Tooling to make disks?

blindstarJune 6, 2009

I need a couple of hundred chipboard disks in 3.25" and 4.25" diameters. They need to be .1"-.2" thick, but the thickness is not critical as I can glue up thinner ones to get the thickness I need. I would gladly purchase them if I could find a suppler.

I make smaller diameters by using arch punches. I have made up to 2" punches out of drill rod, which work fine, but I donÂt think that approach will scale up to 4.25". I would appreciate any suggestions on how to make tooling to make these disks.

I have a basic machine shop; lathe, tool post grinder, mill, drill press, arbor press, welders, torches, pneumatic press, etc.. I have no aversion to buying more tools, but I would like to limit the expense as much as possible.

Thank you for your help.

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Can you clarify for me:

What are you calling chipboard? That means different things to me.
Your stated thickness is one tenth of an inch,(etc.) not one inch, right?
Is it a plain disc or does it (can it) have a center hole?

    Bookmark   June 7, 2009 at 5:44AM
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alphonse - Thanks for responding. The disks need to be made from a non-corrugated cardboard, most paper companies call this chipboard. Yes, the thickness needs to be about a tenth of an inch. As for the center hole; half of each size need a 5/8" the other half of the batch should be solid. However, a small hole would not be too much of a problem. I usually punch the 5/8" hole with an arch punch. Although, I asked about 3.25" and 4.25" disks, being able to make other sizes up to 9.5" would be a real plus.

I build fireworks. The disks are for the ends of canister shells. The ones with the holes are for the end with the spolette (fuse). There are actually 2 disks on each end of the shell. The shells are reinforced with lots of string then covered with layers of pasted paper. Chipboard is the classic material used for the disks. You need something that is strong, slightly flexible and biodegradable. I could consider other materials, but the R&D is expensive, time consuming and a little dangerous.

Until recently I was able to purchase a variety of sizes of disks, but the suppliers have gone out of business. I am very low production so I cannot afford to have a manufacturer setup to die cut them when the minimum order is 10,000 of each size.

By the way, in another thread you mentioned how much fun OSHA is; the BATF inspects me, think OSHA with side arms.

    Bookmark   June 7, 2009 at 8:37AM
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OK, I know what you're describing. A friend of mine does (or did) something similar, and I've heard some BATF stories.
I have a couple ideas but I'll mull some more and get back to you with consideration to your arsenal.
A further question, how many per hour would you have to produce to beat (or match) your late vendor?

    Bookmark   June 7, 2009 at 11:15AM
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They used to run about $40 per hundred of the 3.25" and $50 for the 4.25". Fabrication speed is not as important as consistency. I am currently cutting them free hand on a band saw, not the most consistent approach. I probably have 4-6 hours in building a shell, which might use 10 disks. I would hate to add more than 15 minutes to that total for making disks. Idealy, I would like to spend no more than half a day every few months making 200 of each size.

Thanks for taking the time to think abut this.

    Bookmark   June 7, 2009 at 9:50PM
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Pooh Bear

What size does the raw material come in?

I have quite a few ideas about how to do this.

This would be a great work at home opportunity for someone like me.
Would you be interested in outsourcing the disks again?

Pooh Bear

    Bookmark   June 8, 2009 at 1:01AM
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The friend I mentioned makes plugs from hot glue and fine sawdust. I have a feeling hide glue would work. They were smaller dia. than yours though. (M80's)
So there's one idea, maybe you could cast the product either as a "billet" or near net. A suitable pipe could be used as mold, with appropriate heating to cure, using your press or the like to compress the mix. Post cure extrusion could be turned true between centers, parted or bandsawn off. Or a very accurate mold could be made to produce one-at-a-time. Multiple molds could be tooled into a plate of (on the low cost end) MDF, that has been epoxy sealed.
More traditional methods would be turning a die to your dim'n.- Sch.40 pipe is close, the cutting end could be hardfaced if you have a way to true (tool post grinder).
Or, trepan a groove into a piece of steel plate, cut some banding material or a length of flat spring steel to use as the edge, attach to your press.
Another way, layout and punch for center holes (pivot)the top sheet in a stack pinned/clamped/glued together. Trammel your router with a suitable carbide bit and spin them out. Probably need downdraft/respirator.

