# Pm 935tv/ts - Removing The Collet Alignment Screw From The Spindle



## coolidge (Sep 23, 2015)

I thought I would detail this procedure here for those like me who have never owned or operated a Bridgeport type mill and save you chasing around looking at manuals and procedures.

*Issue:* The collet alignment screw in the spindle of my PM 935TV was properly installed at the factory, the issue is apparently a lot of R8 tools and collets are not manufactured to R8 specs with respect to the depth of the keyway slot in the tool. Its supposed to be .094 deep but two of my three R8 tools (ER 32 collet chuck, Face Mill) were out of spec significantly, over .020 shallow and I could not insert the tools in the spindle.

Further research showed historically the collet alignment screw has a habit of snapping off when you spin a collet or tool in the spindle jamming between the spindle and the quill creating quite a problem. I myself had this happen to me years ago. So I elected to remove the collet alignment screw and kill two birds with one stone.

Reference Schematic

1. There is a grub screw 6 on the back side of the quill 142, this requires a 2.5mm Allen wrench.

2. The collet set screw 140 and grub screw 6 are in the spindle, both require a 3mm Allen wrench.

3. The nose piece 133 needs to be removed to gain access to the collet set screw, this will require a pin wrench.




Here is my 'no fab' pin wrench I assembled with $14 of parts at my local hardware store. Talk about easy the holes were pre-drilled I just screwed it together in a couple of minutes. The pin holes are .190 inch so I just used a couple 10/24 screws, 1/2 inch and 3/4 inch lengths so that the tips were flush with each other. A short 3/8 bolt holds the two together. The nose piece was not that tight, this was plenty stiff enough to R&R it.



Step 1 - loosen the grub screw on the back side of the quill with a 2.5mm Allen wrench. You will need to extend the quill to reach it.



Step 2 - Using the pin wrench remove the nose piece, its reverse threaded you need to turn it COUNTER CLOCKWISE standing in front of the mill looking down at it. Remember you are looking at it upside down so turn the wrench counter clockwise from the left side of the mill to the right side of the mill. Some crud fell down in that ring of grease, I carefully cleaned it out of there.



Here's the other side, I elected to apply some anti-seize to the threads when I re-installed it. It wasn't ridiculously tight when I loosened it, just good and snug so I didn't overtighten it when I reinstalled it.



Step 3 - Remove both the outer locking grub screw and the inner collet alignment screw with a 3mm Allen wrench. These are standard thread turn counter clockwise to remove.



Here they are removed.


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## middle.road (Sep 23, 2015)

I have to do this to my BP, first though, I believe I'll go over all my tooling and verify the depth of the slot.
Thanks for pointing that out.

_Dan


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## ARKnack (Sep 23, 2015)

Very good post with excellent pictures. My Mighty Comet mill already had the grub screw removed from it when I got it. I purchased it directly from a professional machine shop so they didn't see the need for it either. I've read in other places that the pin isn't required either. It is so small I don't believe it will stop a R8 collet from spinning. The only reason I can see for it is to index the collet so it will be installed in the same position each time. My work doesn't require that kind of accuracy.


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## qualitymachinetools (Sep 24, 2015)

Great post!


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## Smudgemo (Oct 1, 2015)

Heh, I could have use the reverse thread information a year and a half ago..

Great post.


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## coolidge (Oct 1, 2015)

Do tell Smudgemo, was it R rated for language and violence?


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## GeneV (Mar 7, 2017)

Here's a pin wrench I fabbed with some #10 screws and some flat stock aluminum I had laying around.


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## Billh50 (Mar 7, 2017)

It was conveyed to me by a machine designer years ago that that pin was not designed for locating but to keep the collet from spinning when tightening the drawbar. Indexing was not considered as the collet should run true no matter what the orientation.
I truly believed this as I have had to remove a few drawbars that were galled up in the collet and the collet just spun when trying to remove. Some of them were very tough to get out. That is why I always make sure there are no chips in the end of the collet or on the drawbar.


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## GeneV (Mar 7, 2017)

Yessir, it's to keep the collet from spinning in there.  From an engineering standpoint makes sense, but from practicality a bit of a pain.  I take it out personally, but totally agree, everything in that spindle needs to be kept clean and burr free, or you're asking for it.


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## Billh50 (Mar 7, 2017)

When I worked somewhere that had the collet rack on the side of the BP. I always kept a rag over the rack so chips would not get into the collets. Made life much easier that way. Use to tell all the apprentices that they would not be allowed to use the BP if I found a rack with no covering on it while they were using one.


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