# Dividing Head for PM-25 Mill



## devils4ever (Oct 2, 2021)

I'm looking to purchase a dividing head for my PM-25 mill. The smallest common size is BS-0. Is this too big for the PM-25 mill?

Assuming this size is okay, which brand should I get?

I see many listed on eBay for under $300 including shipping. Are they decent?

Then, there is the PM one for over $400 with shipping. I suspect this is a step up from the eBay ones.

Lastly, the Grizzly dividing head is over $500 without the chuck and without shipping. 

I'd rather not deal with used since most seem to be missing parts and are of unknown condition.

Thanks!


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## jwmelvin (Oct 2, 2021)

I don’t think bs-0 will be too big but I don’t have a pm-25. It is fine on my pm-30. I bought one for about $240 and it is great. Surprisingly well put together.


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## addertooth (Oct 2, 2021)

Too Big is going to be defined by two things you can measure and determine.

1. Is the distance across the face of it too wide to bolt to your mill table. (will the securing bolt holes hang OFF the front and back of the table). 
2. Is it so tall that you lose too much "Z" distance to work your desired pieces.

You should be able to look up, or infer those two critical dimensions.


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## devils4ever (Oct 2, 2021)

From what I could find on the Internet, the center height is 3.937" (100 mm) which is a little tight, but I think will be okay. The base width is 3.543" (90 mm) which is fine since my table is 7" across.

So, I guess the size is okay. What brand to get? It looks like all of them improve with disassembly, cleaning, and re-oiling/re-greasing based on the YouTube videos I've watched. So, is it worth getting a Grizzly or PM versus a cheap eBay one? Are they any better?

Thanks!


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## WobblyHand (Oct 2, 2021)

I have a BS-0 on my PM25.  Started out with an eBay BS-0.  Suspect it would have been mostly ok, had it not been dropped.  But it had been dropped.  The eBay BS-0 was rough, but functional.  By rough, I mean literally.  Sharp edges, filled with grit, and all of the engraved lines literally would cut you, should you touch it.  The packing in the box did not prevent load shift - most likely leading to the dropping.  I had to disassemble the unit to find the latent damage.  In my case, the bearing casting had cracked.  The bearing casting is N/A.  After much time and persistence, I was able to return it and get my money back.  

Then turned around and bought the BS-0 from PM.  Packing was impeccable, the styrofoam actually fit the contents.  Was double boxed to further prevent shipping damage.  The unit was better finished and smoother turning.  The scribed lines were tolerable, although they could use a light stoning.  The PM BS-0 was so much better that I have not bothered to do a teardown.  It doesn't need it right now.  Yes, it was more expensive, but I have no regrets.  The runout on the mounted 3 jaw is surprisingly good at 0.001".

That's my story.  I suspect the eBay cheap ones are the ones that failed QC.  If I were to do it again, I'd go with the PM one.  

Only mounted the BS-0 along the x axis.  Don't know if it will bolt to the y, might be too long.  I can check if you think that's important.  Picture of BS-0 on table with 4" vise.  Axis is slightly over the vise, but not too high.


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## WobblyHand (Oct 2, 2021)

In all fairness, I think an eBay BS-0, if not damaged or mishandled in shipping, can be made to work.  More elbow grease, so to speak, but workable.  Had it not been for the broken bearing casting, I would have kept the first unit.  Have to agree, for the money, (even what PM charges) they are an amazing value.


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## devils4ever (Oct 2, 2021)

I decided to cry once and go with the PM. I'd rather not disassemble an eBay one as soon as I get it to clean it.

They claim it to be in stock, so I'm hoping it ships next week.

Thanks for everyone's input!!!


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## devils4ever (Oct 7, 2021)

The Eagle has landed! 

I received my PM BS-0 Dividing Head last night. I'm taking a closer look this morning. Overall, I'm very happy. VERY well packed in double boxes with fitted foam in the inner box. Entire head and all accessories are coated in a light oil. Smooth turning with the handle. I do feel a slight amount of backlash which I think I can eliminate. 

Of course, I have nothing to compare this to since I've never owned one before. When I use this in the next few days, I'll report back!

Precision Matthews BS-0 Dividing Head


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## addertooth (Oct 7, 2021)

devils4ever,
I must admit I am a bit jealous of your new toy.  Enjoy!