    Bookmark   June 8, 2009 at 3:41AM
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poohbear2767 - The sheets are 36" x 48", however it would be easy to cut them down.

alphonse - Thanks, I will test a couple of your ideas.

    Bookmark   June 8, 2009 at 7:13AM
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poohbear - The answer to your outsourcing question is yes, if you could hit the same or close price point. There is very little profit in manufacturing elaborate fireworks and like everyone else we are competing with imported goods when we put product into a display. A related problem is the volume, there is a VERY limited marked, which is why the suppliers stopped carrying the disks. There are only a handful of people manufacturing these large multi-break shells in this country who are using the traditional methods. Most of the really good stuff is shot in competitions because they are too expensive to be used in shows. Customers would rathter have 10 Chinese shells than one locally built multi-break and unfortunately, in bang for the buck, they are probably right.

    Bookmark   June 8, 2009 at 7:50AM
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Pooh Bear

Here are a couple of ideas I had:

First up is a disk cutter.
It's just a disk with two sharp blades mounted at the proper distance.
Use a drill press to sit and cut disks out.
The blades would be like those little blades in a pencil sharpener.

Next up is a press die. It's like a pipe with the inside
diameter you want and the outside cutting edge is sharpened.
It could be pressed thru a stack of material to make several at once.
The cutting edge of the die would have to lie completely in
one plane and be perpendicular to the long axis.
Making it and sharpening it would require some machinists work.
Just place it on the material and whack it with a hammer.
Or to make several disks at once, place it on a stack of material
and use a hydraulic bottle jack to press it thru the material.

Or if you wanted really simple (but slow) mount a piece of
wood on a potters wheel and put your material on that.
Start it spinning and use an Exacto knife to cut disks.

There are a number of different ways to do this
but some them would require a bit of expenditure to set up.

For me the cost to make them would depend mostly on the
cost of the raw material. I'm gonna think about this some more.

Pooh Bear

    Bookmark   June 8, 2009 at 10:29AM
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Thanks poohbear.

    Bookmark   June 8, 2009 at 2:39PM
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Pooh Bear

For 36x48 inch sheets you can get 88 of the 4.25 inch disks
out of each sheet and 160 of the 3.25 inch disks out of a sheet.
I can see now why commercial shops don't want the job.
Too much set up time on a stamping press for 2 sheets of material.

Since you have a machine shop at your disposal
you could build a small press to punch out disks one by one.
I could even design it for you. (fun project, no charge).

Any chance you could get the material in rolls that are
just slightly wider than the diameter of each disk.
Or you could use a paper cutter to cut strips out of a sheet.
Then you could just stamp out disks just
like they stamp out sheet metal parts.
This would drop the number of 3.25 inch disks to about 140 per sheet.

If I get a chance later I will draw up a design for a press.

Pooh Bear

    Bookmark   June 11, 2009 at 12:15PM
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Pooh Bear

A few nights ago there was an episode of How It's Made
that showed how sandpaper and sanding disks are made.
Here is a short clip of how one disk is made and
then how they are made production style on a stamping press.

How It's Made - Stamping Disks
Video size is just over 3 megabytes.

The first method uses a cutter like the one I illustrated above.
The guy just places it on the material and whacks it with a mallet.

Pooh Bear

    Bookmark   June 13, 2009 at 2:02PM
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I tried a couple of the fly cutter variations, one with fixed blades and one with rotary cutters. Nether one was very successful. The video got me thinking that punching was the way to go. Since I didn't have any 3 1/4" pipe I machined a punch out of some scrap 4" dia. bar solid stock. I tried it in the small pneumatic press and to my surprise it worked great. 80 psi on a 4" cylinder seems to be about right. However, a hydraulic press is the right tool. I'll cobb something up using the hydraulics from my front-end loader.

Thanks for all the ideas and encouragement.

    Bookmark   June 13, 2009 at 10:18PM
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Machining a punch out of bar seems like it has worked for you.

I have seen adjustable hand operated circle cutters in gasket houses. Maybe google up gasket cutter or gasket circle cutter, etc.
You might find something that will work easier than having to make punches.

    Bookmark   June 21, 2009 at 6:15PM
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sevenecho - Thanks! a good source of ideas.

    Bookmark   June 22, 2009 at 10:05PM
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