PM 932M collet help ***Updated***

RJSakowski said:
A problem with R8 collets is there is no standard as the collet and socket are proprietary to Bridgeport. As a result it is often hit or miss regarding collet compatibility.
At work, we had purchased a Grizzly G0755 which also uses a set screw for the pin. Eveything was fine for the first few months and then it became more and more difficult to insert collets. The problem was there was no way of fixing the set screw position in place and it slowly workjed its way into the socket.
I removed the OEM set screw and machined a dog point on a socket head cap screw. I verified the point would fit all the collets and end mill holders we had and the length of the screw was adjusted so when the point was properly positioned, the screw was tightened securely. As I recall, the final adjustment was done using shim washers.
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Bridgeport had a double screw setup. The key was a short dog point set screw which was locked at the correct depth with a shorter though hole set screw. The short locking screw can be made by cutting off the hex socket of a regular set screw. This setup allowed adjusting the dog point screw by a hex key going through the locking screw into the dog point screw. Locking the screws together in place was a tricky operation to say the least. Most shops left the screws out after fiddling with them too often. Since the R8 taper is a self locking taper, the key did not really function as a drive key but more as a collet lock for installing and removing them. At one point there was a three lobe key wrench available that was used by inserting it into the 3 slots in the collet for tightening and removing.
 
I had an Italian vertical mill, an Induma, 1 -S that used the same dog point screw, when I got it, the screw was sheared off and also the rack gear teeth had been stripped by using it as a arbor press to broach a keyway, so I was able to buy it quite cheaply; a customer who was going to Italy on a equipment buying trip to the same city as the mills were made ordered a new quill and the screw for me and imported it. I installed the new quill and the screw, which had to be installed in the spindle while it was removed from the quill; very shortly after I got it back to running, the key got sheared off again; that was probably 30 years (or more ago), and the screw is still sheared. We mostly used set screw type holders, not collets and really never missed the screw at all.
 
Profkanz said:
....Since the R8 taper is a self locking taper, ......
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The R8 taper is not self locking. A drawbar is required to provide enough force to prevent R8 tooling from spinning.
 
Finally got the beast up to a point i feel like ive accomplished some sort of feat...may not be much to most but this has been a dream of mine for YEARS...and finally (i say this very conservatively) things are coming together...and i do appreciate all of the help and advice ive gotten so far...trying to get a small personal business up and running ut i wanted decent-good machines and tools before i jumped into the fires...
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FYI If you Google 'R-8 specification' a drawing does come up showing the important dimensions for a R-8 collet.

I too ordered some collets. When I tried them some fit and some didn't. I measured the width and depth and the keyway. The depth was consistent across all of them. The width of the keyway varied from .156 (the minimum) to .170. The collets with the wider slots fit and the ones with the narrow slots didn't.

Since the tolerances for width and depth aren't terribly critical I decided that, since in I had the tools and equipment to fix the collets, that would be easier than shipping them back to the dealer and waiting for replacements. Running an 1/8' endmill down one side to make it .010 wider +/-cured the problem.

Ergo, the moral of the story is check to width too.

L
 
So... got the collet issue worked out

I got the DRO back on and i think i may have damaged the Y axis scale so ill have to power it up to check it...pray i didnt but ill eat it if i did due to lack of paging attention when i ran the table back too far and the bracket caught the edge of the reader mount and shoved it backwards and twisted the reader pretty good...and lemme tell ya, i dont envy they guys that install these on a regular basis...the bolt holes for half the brackets are drilled uneven, half crooked, barely usable...the X axis scale can barely be trammed because of the way they mounted it...the way cover actually mounts over the reader head and sandwiches it on the back of the table and the cover wont fully seat because of the bolts on the cover...i expect some corner cutting but man, some of the things ive seen are really half-assed...10mins would have made the whole mounting of the scales 100x better...and more professional
 
Well not gonna let one mishap slow me down or deter me from finishing this beast and seeing her come to life...go the head trammed and man what a bear...the three bolts act nothing alike in reference to each other...rhyme or reason to their seq or tightening pattern...BUT i did manage to get it within .002 over a 14" span so im pretty stoked about that...
 
Gonna aim this question at Matt and hope he sees this...how much is a new Y axis scale if i did break this one?...still have to get a plug for the mill before i can power it up but how would i know if it is damaged or broken?...
 
Re: Tramming the head. I have your machine's little brother, the PM25. I made two blocks that screwed to the head and had screws that pushed on the column mount. They would lock the head in position, and allow tweaking the tramming. I checked it the other day when I had the vice off, it was out .003 in 18 inches. tweaking with the screws got it down to less that the width of the needle on 0 both ends.

Granted, if I were to want to tip the head I'd have to remove one of these, but I don't plan to do that. I have a sine plate for tipped work.
 
Did the tramming mod to my PM25 shortly after getting it. Worked really well.
 
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