[skray775]

Hi all,

I was thinking about building the power draw bar system like Hoss has on his web site (project #7).

Since I have a round column machine my Z axis is on the quill not the column. After thinking about it a while I was concerned the down force on the drawbar might damage the ball screws on the quill with when the power of the air cylinder pushes down on the draw bar to release the tool.

What do you guys think ?

[eartaker]

1500-2000 lbs of force is a lot to be putting on the screws and bearings that Is why you see most of us using a collar of some sort that is gripped when the cylinder is engaged so that no pressure is put on the bearings. Im sure there is a way do go the same but it will be hard to do since the quill is moving. you might be better off going with the air ratche/impact method.

There are a few out there but this is an example.
[ame=http://www.youtube.com/watch?v=G0VK3lQwLwc&feature=related]Power Drawbar - YouTube[/ame]

[gd.marsh]

Kregan,

The design feature you want to include (which Hoss' has) does not use downward force only. But by allowing the cylinder to lift when actuated, it pulls up on a flange that's attached to the spindle while pushing down on the drawbar. This eliminates the downward force from being applied to the spindle bearings & in your case the Z ballscrew & ballnut as well.

EDIT: Just read eartakers reply & it dawned on me with your quill moving you wouldn't be able to attach a flange to pull up on .. my bad!

[vidio1]

POWER DRAWBAR KIT

This is the power drawbar I built and use, works great.

[skray775]

Excellent! I had seen that video and liked the idea.

I do have air in the shop but it is not always on and the electric seems easier to deal with. On top of that I have the belt cover to deal with.

Maybe this cold be mounted to the top of the gear cover... Hmmmmm

1500-2000 lbs of force is a lot to be putting on the screws and bearings that Is why you see most of us using a collar of some sort that is gripped when the cylinder is engaged so that no pressure is put on the bearings. Im sure there is a way do go the same but it will be hard to do since the quill is moving. you might be better off going with the air ratche/impact method.

There are a few out there but this is an example.
Power Drawbar - YouTube

[hoss2006]

Several people have adapted my MAD drawbar to a variety of machines with quills.
Projects2
It uses the same belleville spring washers as used on the ATC you mentioned from project 7.
Projects 7
They give about 750 lbs holding force ( NOT 1500-2000) which is well below the bearings static load rating.
They'd been used for years without trouble on the X2.
It'll provide holding force well enough for 3/8 tooling.
As seen in the videos the MAD is easy to build and gives very quick tool changes
although you have to do the work.
If you can't disengage your quill drive to do it manually, your quill drive may have the torque to do it for you.
Don't know what ballscrew/nut you're running but a cheap Roton 5/8 nut has a running load rating of 750 lbs and 6000 lbs static.
Hoss

[eartaker]

kregan,

If your planning on running over a 3/8 endmill (I'm sure you are) then you will need more that 750lbs of force. I have 1400lbs of holding force on my 45 and have still had a 3/4 endmill 1" DOC work its way out of the holding collet a little while side milling a shoulder.

Either way to change tools you will have to bring your Z up to meet the power drawbar. You can run a lower force and see how that works out. Or you can just use the ratchet method like many others do. Its your decision Let us know what route you go.

[hoss2006]

kregan, I offered my suggestion based on comments you made before.

Hi guy,

Most of my machining is done with 3/8" and smaller mills and a lot of # size drills in aluminum.

Since I have a round column machine moving the head up and down is a problem but mostly the issue centers around the length of the drill chuck. If the head is adjusted high enough to clear a drill chuck, even with machine screw lenth drills then the quill is extended quite far with endmills installed and I loose a lot of my useful Z travel.

I doubled back to your thread and notice that you removed the manual quill and don't think your motor will be able to compress the springs so ignore my previous post.

This guy did a very simple pdb based on the Insight type.

[ame="http://www.youtube.com/watch?v=pPXKGQV5e-0&feature=channel_video_title"]Power Drawbar for Milling Drilling Machine RF45 - YouTube[/ame]

As did this guy who also sells the plans for less than $10.
Harrison Specialties LLC LED lights, Motorcycle backrests, DIY plans and other accessories: Power Drawbar Plans for Vertical Mill
Bob Warfield takes you through building his Insight version here.
http://www.cnccookbook.com/CCMillDrawbar.html
Hoss

[vidio1]

One of the advantages to the PDB in the link I posted is that it's "remote" in that you can attach the up/down controller where it's convenient for the operator. An important feature if you are reaching over an enclosure.......

[skray775]

All great idea's guys... Thank you very much!

I love the manual release Hoss, might have to adapt that on my second manual mill.

[truckeic]

Several people have adapted my MAD drawbar to a variety of machines with quills.
Projects2
It uses the same belleville spring washers as used on the ATC you mentioned from project 7.
Projects 7
They give about 750 lbs holding force ( NOT 1500-2000) which is well below the bearings static load rating.
They'd been used for years without trouble on the X2.
It'll provide holding force well enough for 3/8 tooling.
As seen in the videos the MAD is easy to build and gives very quick tool changes
although you have to do the work.
If you can't disengage your quill drive to do it manually, your quill drive may have the torque to do it for you.
Don't know what ballscrew/nut you're running but a cheap Roton 5/8 nut has a running load rating of 750 lbs and 6000 lbs static.
Hoss

Do you still have your plans on the web.. trying to find them...

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