what do I need for an MT3 collet setup on Atlas 10F?

[spaceman_spiff]

Id like to have a collet setup so I can hold workpieces very precisely and with absolute minimum runout and maximum rigidity by being as close to the spindle as possible and supported inside the spindle by the collet.

I see the MT3 collets on ebay but I'm wondering what I can get away with for the drawbar. Can I just make one? Is it just a threaded rod and custom shouldered-washer and nut? Or is it special somehow?

I've considered ER collets but I think they would not be quite as rigid as the MT3 since they would be outside the spindle and would have a shallower gripping length than the MT3 collet which is very long and nearly completely inside the spindle.

 

[Ulma Doctor]

I see the MT3 collets on ebay but I'm wondering what I can get away with for the drawbar. Can I just make one? Is it just a threaded rod and custom shouldered-washer and nut? Or is it special somehow?

A: allthread cut to the right length ,3/8"- 16tpi will do just fine, they are easy to make. you can turn a custom stop and handle. i assure you there is no magic involved!


I've considered ER collets but I think they would not be quite as rigid as the MT3 since they would be outside the spindle and would have a shallower gripping length than the MT3 collet which is very long and nearly completely inside the spindle.

your best bet , IMHO would be to get the MT3 collets. they are cheap and you can hold fairly large pieces (3/4"max). you have in either case the added bonus of being able to hold endmills, should you desire to mill with your lathe.
the ER chucks are nice, but do stick out a little. the ER's do have good grip, and you can get a set of metric collets that will cover both imperial and metric tooling. but you give up depth of hold as you had said.
i'm sorry but i can't say what is best for you,
but the MT3 collet sets are less expensive and work just fine.
but then again i have both so i'm a little hypocritical i suppose:jester:
good luck in whatever you decide)

 

[wa5cab]

Spiff,

I guess that I'm worse than Mike, because I have a full set of 3MT, 3AT and 5C collets, with the necessary drawbar, draw tube and collet chuck. hew:

If you don't need to be able to pass a long workpiece through the spindle and if you will not need to hold anything between 1/8" and 3/4" that isn't on a 1/16" increment, then the 3MT 11-piece set from CTC Tools in Hong Kong (see eBay) at $60.00 is your cheapest way in. And the collets are excellent quality, not like some of the stuff made on the Mainland. No one in the US seems to make or carry them, however. Except that I forgot to check Enco. The reason you will be restricted to diameters on 1/16" increments is that the 3MT (and 2MT) collet is ground to its marked diameter and if the workpiece is more than .002" or .003" smaller or larger, the collet will only grip one end or the other. The reason for this is that 3MT (and 2MT) collets are actually made as cutter holders. And for example, 5/32" dia. end mills are readily available with 3/16" dia. shanks. So that's the limitation of MT collets. It isn't that they wouldn't work if made for 1/32" or 1/64" increments but that no one makes them.

Making the drawbar is easy, although not real cheap if you make a decent one and have to buy the handwheel. If 1/16" increments meets your needs, I can give you the details or you can buy one off of eBay any day of the week and be done with it.

Before delving any deeper into collet choices, I'll ask what is it that you actually need to be able to do? Length and diameters?

Robert D.

 

[John Hasler]

Id like to have a collet setup so I can hold workpieces very precisely and with absolute minimum runout and maximum rigidity by being as close to the spindle as possible and supported inside the spindle by the collet.

I see the MT3 collets on ebay but I'm wondering what I can get away with for the drawbar. Can I just make one? Is it just a threaded rod and custom shouldered-washer and nut?

That'll work fine. You can get fancy and add a handwheel but it's not necessary. It doesn't take a lot of torque to draw an MT3 up tight. I made a usable drawbar for my Logan from a carriage bolt and a scrap of 1" shaft.

 

[spaceman_spiff]

thanks guys

I saw that 11 piece MT3 set on ebay from cnctools for $60 but they want $40 for shipping , so I think instead I'll get the 8 piece from shars which is $65 shipped:

http://www.ebay.com/itm/8-PC-3-MORS...507?pt=LH_DefaultDomain_0&hash=item4611614e9b

I didnt know the MT3 collets had such a small clamping range. Im not sure how that may or may not affect my plans yet, but I think its worth getting them, worst case I can just sell them.

I already have ER32 collets for a mill so I think I should just get an ER32 to MT3 chuck as well, the very cheapest on flee-bay is only $22 shipped.

http://www.ebay.com/itm/351152682079

My purposes are to be able to make spindles that will be installed in ball bearings. So steel, fairly small diameter (~5/8"), requiring great finish which can be polished easily to ground-like, and high precision diameters and concentricity. All of which seem to point to eliminating the chuck (maximum rpm), moving the workholding towards the spindle (reduced runout), holding things as rigid as possible (MT3 collets which grip inside the spindle with minimum stickout).

If I can clock the collet and workpiece to reduce runout that would be great, because I may need to flip pieces around. Have you tried that with the MT3 wa5cab? What kind of runout repeatability can you get randomly re-installing the work?

 

[spaceman_spiff]

okay I bought the ER32 chuck but not the MT3 collets

the chuck is way less expensive and will let me use my existing collets, plus it can hold larger stock than the MT3 collets, and the ER collets have a much larger clamping range

Ill see how it works. If it doesnt cut the mustard then I'll try the MT3

 

[wa5cab]

If you had bought the Shars set, you would have only effectively saved $10, because you would have only gotten 8 collets.

I haven't actually checked runout using my set of MT3 collets, because I use them for holding milling cutters. I'll try to do that in the next few days. I will be surprised if their repeatability isn't better than the ER's, though, because they are 4 or 5 times as long.

Robert D.

thanks guys

I saw that 11 piece MT3 set on ebay from cnctools for $60 but they want $40 for shipping , so I think instead I'll get the 8 piece from shars which is $65 shipped:


If I can clock the collet and workpiece to reduce runout that would be great, because I may need to flip pieces around. Have you tried that with the MT3 wa5cab? What kind of runout repeatability can you get randomly re-installing the work?

 

[GarageGuy]

I see the MT3 collets on ebay but I'm wondering what I can get away with for the drawbar. Can I just make one? Is it just a threaded rod and custom shouldered-washer and nut? Or is it special somehow?

That's *exactly* how you do it! I used threaded Redi-rod and turned some steel ends and aluminum shoulder washers to make mine. A little Loc-Tite or a lock nut and you're ready to go. They work perfectly. I love turning with collets, and plan to add 5C and maybe even ER-40 collet chucks to my lathe someday. But in the meantime MT3 collets are cheap and easy.

GG

 

[spaceman_spiff]

That's *exactly* how you do it! I used threaded Redi-rod and turned some steel ends and aluminum shoulder washers to make mine. A little Loc-Tite or a lock nut and you're ready to go. They work perfectly. I love turning with collets, and plan to add 5C and maybe even ER-40 collet chucks to my lathe someday. But in the meantime MT3 collets are cheap and easy.

GG

whats your experience with the runout of the MT3 collets? can you clock the collets and the work repeatably and drop runout to extremely low?

 

[GarageGuy]

whats your experience with the runout of the MT3 collets? can you clock the collets and the work repeatably and drop runout to extremely low?

I haven't measured. I know it is very low. It makes my 3-jaw chuck feel barbaric by comparison :lmao: The aluminum shoulder washer keeps the draw bar centered in the head shaft, so it should be as accurate as your head shaft taper. Be sure to use a spindle thread protector to protect your head shaft when using collets.

I machine anything important in either the 4-jaw chuck, or a collet.

GG