# R-8 Spindle Key



## rakort (Dec 21, 2015)

I'm about ready to assemble my spindle for my mill.  I have acquired and installed a new set screw for indexing tooling into the R8 spindle.  I've read a number of things regarding whether or not it's a good idea to have this in the spindle and want to hear what other may offer regarding this

thanks
Brian


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## Bob Korves (Dec 22, 2015)

In my first R8 machine the screw was broken off when I got the machine.  I used it that way for a long time.  My second R8 machine, same brand and type, has an intact screw.  So I have used both ideas on the same basic machine.  In reality, both have benefits and problems.  I am equally happy with using them either way.  It is certainly not worth it for me to take the spindle apart to fix or remove one of those pins.  In my opinion, decide for yourself.  The only thing I would never accept is a spindle with a screw that has the tip broken off and that still sticks out into the collet space, even a tiny bit.  That will cause gouging of collets and wedging of collets out of proper alignment, causing inaccuracy and damage to tooling.  Regardless, your choice is reversible either way if it turns out you don't like it.  The important thing is to be conscientious about cleaning and getting the oil and crud off the tooling and spindle, tightening them properly every time, and trying really hard to never crash your machine and spin the R8 tooling in the spindle.  R8 is not that secure of a mounting system.  Don't push your luck.  No good (and much bad) can come of it...

I used to fly an aerobatic single seat aircraft that had a placard on the panel that stated:  "Don't try anything stupid."  We should post that on our machinery as well...


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## Billh50 (Dec 22, 2015)

if you have it apart anyway, I would put it in. I have had problems getting a collet out of bridgeports because someone tightened up a collet with chips in the threads. The drawbar bound up and the collet just turned when trying to loosen. It can be a real pain in the a$$.


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## Badspellar (Dec 22, 2015)

Billh50 said:


> if you have it apart anyway, I would put it in. I have had problems getting a collet out of bridgeports because someone tightened up a collet with chips in the threads. The drawbar bound up and the collet just turned when trying to loosen. It can be a real pain in the a$$.



Shars sells a collet wrench for just that problem. #202-5596   I have never used one but think I will order one just in case. I pulled my pin when I got my PM935  mill.

Mike


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## wawoodman (Dec 22, 2015)

My old RF had a pin, and since it was my first mill, I thought thatwas the way it was supposed to be. My current Rockwell doesn't have one, and I wish it did. I have a couple of collets that don't thread up nicely, even after chasing the threads on the drawbar.

The wrench from Shars looks like a winner!


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## T Bredehoft (Dec 22, 2015)

I can't imagine (I know, others do it) running an R8 collet without a pin. Won't the collet spin as you try to tighten it?


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## f350ca (Dec 22, 2015)

My R8 mill doesn't have one and I've never had a collet spin, maybe lucky. My Hardinge lathe has the spindle machined for 5C collets and has the pin. Its old and has seen a lot of use before I got it. Because the collets always go in with the same orientation you can feel a slight 3 sided wear pattern in the bore. Without the pin I wonder if the wear would be more even.

Greg


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## wawoodman (Dec 22, 2015)

T Bredehoft said:


> I can't imagine (I know, others do it) running an R8 collet without a pin. Won't the collet spin as you try to tighten it?



It does, unless the drawbar goes in easily. I have to set the collet up into the spindle, and snug it up by hand. Once it's there, I can apply the spindle brake, and use the drawbar wrench.


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## TOOLMASTER (Dec 22, 2015)

no big deal to stick a bolt in the side on my mill if it spins, haven't needed to ever...


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## Cobra (Dec 22, 2015)

Never had one move.


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## Bob Korves (Dec 22, 2015)

If the collet spins while installing it and causes trouble with tightening the collet, then the drawbar threads and/or collet threads are damaged or dirty.  A tap, a die, and some solvent will cure that.  Sticky drawbar to collet threads are a PITA regardless and need to be dealt with.  You should be able to easily screw the drawbar into the collet with your fingers all the way until the collet seats in the taper, then switch to the wrench for final tightening.  An overly long drawbar thread can also be a problem.  If it goes into the R8 collet more than about one and a half thread diameters, two diameters at the very most, the drawbar is too long and should be shortened.  I had to shorten and chase the threads on the drawbar of my newer mill.


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## Bob Korves (Dec 22, 2015)

Badspellar said:


> Shars sells a collet wrench for just that problem. #202-5596   I have never used one but think I will order one just in case. I pulled my pin when I got my PM935  mill.
> 
> Mike


That tool sounds like an interesting project to design and make!


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## middle.road (Dec 24, 2015)

Bob Korves said:


> ................
> I used to fly an aerobatic single seat aircraft that had a placard on the panel that stated:  "Don't try anything stupid."  We should post that on our machinery as well...


