Dimple Dies....which ones

[wibaja]

I got a cheap 3/4" off ebay for 20 bucks shipped and did my shock towers with them. I think they worked nice for the price and if you are not using them for production I think they will be fine.

[DesertGuy]

I bought the whiz-bang set some time ago. In my experience, when just "dimpling" for effect, typical sizes used were/are 1.00"-1.75". The smaller/larger sizes were used for specific purposes (and sparingly), such as: smaller size on a gas pedal or passenger foot rest.

I use a 20 ton press to dimple the material, a press is needed for the bigger stuff. The most that I will dimple is .128" 4130, that will take upwards of 15 tons to get a nice effect.

Even now having the lathe, I still dont see it being cost effective to make your own, unless you needed some one-off, oddball size... time is money also.

[ntsqd]

MISF makes his own from the races out of retired bearings. Welds a plug into both made by running a hole saw thru some 3/8"-1/2" plate, and then opens up the pilot hole for a draw bolt of appropriate size.

[Ol'fogasaurus]

I blew almost $500.00 on my set at kartek, and then found tthis guy... Fabbed his own dimple die set using different sized trailer balls and bearing races... would probably go this route if I were to do it all over again

I have been quite amused by the ingenious simplicity of a couple of the methods of creating dimples (ingenuity is not dead, that is for sure) but I think I should say something about a couple of the methods. The trailer ball/bearing race method (STOICH, this is not meant as a criticism to you or anyone else, I just picked this one as I was intrigued by the over the simplicity of it which could cause others to try it) while cute has some aspects to it that bother me (remember, Isaid that a lot of things bother me ).

Dimpling or (stiffening) flanged holes (two different objects) are usually considered structural things (there are other uses for them too which are not structural) you can do to stiffen flat stock but doing it wrong can off-set the good of them. There is a material thickness limit to each of the two methods; dimpling is usually used in material over a certain thickness and flanging of a hole is used on material thinner than that certain level of thickness. The two main reasons between the two methods are minimum bend radius and stretching of the material during forming. (removed sentence) You can also add to this: minimum spacing (usually 2 ½ D) between holes and the pattern of holes. You can also add a stiffening flange ovals or larger slot shaped holes. Dimpling of thin material us usually relegated to multiple layers of material and is usually considered for recessed/flush faced fasteners as it does not really add much strength to the material as it is too easy to overcome the bending with small loads. There is another type of stiffening hole for this (usually a “Zee” shaped flange)

The using a die set that is unguided (trailer ball and wheel bearing for example) can cause the dimple to be off-set causing the flat stock to behave different that what the idea of the design was to be. If you notice, the dimpling/flanging die sets have a matching guide setup to align the dimple of flanged hole to the center of the (lightening?) hole and it also causes the dimpling/flanging to be perpendicular to the stock being bent; that is one thing. The other thing is that the minimum radius of the material in the bend probably not being kept. This is because a bearing race itself has an almost nebulous/minimal radius in it and this radius can be transferred to the flat stock causing damage to both the inner radius of the bend (remember, the inner radius of a bend is compacting as it has no place do go) and the outer radius of the bend (to over stretch as it has to accommodate the longer distance it has to cover) to thin out and maybe start to tear.; it can also cause the material/grain of the stock to compact and weaken at the bend.

In most cases, the chord shaped bent flange of the dimple probably won’t make a difference if the material is thick enough but in thin stock it could. As kids, we all took a piece of metal and bent it back and forth until if work hardened and fractured, If you took a piece of flat stock and made a bent flange on it then tried to bend and break it the closer the flange was to 90*s the harder it would be to bend. The flange would usually try to straighten out until you had enough force to get it to start the bending process. If you bent the flange to an angle more than 90*, the flange will have a tendency to start to bend in on itself and then the bending process could begin albeit the edge of the part would resist a bit more because you are now bending four surfaces, not two… plus the radius.

Anyway, I am sure that again, it is more than you wanted.

Off to the ocean and unless it rains (which it is supposed to) I hope to be kite flying again after many years of not being able to.

Lee

Edited to remove the sentence about not getting into a discussion on this. It sounded a little arrogant to me and I hope I am not like that.

Lee

[Ol'fogasaurus]

Edited previous post to remove a sentence that should not have been added.

Sorry!

Lee