# Draw bar issues on PM833TV



## LVLAaron (Mar 2, 2022)

My 833TV doesn't have flats on the spindle. So tightening the draw bar is a complicated matter. I do have the black wrench to keep the shaft from spinning, but it only slides over the draw bar if the draw bar is is in the exact right spot - and can't be used at all with my fancy shims in there. The shims are less of a problem, I can make smaller ones... but the overall problem / question remains. What do?


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## parshal (Mar 2, 2022)

I think I found a spline wrench on Amazon or somewhere that fit mine.  But, about the same time, I started using a small butterfly impact to change tooling so I don't need to worry about holding the far to tighten/loosen.  It's very quick and easy.  I'd look into that if I were you.


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## LVLAaron (Mar 2, 2022)

parshal said:


> I think I found a spline wrench on Amazon or somewhere that fit mine.  But, about the same time, I started using a small butterfly impact to change tooling so I don't need to worry about holding the far to tighten/loosen.  It's very quick and easy.  I'd look into that if I were you.



I've been using a small 12v impact on mine as well. The tolerances on my spline wrench are so good it's a pain in the a@@ to use


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## parshal (Mar 2, 2022)

With a strong impact you don't need to hold the bar so the wrench is unnecessary.  I ran an air hose from my compressor to the top of the mill.


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## LVLAaron (Mar 2, 2022)

parshal said:


> With a strong impact you don't need to hold the bar so the wrench is unnecessary.  I ran an air hose from my compressor to the top of the mill.



Yep. Appreciate it. Just wanted to make sure I wasn't missing something obvious about the machine.


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## parshal (Mar 2, 2022)

Unfortunately you're not missing anything.  It'd be great if they had a spindle lock.

I asked very similar questions in this thread.  Take a look at the responses.


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## davidpbest (Mar 2, 2022)

Have a look at this post.  You can make or buy a spring-loaded plunger that will lock spindle rotation (bottom photos), or this would be a good time for a PDB install.









						Becoming hobby machinist in the near future.
					

Personally, I think it would look great and perform very well with a Maxi Torque-Rite PDB.     It would need stand-offs or a custom riser block turned on his new 1340 lathe but simple enough.   :)  The machinist hobby has as many cool toys as the classic car hobby.  Haven't had this much fun...




					www.hobby-machinist.com


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## 7milesup (Mar 2, 2022)

What are the washers for?  If I remember correctly, I cut my drawbar off a little.  

I am assuming yours does not have a Hi-Lo range due to it being an 833TV.  I have the geared version and just put it in low range to tighten the drawbar up.


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## LVLAaron (Mar 2, 2022)

Draw bar is a little long, so I washer-ed it. Correct about not having hi-low - it's belt driven so it always spins freely. I'll happily keep using a small impact, just wanted to make sure I wasn't missing something stupid.


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## Christianstark (Mar 2, 2022)

7milesup said:


> What are the washers for?  If I remember correctly, I cut my drawbar off a little.
> 
> I am assuming yours does not have a Hi-Lo range due to it being an 833TV.  I have the geared version and just put it in low range to tighten the drawbar up.


The manual has instructions on shortening the draw bar. Mine worked either everything aside from a slitting saw arbor, so I machined a 1/2 shim (bushing) that is small enough that the spline wrench I have goes over no issues. I had to chase a tap into some of my holders, but now they thread nicely all the way till the R8 seats, and then I give it a quarter turn or 3 and line up one of the corners of the drawbar bolt to a spline, and the spline wrench comes right off. Clocking the hex to a specific location in relation to the splines is key.


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## xr650rRider (Mar 2, 2022)

LVLAaron said:


> The tolerances on my spline wrench are so good it's a pain in the a@@ to use



Machinist should always have some files on hand.  Just think, John M. Moses (really his brother) built firearms, that have still not been superseded, by hand.


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## LVLAaron (Mar 2, 2022)

xr650rRider said:


> Machinist should always have some files on hand.  Just think, John M. Moses (really his brother) built firearms, that have still not been superseded, by hand.


Heh, I have a drawer full of sharp files and stones. I'm lazy, however.


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## xr650rRider (Mar 3, 2022)

Well if you don't want to make the spindle wrench fit, I hope you have a drill chuck with a key and not hand operated.  Providing a backup to tighten and loosen the drill chuck is the majority of what I use one for.


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## LVLAaron (Mar 3, 2022)

xr650rRider said:


> Well if you don't want to make the spindle wrench fit, I hope you have a drill chuck with a key and not hand operated.  Providing a backup to tighten and loosen the drill chuck is the majority of what I use one for.



Yeah, my chucks require a spanner. I'll work on filing out the spindle wrench a bit so it's less miserable to use.


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## ahazi (Mar 3, 2022)

parshal said:


> With a strong impact you don't need to hold the bar so the wrench is unnecessary.  I ran an air hose from my compressor to the top of the mill.


I am also using a small impact driver to tighten and release the drawbar on the PM833T. I find that in most of the cases I need to also hit on the hex head of the drawbar to release the R8 collet. Am I the only one having this experience or is it universal?

