# Dreaming of a power draw bar



## DPittman (Oct 22, 2021)

Well I seem to have to dream and pontificate about a project for ever before anything happens, so I start that part of the process pretty early so the actual project might have a chance of materializing.

I am eventually going to get a riser block made for my 6x26 milling machine but that means I am also going to have to have a power draw bar in place as I already have the machine up pretty high. 
I think I want to do something very similar to the power draw bar that  @John Conroy has done and the one seen on Tom's Techniques YouTube. 

I'm not familiar with Bridgeport style machines but on my little mill the impact setup has to sit on top of the belt cover and be able to flip open to change belts and occasionally change the drawbar itself out for a metric threaded one. 

Just looking for some basic tips and advice from those that have made one and might make some changes to their own design now that they have run it for awhile.


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## YYCHM (Oct 22, 2021)

Post and image or two of the top if the machine so that we can see what you're up against.

I to dither about projects, should I do it this way, or, should I do it that way, to the point where I end up saying just do something then it's started.


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## kevin.decelles (Oct 22, 2021)

I picked up a butterfly impact on impulse last week..... I have the same dream [mention]DPittman [/mention] 


Sent from my iPad using Tapatalk


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## YYCHM (Oct 22, 2021)

How often do you change belts?  I haven't change a belt since I installed my VFD.


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## DPittman (Oct 22, 2021)

kevin.decelles said:


> I picked up a butterfly impact on impulse last week..... I have the same dream [mention]DPittman [/mention]
> 
> 
> Sent from my iPad using Tapatalk


Yup Princess Auto has one on sale ((right now or soon) and that has again started the long project process...


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## DPittman (Oct 22, 2021)

YYCHM said:


> How often do you change belts?  I haven't change a belt since I installed my VFD.


Not often either but I would like to have the option of doing so without having to remove the power mechanism to do so (at the very least to change draw bars as that is something I do relatively often).


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## YYCHM (Oct 22, 2021)

DPittman said:


> Not often either but I would like to have the option of doing so without having to remove the power mechanism to do so (at the very least to change draw bars as that is something I do relatively often).



Can you get at your draw bar without opening the belt cover?  I can't.


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## DPittman (Oct 22, 2021)

YYCHM said:


> Can you get at your draw bar without opening the belt cover?  I can't.


No sorry I wasn't clear. No I can not get at drawbar or belts with out flipping open the cover that the power drawbar mechanism would have to attach to.


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## Tom Kitta (Oct 22, 2021)

Oh, I used butterfly wrench. System works OK, not great. I mean it does its job but is a bit "non professional". Main issue is that my BP clone is huge as its like a clone of series 2 and the butterfly is like 7ft over the ground. It would work far better for this size machine if it was a button based system - i.e. I press a button much lower, it removes DB, press it again and it puts it back in.

I used PA butterfly - the weaker one, not the PRO series. the weaker one is 75 lbs

Even with this hilly billy setup it is way faster then doing it by hand. I can post some pics.


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## Janger (Oct 22, 2021)

https://canadianhobbymetalworkers.com/threads/r8-collet-set-or-r8-er32-collet-set.2406/post-29324 

red neck or hill billy power draw bar. it just works. no project. get back to milling.


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## Janger (Oct 22, 2021)

And for you guys with the tall mills: 
https://www.canadiantire.ca/en/pdp/maison-kleen-folding-step-stool-white-1424388p.html#srp


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## trlvn (Oct 23, 2021)

I don't know if it would apply to the mill you have but Mark Presling created a power drawbar system for his Bridgeport.  There is a series of videos on the build:






Craig


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## historicalarms (Oct 23, 2021)

DPittman said:


> No sorry I wasn't clear. No I can not get at drawbar or belts with out flipping open the cover that the power drawbar mechanism would have to attach to.


I removed the cover on mine 20 yrs ago and it has never been back on, those exposed belts are way above any danger area. I keep the cover beside the machine just so's I can read the speed charts periodically.


