EDM for moulds?

[dubber123]

Talking to a guy at the range today, and he said he has easy access to an EDM machine, and is very interested in trying to make some boolit moulds with it. I have a couple I will offer up for him to practice on.

It is supposed to be a very quick and accurate method of machining, and he was quoting roundness to within .0001". Anybody have any thoughts?

[454PB]

Sounds like the EDM would be great for making a cherry, but I don't know if it could be used to cut the mould cavities. I think you'd have trouble controlling the depth of machining in the cavities.

[dubber123]

I'll have to see, this guy sounds pretty confident in his abilities. I told him you can buy mould blanks, but didn't see why you couldn't use an existing mould to go to a larger caliber.

He said an uncut blank wouldn't even be a problem as he can do plunging cuts to a specified diameter, then cut the detail from there.

He has a computer scanner that he says will copy an existing boolit, and that can be programmed into the machine as well if I just want to copy an existing design. It sounds great, but I'll wait to see what his results are.

[HeavyMetal]

EDM could be just the ticket for mold making!

I've seen EDM in use and know thats how the Mag Na Port is done!

As suggested the skill of the poerator is everything in this case!

Keep us posted!

[johnch]

I would think
Pre drilling a hole to slightly undersized and shallow would speed the process up considerabley

John

[dubber123]

I would think
Pre drilling a hole to slightly undersized and shallow would speed the process up considerabley

John

John, this is a suggestion I made to him, and he agreed totally. This is one reason I am going to have him practice on a few of my less than perfect moulds. The blocks are already fitted, and have a pre-drilled hole to start from. I have high hopes for this project, it would sure beat waiting for a custom mould.

[carpetman]

I think EDM would be the way to go to get a precise mold. I just cant see any other method being better. BTW what is EDM--I never heard of it.

[hornsurgeon]

there are a couple of custom barrel/rifle makers that use edm to cut their chamber, no reamers used.

[45nut]

Actually, there is only one custom barrel maker using EDM for chambering, the patent holder, On Target Technology. OTTLLC.com His name is Mike Sirois and his background was tool and die and metal injection molds to my knowledge. I have not owned anything more accurate than a OTT bbl. He generally stays with TC bbls but has recently branched out to bolt guns and even AR barrels.

Here is a pic with 2 dummy rounds I made up with the dies I had on hand for 458WM and 50 AK, he measured those and then cut the carbon EDM cutter to precisely match. Imagine a chamber that precisely matches your dies and not a reamer that can be thousandths either way.

http://img.photobucket.com/albums/1003/45nut/100_1162.jpg


Mike is a very talented and inventive type that has done consulting work for Henry Arms as well. I will see if I can get him to add some info to this thread.

[HeavyMetal]

Carpetman:
EDM stands for: Electric Discharge Machine. The idea is to shape a piece of carbon to the exact diamension of the part or hole wanted. Then when everything is "chucked" up and stable a current is run through the carbon to the metal, shaping the metal to a mirror image of the carbon "bit".

This is how Mag na Port got started and the process leaves no burrs or dings in the finished part.

Please be aware that I am strictly an observer in this process so my explaination my not be completely accurate but it is the basic idea behind EDM!

[45nut]

Correct ,, and OTT also cuts brakes using EDM....

http://img.photobucket.com/albums/1003/45nut/SRH/100_0377.jpg

http://img.photobucket.com/albums/1003/45nut/SRH/100_0378.jpg

[bobk]

Wow! How about having someone with this capability do a chamber AND the dies for it? Can't get any better than that. Design your own wildcat, maybe at an affordable price.
Bob K

[leftiye]

If you wanted lube grooves, you'd still have to have a double acting self centering vise to close the mold halves on the carbon "shape". It would have to close by increments as the EDM removed metal. It would also leave a frosted surface that would either be lapped out, or make frosted surface boolits. Things would be greatly speeded up by boring a hole about the size of the minor diameter of the lube grooves, and approximating the nose profile. Some of the best EDMs use a bath and do the cutting under the surface, I don't know what the liquid used is.

