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View Full Version : Can removing MT 2 collets damage roller bearings?



jpazzz
04-12-2012, 12:32 AM
Hello, I have a feeling that somewhere on this forum I've seen a comment about the dangers of removing MT 2 collets from lathe roller bearing headstocks, but I can't seem to find the proper thread.

If I remember correctly, the gist of the the comment was that using MT 2 collets in the spindle of a lathe with tapered roller bearings was dangerous to those bearing because they could be damaged when the collet had to be removed from the spindle. I've recently gotten a set of MT 2 collets for my little Atlas, and I did notice that when I inserted and drew tight a collet, it needed to be prodded (heel of hand to draw bar) to come free.

So, is this a real problem with this bearing/collet combination? If so, are there any safeguards one might use?

Thanks for any thoughts on the subject.

Cheers,
John P

J Tiers
04-12-2012, 12:44 AM
I have an MT3 spindle on one of the mills.... I got really tired of whanging on the drawbar to eject the arbors, etc, and made an "ejecting" drawbar.....

Essentially, it not only pulls in the arbor etc, but it also pushes it out if turned the other way. I like it.... no rough stuff.

My way you have to be able to screw-on a threaded cap to the rear of the spindle.... unfortunately not all have room for that on whatever screwthread is exposed (if any).

I not only put the nut on the rear of the drawbar, I also pinned a collar on under the threaded cap. So now when I unscrew it, the threads in the arbor etc push the drawbar back until the collar hits teh cap. then the threads pop the arbor out.

Should work for collets too. They need a somewhat longer push than a solid arbor taper, though.

Carld
04-12-2012, 10:17 AM
Considering all the forces on the bearings in a lathe headstock I doubt your going to hurt the bearings by hitting the center to set it in or hitting it to remove it.

Think about it for a while, lathes have been made and used for way over 100 years and many used for more than 8 hours a day six days a week and some for 24/7 and installing or removing a Morse taper from the headstock has not caused them to fail.

I think your being a little over the edge on this.

EVguru
04-12-2012, 10:28 AM
You're unlikely to Brinnel taper roller bearings.

On the other hand, some of the Mini lathes went to deep groove ball races which could suffer damage.

There's an article on the ArcEurotrade site on upgrading to taper bearings in the C3; http://www.arceurotrade.co.uk/projects/C3_BC/pages/index.html

J Tiers
04-12-2012, 10:59 PM
I think your being a little over the edge on this.

I don't....

forget the idea of messing the bearings up, and think about convenience.... If you enjoy whacking away on the drawbar with a hammer or other "impact device", OK.... but I sure do find it a lot easier to give a pair of wrenches a slight squeeze and have the taper pop free....

Almost no effort, no hammers, no drama...... just squeeze-pop and I'm done.

lynnl
04-13-2012, 11:07 AM
If popping out a collet is likely to do damage, then I'd think an interrupted cut toward the tailstock would spell certain destruction.

Are these collets rusted in place, or something?

jpazzz
04-20-2012, 10:30 PM
Hello, I'd like to extend my thanks to all who contributed their thoughts regarding my question. They were all most interesting and helpful.

Cheers,
John P

Clevelander
04-24-2012, 08:33 PM
Those that are self releasing and those that are not...the MT2 need to be "motivated" to be released. As has been mentioned previously it shouldn't be an issue with taper bearings. The other thing of course is to not tighten them like you're grasping the hand of God.

Mcgyver
04-25-2012, 08:49 AM
If popping out a collet is likely to do damage, then I'd think an interrupted cut toward the tailstock would spell certain destruction.


its almost a none point this discussion because I agree with you, but technically roller elements bearings ability to endure is very different when moving....but I agree there is worry about nothing.

Every lathe I've owned had a MT in the headstock, and when you used with a centre ends up with a bit of tooling firmly seated in the spindle that requires a bump to remove. Obviously if you're are wailing on it, it's a problem, and use something soft - like a brass or AL cap on a bar, but bumping tooling out of the MT centre is SOP. heck Monarch even provides the bar and little brackets for it to sit on on the front of the lathe

JCHannum
04-25-2012, 10:53 AM
There is a difference between the bump needed to eject a MT center or drill from a lathe spindle and the force needed to eject a MT collet. The collets do not provide a secure hold on end mills in particular and need to be cinched up such that ejecting requires more than a bump.

Jerry's ejecting drawbar is a solution to this problem. Bridgeport fitted a similar system to their M head mills which had MT and B&S taper chucks for this purpose.

dian
04-25-2012, 02:33 PM
are there any torque values available for mt spidles?

hareng
04-25-2012, 05:58 PM
The collets do not provide a secure hold on end mills in particular and need to be cinched up such that ejecting requires more than a bump.

If its any use i have been using MT3 collets for 13 years and refuse to use anything else with that taper. Granted R8 far superior.
Er and similar i always get cutter dropping, MT's extremely rare.
Further to that MT collets dont induce as much force on the bearings and gain more working height. Abundance of cutters with MT2 and 3 shank drawbar fit.
I have a 1/2lb hammer and 16mm spanner permanently near. Undo and slacken drawbar 1 rev and no more than 4" from drawbar sharp tap holding hammer stale close to the hammer head. Cutter pops out all within 6 secs.

Black_Moons
04-25-2012, 06:34 PM
Er and similar i always get cutter dropping, MT's extremely rare.


That would likely be the insane torque 'recommendations' that ER (32/40) have.

ER-32 tightening procedure: Get 12" collet wrench. Hit with large hammer. After shearing spindle lock on mill, make dedicated fixture, clamp to vise on table.
Tighten.
After spinning table around on the floor, Bolt table to floor.
Tighten.
After snapping table legs, clamp fixture to forklift
Tighten.

Clean forklift skid marks off floor.

Removal: Simply reverse the above procedure.

darryl
04-25-2012, 09:05 PM
My mill has the mt3 taper. To remove the tooling, I whack the top of the drawbar with a mallet while turning the spindle by hand. I made a mallet specifically for this use using uhmw. I figure that by turning the spindle during the time of the whack, it would help spread the load. I doubt that I'd damage the bearings anyway, but that's how I do it.

One day I'll do as JT has and make up an 'easy removal' mechanism.

Carld
04-25-2012, 09:14 PM
Black_Moons, it's more fun if you make a wrench with a flat disc about 6" dia x 1/2" thick and use a M1911 .45 with full magazine to shoot against the disc to tighten the collets. You can practice rapid fire and getting on target as you move around to follow the disc.

To remove a MT from a lathe headstock simply point the .45 down the spindle bore and shoot the MT out of the bore. You may want to hold the barrel back some and shoot at an angle so the bullet don't hit you on the way back out. It may only take two shots to blast the MT out.