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## Mcgyver (Oct 23, 2021)

I to pine for a PDB....but I probably only turn the air on 10 or 20% of the time I'm  in the shop.  Waiting for to cycle up, the noise and so on makes (for me) the ultimate power draw bar one that doesn't use air.  I  haven't seen an electric impact gun that would lend itself to this application so I keep hoping one of you smarter guys comes up with an idea


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## DPittman (Oct 23, 2021)

Mcgyver said:


> I to pine for a PDB....but I probably only turn the air on 10 or 20% of the time I'm  in the shop.  Waiting for to cycle up, the noise and so on makes (for me) the ultimate power draw bar one that doesn't use air.  I  haven't seen an electric impact gun that would lend itself to this application so I keep hoping one of you smarter guys comes up with an idea


You know I share those same thoughts.  I hate my noisy air compressor but I have an air blast oiler spray mechanism that I think I will occasionally use and that needs air at the mill anyhow.  I too was hoping someone had devised a rechargeable electric version of the power drawbarbut I don't think I'm the one to bring it to fruition.


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## Janger (Oct 23, 2021)

I'm telling you guys the portable power impact driver works great. No air. It sounds and looks like a joke but it's fast and simple. try it!


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## DPittman (Oct 23, 2021)

Janger said:


> I'm telling you guys the portable power impact driver works great. No air. It sounds and looks like a joke but it's fast and simple. try it!


I don't doubt that at all and the only reason I'm not doing the same is because the stretch and height difference between the top of my mill and the spindle.  It would be a tough stretch to the power with one hand while holding the collet with the other.

Edit...maybe I should try and not dismiss until then!!!

Ps. My email notifications seem to have started again


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## PeterT (Oct 23, 2021)

Janger said:


> I'm telling you guys the portable power impact driver works great. No air. It sounds and looks like a joke but it's fast and simple. try it!


I use a cordless wrench with a socket, but its also within within my tippee-toe reach. My mill has a brake so I hold that when tightening/loosening. The wrench lever is quite sensitive so you can feel the torque. I never drive it home. I've wondered about a permanent electric version by gutting an e-wrench, hook up DC power, remote switch etc. But still have to solve how to disengage during long stretches of mill running, either mechanically or electrically. Also sometimes my drawbar still needs a light tap to disengage the quill seat even with drawbar unthreaded. Nobody seems to talks about a hung up tool after drawbar disengagement on the pneumatic systems. Maybe higher frequency pneumatic ratchet action imparts just enough shake?


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## jcdammeyer (Oct 23, 2021)

Mine is progressing slowly.  I 3D printed all the parts to test the theories.  The blue tab on the RH post holds a hall effect sensor and there's a magnet on the socket.  The idea is that I don't want to unwind the draw bar too far for the TT holders since they only need about 1 to 1.5 turns to loosen enough to be removed without the entire R8 part falling out.

For tightening max 3 turns or X seconds.  I have a Load and Unload button and if they are tapped the behaviour is as above.  If they are held then the draw bar runs for longer or until released.  So it can still drop out the R8 TT Collet Holder or pull it or some other R8 tooling all the way up.  The controller runs a couple of pneumatic valves to separately move the assembly down and separately engage the butterfly impact wrench.  I found when I tee'd them together the way they were done in the plans I bought that the impact wrench bled too much air away from the cylinder and so it wouldn't go down.

The small collar on the bottom right unfortunately snapped the other day while putting the castings together. 

So I took the 3D printed drawing, exported to the CAM software and then spent lots of time milling the inside 5/8" hole starting with the 1/2" drilled hole and then the outside.

Oh and the module also talks to LinuxCNC via CAN bus and lights a couple of indicators on the AXIS display.  At some point it will all be integrated as part of an automatic tool changer.


