Author Topic: Air powered Draw Bolt (Read 33332 times)

Darren · « **on:** July 02, 2009, 04:43:09 AM »

I can't find it now, but someone in the US mentioned they had built an air powered drawbolt device for their milling machine...

Would you please care to expand?

Ta...

kvom · « **Reply #1 on:** July 02, 2009, 08:52:10 AM »

I've seen several home-made versions. They use an impact gun or ratchet. Fabricate a bracket to mount it to the top of the mill attached to the drawbar. Then it's a matter of figuring out how to operate the trigger and reverse.

Darren · « **Reply #2 on:** July 02, 2009, 08:56:30 AM »

Thanks, I have seen a few Utube vids, I was just wondering if anyone can give first hand exp and some greater details...

spuddevans · « **Reply #3 on:** July 02, 2009, 01:49:29 PM »

Quote from: Darren on July 02, 2009, 08:56:30 AM

Thanks, I have seen a few Utube vids, I was just wondering if anyone can give first hand exp and some greater details...

I dont have any 1st hand experience, but I remember reading about powered drawbars on cnczone.com,

Click Me

I'm sure that there's many other threads on there about powered drawbars, but my net connection is painfully slow at the moment (I'm not at home so am using a mobile internet dongle thingy), do a search on there and that'll turn up more info.

Tim

bogstandard · « **Reply #4 on:** July 02, 2009, 03:23:53 PM »

Hi Darren,

Done a little searching for you, and have come up with these two.

The second one might give you a better insight.

http://home.insightbb.com/~joevicar3/cheap_drawbar.htm

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

Bogs

John Hill · « **Reply #5 on:** July 02, 2009, 03:38:37 PM »

I no idea what you chaps are talking about, the last powered drawbar I had anything to do with was hanging out the back of a Lanz Bulldog.

Darren · « **Reply #6 on:** July 02, 2009, 04:00:19 PM »

Thanks guys, sorry to make you all run ragged but I'd pretty much seen all of those links....

You have my gratitude all the same tho, nice to have friends.....

What I was really looking for was if someone here had built one and perhaps get a thread going....AND like I always try to do before committing myself to anything is to see if I can weed out all the options. This often helps to prevent me or anyone else following the wrong path.

But I think that guy who sells the plans has it pretty well sussed, seems like it.

The parts are cheap, very cheap, so I was thinking of having a go for the Beaver mill at some point. After I get it up and running of course.....

The idea of smacking the draw bolt to release the collet really goes against my idea of machinery care. lets be honest, sometimes you have to give it a pretty good belt....

To me the quick change is the second benefit, not the first.....

bogstandard · « **Reply #7 on:** July 02, 2009, 05:15:49 PM »

Darren,

Just to add a little to this discussion, has anyone ever used a powered drawbar with a morse taper fitting?

Out of pure experience, MT's can be a real PITA to release. Thank goodness I now use R8, which come apart just by farting in their general direction.

What I can't see, is how a power drawbar can release such a nasty monster as a stuck MT taper. Surely they don't have the same clout as a big heavy hammer, which can and usually is the normal method of release. Or is it the continuous knocking feature of the wrench that knocks the joint apart?

Also, what happens if you get one that is REALLY stuck. Do you have to strip all the stuff off the top so you can get a mini sledge hammer in there? Or again, will this never happen because of the torque setting of the wrench?

Bogs

Darren · « **Reply #8 on:** July 02, 2009, 06:21:29 PM »

Well I think I have a pretty good idea how it would help with the barstewards known as MT tapers

But there are plenty of engineering types on here so maybe it's about time someone else actually spoke up....

Come on lads....this IS a forum after all....a place to chat, mull and exchange ideas away from the toils of our normal lives....oh and 'er indoors....

John Stevenson · « **Reply #9 on:** July 02, 2009, 07:19:40 PM »

My Beaver has a powered drawbar, air over hydraulic, no stupid air wrench.

John S.

