Forum:  Workshop & Tools
Topic:  Dimple dies
Select messages from #through #
FAQ
Print

Post #1
Subject: Dimple dies
Author: CalKid
Posted: Wed Feb 13, 2008 5:26 pm


Started to use the #30 dimple die on a the rear hzstab and noticed that the resulting hole looked bigger to my eye. I measured it and sure enough was .011 bigger in dia after dimpling. Wierd. Wondering if the cause was that I had perhaps turned the dies down too tight rather than just too touch if that makes sense.
Post #2
Subject: 
Author: cjensen
Posted: Wed Feb 13, 2008 5:33 pm


Nope. The resulting hole is always going to grow a slight amount because you are moving the edges away from each other in the circle. It's normal.

The dimple dies will only go so far, meaning you can't over-dimple a #30 hole with a #30 dimple die. You can under-dimple if it doesn't seat all the way, but once the dies come together, that's as far as they'll go.

No worries!
Smile
Post #3
Subject: Thanks
Author: CalKid
Posted: Wed Feb 13, 2008 5:48 pm


Thanks Chad. That makes perfect sense.
Post #4
Subject: Re: Dimple dies
Author: TomNativeNewYorker
Posted: Wed Feb 13, 2008 7:19 pm


CalKid wrote:
Started to use the #30 dimple die on a the rear hzstab and noticed that the resulting hole looked bigger to my eye. I measured it and sure enough was .011 bigger in dia after dimpling. Wierd. Wondering if the cause was that I had perhaps turned the dies down too tight rather than just too touch if that makes sense.


Assuming you drilled the holes using a #30 drill bit, you 'stretched' the hole to a diameter at least .1395". If I recall correctly, max diameter for a 1/8" rivet is .141" meaning you are one and a half thousandths from max diameter assuming you drilled a perfect #30(.1285") hole.

I would use a micrometer to measure the diameter of the dimple die pilot. Usually you should come up with a .125" diameter dimple die pilot. If that is the case, you could drill your holes with a .125"(1/8th) drill bit keeping your final hole diameter away from the max allowable diameter for a 1/8" solid rivet.
Post #5
Subject: 
Author: Wicked Stick
Posted: Wed Feb 13, 2008 8:35 pm


I adjust the dimple dies so that when the pneumatic squeezer is full travel, the dies are just touching each other. Any more than that is overkill. I watched a video from one of the tool manufacturers when I first started building and the technique was to have them touch, but you could still spin the die a bit. If you couldn't spin the die by hand when it was full travel, you had them too tight.
Post #6
Subject: 
Author: cjensen
Posted: Wed Feb 13, 2008 9:23 pm


I use the same technique WS...but, it doesn't really matter all that much. If they are a little tight, all that's gonna happen is the yoke will flex a little. You still can't "over dimple" the hole if they are too tight.

Just shoot for 'em touching, still able to spin, and you're good!

Cool
Post #7
Subject: 
Author: JohnR
Posted: Thu Feb 14, 2008 1:10 am


The above is correct, the hole is a little larger.

My tech counselor told me the biggest mistake people make is not dimpling enough. He then showed me the procedure as WS and Chad have talked about. We looked at an under dimpled hole and one that was dimpled to the point of a little "coining" (you can see where the dies were) and sure enough the ones dimpled more were much better and provided a smoother flatter surface when the rivets were set.

I also found I seemed to get better dimples with my Cleaveland Tool spring back dies than the cheap ones I had so I bought a complete set and always use them.


My $.02 worth, and probably about what it is worth. Wink
Post #8
Subject: 
Author: captain_john
Posted: Thu Feb 14, 2008 1:15 am


JohnR wrote:
My $.02 worth, and probably about what it is worth. Wink


Overpriced!

I ain't buyin' ANY of it!

Laughing CJ
Post #9
Subject: 
Author: JohnR
Posted: Thu Feb 14, 2008 1:29 am


Heh!

Laughing Laughing
Post #10
Subject: 
Author: dons
Posted: Thu Feb 14, 2008 2:22 pm


Not to start anything, but I too believed you couldn't over dimple, so I did some testing and did find you could easily compress the dimple area beyond the point where only metal under the dies was being affected. I really set out to find out what the ideal dimple should look like using a DRDT-2 and in the process found I could over do it. Here is a link to something I wrote about it.