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## John Conroy (Oct 23, 2021)

Janger said:


> I'm telling you guys the portable power impact driver works great. No air. It sounds and looks like a joke but it's fast and simple. try it!


The reason I'm a fan of power draw bars is my old mill and the new one both have draw bars over 7 feet off the floor. That requires a 2 step stool for me as my butt is built too close to the ground. It only takes one slip off the stool to break some body part that will takes months to heal and I've had some close calls. It's a matter of convenience but also self preservation. It was a fun project on my old mill and I don't think the system on the new mill works any better than the one I built for the old one but it is prettier.


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## Janger (Oct 23, 2021)

I didn’t think of the safety angle - good call John.


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## Mcgyver (Oct 24, 2021)

Janger said:


> I'm telling you guys the portable power impact driver works great. No air. It sounds and looks like a joke but it's fast and simple. try it!


To use in the making of a PDB, or instead of?

I haven't seen one that would lend itself to adoptation into a PDB the easy way the butterfly wenches do


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## John Conroy (Oct 24, 2021)

Janger said:


> I didn’t think of the safety angle - good call John.


The older I get the easier I break! LOL But I've had 2 ankle fractures in the past 6 years that have really affected my thinking. I never thought about safety when I was young and unbreakable.


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## DPittman (Oct 25, 2021)

So my mill doesn't have any sort of spindle lock.  Right now when I'm tightening up the draw bar I simply hold the pulley with the other hand.  Is my spindle just going to spin with a power draw bar and no spindle lock?


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## YYCHM (Oct 25, 2021)

DPittman said:


> So my mill doesn't have any sort of spindle lock.  Right now when I'm tightening up the draw bar I simply hold the pulley with the other hand.  Is my spindle just going to spin with a power draw bar and no spindle lock?



Good point.  Mine is the same.


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## DPittman (Oct 25, 2021)

YYCHM said:


> Good point.  Mine is the same.


The bottom end of my spindle does have two flats on it so I guess I could make a spanner for that if it does spin?


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## DPittman (Oct 25, 2021)

DPittman said:


> The bottom end of my spindle does have two flats on it so I guess I could make a spanner for that if it does spin?


Although that's going to require 3 hands...1 for the powerdrawbar operation, 1 for the spindle wrench and 1 to hold the tool/collet in place.   Hmnnn I gotta rethink things.


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## DPittman (Oct 25, 2021)

DPittman said:


> Although that's going to require 3 hands...1 for the powerdrawbar operation, 1 for the spindle wrench and 1 to hold the tool/collet in place.   Hmnnn I gotta rethink things.


Oh boy I better go to bed, I'm not thinking clearly.
Why would the spindle turn if I can hold it with my hand on it just as well as holding it up top on the pulley?
Good night!


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## YYCHM (Oct 25, 2021)

DPittman said:


> Although that's going to require 3 hands...1 for the powerdrawbar operation, 1 for the spindle wrench and 1 to hold the tool/collet in place.   Hmnnn I gotta rethink things.



Ya, nothing to grab onto on mine either  My mini-mill came with a locking rod and a hole to lock the spindle from turning.....

I think inertia just breaks those PDBs loose and sets them?


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## John Conroy (Oct 25, 2021)

On mine you need to lock the quill fully up or the down force of the power draw bar will push it down and not allow full engagement of the socket onto the top of the drawbar. You can hold the spindle from turning with the same hand that is inserting the collet or tool.


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## DPittman (Oct 26, 2021)

John Conroy said:


> On mine you need to lock the quill fully up or the down force of the power draw bar will push it down and not allow full engagement of the socket onto the top of the drawbar. You can hold the spindle from turning with the same hand that is inserting the collet or tool.


Ok that makes sense. Thank you.


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## Susquatch (Oct 27, 2021)

YYCHM said:


> I to dither about projects, should I do it this way, or, should I do it that way, to the point where I end up saying just do something then it's started.