[JIMinPHX]

EDM comes in two flavors, wire & carbon electrode. If the guy’s machine can plunge, then it’s the carbon electrode type. EDM is the preferred method for cutting into very hard metals & doing some types of complex shapes. There can be finish problems with an EDM cut. Aerospace specs that I used to work to required that any EDM surface be later ground to a minimum of .010” depth to assure proper surface finish. EDM has it’s place in the part making world, but it is not the answer to every question. It is slow & expensive.

[Red River Rick]

Copper is also used for electrodes in Ram Type EDM machines. As JIMinPHX mentioned, EDM's have their place and making a bullet mould is not one of them. There is the problem of overburn, the cavity ends up being larger than the electrode. So unless you know exactly how much smaller to make the electrode, you'll have a oversize cavity. Finish is the sh*ts as well.

RRR

[dubber123]

Well, it doesn't sound so good after all. I have a couple moulds I can donate to see how it works, hey maybe he will surprise me. My dreams of an on demand custom mould maker looks a little bleak now though.

[leftiye]

Dubber,
Hey, It can be done. If the guy wants to put the effort into it, why not? As someone just said though plunge cut, and wire feed are the types of EDM. To get lube grooves though, the vise will have to do the plunging. Surface could be lapped with a bullet, or a shaped lap if the mold were cut a little small. Easiest way yet to make molds is the CNC lathe used after the shaped drill prep. (Mountail Molds approach)

[OTT]

Thanks Ken,

Conventional EDM can be used to create the mold cavities. With the machinery available today the surface finish requirements can be met. To achieve the lube grooves and profile in one setup, the machine would need to have orbiting capabilities. Overburn is present in all applications of EDM, and is planned for with the proper electrode material for given material to be cut. A high grade of graphite will give great definition and maintain a less than 1% of wear. An operation to remove as much material possible greatly reduces the machine time. But the machine time is still longer than the way the split cavity molds are cut today. EDM is a more expensive route to these for manufacturing. CNC EDM will make the orbiting much easier than the orbiting heads of the past, wish mine was up and running, LOL. The penetration from recast is under a .001 as far as the shell goes. Carbide can also be cut, but that is a much different and timely beast, where amperage in the gap must be kept low as to prevent any potential cracks, so I can understand the safety factor with Aerospace type components.

Thanks again Ken,
Mike

[dubber123]

Thanks Ken,

Conventional EDM can be used to create the mold cavities. With the machinery available today the surface finish requirements can be met. To achieve the lube grooves and profile in one setup, the machine would need to have orbiting capabilities. Overburn is present in all applications of EDM, and is planned for with the proper electrode material for given material to be cut. A high grade of graphite will give great definition and maintain a less than 1% of wear. An operation to remove as much material possible greatly reduces the machine time. But the machine time is still longer than the way the split cavity molds are cut today. EDM is a more expensive route to these for manufacturing. CNC EDM will make the orbiting much easier than the orbiting heads of the past, wish mine was up and running, LOL. The penetration from recast is under a .001 as far as the shell goes. Carbide can also be cut, but that is a much different and timely beast, where amperage in the gap must be kept low as to prevent any potential cracks, so I can understand the safety factor with Aerospace type components.

Thanks again Ken,
Mike

Thanks for the additional info, this fellow did specify graphite as the material he would be using. I believe the equiptment he has acess to does orbit, as he never mentioned having to close the blocks. It sounded like he would bore a slightly undersize hole, and the EDM would do all the detail work, lube grooves, GC shank, etc.

[leftiye]

I don't see the "EDM" surface to be a negative thing if left in the cavities, especially if you wanted to MDS coat them (the boolits).

[BAGTIC]

EDM is used to rifle the USAF's 25mm cannon barrels.

[dubber123]

Well, the guy has one of my unused 2-cavity Lyman moulds, and a sketch of the .45 cal WFN plain base boolit I want. I am having him cut the cavities at .454", looking for a .452-.453" boolit.