I may just put that on the door into the shop... 

- I've been contemplating repairing the guide pin on my BP and haven't decided which way to go - yet.
The drawbar threads were messed up when I got it, and I cleaned them up and added a spacer to keep the threads
from bottoming out. So far collets snug up fine, except for one. I'm thinking that I should get a new drawbar sometime
in the future.


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## coolidge (Dec 24, 2015)

There are countless stories of the alignment screw snapping off and jamming between the tool and the spindle. I had this happen to me years ago and had to beat the tool out of the spindle with a hammer. I did quite a bit of research on this recently when I purchased my new PM-935 and decided to remove the screw. That was the consensus of maybe 70% of the people. 

Its an alignment screw its not designed to take the torque of cranking on the drawbar. Its just a set screw with a little pin sticking out, its hollow, its entirely possible to snap it in half. Its not exactly a precision tapped hole its in either so if it doesn't have a grub screw behind it to lock it in place it will bend a bit in the tapped hole making breaking it off even more likely. Some mills have the second grub screw some don't, the one I snapped in half didn't.

I have been using a power draw bar and its been no problem not having the alignment screw in there the spindle taper keeps the tool from spinning. Now if your drawbar threads are messed up or your tool is full of gunk or whatever then address that problem. That's my 2 cents worth.


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## JimDawson (Dec 24, 2015)

coolidge said:


> There are countless stories of the alignment screw snapping off and jamming between the tool and the spindle. I had this happen to me years ago and had to beat the tool out of the spindle with a hammer. I did quite a bit of research on this recently when I purchased my new PM-935 and decided to remove the screw. That was the consensus of maybe 70% of the people.
> 
> Its an alignment screw its not designed to take the torque of cranking on the drawbar. Its just a set screw with a little pin sticking out, its hollow, its entirely possible to snap it in half. Its not exactly a precision tapped hole its in either so if it doesn't have a grub screw behind it to lock it in place it will bend a bit in the tapped hole making breaking it off even more likely. Some mills have the second grub screw some don't, the one I snapped in half didn't.



:+1:  I've had that happen to me too.  I've been running without a pin for years.  Every time I got a mill, I removed the pin.


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## rakort (Jan 13, 2016)

Thanks for all the input....sounds like one of those debates that no one will win.  I'm about ready to assemble the spindle finally.....still on the fence, but I'm thinking I'm going to install the set screw.  I believe the screw is there to help establish the initial resistance when pulling the tool up into the spindle, but shortly after the taper will take over.  It certainly isn't there to provide torque to drive the tool.


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## Subwayrocket (Aug 21, 2016)

How did you all remove that grub screw ? My is a little galled over and my collets have been a little rough going up in. I'd like to remove this grub screw out of my spindle before I have problems. Thanks much !


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## rakort (Aug 21, 2016)

Yeah. No surprise,  trying turning it in verses out


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## Subwayrocket (Aug 21, 2016)

The problem is that I can't get access to the screw to turn it. I figured I'd ask before I start taking everything apart. I can see it when I look up I to the spindle from below


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## JimDawson (Aug 21, 2016)

What kind of machine?  If it's a BP or clone, then there is a small set screw that secures the bottom nut.  Loosen that, unscrew the nut and then you can get to the pin.


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## Subwayrocket (Aug 21, 2016)

I posted a new thread in Precision Matthews, no replies yet. Its a PM940 . I removed the quill base but I see no way to lower the spindle down a little so I can access the back of that grub screw. Sorry to hijack this thread


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## rakort (Aug 21, 2016)

As i recall my screw burried behind the bearings it didn't bother  me as i had the whole thing apart. ... not much help for  you though


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## Subwayrocket (Aug 21, 2016)

No prob , but I appreciate the response though !    Another guy just posted the answer in the thread I posted in the Precision Matthews section. Problem solved . Simple too !    
http://www.hobby-machinist.com/posts/418814/


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## randyjaco (Aug 22, 2016)

I  have replaced my screw 3-4 times on my BP clone.   I finally just gave up.  I like having the pin, but it is not worth the effort to replace them. 

Randy


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## chips&more (Aug 23, 2016)

I have the same pin in the spindle with no problems ever since I got my BP about 25 years ago. Never nicked the slot in any of my holders with the pin either. I do have a few holders and such that are nicked from a pin and they remind me to be careful and mindful of that problem. Never had an end mill spin or move in a R8 collet. And still using the same drawbar, threads looks great. I do clean and oil the drawbar threads and do the same to the holder threads. But my shop is not perfect, you oughta see the owner…Dave


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