DPittman said:


> Well I seem to have to dream and pontificate about a project for ever before anything happens, so I start that part of the process pretty early so the actual project might have a chance of materializing.




You guys are just like me. I swear I dither about projects for years before I finally get at them and then I wish I did them years earlier. Insert huuuuge sigh here..... 



Janger said:


> And for you guys with the tall mills:
> https://www.canadiantire.ca/en/pdp/maison-kleen-folding-step-stool-white-1424388p.html#srp



No way. A guy my size would collapse that thing and I'd knock over my BPort. Thankfully, I don't need one. If I did, I'd make a big one out of wood with outset legs so it would never flip on me. The only thing stools get used for in my shop is temporary workbenches to put tools and parts on.


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## Susquatch (Oct 27, 2021)

Related question for you drawbar focussed guys:

Assuming that we are talking R8, how tight is tight enough?

I would think that its a function of the size/area of the tool engagement. A 3/4" tool needs more torque than a 1/4" tool. But maybe there is a standard that works for all. 

I sometimes worry I'm too tight. I've seen what insufficient torque does. 

I asked this same question in another thread but nobody volunteered an answer. It probably got overlooked or its a dumb question and I'm too dumb to know it.....


Susquatch said:


> One more related question guys...
> 
> I've been thinking about that groove and how it got there....
> 
> ...


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## cuslog (Oct 27, 2021)

I wished for a PDB for years - reaching up there for manual tooling changes just wore me down. Finally built a simple one using a Princess Auto Butterfly wrench. It was a great improvement - with one caveat : watch your air pressure and think twice before making any heavy cuts. In the last 6 months since I built mine, I've had 2 incidents where an endmill pulled itself down in the collet. My air compressor is a bit on the noisy side and I don't always turn it on. If your air pressure has "sagged a bit" and you step into a heavier cut, you may be at risk of an end mill slipping down. I saw a comment a few days ago saying that PA has a heavy duty butterfly - I probably got the weaker one. Gonna turn my air pressure regulator up a bit when I go out there today.


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## DPittman (Oct 27, 2021)

You know what they say about dumb questions...no such thing as a dumb question only dumb answers.  I too have been wondering about the correct amount of torque on the drawbar.

I have found out the hard way what too little torque does but I really don't have a clue what enough or too much really is.  The cheap butterfly impact wrench I bought has maximum torque of 75lbs.  I relate that to how much torque I put into tightening wheel lug nuts on my minivan, (recommended about 75-80lbs. I would think that sort of torque on my draw bar would be certainly adequate but not excessive.  I considered the higher end impact wrench that delivered 180 lbs but was worried it would be too easy to over torque the drawbar with that. Now I don't know if the cheap impact wrench will actually deliver that sort of torque easily and consistently or only with oiled threads, 120 psi and on a sunny day.  I guess I should test that.  
???


Susquatch said:


> Related question for you drawbar focussed guys:
> 
> Assuming that we are talking R8, how tight is tight enough?
> 
> ...


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## jcdammeyer (Oct 27, 2021)

I referred to this article in my thread on the CNC conversion.
Posting with link to Rick Sparber's WUT
I find that for normal wrench based draw bar work that I don't need a spindle lock.
The impact wrench when just used by hand on my mill without using the second wrench for the WUT doesn't really turn the spindle. But now that I have an AC servo I'm finding it acts as a brake and prevents the spindle from turning.

However, depending on how your upper drive section is configured, if you use pneumatics to bring the impact wrench down then as it goes down it could push a spring loaded pin that would drop into a hole in the pulley if the spindle did make one turn.  Or put in 3 or 4 holes to keep things balanced. 

Doesn't even have to be pneumatics.   If you have a lever you pull down to engage the socket that then closes a switch to enable an electric impact wrench you could have that also push a pin into the pulley.  That leaves one and on the lever, perhaps even twisted clockwise or counter clockwise to load or unload the draw bar.  The other hand to hold onto the tool or catch it.


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