Material for making a stamping die

[Chuck Keysor]

Hello, Chuck here again asking to tap into the wisdom of the ages.

Background: I would like to make a large detailed die for impressing images of an owl (I posted that image a few months ago) into clay. I have a kiln and am interested in ceramics. I don't want to cut clay, (wet, air dried or bisque fired), so making a die to press this image into the clay, to make lots of tiles makes sense. But I also want to use this same die to experiment with pressing the heated die into wax and various soft plastics.

In essence I want to make a die, so that I can stamp what will in the end result, look like a "v-carving". I want to make two sizes of tiles: One that is 6" by 6" and the other 12" by 12".

In the finished 12" x 12" ceramic tile, the deepest lines are .1" and are .06" wide. But most lines are about .015" wide and maybe .020"deep. Some lines are The closest lines are about .030" apart. I have carved this image in wood and plastic successfully using my 60 degree CMT "laser" bit, but it takes about 3 hours.

It seems as though aluminum and brass would be logical choices to make the die. The die will have many fine fins, that I would assume I would cut with my CMT laser bit.

Questions: Would either brass or aluminum have any obvious advantages? I know there are many grades of aluminum, and I assume many types of brass. So can someone in addition to directing me to use either brass or aluminum, also tell me what type of brass or aluminum should be used? And how thick should the back/unmachined base of my die be?

Lastly, are there retail on-line sources for aluminum and brass that sell, small amounts, such as 14" square and possibly only 1/4 or 3/8" thick? Or will I expect to buy a bigger piece? If so, what are the standard sizes?

Thank you for any suggestions you can offer. Chuck

[harold_weber]

My dad was a tool and die maker, the dies he worked on were made from hardened tool steel and literally made millions of parts.

For stamping clay you will get some abrasive wear. See the following link to folks who make logo stamps for concrete. They will make you one from aluminum,but they say for longer life, they recommend bronze.

http://www.behrendsgroup.com/business-signs/concrete-stamps/

[Chuck Keysor]

Thanks Harold. But I do want to make this die myself using my Shopbot.

Last night I talked to a friend of mine who is a mechanical engineer. He recommended Brass - 360 for durability, easy machinability, but high cost. Or he said for lower cost and less durability, I could use Aluminum T6511 or T6. He also said I could easy purchase these materials from McMaster Carr.

However, my friend is not a machinist, and had no information to offer in regards to cutting strategies/speeds/feeds/number of passes/bits/cooling. Any suggestions in these areas would be appreciated. Would my CMT "Laser" 60 degree V bit be a good choice as the cutter?

Thanks, Chuck

[knight_toolworks]

I would use hdpe. I have used it for tile molds for a big company. the only issue with using something that does not adsorb moisture is your clay goign to stick?

[Chuck Keysor]

Hello cloud brain of the Shopbot universe: I snapped my first bit! Any suggestions will be appreciated!

Details: To make a test stamping die for my owl, I used a piece of .045" brass (from an old door "kick plate"). Using V-carving, the first tool path was a pocketing path, limited in depth to .039". I used a solid carbide straight two blade Freud 1/4" bit, running at 10,000rpm, stepover of .1", feed rate 2 inches per second, plunge rate .5 inches per second. I used an offset machining strategy, and just now as I am typing, I see that I was set for "climb" mode. (Yikes, I did not realize that before this moment and would not have used that had I been paying attention!)

As soon as I started to cut, it did not sound good, but I had never cut brass, or any metal before. Then I could smell something getting hot.... After cutting for only maybe 5 minutes, the bit snapped off.

The first two pictures show my brass, with a detail on an over-heated part. The third picture shows the remaining 1/4 flat end-mills (??) that I have.

Did my brass over heat, and the bit snap because I was in "climb" mode? :confused: Or do my settings suggest some other problem?

Also, of the pictured 1/4" bits I have on hand, which would be best for doing the pocket pass on my brass plate????

Thanks for any advice you can offer, Chuck

PS: The middle bit does not look broken, but unlike the other 4 bits which have two wings/cutting teeth at the end of the bit, this one only has one wing/cutting tooth. That doesn't make any sense to me. Is this on purpose, or is the bit broken?

[Chuck Keysor]

:( After looking at some old posts, I have a new sinking feeling that my bit snapped because I was running at 2inches per second. I am so used to running at that speed for V-carving...... I now think I should have been running at 2inches per minute.............. Duh.........

Comments please, or I won't be able to sleep as I will be imagining all the things I did wrong to snap this bit. Thanks, Chuck

[myxpykalix]

Chuck,
I have no experience cutting metal but only ask questions in case you haven't thought of this.

Because clay would be soft and these lines so close together do you think you will have problems when you try to stamp your design because of such a shallow depth and close lines?

