deep seated flush "cosmetic" rivets. For internal dimples (ribs, bulkheads etc) I used a pneumatic squeezer wherever I could gain access.

I tried a friend's DRDT for comparison and it just does not produce the same quality. This is not defence of choice...it's just a fact.

I suspect that some people who use a DRDT for dimpling are satisfied with it because they don't know any better. Or maybe it just comes down to how fussy one is.
 
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part numbers

I noticed the Cleaveland dimple die part numbers are similar:
Tank die 4263T, Sub structure die 4263SS, and I guess the standard die is
simply 4263. I can see where these could be easily mixed up.
 
I noticed the Cleaveland dimple die part numbers are similar:
Tank die 4263T, Sub structure die 4263SS, and I guess the standard die is
simply 4263. I can see where these could be easily mixed up.

NO mixup standard dies 426-3 NOT-T NOT-SS
 
+1 for this. The DRDT uses static pressure to make an impression. As a result the DRDT does not produce enough pressure to produce a really crisp dimple profile, especially in .032 aluminium. The C frame uses dynamic pressure and therefore produces a much more defined profile.

I used a C frame and 2 solid whacks with a heavy computhane hammer....perfect dimples with well seated rivets. You can actually feel when the dimple is fully formed....you can feel it "bottoming out".

I used the C frame for all external skins where I obviously wanted deep seated flush "cosmetic" rivets. For internal dimples (ribs, bulkheads etc) I used a pneumatic squeezer wherever I could gain access.

I tried a friend's DRDT for comparison and it just does not produce the same quality. This is not defence of choice...it's just a fact.

I suspect that some people who use a DRDT for dimpling are satisfied with it because they don't know any better. Or maybe it just comes down to how fussy one is.


Ok going to Hangar tomorrow for couple of Wacks on C-frame!!!
 
I did have a look. There are some imperfections. But what I don't really know is, how is that different than mine or anyone else's kit? I am not looking at it with the same eye for perfection as Julian. I think I am more typical - "well, that's how they work, and there are 9000 of them, so it must be ok".

He notes that there are gaps that open up between the 2 sheets in the areas between rivets. That seems normal to me, because the dimpling stretches the skin locally, so we can't expect it to lay perfectly flat. So there is distortion. Not too much, but a couple of thou. I don't see a way around that. Also, when you dimple, the hole opens up, so the rivet sits a bit loose in the hole. That seems pretty normal as well, and I don't see what you can do to change that. Julian really wants perfection.
 
All this obsession over the dimples is fine, but what are the finished results? You set the rivet with either gun or squeezer and you think the rivet is the only thing that distorts? The most important feature of good dimples is that there are no cracks around the holes. To me, there is always a noticeable difference between a rivet simply sitting in a dimple and a set rivet - the act of riveting helps the rivet and dimple conform more tightly to each other.
 
Comparing to your objectives for dimples, I only wanted the rivet edge to seat. Rather than look at tools I just make 2-3 turns of a deburring tool and they sit well after setting. There is a difference between bucking, back riveting and squeezing in this regard as well. Bucking seems to make them look better and squeezing means more care in the process to yield the same result.

Thanks for sharing your results. Oh - I use the c-frame with the delrin hammer from avery. One whack to make the initial bend then a second whack to set metal to metal. A habit from setting a cold chisel I suppose. I think more force makes a better dimple, that is true from the hand to pnuematic squeezer. Also, the tape seems to help sink the heads in better than mushroom set on metal. No data.

Keep up the good work on future investigations!
 
I tried a friend's DRDT for comparison and it just does not produce the same quality. This is not defence of choice...it's just a fact.

I suspect that some people who use a DRDT for dimpling are satisfied with it because they don't know any better. Or maybe it just comes down to how fussy one is.

I humbly disagree. I have owned, used and analyzed the dimples made by both a C-frame and DRDT-2 (same dies). In my opinion (as that's all that it is), a properly set up DRDT-2 makes a perfect dimple every time. The c-frame is certainly capable, but I think it relies too much on the user's ability to judge how much force in the blow is adequate. Too little and you have under-formed dimples. Too much and you can distort and thin the metal under the dies. It also introduces the risk of accidentally creating additional holes, if you whack it with the material in the wrong place.
 
It would take a pretty big ---- [edit: mallet] and a pretty strong arm to overcompress 2024 sheet. Using a soft head mallet virtually guarantees that the sheet can't be overcompressed.

And all the things listed as downsides to a C-frame also apply to a DDRT-2. (Not compared is cost....)
 
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I dimpled for the first time on an RV10 Vertical Stabilizer skin over the last weekend. I have both DRDT-2 and C Frame. I made a test sheet with about 8 holes lined up side by side.

I found that too little, or too much preload, either way, would make a concave area in the sheet around the dimple. I found it was most satisfactory, for my setup, for a 1/3 turn preload (I have read anywhere from 1/4 to 1/2 turn).