I started to build a pneumatic drawbar PDB with a butterfly impact driver but I am afraid that it will not release the R8 collet. Interested to know of others experience before I continue with the build.

Ariel


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## davidpbest (Mar 4, 2022)

ahazi said:


> I am also using a small impact driver to tighten and release the drawbar on the PM833T. I find that in most of the cases I need to also hit on the hex head of the drawbar to release the R8 collet. Am I the only one having this experience or is it universal?
> 
> I started to build a pneumatic drawbar PDB with a butterfly impact driver but I am afraid that it will not release the R8 collet. Interested to know of others experience before I continue with the build.
> 
> Ariel


The jolts of the impact driver combined with downward pressure jostle the R8 collet loose. If you want an excellent design example for DIY, check out this system (most compact and elegant design I have seen - this is the end of a series - skip to 35:45 to get an idea of the finished design):


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## parshal (Mar 4, 2022)

ahazi said:


> I find that in most of the cases I need to also hit on the hex head of the drawbar to release the R8 collet. Am I the only one having this experience or is it universal?



Mine does the same.  I keep a small, plastic deadblow by the mill for that purpose.


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## Asm109 (Mar 4, 2022)

Nylon strap wrench on the spindle snout?


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## parshal (Mar 4, 2022)

I tried that.  It worked but it takes longer than a small butterfly impact.


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## Jason812 (Mar 4, 2022)

parshal said:


> Mine does the same.  I keep a small, plastic deadblow by the mill for that purpose.


I use a wooden hammer.


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## parshal (Mar 4, 2022)

Sometimes I grab the rubber mallet.  It doesn't take but a tap.


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## Lucas E (Mar 4, 2022)

Here's another good design if you don't want to mess with the air cylinder. This adds an extra rod that de-couples the handle from the butterfly valve. That way when you pull down on the slide you aren't putting a lot of force on the butterfly valve handle.

I'm planning to make this style for my 833tv as I prefer a simpler mechanism.


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## ahazi (Mar 4, 2022)

parshal said:


> Mine does the same.  I keep a small, plastic deadblow by the mill for that purpose.


So it seems that we are all experience the same stickiness in the R8 collets on the PM833T. 

Is this kind of stickiness normal on the BP knee type milling machines? 
Is this an *isolated issue* because of how the R8 quill in the PM833T or PM833TV is built?
The reason that I put on hold my PDB built is that I am not convinced that it will release the R8 collet. I tried the butterfly pneumatic wrench by activating it and pushing it down by hand but it did not release the collet, it still needed a tap by a mallet. Maybe it needs to be mounted rigidly to the mill to actually release the collet. 

@David - the design that you linked to is similar to what I was working on. I have it all figured out on how to use existing cover screws etc. He added a *pneumatic actuator* to push down the drawbar and maybe this is what makes the difference. 

I think that resolving this issue and coming up with a PDB design that actually works reliably on the PM833T is what this group can help with.

Ariel


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## davidpbest (Mar 4, 2022)

ahazi said:


> So it seems that we are all experience the same stickiness in the R8 collets on the PM833T.
> 
> Is this kind of stickiness normal on the BP knee type milling machines?
> Is this an *isolated issue* because of how the R8 quill in the PM833T or PM833TV is built?
> ...


None of this is unique to the 833.  R8 collets in my RF-45 needed a tap on the top of the drawbar once it was manually unscrewed.  So did my 935 until I added the PDB.  Most PDB's have some means of pushing down on the drawbar cap nut while the impact wrench hammers away.  If the drawbar is given sufficient downward pressure while simultaneously being unscrewed, it will force the collet downward and it will drop free.  If you don't push down on the drawbar while unscrewing it, the collet will remain in a wedged position as the drawbar moves upward during the unscrewing action.  

I have seen PDB designs that required the operator to pull down against the drawbar cap nut while articulating the impact driver.  _*This*_ is one example of that type of design. And there are others (such as the Maxi Torque-Rite and Kurt) that have a pneumatic actuator pressing down on the drawbar during the operation.


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## ahazi (Mar 4, 2022)

davidpbest said:


> None of this is unique to the 833.  R8 collets in my RF-45 needed a tap on the top of the drawbar once it was manually unscrewed.  So did my 935 until I added the PDB.  Most PDB's have some means of pushing down on the drawbar cap nut while the impact wrench hammers away.  If the drawbar is given sufficient downward pressure while simultaneously being unscrewed, it will force the collet downward and it will drop free.  If you don't push down on the drawbar while unscrewing it, the collet will remain in a wedged position as the drawbar moves upward during the unscrewing action.
> 
> I have seen PDB designs that required the operator to pull down against the drawbar cap nut while articulating the impact driver.  _*This*_ is one example of that type of design. And there are others (such as the Maxi Torque-Rite and Kurt) that have a pneumatic actuator pressing down on the drawbar during the operation.


Is the quill down movement needs to be locked while doing this? With a tap from a mallet there is no need to lock the quill. This might be why just pushing down on the pneumatic butterfly wrench was not enough.