John Hill · « **Reply #10 on:** July 02, 2009, 07:34:19 PM »

John Bogs, re stuck tapers, surely the drawbar can be arranged to push down on the taper instead of pulling it up? Otherwise I suppose it could be a bit like releasing the rear wheel on a car by loosening the nut and driving around for a few days, in this case slacken the draw bar then mill a bit of scrap.

Darren · « **Reply #11 on:** July 02, 2009, 07:43:14 PM »

Quote from: John Stevenson on July 02, 2009, 07:19:40 PM

My Beaver has a powered drawbar, air over hydraulic, no stupid air wrench.

John S.

I have no idea what "air over hydraulic" means, unless it's like a car braking system? Cept that uses a vacuum....but how that turns a nut I don't know....

John Stevenson · « **Reply #12 on:** July 02, 2009, 08:01:47 PM »

No nut, the chuck has a pull stud on the top, like that one you bought.
A hydraulic ram forces a set of stacked springs down and a set of springy fingers grabs the chuck and pulls it in,

Imagine those long spring things for getting dropped bolts from ~~inexesable~~ hard to get places.

Push a button and air forces a big cylinder to push a smaller hydraulic cylinder that then goes to push the drawbar with springs on.

The springs actually holds the tool in so if it looses air or dry bollocks it doesn't drop the tool.

John S.

Bernd · « **Reply #13 on:** July 02, 2009, 08:52:36 PM »

Darren,

What's the difference between an air wrench beating on your spindle versus a hammer? Your still pounding on the spindle aren't you?

Bernd

Darren · « **Reply #14 on:** July 03, 2009, 04:10:19 AM »

Hi Bern,

If I understand how an air wrench works (and I may have it wrong)
There is quite a big difference between lumping the spindle with a 4Lb hammer and the air ratchet shocking the draw bolt in a rotary fashion.
It's the air cylinder that provides the downwards pressure which is constant, ie smooth, unlike the hammer.

Sometimes it takes so much effort to free the 3MT taper I'm really scared of breaking the mill itself....!!! It can't be doing it or the bearing much good at all.

Now that I have an ER32 collet holder I just leave it in and fit everything to that, I really don't like taking it out.

There has to be a better way than this primitive method, we left the caves a few years ago now.....

Darren · « **Reply #15 on:** July 03, 2009, 05:01:09 AM »

Quote from: John Stevenson on July 02, 2009, 08:01:47 PM

No nut, the chuck has a pull stud on the top, like that one you bought.
A hydraulic ram forces a set of stacked springs down and a set of springy fingers grabs the chuck and pulls it in,

Imagine those long spring things for getting dropped bolts from ~~inexesable~~ hard to get places.

Push a button and air forces a big cylinder to push a smaller hydraulic cylinder that then goes to push the drawbar with springs on.

The springs actually holds the tool in so if it looses air or dry bollocks it doesn't drop the tool.

John S.

Ah, I did take a good look at that pip and guessed it was something like that. Are these draw bars obtainable, or are they like rocking horse......?

Does it have a name, to do a search.....

Darren · « **Reply #16 on:** July 03, 2009, 05:29:57 AM »

Another one....looks good

This has the air cylinder inc, at this price you have to wonder if it's worth building your own...

http://cgi.ebay.co.uk/ws/eBayISAPI.dll?ViewItem&item=280364743376&viewitem=&sspagename=STRK%3AMEWAX%3AIT&salenotsupported

The utube direct link for when the ebay sale has gone

dsquire · « **Reply #17 on:** July 03, 2009, 05:43:43 AM »

Quote from: Darren on July 02, 2009, 04:43:09 AM

I can't find it now, but someone in the US mentioned they had built an air powered drawbolt device for their milling machine...

Would you please care to expand?

Ta...

Darren

This might be the one that you are thinking about. There certainly are some good ideas in this thread.

Here is the link to Hoss ATC Project

http://www.cnczone.com/forums/showthread.php?t=43651

cheers

Don

Darren · « **Reply #18 on:** July 03, 2009, 06:05:38 AM »

That's a very interesting concept. Using the lever system to increase the cylinder thrust was clever....

Much to think about......

