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lazlo
01-03-2007, 10:04 PM
I found a nice MT3 floating tap/reamer holder on Ebay, but it uses those rare (and expensive!) Kennametal/Erickson LTC tap collets. John's posts about the advantages of the ER collet system got me thinking about modifying the floating holder to take ER-32 collets. I already have a 5C setup for the headstock, so I'm just looking for a flexible toolholder system for the tailstock, and taking advantage of the floating holder would be slick.

Has anyone seen any articles, either in print or on the web, building an ER collet chuck? I'm basically looking for the internal ER chuck dimensions including the taper and the correct thread pattern.

Tallgrasstools has an ER-32 collet chuck spindle kit here, but you should only need about 3" of tubing stock, so I'd rather just download (or buy) a set of plans.

http://www.tallgrasstools.com/Page.html

http://www.tallgrasstools.com/images/Img7.png

Thanks!

Robert

mbensema
01-04-2007, 09:19 AM
Rego-Fix had an online catalog with all the dimensions you would need, but it looks like they changed the website and I couldn't find it again. If you call them, maybe someone can email it to you.

gzig5
01-04-2007, 10:20 AM
http://shopswarf.orcon.net.nz/colletmill.html

The link goes to a table that will give you some outside dimensions. I think the angles are 8 degrees on the back and 30 on the nose, but don't quote me. I know I have seen the complete spec but can't find it at the moment.

Greg

TGTool
01-04-2007, 12:30 PM
Lazlo,

No problem. The whole ER series is 8 degrees on the back end and 30 on the nose. The ER-32 should be 32mm at the large end of the collet holder body. If you make your own nut, a 1-1/2" works out to be close to the official M40x1.50 nut, or you can buy the replacement nuts if you can cut a metric thread. The adapter body size will need to fit your spindle, and 1-3/4" hex stock works nicely for 1-1/2" spindles. Adjust as required.

Of course I'm happy to sell kits, drawings and instructions, but also fine with people striking out on their own. Heck, most machinists have a compulsion to do that anyway.

Jan Michael
Tallgrass Tools

TGTool
01-04-2007, 02:52 PM
Sorry, additional dimensions you may want. The through hole can be about .93" and you should allow a total cavity depth of about 1-3/8" so the fully compressed collet doesn't run into anything behind it.

jm

lazlo
01-04-2007, 10:21 PM
If you make your own nut, a 1-1/2" works out to be close to the official M40x1.50 nut

Doh! I forgot about the metric threading. Arghh!

Is the chuck body in your kit pre-threaded? Is the nut in your kit hardened?
If that's the case, the price for your ER kit is a bargain.


Of course I'm happy to sell kits, drawings and instructions, but also fine with people striking out on their own.:D

Thanks Jan!

Robert

dp
01-05-2007, 01:34 AM
Question for you old pro's - what kind of metal would be appropriate for making collets, and what treatment would be required in making collets from scratch? I made a couple emergency collets from brass but they have pretty short life expectancies. The reason I ask is I have some Grizzly collets that came in a set but there's no growing the set off the shelf. They're an odd size and I've never seen singles sold or replacements for that matter.

I used a slitting saw in making them and that's about 99% art without having any kind of indexer. Needless to say they were a bit rough but functional for the brass whistles I was making at the time.

TGTool
01-05-2007, 10:17 AM
Lazlo,

There is no machining already done on the kits. Still a bargain, but not THAT good a bargain. If you'd like some operations done we could discuss it offline. The parts aren't hardened. That's one of those choices where you get both advantages and liabilities whichever way you go. IMO (and my experience) not having the pieces hardened is not so much a liability as it would be in production operations. I've used my original set for about 3 years with no discernable wear or degradation. Of course I always wipe out chips, give it a drop of oil, etc. When you're trying to make rate in production those little things take short shrift. On the upside, if the body at least is not hard, you can always skim out a little more if you get a serious ding, or simply to true it precisely to the C/L of your own spindle.

If you get parts hardened, you should expect that some distortion will take place. That means if you have threaded parts you make them a little looser to accommodate that, or if they must be a close fit that you're prepared to grind them to fit afterwards. So, a collet body that was machined accurately and used soft would be more accurate than when it came back from heat treat and was just reinstalled without grinding.

