Using stamps for numbers and lettering.

[MrMetal]

Good idea for spacing the letters. Getting uniform indents is a challenge. Uniform hammer blows is one thing but another aspect is that different letters require different blows. For example the letter "I" requires less force than the letter "M". Most of my stamping is in steel which requires a heavy strike. I use a heavy hammer to assure a good imprint with one strike. I hold the letter stamp in a pair of vise grips which prevents having the stamp fly off to a well hidden place in the event of an uneven strike. I've been thinking about a simple jig that would hold the stamps perfectly perpendicular to the work and also some spacers that would help get uniform spacing. After stamping one letter, replace the stamp with a short spacer of the same dimensions so that the next letter can be placed against it. Any ideas?

[tonyfoale]

I've been thinking about a simple jig that would hold the stamps perfectly perpendicular to the work and also some spacers that would help get uniform spacing. After stamping one letter, replace the stamp with a short spacer of the same dimensions so that the next letter can be placed against it. Any ideas?

http://www.homemadetools.net/forum/m...882#post105674

[Thunderbelch]

I made a simple jig that ensures even spacing. It is only really useful when you have a large enough flat surface to clamp it to. Even pressure was obtained by dropping a weight down a tube onto the punch. But as already mentioned, different characters need different striking pressures...

Tony - I much prefer the design you just posted!

[DIYer]

Thanks Thunderbelch! We've added your Stamping Tool to our Metalworking category,
as well as to your builder page: Thunderbelch's Homemade Tools. Your receipt:

Stamping Tool by Thunderbelch

tags: stamp

[rjitreeman0909]

Will take a little surface grinder or belt sander time but letter stamps could have left and right surfaces ground equally on letters such as an I to achieve the correct spacing. Would then require some rethinking of equally spaced guide holes if a secondary punch plate is part of the fixture design.

[Saltfever]

This is an old thread that just appeared in today's email. But it is an age old problem that every fabricator has been faced with. Most don't care if working for wages, but people in their own shop seem to take it personal! As indicated the problem is the unequal total line length that makes up all characters of the alphabet. I think the solution is probably something like Tony mentioned in his post #6 . However, quantifying the various weights would be the breakthrough. After that it is just a simple matter of sizing springs, fall distance, mass, or friction, of the application device you invent. So I was just playing and visually separated the alphabet into what I think might fall into about 6 weight groups. This is just a visual and some of you may think my focus is distorted or visually impaired! I did a serious search trying to find the total line length of each character but no joy. There is probably something in the art community, or those that design fonts for a living, but I found zero on the subject. A CAD system could do a much better job.

B E V L S T
M W X
I J
A H K N F Y Z
G P R
C D O Q U

There are 6 "weight" groups loosely based on the number of segments in the character or how I interpreted the amount of pressure was needed. Certainly you will think I messed up. LOL For instance the "I" and "J" are in the same group but depending on the dogleg of the "J" it might also have to stand alone. The idea would be test each group on a sample piece to set the correct pressure. I don't think each character in a group needs to be tested. Picking one character from each group to set that groups "pressure ratio" should get good results.

[delalio]

Hey Gents,

Very interesting thread. And something I've struggled with a bit in the past too.

Continuing on from the work of @Saltfever , @MrMetal , etc, I knocked up this.

It's based on the number of LEDs required for a given letter for a typical LCD digital display.


0.25 - .
1 -
2 - I
3 - J, L, T, Y,
4 - C, F, V, Z
5 - A, E, H, K, P, S, U, X
6 - D, G, M, O, R,
7 - B, Q, W
8

Let me know what you gents think. I'm going to have a play over the coming days and see how this works out...

Cheers,

Del

[CanBeDone]

It would not be too difficult to make some form of stamp holder with a vertical extension to hold some form of weighty block at an appropriate height, on a slide. Add a trigger (for example) release and hey presto - even indents every time. A little experimentation prior to building would soon get the mass and height of the block determined.

I have tried that years ago - it produces multiple imprints because punch and hammer rebound. And I have also learned that I cannot suppress rebound even if I build the hammer as deadblow: my stamp, the item to be stamped, and the support upon which the item rests are all elastic, and will cause rebound. Once you look at the physics, you'll see why: dropping a hammer plus stamp of mass m a distance h stores energy
E=m.g.h
in it (g=9.81m/s is the acceleration of earth). When the stamp then penetrates a distance x, leaving its imprint behind, the (dynamic) force F it exerts is
F=Edx²/dt²
And in this formula all the problems with non-repeatable penetration depth are represented but not visible, since much of what goes into it is hidden: how the item deforms as the stamp starts to penetrate is a function of x, how much it is accelerated downwards due to the force applied to it, the mass and elastic properties of the support it rests on, you name it, all contribute to x, and as a result it muddies up the penetration depth x to make it as good as unpredictable. Since the stamp's downward moving velocity v is
v=dx/dt
it follows that, for repeatable penetration depth, the first derivative of x, the velocity with which the stamp moves downward must be close to zero, and thus the force, dependent upon the second derivative of x with respect to time t, exerted by the stamp on the item must be static in nature, not dynamic. And static forces require a press, not a hammer blow.
How potent a press? I have progressed so far that I can say for a 4mm number stamp I need a force in the vicinity of 5 ton for a decent impression in mild steel, i.e. an arbor press is ruled out as not powerful enough. The next question I need to decide is whether I want to measure and control the force acting on the stamp, using a strain gauge, or do I want to measure and control its travel into the item using a DTI? On that I am currently undecided, what is more robust? and what is more repeatable, to a measuring error of, say, 20 micrometer? After all, my eyes are quite capable of perceiving such a step, and that is the measure I need to apply.

[Saltfever]

Interesting and thanks for clarifying the rebound issue. Obviously, the rebound energy is dictated by the characteristics of the substrate. Stamping lead vs. hardened steel yields different rebound force. It could be by putting friction into the equation you can react the rebound energy. I have often just simply held the stamp between two fingers to lesson rebound. Applying friction may eliminate the need to apply differential force. Applying equal force, but adding variable friction may accomplish two things. It could overcome the rebound energy and also vary the force applied to individual letters. There are many creative ways to apply friction to a stamp. An example could be a pad pressing against the stamp with the friction adjusted by a bolt changing the length of a spring. To add some precision the spring could be calibrated and the bolt pitch would be selected for the appropriate change in length per revolution.