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## davidpbest (Mar 4, 2022)

*Here's an example*_ of a DIY PDB that has a pneumatic actuator that pushes down on the drawbar during operation (part 4 of 4)._


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## davidpbest (Mar 4, 2022)

ahazi said:


> Is the quill down movement needs to be locked while doing this? With a tap from a mallet there is no need to lock the quill. This might be why just pushing down on the pneumatic butterfly wrench was not enough.


I do NOT have to hold or lock the quill travel during PDB operation.


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## davidpbest (Mar 4, 2022)

Have you removed or checked the interference for the dog-point set screw that meshes with the slot in the side of the R8 collets?  I removed mine completely.  But if that set screw is in too far, or has a point that's too wide, it will contribute to the "stickiness" of the R8 not dropping free.



			https://www.precisionmatthews.com/wp-content/uploads/2017/01/What-do-you-do-if-your-R8-tooling-will-not-go-in-to-the-spindle.pdf


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## parshal (Mar 4, 2022)

I took the set screw out of mine too.  No need to find the correct orientation for the collet now.


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## Doug Gray (Mar 4, 2022)

The draw bar on my wrong-fu 45 has two nuts, one sits on the top of the spindle and one is fixed (pinned) to the top of the draw bar. So you just use two wrenches to tighten/loosen, no worries about trying to lock the spindle.


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## ahazi (Mar 4, 2022)

davidpbest said:


> Have you removed or checked the interference for the dog-point set screw that meshes with the slot in the side of the R8 collets?  I removed mine completely.  But if that set screw is in too far, or has a point that's too wide, it will contribute to the "stickiness" of the R8 not dropping free.
> 
> 
> 
> https://www.precisionmatthews.com/wp-content/uploads/2017/01/What-do-you-do-if-your-R8-tooling-will-not-go-in-to-the-spindle.pdf


I removed the set screw. It is not really needed with the small electric impact wrench.


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## ahazi (Mar 4, 2022)

davidpbest said:


> *Here's an example*_ of a DIY PDB that has a pneumatic actuator that pushes down on the drawbar during operation (part 4 of 4)._


Thanks David!

I guess the only way I will know is to just finish my build and see if it works.

I am not sure if the pneumatic cylinder is just for convenience or it actually bumps the head of the drawbar with an impact that releases the R8 collet especially when the release is done in pulses as it looks like in the videos:
1st pulse pushes the wrench into the drawbar and turns it CCW
2nd pulse after the drawbar is not tightly holding the R8 collet the actuator is hammering the drawbar down and releases the collet from the quill


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## ptrotter (Mar 4, 2022)

Why not go with the air cylinder version of the PDB like Priest Tools sells?  I built one for my PM-940V and it works great.  Since it pushes down on the drawbar to release the collet, the tool just drops into my hand.  It was very easy to build and is fast to operate.  Probably a little more expensive though.


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## davidpbest (Mar 4, 2022)

ptrotter said:


> Why not go with the air cylinder version of the PDB like Priest Tools sells?  I built one for my PM-940V and it works great.  Since it pushes down on the drawbar to release the collet, the tool just drops into my hand.  It was very easy to build and is fast to operate.  Probably a little more expensive though.


The Priest Tools system is not an R8 power drawbar.  It’s a TTS pneumatic tool changer.  Yes, it does install into an R8 spindle, but all tooling must be mounted on TTS-style tool holders rather than R8 shanks.  In that sense, it is functionally more akin to something like the* Royal EasyChange* QC tool system.


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## parshal (Mar 4, 2022)

David, I discovered exactly that after I installed Priest Tools' system on my 833TV.  I should've known what I was installing.  LOL


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## davidpbest (Mar 4, 2022)

parshal said:


> David, I discovered exactly that after I installed Priest Tools' system on my 833TV.  I should've known what I was installing.  LOL


I actually think Priest and Tormach should stop calling it a Power Drawbar.  It’s a TTS pneumatic collet closer.  It has the advantage of consistent and precise tool offsets and the ability to support an automatic tool changer which are both important in the CNC arena.  But it does require all tools to be mounted on TTS spindles, and compared to R8 tooling is less suitable for aggressive milling situations.


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## ptrotter (Mar 4, 2022)

You are right David, I am so used to using my TTS tool holders that I forget that It only works with 3/4" tool shanks.


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## Lucas E (Mar 4, 2022)

On the pneumatically actuated butterfly units the cylinder holds the socket against the drawbar while it unscrews. In a manual one you pull down on the handle which holds it against the drawbar.

You need to make sure you use a shallow socket so the drawbar bottoms out in it. When the drawbar hits the back of the socket it stops going up and if you continue to unscrew it will eject the collet. You don't need a separate hammering action of the air cylinder. Just the force of it holding down is enough to create a backstop for the drawbar to run in to.

On a manual one you'll need to pull down on the handle to put pressure on the top of the drawbar with the back of the socket. This is the reason it doesn't seem like a good idea to mount a handle directly to the butterfly valve. In the video I posted you can see there is a vertical bar supporting the handle. That way the downward pulling force isn't trying to jerk the pivoting handle off the impact wrench.


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