Link
Post #11
Subject: 
Author: cjensen
Posted: Thu Feb 14, 2008 2:35 pm


I kinda figured it was only a matter of time before somebody presented something about over dimpling. Wink

I almost changed my post to reflect the fact that you can distort the metal by using too much pressure, but the dimple itself can only fit the shape of the tool moving the metal.

Using the common sense all of us have, adjusting the dies to contact each other when the air valve is fully open, will result in the desired dimple. If it's adjusted beyond that, of course the metal will distort.

It's not over-dimpling the hole, it's distorting the metal around the dimple because of too much pressure...
Post #12
Subject: 
Author: dons
Posted: Fri Feb 15, 2008 2:43 pm


Chad is right, it is a splitting hairs kinda thing, put too much pressure on the dies and you can push a very very small amount of material out of the dimple area into the surrounding metal and thus cause some (and very little at that ) distortion. The only way I could 'measure' it was with light reflection, which can be a very sensitive and powerful tool in the right situation.

From my experimentation, it is far better to error on the side of more pressure making the dimples than too little.

You can make quite a mess with a 5 pound sledgehammer and a c-frame with dimple dies, but that was done on purpose knowing it was way over kill just to what would happen. My testing for the 'over dimpling' was more for the curiosity (substitute another word if you like) of knowing, and since I calibrated my DRDT-2, it was easy to pick a close to ideal pressure repeatably anyway. Yes, I over analyze and engineer a lot of things I do, that's why I could never design my own plane, I would never get it done!
Post #13
Subject: Work Shop Tools
Author: Mike Balzer
Posted: Thu May 22, 2008 1:16 am


I have used spring back tank dies in all my ribs and under structure and regular spring back dies on all skins. I have used a hand made DRDT and have had great Flush results.
Post #14
Subject: 
Author: dons
Posted: Thu May 22, 2008 6:08 pm


Welcome to rivetbangers Mike. I have been using tank dies for under structure and regular ones for skins as well, works great. If there are three layers, I only use the tank dies on the bottom layer and use a counter sink tool to slightly hit the middle layer.
Post #15
Subject: Workshop & Tools
Author: Mike Balzer
Posted: Fri May 23, 2008 1:39 am


I do the same when I have three layers. I welded up my own DRDT with 2x4 steel 3/16 thick and cut gusets to reinforce the DRDT from bending. I under cut the DRDT so I could use it to dimple all the way to the trailing edge of the elevator and rudder.

I am new to the site and would like to know what the class code means under the name of the members.
Post #16
Subject: Re: Workshop & Tools
Author: Brantel
Posted: Fri May 23, 2008 12:25 pm


Mike Balzer wrote:
I am new to the site and would like to know what the class code means under the name of the members.


It changes depending on the number of post you have. And if your lucky or unlucky depending on which way you look at it, one of the moderators will brand you with a nickname we can all make fun of. Grin

Oh yeah!

Welcome
Post #17
Subject: 
Author: jakec
Posted: Sat May 24, 2008 1:40 pm


Don,

Great write-up on the DRDT-2. One question for you. You mentioned in your article that there was a different turn setting for each thickness of sheet. Do you re-calibrate it with the scale each time you change thicknesses or is it simply a matter of remembering how many turns gives you good results for each thickness and setting it accordingly?

I'm not looking to build a show winner but I would really like my skins to be as smooth as possible. Thanks.

Can't wait to get started.
Post #18
Subject: 
Author: dons
Posted: Sat May 24, 2008 3:00 pm


Thanks Jake. Each time the thickness of the material changes I follow this very quick procedure:

1- loosen the lock nut
2- turn the adjustment screw a couple of turns so the dies will not touch when the handle is fully pulled down
3- pull the handle all the way down
4- turn the adjustment screw by hand until the dimple dies touch
5- read the scale on the adjustment screw
6- lift the handle
7- turn the adjustment screw for the optimal pre-load for the new thickness
8- tighten the lock nut

It looks like a lot of steps, but it only takes 15 or 20 seconds. The amount of pre-load required will vary depending on the stiffness of your frame, in my case with the factory built version, about 1 turn works for 0.025" material as an example.
Post #19
Subject: 
Author: jakec
Posted: Sat May 24, 2008 3:21 pm


Thanks Don. Appreciate it!
Page 1 of 1

Powered by phpBB © 2001, 2005 phpBB Group