Stuck collets

[rons]

I hAfter beating on the rod that tightens the collets in, and I mean beating on it it let loose. I was hitting it so hard I thought something else was going to give.

I've seen a aluminum mallet for the task.
I make wooden mallets for this.
Wood won't tend to deform the part you're pounding on.

 

[jim rozen]

J head bridgeports have a taper that's not self holding. M heads with MT2 or BS7 collets have a self-holding taper.

That's why bridgeport made the M head drawbars so they could push out the collets. Anyone who's ever replaced spindle bearings on an M head would never beat on the drawbar - that will brinell the lower bearing pretty fast. After it's been done a few times, might as well keep on doing it, they won't get much worse.

 

[krhoover]

I was worried I was going to bust something. Has anyone ever made a replacement drawbar, or know where drawings may be found?

 

[jim rozen]

Nobody has an M head these days? All that would be needed is one snapshot.

 

[M.B. Naegle]

Both of my M-heads don't have the ejecting collet feature. I don't think they're missing parts either as there is no threading at the top of the spindle splines, and both currently have typical knee mill draw bars with a long piece of hex stock fastened to the rod. I'm guessing it's a generational thing which had it and which don't. One head is a B&S #7 on a 1941 BP base, the other is a Morse #2 head only on a horizontal mill, and both have a tang slot in the back of the spindle taper. On mine the captive drawbar would get in the way as I often use tang ended tools with no draw-in threads, like end mills and drill chucks. It's helpful to pull the drawbar out then use it as a driver to pop out the tool later.

Both of the Midgetmill heads I used to have had the feature at one point, though were missing the captive nut on top. I had planned to make new nuts, but wasn't looking forward to single point threading the ID left hand thread to a shoulder, so just used a long Allen bolt and hardened washer. I sold them with my K&T 2H last year.

When we had a few J-head Bridgeports in the shop with R8 spindles, we often had to wack the drawbar to eject the collet. A couple we updated with automatic drawbars, but the others we used one of those combination brass hammers with the 3/4" socket on the end. I wouldn't worry about damaging spindle bearings unless they were class 00 precision in a jig borer.

I'd just keep using the simple drawbar. It looks like the OP has the captive nut though so reverse engineering the original drawbar wouldn't be hard.

 

[jim rozen]

Whacking the drawbar on a J head is not hard on the spindle bearings as R8 is not self-holding. The M head collets are self-holding so hammer-to-drawbar beats up the (smaller than J head) bearings which are 6203 size.

 

[moonlight machine]

I give the collets a shot of Hornady one shot case lube. Available wherever reloading supplies are sold. No more stuck collets. It's magic!

 

[bjmh46]

Whacking the drawbar on a J head is not hard on the spindle bearings as R8 is not self-holding. The M head collets are self-holding so hammer-to-drawbar beats up the (smaller than J head) bearings which are 6203 size.

Agree--hammering can produce bearing loads many times higher than ejecting with the correct drawbar setup. Bearings are actually modified 6205 in the original configuration, 7205 in a modern rebuild.
Bob

 

[michiganbuck]

Perhaps over-tightening is the problem. If over-tightening to hold an end mill a set screw end mill holder might be due.

 

[jim rozen]

Right, sorry. 6205s that were set up special by bridgeport.

 

[michiganbuck]

Whacking the drawbar should include cranking in a number of threads so the end of something is not damaged.
A taper-locking device should consider that the amount of whack-in is usually an experience thing....and often the wack-out device should not be a hard whacker. I have one whacker for use on my Cincinnati Tc grinder work head that is made of brass.

 

[krhoover]

Thanks for your replies and advice, I’m thinking I need the correct drawbar to push it out. Would like to try to make one if anybody could help with drawing or videos

 

[TedinNorfolk]

The drawbar is captive,the collet is ejected by unscrewing drawbar further.

 

[jim rozen]

HIS drawbar isn't captive, it's not the correct one. Do you have the correct one, if so please post up a photo. I sold my M head years ago, or I'd put the picture here.

Where's the late great Dave Sobel when ya need him?

 

[Rik75]

I have an old m-head that had a stuck 1/2 inch collet in it with a chuck. The chuck and collet had been in it for several months as I couldn’t get it out. Today I needed to do some milling. After beating on the rod that tightens the collets in, and I mean beating on it it let loose. I was hitting it so hard I thought something else was going to give. How can I keep this from happening agian. Should the collets be removed after each use? Or is there like neverseeze type compound etc.
Thanks

Rest the headspindle nose on top of the vice on the table, put suitable protection blocks in between while hitting op top of the drawbar with a heavy brass or bronze mallet.
This way there is a lot more mass helping the impact, as well as protecting the spindle bearings.
If necessary replace drawbar with a massive rod the biggest possible diameter, helps minimize vibrations.

 

[Rik75]

Rest the headspindle nose on top of the vice on the table, put suitable protection blocks in between while hitting op top of the drawbar with a heavy brass or bronze mallet.
This way there is a lot more mass helping the impact, as well as protecting the spindle bearings.
If necessary replace drawbar with a massive rod the biggest possible diameter, helps minimize vibrations.

Mine (mt3) was stuck again think she just wanted her picture taken.

 

[guythatbrews]

The MT and B&S drawbars don't need tightening much. If you crank em you'll have more trouble later. They really get in there tight.