Enlarging a small collet, any suggestions?

Strouty · Mar 23, 2015

I just bought an imported die grinder, it has a 6mm collet and all the standard bits that I have are ¼". I have played around with it and the ¼" collet will fit into the end and tighten down on the bits. It also seems to center itself well and be stable. The main trouble is that it gets really wedged in and is a pain to remove. I figure if I can bore out the 6mm collet to fit the larger ¼" size that would be the best solution. I could also rethread the nut from the US version die grinder and try that. I was looking for opinions and advice. Here are some pictures. The ¼" collet is on the left.

larry_g · Mar 23, 2015

If it were me I would spend some time trying to find the proper collet for your spindle. What is going to happen if you try to put that tapered collet into the spindle for the machine is that you will loose the ability of the collet bore to be inline with the spindle centerline. have you checked withthe manufacture of the grinder?

lg
no neat sig line

Strouty · Mar 23, 2015

They only make 6mm in this model, it was not intended for the US market. I went around that and purchased from another country.

I figure I can buy the 6 mm shank burrs, but I would rather make it work with my current ones. Also if I have to buy one local it would be ¼" as well.

404 · Mar 23, 2015

1/4 inch drill rod and lapping compound. Hold the drill rod in another drill to turn it, Put the collet alone on the drill rod and find some way to hold it that is even force all around. Piece of thick hose around the collet and wrap tight with many layers of thread maybe.

Strouty · Mar 23, 2015

It is only 0.0137795 small, I can physically get the bit in the spring end of the collet, but not very far.

Another member is getting one of these as well, so we will both be trying to solve the problem.

Strouty · Mar 23, 2015

I dug out another die grinder, this one has a much similar collet, but still no dice.

Mcmaster offers a set, but no details on dimensions.

Machinery handbook shows nothing near this size as a standard.

CNGsaves · Mar 23, 2015

Why not disclose what BRAND as maybe folks across the pond may have already "Americanized" their metric instead to inch ??

Strouty · Mar 23, 2015

I think I have found a winner!

http://www.ebay.com/itm/Bosch-GGS27...-4-Collet-2608570048-/181152300194?rmvSB=true

Strouty · Mar 23, 2015

CNGsaves said:
Why not disclose what BRAND as maybe folks across the pond may have already "Americanized" their metric instead to inch ??

Sorry, I just assumed you all new that IGN and I had begged people from Australia to send us a couple.

Strouty · Mar 23, 2015

The only issue I can see assuming the collet from bosch is similar to the one in my porter cable, is that the diameter of the collet is a little bit too small to fit tight on the inside of the head/spindle or whatever you want to call it. I don't know if that will be catastrophic or if it will be fine. It would allow the burr to tilt slightly off center when you apply any side pressure and that would be most of the time using it.

kerrynzl · Mar 23, 2015

Why don't you try re-setting all the slots by driving a 1/4" shaft down it and then heating the ends.

Being tapered it will just sit out a bit more.

Strouty · Mar 23, 2015

kerrynzl said:
Why don't you try re-setting all the slots by driving a 1/4" shaft down it and then heating the ends.

Being tapered it will just sit out a bit more.

Maybe I could do that, then drill the end out to match? That way I have only made one area out of round versus the entire collet.

No matter what, I need to get a spare collet so I can experiment.

Strouty · Mar 23, 2015

Wow, I feel dumb, I just found the right part. I think I was searching with the wrong part number before. I guess actually having the tool in hand can be a benefit to some knuckleheads.

http://www.toolspareparts.com.au/shop_image/category/HD28SGA.PDF

iajonesy · Mar 23, 2015

I was going to say a Dremel tool with a small stone could do the trick,but the replacement collet is much better.

Mike

Kevin54 · Mar 23, 2015

Strouty......normally opening up a collet take a diamond grinding stone as a collet is pretty damn tough. Carbide may do it, but you will most likely ruin the carbide for use on anything else.

Can you make something to hold the collet centered in the lathe? If so, you can use a carbide 3/16" burr. You can work it in and out a little at a time until you get the size you need. If you have a good brand of carbide burr that has a little length, you can use that, but rotate it when you get close to your final sizing.

OR........make up a piece with a through hole that will hold the collet. Go to your local NAPA if they have a machine shop and a Sunnen Hone, and have the collet honed out. It may take them 15-30 minutes, and may cost a couple of dollars, but SOMEONE with a hone should be able to hook you up. And it shouldn't take too long to make a piece to hold the collet. It could even be made out of a piece of aluminum. Just make it long enough that whoever is running the hone can hang onto it, and if you can, knurl the handle

buildyourown · Mar 24, 2015

The collet on the left is a standard AF collet. The other one I dont recognize.
Trying to machine them is a waste of time. They are hard and they need to be really concentric. I have reworked them with a wire EDM, but that is not affordable unless you have one sitting in your shop.