He says he can program the machine to make light final cuts, and assures me the internal finish will be good. His machine can do plunge cuts and orbit, so there is no need to close the mould over the tooling. It will be interesting.

[hornetguy]

I would think that EDM would be useful mainly for really odd shaped boolits, something that it would be difficult to "turn".
I've seen toolmakers do some really nice threading, and other features using edm, but I don't know if they had to polish out the finished product or not.

I know that some edms use a dielectric fluid to submerge the work in, and the one we have here at work (wire edm) uses de-ionized water as the fluid.

I'm interested in hearing and seeing the results....

[dubber123]

I'm pretty interested too, he says the finish will be nicer than expected, so hopefully I won't have to lap it. This will be great if it works, as I have run into quite a few new old stock Lymans, and several of them have a factory mis alignment, so I won't use them. These could be re cut to whatever I want.

I have a new 4 cavity Lyman I got cheap that will become a 420 grain WFN plain base for the .475 Linebaugh if this really works. I'm excited.

[dubber123]

Well, it's done, I hope I can get some pics on, it's pretty nice! I took a guess at the actual cavity diameter, and it BARELY makes my final spec when cast, purely my fault, boolits shrink more than I thought.

He says he learned alot on this one, and future ones will be better and quicker. This one casts and drops easily, and is cut right to specs. I am very pleased with his work.

[Nueces]

Very cool, Dubber. I look forward to the photos. Y'all's work has great potential, thanks for sharing your results.

Mark

[leftiye]

If that guy has an interest in making more molds let us know.

[Blammer]

just curious, what does the EDM equipment cost?

[dubber123]

just curious, what does the EDM equipment cost?

I'm not sure to tell you the truth, but I think this one is around 1 million or so. I will ask next time I see him.

[badgeredd]

Sounds to me like your source has access to a CNC EDM that is able to orbit out in a sphereical mode, by this I mean a circular orbit. Like has been already said, they are capable of a pretty fine finish. One might be better served to cut (EDM) a couple thousanths small on the diameter and then lap the surface like in "LEMENTING." Really I see no reason it shouldn't work, especially if your source is going to be doing it for a small price.

[badgeredd]

For those of you that would like to know more about EDM, here is a link to an AMERICAN manufacturer of the equipment.

http://www.charmillesus.com/

[dubber123]

Sounds to me like your source has access to a CNC EDM that is able to orbit out in a sphereical mode, by this I mean a circular orbit. Like has been already said, they are capable of a pretty fine finish. One might be better served to cut (EDM) a couple thousanths small on the diameter and then lap the surface like in "LEMENTING." Really I see no reason it shouldn't work, especially if your source is going to be doing it for a small price.

I did lap this one, but not because the finish was too rough, it just cast a tiny bit smaller than ideal. By my measurements, I opened it maybe 1/2 thousdandths, but it did make a noticeable difference in the boolits release. It occasionally took a tap or two at first, but rarely does after lapping. I spent maybe 5 mins total time lapping both cavities, so you can tell I didn't do much.

[dubber123]

Not the best pics, but here it is: http://i254.photobucket.com/albums/hh83/dubber123/IMG_3027.jpg

The mould #'s don't show, but this was a 115 gr. .30 cal mould. It is now a .452" 275 gr mould.

[jhrosier]

Dubber,
the cavities appear to have a very nice finish.
Perhaps thos method works better than we expected.
The remaining question is about cost.
A couple of hours of setup and machine time might make a custom mould a better deal.
Does your contact intend to offer this service?

Jack

[dubber123]

Jack, it would be very cost prohibitive. He used Tungsten Copper for the probe material, and I think he said it was something like $40/square inch. He wouldn't even tell me how long it took.

The big plus to it is the blocks are clamped tight when machined, and the cavities are super round. He told me what the out of round tolerance is, and it's pretty much non-existant. I couldn't measure any.

[JIMinPHX]

just curious, what does the EDM equipment cost?

The one that I worked on was a carbon (graphite) electrode plunge type with an oil bath. It was about 15 years old when we got it & cost around $50k used.