The dimples in the C Frame with hammer were fine as well. A good CFrame dimple vs a good DRDT2 dimple, visually for my eye, I couldn't tell a real difference. I however found I personally produced a more consistent, better looking row of dimples with the DRDT2. I am using Cleveland dies.

I found it is more critical to have the aluminum sheet level with your dimpling surface. Where I had the sheet at a slight angle to the dies or did not have it supported, I produced a poor dimple with any tool I used.
 
I dimpled for the first time on an RV10 Vertical Stabilizer skin over the last weekend. I have both DRDT-2 and C Frame. I made a test sheet with about 8 holes lined up side by side.

I found that too little, or too much preload, either way, would make a concave area in the sheet around the dimple. I found it was most satisfactory, for my setup, for a 1/3 turn preload (I have read anywhere from 1/4 to 1/2 turn).

The dimples in the C Frame with hammer were fine as well. A good CFrame dimple vs a good DRDT2 dimple, visually for my eye, I couldn't tell a real difference. I however found I personally produced a more consistent, better looking row of dimples with the DRDT2. I am using Cleveland dies.

I found it is more critical to have the aluminum sheet level with your dimpling surface. Where I had the sheet at a slight angle to the dies or did not have it supported, I produced a poor dimple with any tool I used.
__________________

I couldn't agree more. I too have both the C-Frame and the DRDT. I guess my eye isn't good enough as I can't tell the difference either. The DRDT-2 produces a significantly more consistent dimple.

One other idea would be to have somebody else try the dies in their C-Frame or DRDT-2 and evaluate. Easy to ship and relatively inexpensive compared to many other tools.

Tough way to start, I admire your persistence and patience.

Fred
 
ATS Avery dies

I ordered AVERY tools Dies from ATS must have them tomorrow
and will compare and make some new pictures
 
All this obsession over the dimples is fine, but what are the finished results? You set the rivet with either gun or squeezer and you think the rivet is the only thing that distorts? The most important feature of good dimples is that there are no cracks around the holes. To me, there is always a noticeable difference between a rivet simply sitting in a dimple and a set rivet - the act of riveting helps the rivet and dimple conform more tightly to each other.

In my understanding if rivet head conical surface do not fully touch dimple
+
Dimple not fully touching underlying dimple ( Nesting )

this situation creates too much empty spacing that getting compressed during riveting this creates unnecessary distortion on skin that can be avoided
and perfect reflection that is achieved by Mike from Cleveland videos
would look all distorted.
 
Dimple not fully touching underlying dimple ( Nesting )

Now you're opening a REAL can of worms. The tech counselor (since passed away) who came to inspect my RV-6A just prior to final assembly wanted me to scrap the whole project because I had not used airline-style die tooling for all my dimples. (Actually, he just wanted me to dump the plane on the market so he could buy it cheap; thanks to advice from several local A&P IAs, I avoided the trap). I inquired into such tooling. You need different dies for every different thickness and also for every underlying stack, because each underlying dimple must be larger to accommodate the overlying dimple and the size depends on the size of the overlying material. You can guess what a nightmare that would be to keep straight, not to mention the cost.

Fortunately, for the sheet thicknesses used in most of our aircraft, it's not that critical. As for cosmetic results, let's see if the folk who polish their aircraft will weigh in. Otherwise, it's not really worth your time. In some threads that have gone before on VAF discussing show quality aircraft, one thing that stuck with me was that judges want aluminum aircraft to look like aluminum. In other words, the rivets should be visible, even under paint, but not sitting proud or excessively gapped.

Don't let me rain on your parade in search of perfection. It's not a bad thing. But be sure to consider the costs, both in time and money, and don't let it prevent you from finishing your aircraft.
 
You need different dies for every different thickness and also for every underlying stack, because each underlying dimple must be larger to accommodate the overlying dimple and the size depends on the size of the overlying material. You can guess what a nightmare that would be to keep straight, not to mention the cost.

Yes this is the filling i have!! If most people are happy with 1 size fit all approach you will not find fine-tuned dimple dies in usual places we shop


Don't let me rain on your parade in search of perfection. It's not a bad thing. But be sure to consider the costs, both in time and money, and don't let it prevent you from finishing your aircraft.

I am not in rush I have Nice Rv7 to enjoy. Building for me is self education
Isn't it what experimental aviation supposed to be???
 
This thread reminds me of a comment made by my EAA Tech Counselor and friend who inspected my empennage. He said,"Don, you need to decide if you're building a showplane or an airplane to fly."
 
This thread reminds me of a comment made by my EAA Tech Counselor and friend who inspected my empennage. He said,"Don, you need to decide if you're building a showplane or an airplane to fly."

I agree with this sentiment, but not in this instance. Takes the same amount of time to make a poor dimple or a nice one. All things equal, I'll always choose the latter.
 
... Takes the same amount of time to make a poor dimple or a nice one. All things equal, I'll always choose the latter.

Jon, what I was referring to was the idea of using different dies for different thicknesses and for every underlying stack, as described in flion's post above. And to quote flion's summary statement, "...But be sure to consider the costs, both in time and money, and don't let it prevent you from finishing your aircraft."
 
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