That may be something for dp to consider too. In the hobby machining environment where tools get occasional use, and if you're willing to take care of your tools, unhardened parts can give you a lifetime of service.

lazlo
01-05-2007, 10:57 AM
Question for you old pro's - what kind of metal would be appropriate for making collets, and what treatment would be required in making collets from scratch?

I'm not an old pro, but I've read a bunch of British Model Engineering articles where they made custom collets out of mild steel, and in a home shop environment they were fine.

The reason I'm asking about the hardened cap on the ER-32 collet chuck is because the ER cap has an eccentric clamping mechanism in the ER collet system. The high quality ER collets are hardened, so if you clamp an unhardened cap down on a hardened collet, you'll eventually have wear problems.

That said, I'm probably going to make my ER collet body out of 4140 Prehard. Pretty hard (around 32 Rc) but still machinable.

GadgetBuilder
01-05-2007, 12:21 PM
I bought a pair of HSK50 type tool holders off eBay; the seller wasn't exactly sure what he was selling and I wasn't sure exactly what I was buying so I guess it was a fair exchange (at a modest price now that I've checked prices on these things). They seemed to be ER-32 tool holders from the description, where my thought was to use the ER-32 nuts on a home made chuck. Making and hardening these nuts didn't look to be within my skill level.

Once I saw what I bought it seemed a shame to only use the nut and I had material for a holder-holder :) but not a chuck so I cobbled together a holder for the HSK50.

This shows the HSK50 tool holders and the backplate prior to adding the clamp:
http://img441.imageshack.us/img441/943/chucker32007ai8.jpg

Here it is mounted on my minilathe:
http://img440.imageshack.us/img440/2932/chucker32np8.jpg

There are a couple of problems with this approach. Overhang is 4 inches from spindle to collet face. The HSK50 holder has only a 1/4" through hole and it is made of hardened steel so I don't know how to enlarge it...

The inexpensive Chinese collets I bought vary in their runout by over a thou so I made the opening for the register slightly over size - this allows using my Bump-Tru scheme to handle the runout problem.

This lashup works well enough to allow evaluating using the collets in my shop; I'm not sure yet whether I'll use collets a lot for work holding in the lathe. But I'm watching for some material suitable for an ER-32 chuck so I found this thread interesting.

TGTool
01-05-2007, 01:02 PM
The reason I'm asking about the hardened cap on the ER-32 collet chuck is because the ER cap has an eccentric clamping mechanism in the ER collet system. The high quality ER collets are hardened, so if you clamp an unhardened cap down on a hardened collet, you'll eventually have wear problems.


The eccentric part is only for tugging the collet when you unscrew the nut. The closing part is full contact on the 30 degree angle so I don't think you'll find wear to be a problem.

lazlo
01-05-2007, 07:10 PM
The eccentric part is only for tugging the collet when you unscrew the nut.

Oh, that's good to know.

Now if I can just figure out how to cut 40mm - 1.5mm threads, I'd be set :p
(My Clausing 5914 has a quick-change gear box, and a non adjustable banjo, so I can't use outboard change gears
to approximate metric threads)

TGTool
01-05-2007, 08:40 PM
Now if I can just figure out how to cut 40mm - 1.5mm threads, I'd be set :p
(My Clausing 5914 has a quick-change gear box, and a non adjustable banjo, so I can't use outboard change gears
to approximate metric threads)

Uff Da! That's a problem. However, you might talk to the folks at New England Model Engineering Society (NEMES). At the NAMES show last year, one of their guys had made a gizmo for his lathe to let him cut ANY thread pitch. Essentially it's an auxiliary slide under the toolholder, with a bellcrank and an adjustable track and follower aligned roughly along the ways. The idea is, that you pick a thread close to the pitch you need and adjust the track a little bit diagonally from the carriage travel. As the carriage moves, the bellcrank advances or retards the actual tool movement relative to the carriage. So, you set up approximately, start the tool marking something, turn the spindle maybe twenty or thirty turns and measure how far off you are from the desired pitch distance (times twenty or thirty). Adjust as required. Heck of a clever idea. You're limited in the length you can cut since you'll run out of track sometime, but for two or three inches of thread, it's the cat's pajamas.

jm

John Stevenson
01-05-2007, 08:40 PM
Lazlo,
If you are making the nut and holder then just stick a thread on that's easy to do.
1-/12" x 16 sounds OK as 16 can be cut on an imperial machine at any half nut position.