Bernd · « **Reply #19 on:** July 03, 2009, 08:51:33 AM »

Quote from: Darren on July 03, 2009, 04:10:19 AM

If I understand how an air wrench works (and I may have it wrong)
There is quite a big difference between lumping the spindle with a 4Lb hammer and the air ratchet shocking the draw bolt in a rotary fashion.
It's the air cylinder that provides the downwards pressure which is constant, ie smooth, unlike the hammer.

Ah yes that makes sense now. I do believe your right on that one.

If it's so hard to get out could it be that maybe your tightening the drawrod "to much"? In other words making it to tight.

Bernd

Darren · « **Reply #20 on:** July 03, 2009, 11:38:24 AM »

Not sure there Bernd, I don't do it very tight as it is. Once I had to re-tighten due to vibration, just nipped it up a tad further.

I believe this is just am MT thing....or at least they are the biggest offenders.

Stilldrillin · « **Reply #21 on:** July 03, 2009, 12:33:57 PM »

I insert my MT3 mill tools, as I would any MT taper tool, then nip up the drawbar finger tight, just to keep it from falling out.

IF it slips under load, (very rare), I nip it gently with a small spanner.

Never had any drive problems, and only a gentle clunk from a small lead tup loosens the assembly.....

David D

kvom · « **Reply #22 on:** July 03, 2009, 01:34:21 PM »

At least on mine, the downward pressure results from the impact wrench turning the drawbar which is screwed into the R8 collet. The impact itself imparts torque that helps to break the taper.

Darren · « **Reply #23 on:** July 03, 2009, 03:37:57 PM »

Quote from: kvom on July 03, 2009, 01:34:21 PM

At least on mine, the downward pressure results from the impact wrench turning the drawbar which is screwed into the R8 collet. The impact itself imparts torque that helps to break the taper.

What do you have on yours? Home made or commercial? Briggy init?

Any chance of a pic....

kvom · « **Reply #24 on:** July 03, 2009, 08:09:16 PM »

Mine is a clone (apparently) of the Kurt unit.

Darren · « **Reply #25 on:** July 04, 2009, 05:28:43 AM »

I can't seem to find much info on the Kurt unit?

Is it like this one? http://cgi.ebay.com/-Air-Power-Drawbar-MILL-Bridgeport-Kurt-Maxi-Torque-A&T_W0QQitemZ290320215582QQcmdZViewItemQQimsxq20090528?IMSfp=TL090528152001r2775

John Stevenson · « **Reply #26 on:** July 04, 2009, 05:43:47 AM »

Darren,
The secret to these thing is a 3/8" drive air wrench called a butterfly wrench.

http://www.machinemart.co.uk/shop/categories/search/air-ratchets-wrenches

4th down, £34.50

However for some reason the Yanks can get these from Harbor Freight at stupid prices like $15 when on offer.

http://www.harborfreight.com/cpi/ctaf/displayitem.taf?Itemnumber=93100 $20 at the moment

[EDIT] £20 on Ebay inc postage if you do a search for Butterfly wrench.

This type of air wrench allows the forward reverse mechanism to be remotely controlled. Bob Warfield has one of the best sites for explaining it

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

John S.

Darren · « **Reply #27 on:** July 04, 2009, 06:17:10 AM »

Thanks John,

I think Bob Warfield has done a pretty good site on the subject and it looks simple enough to build.

Those darned Yanks don't know how lucky they are. For the last decade and a half they have been able to get things at about half the price we have to pay for the same things.
No wonder they have big workshops AND fill them with quality tooling....just not fair....

I remember when I wanted to buy a brand new Japanese sports bike about ten years ago , 10K here, 4.5K over the pond.....it upset a lot of people at the time and eventually the Grey Import scene started by importing from the US instead of Japan. We still paid more than the US, but prob saved about 2-3K all the same.

And now they complain about petrol prices.........

Try about $9 a gal....it's getting tough over here. In this area the roads are far, far quieter than they used to be cos people just don't use there cars like they used to. Inc me, my car goes out about once every two weeks now and I run on Gas not petrol.

