S

Skyhawk

Member
Hi fellow builders.

I?m concerned over my dimple metod.
I have read that there is almost impossible to "overdimple" with the c-frame tool. But also that after dimpling the rivet must not be lower than material around.
If I dimple so the rivet sits in the same height with the structure there is a gap under the rivethead. Is that normal?
On the other hand, dimpling so the rivethead sits flush makes the rivet far below the structure (overdimpling?).
I have tried whith a scrap piece different ammount of dimpling, but can never be really satisfied. Finaly I dimpled two holes in the spar.
Does those looks ok?

Also, i managed to countersink a bit to much in the reinf. angles. The pieces can be moved a bit when hold togheter, if you understand what I mean... :(
(Dimpled against the machined piece)

Thanks in advance.

2828.jpg
 
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If that picture shows a rivet in a dimpled hole, I would say that you used the wrong dimple die in the C frame........or did not whack it hard enough, one or the other.

When I machine countersink, I micrometer the width of the female dimple die and that measurement is how wide my machined countersink will be when finished :)
I have not been to Sweden in 20 years but I remember it being a very beautifull place. You will have some awesome scenery to see when your flying your new plane around !
 
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Use a metal hammer with the c-frame (I use a 20oz. Estwing).
I have heard people recommend dead-blows but I get a better transfer of energy with the metal hammer. The rubber absorbs a lot of energy and you don't get a crisp dimple.
 
Thanks for your help.
I switched to a heavy metal hammer and now i?m pretty happy with my dimples. :)

What do you think about the machine countersunk reinforcement angle? A little bit too wide, is that critical?
(Dimple width: 0,25 in, Machined width: 0,30 in)

Vansrv8: Thanks. Yepp, i?m really dying for take my rv8 up to the mountains and all over the country. :) Many years left though.
 
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IMHO, the machine countersink is to big. I remember that I did this to the exact same piece when started. It is the first machine countersinking that you do, so the learning curve is high. If you use the measurement that I stated above, you will be OK.

I mesured my 1/8 " die and it was .255" wide..........
 
Work Surface

briand said:
Use a metal hammer with the c-frame (I use a 20oz. Estwing).
I have heard people recommend dead-blows but I get a better transfer of energy with the metal hammer. The rubber absorbs a lot of energy and you don't get a crisp dimple.
Click to expand...

If it's on a table/workbench, the structure stability makes a big difference.

A hefty workbench is needed, or put the dimpler frame on the concrete floor...

gil in Tuson
 
Skyhawk said:
Thanks for your help.
I switched to a heavy metal hammer and now i?m pretty happy with my dimples. :)

What do you think about the machine countersunk reinforcement angle? A little bit too wide, is that critical?
(Dimple width: 0,25 in, Machined width: 0,30 in)

Vansrv8: Thanks. Yepp, i?m really dying for take my rv8 up to the mountains and all over the country. :) Many years left though.
Click to expand...


Make 4 gages out of scrap .032 sheet. Drill and dimple for #40, #30 #6 screw (#27 drill) and #8 screw (#19 drill).

I have 3 (had 4 but the shaft on 1 got bent) micro-stop c-sink cages that I keep set but I still check using the gages from time to time. You can buy surplus new Zephyr cages off e-bay for about $10/ea. if I remember right.
 
briand said:
I have 3 (had 4 but the shaft on 1 got bent) micro-stop c-sink cages that I keep set but I still check using the gages from time to time. You can buy surplus new Zephyr cages off e-bay for about $10/ea. if I remember right.
Click to expand...
I echo this advice. The cages allow you to "set it and forget it". If you have several of them set for different sizes then you just need to grab the size you need and go. Assuming no one else is messing with your tools this should keep things moving along with little need for measuring and re-measuring settings all the time.
 
briand said:
Use a metal hammer with the c-frame (I use a 20oz. Estwing).
I have heard people recommend dead-blows but I get a better transfer of energy with the metal hammer. The rubber absorbs a lot of energy and you don't get a crisp dimple.
Click to expand...

Just a note of caution... hammering hardened steel (brittle) with a metal hammer runs the risk of fracturing a sliver or chunk off the steel which can become a very sharp, very fast moving projectile. I have personally seen this happen (hammer on a bearing) that resulted in a trip to emerg for extraction and stitches (after going through a leather glove). Victim said it was so sharp and fast he hardly felt it when it happened.

I don't know if this is a risk with the die mandrel on the c-frame, but thought I'd mention it for general consideration.
 
Dimpling issues...

One thing you might try is to use a dimpling block to "pre-set" the rivets after dimpling but before you drive them. This will give you a near perfect fit. You can buy a dimpling block but they are easy to make from a bucking bar or other chunk of steel. Here is a link showing a dimpling block http://www.planetools.com/Dimpling Block.jpg
Glenna
 
java said:
Just a note of caution... hammering hardened steel (brittle) with a metal hammer runs the risk of fracturing a sliver or chunk off the steel which can become a very sharp, very fast moving projectile.
Click to expand...
DO NOT FORGET SAFETY GLASSES!
 
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