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BobWarfield
02-07-2008, 02:04 PM
My latest Harbor Freight flyer shows their butterfly impact wrenches are once again on sale. They're $14.99, regular $29.99.

Why would you care?

I built a really neat powered drawbar from one for my mill:

http://www.cnccookbook.com/img/MillStuff/PowerDrawbar/PC173693.JPG

That and a power feed can really improve your mill productivity.

But here's another tip: you can use the butterfly impact wrench without building the drawbar too!

Here's what I mean by a butterfly impact wrench:

http://www.cnccookbook.com/img/MillStuff/PowerDrawbar/PB103670.JPG

It's a little fist-sized bundle of goodness for drawbars. Snap the right socket on it and you can reach up and zzzzzzzzzzzzzzzzzzzziiippppp, DONE!

A air ratchet works too, but there's a reason the drawbar wrenches have a little hammer as well as a socket, and the impact wrench is 2 in 1.

Try it, you'll like it! And when you get around to it, build the power drawbar too!

Best,

BW

Wirecutter
02-07-2008, 02:44 PM
Those are some stout little springs on the support rods, Bob. Did you use a cylinder without spring return, or was it simply not "crisp" enough on the return stroke?

Also, did you make a gasket for the back of the wrench, or were you able to salvage the original? If you made it, what material did you use?

In any case, nice job, and thanks for the heads-up on the HF sale.

-Mark

BobWarfield
02-07-2008, 04:48 PM
It was built to Joe Vicar's plans. More on my web site:

http://www.cnccookbook.com/CCMillDrawbar.html

The best thing about the sale is you can use the impact wrench to speed up tool changes whether or not you go on and build a powered drawbar. I'm probably going to order up another because there's something cheap I want from HF and the little wrench works real well. I think it'd be handy to have one kicking around.

Best,

BW

j king
02-07-2008, 06:15 PM
Hey Bob. I have mine built.It isnt 100 % done.I am going to make a cover for mine and i need to find a 1/16npt fitting to finish it but have ran it and I am tickled to death on the operation of it.I plumed mine with electric over air solenoids.I have a double acting cylinder that pushes the wrench up and down.I wanted the wrench to be down before spinning so it wouldnt tear up the drawbar end or the socket.I always have to make things a little harder than they need to be..

BobWarfield
02-07-2008, 07:44 PM
Hey Bob. I have mine built.It isnt 100 % done.I am going to make a cover for mine and i need to find a 1/16npt fitting to finish it but have ran it and I am tickled to death on the operation of it.I plumed mine with electric over air solenoids.I have a double acting cylinder that pushes the wrench up and down.I wanted the wrench to be down before spinning so it wouldnt tear up the drawbar end or the socket.I always have to make things a little harder than they need to be..

There is perhaps an element of "need to be". I've been using mine non stop for a little over a year. The drawbars on these Asian mills are extremely mild steel, and I'm here to tell you that there is significant "gnawing" on the nut over the course of a year.

There are several things you can do about this. First, you can simply face the nut and adjust your drawbar once a year. Eventually it's too short and you buy a new one for circa $15. That's what I paid for my spare.

You can modify the design as you have. Haven't gone there myself.

You can harden the drawbar or buy a hardened drawbar. I had a chance to buy a nice hardened drawbar from Aaron Moss that I plan to put on mine. However, if I were doing this powered drawbar for the first time or refacing the nut, I'd be tempted to try to harden the nut in the usual way.

One thing that really accelerates the wear is forgetting to raise the quill all the way before firing up the powered drawbar. That right there is what we call a "bad idea".

Also, do make a spacer so the drawbar doesn't float around in the bore. That helps a lot too.

Cheers,

BW

J.Ramsey
02-07-2008, 08:21 PM
Not all "Asian " draw bars are soft,the one on my Grizz 9x49 is about 9points harder than the back of Supermans head, a file won't hardly touch it.
Use a 12 point flank drive socket and drawbar wear won't be a problem.
Don't worry about the socket spinning before engaging with the drawbar as the air cylinder will have the socket engaged faster than a blink of the eye.

BobWarfield
02-07-2008, 08:37 PM
Not all "Asian " draw bars are soft,the one on my Grizz 9x49 is about 9points harder than the back of Supermans head, a file won't hardly touch it.
Use a 12 point flank drive socket and drawbar wear won't be a problem.
Don't worry about the socket spinning before engaging with the drawbar as the air cylinder will have the socket engaged faster than a blink of the eye.

JR, negative, even with a 12 pt you can still get wear. Some are just soft.

BW

J.Ramsey
02-07-2008, 09:02 PM
JR, negative Some are just soft.

BW

I guess some drawbars need Viagra.

BobWarfield
02-07-2008, 10:04 PM
I guess some drawbars need Viagra.

ROFL!

Good one!

Bill Pace
02-07-2008, 11:28 PM
Y'all got me curious ---- I built this power draw bar also about a year ago, and so I went out and took a good look at my drawbar head ....it looks just like it did when new!! I used a 12 point, -- I couldnt see how a 6 pt would do at all. And my quill is sometimes sluggish to return and consequentially I'll reach up and hit the switch without it fully retracted:( ....hasnt affected it.

One possible? reason mine isnt showing wear --- I used 1/4" fridge line instead of the 1/8" copper and it seems to function on the edge, running about 110-120psi. These little butterflys in use as a wrench really have a 'rrraapp' to them and are quite potent, but in use on my drawbar is more 'sedate?' Whatever,-- it functions flawlessly and I'm a believer in leaving well enough alone ... that is one more neat addition and well worth your time to make one up , and cheap too!!