Kevin54 · Mar 24, 2015

buildyourown said:
The collet on the left is a standard AF collet. The other one I dont recognize.
Trying to machine them is a waste of time. They are hard and they need to be really concentric. I have reworked them with a wire EDM, but that is not affordable unless you have one sitting in your shop.

If you have a good tooholder, you can make them concentric. That is the easy part. Trying to wire EDM something like .013 out of a collet is not cost effective, and the setup better be dead nuts on. Honing will follow the hole that is already there, but the collet has to be under slight compression. If honing won't keep it concentric, then there are a shitload of cars out there that have pistons flopping around in a non-concentric hole :lol:

IIRC, Strouty has the machines to do it, but just may not have the right tooling.

And Strouty.......if you need it opened up, but don't have the equipment to do it, send it to me and I'll do it for you.

Strouty · Mar 24, 2015

Thanks Kevin, IGN has an idea as well, he has bought the same tool. I am going to see if I can get the actual collet, this is not a tool I need right this minute. Uart is looking for the actual part in Australia, I will be honest, I have not contacted milwuakee directly. I think I should try that before I hound everyone else. I honestly had not seen that they offer the ¼" collet for the tool until yesterday.

Ign · Mar 24, 2015

I found a US-made solid carbide reamer on eBay for under $20....I'm not opposed to trying this in my 5C collet holder which is concentric enough IMO (assuming my tail stock is not offset LOL). I realize it's probably one-time use on the reamer.

racingtadpole · Mar 24, 2015

If you guys aren't in a rush, I have a Milwaukee agent not far from home, pm me if you want a hand sourcing from Aus.

ModelTBrian · Mar 24, 2015

Graphite, little pencil lead on sandpaper wipe it on. Easy n always available.

Ign · Mar 24, 2015

ModelTBrian said:
Graphite, little pencil lead on sandpaper wipe it on. Easy n always available.

To take out 14 thou....I dunno. That's a lot.

brianh · Mar 25, 2015

I have a bunch of cheap die grinders they came with 6mm collets I chucked them in the lathe and ran a 1/4 end mill in it worked fine for all five.

gtermini · Mar 25, 2015

Ign said:
To take out 14 thou....I dunno. That's a lot.

This guy gets it. You don't realize how big a thou is until you try to take it off something hard with emery.

Greyson

Strouty · Mar 29, 2015

brianh said:
I have a bunch of cheap die grinders they came with 6mm collets I chucked them in the lathe and ran a 1/4 end mill in it worked fine for all five.

I am tempted to just do this. My equipment is all tucked into a corner waiting to be setup, so I can't just do it. I am not in a rush, so I may order one from Australia anyways.

Ign · Mar 30, 2015

I got to looking at this today next to my M28 4.5" angle grinder which also just happened to be on the bench. They used the exact same body (and thus motor I'd bet) between the two tools. The only difference on the die grinder is the speed control, which they would have been wise to put on the angle grinder too for sanding discs or flap wheels. Why the hell they never brought the die grinder to the US market I'll never understand.

More on topic, haven't had time to do anything with the collet.

Strouty · Mar 30, 2015

Glad you got it! I wonder if we could switch them so you have multiple speeds for the grinder. My future may hold more packages from Australia.

Ign · Apr 26, 2015

I chucked up the collet today. The major OD at the bottom of the collet is .412. I was able to get it in a 13/32 5C barely. I threw a 1/4" carbide 4 flute end mill from SGS in the tailstock and went for it at 329 rpm (no logical reason for spindle speed, use whatever you want). Oh I did first wrap the collet (poorly) in electrical tape thinking this might reduce spreading of the fingers -- no idea if it helped. I used cutting oil & didn't get the impression the collet put up much of a fight.

Regardless, 1/4" shank tooling now fits, and it's very snug. Actually annoyingly snug, I'd prefer another thou out of the collet, but it works and I'm leaving it.

Crappy iPhone pic attached

Strouty · Apr 26, 2015

Nice, now all I need to do is hook up my lathe and figure out how to use it. Mind if I mail you mine and have you open her up?

Ign · Apr 26, 2015

I also took the time to engrave the necessary wrench sizes on the flats of the spindle & nut (15 and 17mm). The bur is an Atrax, 1/4" shank. (Sorry, can only attach one pic per post from my phone).

edit: yeah Strouty, send me yours. I owe you that and more for all your legwork importing!

Strouty · May 29, 2015

The collet works great, I played around with it a bit the other day. I can't wait to give it a good test. Thanks again for the help!

Enlarging a small collet, any suggestions?

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