How will you control the depth of stamping so as not to include the cut of the background?:confused:

[bob_reda]

Since you are using clay, which I gather is relatively soft. I would try making a die with a very hard wood, using the technque that is shown on vectric about easy inlays. You could use the techique that makes the male inlay part with a v bit that when pressed into the clay will give the v carve appearance. Since it is wood you would probably have to make some at an a point down the road but that would be true with any die you make.

Bob

[jerry_stanek]

Solid surface like corian may be a better choice

[bob_reda]

Jerry, good choice, never thought of that.

Bob

[Chuck Keysor]

Thanks all for your replies. Since my first post, some aspects of my inquiry have changed.

Originally my primary intention was to stamp clay. That is still of great interest to me, as I am into clay, and know that it is possible for it to hold great detail. But it also moves a lot in the firing process, which can sometimes be wonderful, but can also be disaster.

But after my first post on this, I heated a quarter with a simple heat gun, set it on a piece of my vinyl, and tapped it with a hammer. It left a perfect impression of the coin. That made me put my immediate focus on using brass, or aluminum, which I could then use for either vinyl or clay. So, that is why I haven't gotten into the other materials suggested so far. (Corian/solid surfacing will be of great value to me when I am not trying to hot stamp plastic, as wood of every sort I have worked with is very problematic for staying flat, and or not crumbling away with this huge level of detail.)

And, I happened to have in my stash, over 30 old door kick plates that I bought for a total of maybe $3 or $4 for the entire lot at a salvage auction 25 years ago! These are only .045" thick, and 8" tall, and around 30 or more inches long. So I can experiment a bunch, and after I dial things in, I can buy a chunk of brass that is 12" x 12" and 3/8" thick. (I have envisioned a jig to hold my die in position relative to the vinyl tiles.)

So, while I have lots of brass to practice on, I don't have lots of bits to snap! Any advice on machining the brass will be appreciated.

Thanks again, Chuck

[myxpykalix]

And, I happened to have in my stash, over 30 old door kick plates that I bought for a total of maybe $3 or $4 for the entire lot at a salvage auction 25 years ago!

and Chuck...can you say "Hoarder"!!!:D The only difference between you and me is that you can find what you have been saving for 25 years, i have stuff, just can't find it when i want it!:eek:

[Brady Watson]

Chuck,
Don't give up on the brass or aluminum. You just need the right geometry bit - such as an upcut single spiral-O or a 2-flute HSS end mill made for machining AL and non-ferrous metals. The bit you show in your pic in the center is the correct bit for machining non-ferrous metals with a router. The others have a 'fishtail' tip that is made for wood cutting & they are not truly center cutting.

Give it a try with the single flute spiral-O - start with an RPM 13,000-15,000, MS,1,0.5 and keep your stepdown distance at 0.02" per pass. If doing a pocket/area clear, reduce your stepover distance to 15-20% instead of the 40% that is appropriate for wood and softer materials. Hold down with metals can be tricky, but it is VERY important that you eliminate material vibration. Try to avoid using screws because they distort the material and cause it to bubble up and down in ways that are not apparent.

Hope that helps.
-B

[Chuck Keysor]

Hello Jack and Brady:

Jack: Sorry for my slow reply. After seeing your recent post with your stack of wood, I know you definitely have a bigger stash than I do! But, I also had something else in my stash that I wanted to get, photograph and then post. It took me so long to get back to you, not because I had a hard time finding these items, as I knew right where they were. But I had thought I would clean them up some, so it would be easier to see what I had to show you. But ultimately, I realized I'd never get around to cleaning these up for you, so they are hard to study. As antiques, these were trashed (as you see them) when I bought them, maybe 20 years ago. But I had seen similar framed plaques made of brass over the years and thought it would be cool to be able to make some someday. Can you guess why I bought all those brass kick plates all those years ago???? I can't tell how these plaques were made. The back sides are smooth, so I don't think these were stamped. But they don't have real sharp lines like machining would have produced. I wonder if they were photo-chemically etched.

Brady, thanks again for your good help. I ordered a 1/8" collet from SB today, but still haven't gotten into checking out the bit sources you recommended. (I'm too tied up painting my house....) However, I did go back to use Google to search through the Shopbot forum posts looking for information on machining brass. I was quite suprised at how little useful information had actually been posted. But your engine machined brass was certainly the most elaborate brass work of any post. However, I did see some impressive brass that had been machined with a diamond drag bit. (Even though that won't help with my immediate project, I will certainly look into that in the future. When I took a print making class a few years ago, one way we made printing plates was to scribe onto copper by hand. CNC would be lots more fun!)

Thanks again, Chuck