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## T Bredehoft (Oct 7, 2021)

I've been trying for  six months to find a use for that rascal. No joy yet. 

I'll bet if I had one I'd use it for something....
We'll see.


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## addertooth (Oct 7, 2021)

I would use one to cut precisions flats on round stock at precise angles, or to cut gears.  Perhaps even a precision slotted tachometer wheel.


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## devils4ever (Oct 7, 2021)

I've been using hex and square collet blocks, but sometimes you need to divide by other than 4, 6, 8, 12. Right now I'm making a tailstock tap/die holder that is 2" in diameter. I want to flute it for grip since my knurling tool is too small. Planning on 36 flutes around the circumference.

I do plan on cutting some gears in the future although I'm not how possible that is on a PM25 mill.


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## Winegrower (Oct 7, 2021)

I bought the cheapest BS-0 on eBay.   It’s impressively great.  No sand, beautiful ground surfaces, smooth operation, etc.   It was in the $240 region.  Fully satisfactory.


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## devils4ever (Oct 7, 2021)

Now, I've got a problem. I tried to remove the 3 Phillips head screws hold on the indexing plate and one was so tight I rounded out the head.

I was extremely careful doing this knowing these were tight and the put my full body weight on it and it still rounded out.

I'm not sure what to do!


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## jwmelvin (Oct 7, 2021)

Drill it. Unfortunate.


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## jwmelvin (Oct 7, 2021)

edit: oops double post.


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## devils4ever (Oct 7, 2021)

Well, I talked to Precision Matthews and they suggested drilling it out. I used a large right angle plate to mount it to my mill. Then, I used a gage pin to center the mill over the hole. I started with a large center drill. I quickly realized that I could mill off the head to remove the index plate and gain access to whatever is sticking out. I milled off the head carefully and removed the plate. Surprisingly, the remaining stud was finger tight and came out easily. SUCCESS! I'm going to replace these Phillip head screws with socket head (hex) cap screws so this doesn't happen in the future. They are 10-32 screws and not metric.


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## jwmelvin (Oct 7, 2021)

Good save


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## devils4ever (Oct 19, 2021)

Another question for everyone. How do I remove the 3-jaw chuck? There are 3 socket head screws on the back, but there is no way to access them.

Obviously, they were put in somehow. But, I can't figure out how.


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## Aaron_W (Oct 19, 2021)

devils4ever said:


> Another question for everyone. How do I remove the 3-jaw chuck? There are 3 socket head screws on the back, but there is no way to access them.
> 
> Obviously, they were put in somehow. But, I can't figure out how.
> 
> View attachment 382563



Those screws just hold the chuck to the back plate, the chuck is threaded onto the spindle of the dividing head.


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## BROCKWOOD (Oct 19, 2021)

Devils4ever. Thinking the chuck adapter screws off. Then the 3 bolts are exposed for easy access.


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## devils4ever (Oct 19, 2021)

Aaron_W said:


> Those screws just hold the chuck to the back plate, the chuck is threaded onto the spindle of the dividing head.



So, to remove, I would just turn the entire chuck CCW?


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## devils4ever (Oct 19, 2021)

In any case, I was successful in using the dividing head for the first time. I used it to put 36 flutes around a 2" (50.8 mm) cylinder. My calculations for rotations was correct at 40/36 = 1 4/36 = 1 2/18 holes. One whole turn plus 2 holes on the 18 hole plate.

I used the edge of the end mill to cut the flutes effectively making it a 45 degree cut. That was the tricky part--figuring out the location correctly. A little geometry and trig and I got it.


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## Aaron_W (Oct 19, 2021)

devils4ever said:


> So, to remove, I would just turn the entire chuck CCW?


 
Yes it is a 1-1/2"-8 thread which is a common thread for many older 9" and 10" lathes. It might be tight since it hasn't been off, but it should just unscrew.

Handy as you can easily find other types of chucks with this thread if you want to use a different size chuck, a 4 jaw chuck, collet chucks etc. Once you get the chuck off the spindle bore has an MT2 taper so it can take a center or other MT2 accessory. This was one of the reasons I went with the PM dividing head, because the 1-1/2"-8 / MT2 matches my lathe so I can share some tooling between them.


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## devils4ever (Oct 19, 2021)

Ok. Thanks!


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