.

lazlo
01-06-2007, 05:12 PM
The idea is, that you pick a thread close to the pitch you need and adjust the track a little bit diagonally from the carriage travel. As the carriage moves, the bellcrank advances or retards the actual tool movement relative to the carriage.

That's pretty clever -- it sounds like a mini taper attachment to stretch the linear travel by the hypotenuse of the taper you're creating.

I read a couple of posts on mwmills where the guy did that with a tailstock setover to "stretch" the thread spacing on a hob.

I searched the NAMES web page (including the 2005 and 2006 exhibit pages) and couldn't find it, but I shot an email to Errol to see if he could point me in the right direction.

lazlo
01-06-2007, 05:29 PM
If you are making the nut and holder then just stick a thread on that's easy to do.
1-/12" x 16 sounds OK as 16 can be cut on an imperial machine at any half nut position.

John,

I was trying to follow your advice and build the chuck body, and buy a hardened ER nut. But I'm going to have to cut that 1.5 mm thread to use an off-the-shelf ER nut.

I'm also thinking about TG collets -- which appear to be an Americanized version of the ER collet system. The TG collets have Imperial dimensions, so I'm guessing that the TG nut uses imperial threads.

I found this link on the Hardinge collet FAQ about DA, ER and TG collets from a thread on PM:

From http://www.hardingetooling.com/faq.asp

"I am trying to drill a very accurate hole using a DA-style collet system without any success. Any suggestions?

Here are several things to consider. Extremely accurate drilling requires a very good holder and collet. With the considerable flexibility of the DA, TG, and ER Collets, we tend to forget the cardinal rule for collets: the bore of the collet should be the exact size of the diameter being gripped for the best TIR and gripping force. Therefore, for extremely accurate drilling, the collet bore should be the same size as the shank of the drill. Second, if you have a choice of holders, it is best to use the ER collet holder over the DA collet holder. The DA holder is a double-angle holder, with a closing angle on the front and back of the collet. The theory is that the collet will close parallel to the centerline of the holder. Unfortunately, it is very difficult to manufacture a holder and collet that accurately mate. For standard drilling tolerances, this usually is not a problem, but can be when doing extremely close tolerance drilling. The ER is considered a single-angle collet because the major closing angle is long and shallow. This results in better concentricity than the double-angle system. The TG collet system is better than the ER system because it has an even shallower closing angle. Unfortunately, this system is usually for larger shanks and most holders that use these collets are for vertical machining centers. "

Alistair Hosie
01-06-2007, 05:32 PM
Looks very nice gadget H well done laddie Alistair

lazlo
01-07-2007, 03:34 PM
I got a reply from Errol (one of the NAMES officers) -- the guy who built the "arbitrary threading attachment" (my poor terminology) that Jan saw is Rollie Gaucher. Errol said that he built the device from a set of plans he found.

He gave me Rollie's phone number -- I'll talk to Rollie and see what I can find out.

Robert

S_J_H
01-09-2007, 02:11 PM
Here is a ER32 chuck I just finished making for my 9x20.
It is made from 1144 stress proof. Internal threads are 39x4mm and external are 40x1.5mm. Internal taper is 8' but I used a test indicator to set the topslide angle with a mt3 ER chuck in the spindle.
The 4 adjusters at the base simply allow the chuck to be exactly dialed in to .0002" runout in a couple of minutes by locating it on the register exactly as it was turned. They basically only serve to put the chuck back to exact position as it was turned on the lathe as well as lock the chuck for reverse turning.
The nut is a ETM brand.
Steve
http://i109.photobucket.com/albums/n48/S_J_H/39x4gearsetup009.jpg
http://i109.photobucket.com/albums/n48/S_J_H/39x4gearsetup008.jpg
http://i109.photobucket.com/albums/n48/S_J_H/39x4gearsetup013.jpg
http://i109.photobucket.com/albums/n48/S_J_H/39x4gearsetup011.jpg

lazlo
01-09-2007, 04:51 PM
Here is a ER32 chuck I just finished making for my 9x20.

Nice job Steve!

You know, it didn't even occur to me -- I have one of those little 7x20 lathes up in the attic. I could dust that off and cut those 40x1.5mm threads quicker than building Rollie's threading attachment.

I guess old American iron distorts your brain to some extent :p