I'm not really wining, just jealous.....

kvom · « **Reply #28 on:** July 04, 2009, 08:21:41 AM »

Darren,

That eBay item is the Kurt; mine is a similar clone (no labels on it). It has its own drawbar, and the cylinder mounts on top of the mill. The control unit consists of a regulator-oiler plus a box with two button, "in" and "out". There are two air lines going from the control box to the cylinder.

To operate, I move the spindle to the top and engage the lock. I then set the spindle brake and press the appropriate button with one hand holding the tool/collet with the other. Takes about a second to either lock or unlock.

Darren · « **Reply #29 on:** July 04, 2009, 01:17:31 PM »

Thanks, it sounds like you like the unit.....

Darren · « **Reply #30 on:** July 06, 2009, 08:21:10 AM »

As an experiment I have tried an air ratchet gun on my mills draw bar whilst at the same time holding it down in an effort to loosen the 3MT taper...

It didn't work, the tool holder stayed stuck fast in the machine.

I realise this is not the same as the "proper" tool, but thought it might be worth the experiment.

Just relaying an observation, not meant to be a comment about any other tools out there....

John Stevenson · « **Reply #31 on:** July 06, 2009, 08:53:01 AM »

Air ratchet or air impact ?

John S.

Darren · « **Reply #32 on:** July 06, 2009, 08:55:49 AM »

Sorry, it was an impact type...

chalky · « **Reply #33 on:** July 06, 2009, 12:41:08 PM »

If you have a captive drawbar then unscrewing it with a spanner pushes out the taper. Stuck tapers and bashing on the drawbar are then a thing of the past. Tightening and releasing a captive drawbar, even for a MT3 taper, requires very little torque but does need quite a few turns on the spanner for complete insertion and release of a taper. This can get a bit tedious so I simply use an electric screwdriver to insert and release my taper tooling. Ultra simple powered drawbar! Its usually very easy to convert an existing machine to get a captive drawbar.

Darren · « **Reply #34 on:** July 06, 2009, 12:44:34 PM »

Sounds interesting, and simple....any chance of a pic or two....I'm not too sure how I could make my nut captive but if i thik hard enough I'm sure I could come up with something....

Ohh, an idea already.....

chalky · « **Reply #35 on:** July 06, 2009, 01:07:18 PM »

You need to put a cap on the top of the spindle with a hole in it to allow the top of the drawbar to poke though it. The drawbar itself needs a small annular ring around it near the top ( braze one on ) so that when the cap is fitted the drawbar cannot be removed from the spindle. Fit your taper in the usual way but when it comes to release just keep unscrewing. First it will be easy because you're simply unscrewing the drawbar from the taper but then the annular ring will hit the bottom of the cap and further unscrewing will jack the taper out of the spindle. Both my mills came fitted with captive drawbars but in the case of the smaller one it was a modification that the importer used to do himself. I may have some pics around somewhere but if not I'll go and take some in a couple of days. Not up to it at present as I'm still recovering from a nasty ( but innocently acquired ) infection.

chalky · « **Reply #36 on:** July 06, 2009, 01:28:02 PM »

Just noticed the "Morse Taper Ejector on Clausing Mill" thread has pics which illustrate the principle of the captive drawbar. Not quite as convenient as "the real thing" because you have to remove the extractor after use, but still infinitely superior to the lead hammer.

sbwhart · « **Reply #37 on:** July 08, 2009, 02:45:49 PM »

Chalky

Your post has just prompted me to check something out on my Siege X3, when the machine came it had this great chunk of metal that you had to unscrew to get your draw bar in, I just parked it to one side not knowing what it was:- its a draw bar ejector just as decribed

Her it is against the draw bar

And with the draw bar wound back engauging with the ejector it work like a dream

Thanks for showing explaining this I'd have ended up making something out it and waisted a darn usfull bit of kit.

Slightly embaresed

Stew

Darren · « **Reply #38 on:** July 08, 2009, 02:56:23 PM »

Spot on there Stew.....that will save a headache for you....

chalky · « **Reply #39 on:** July 10, 2009, 10:44:33 AM »

Hi Stew. You are not alone. When I bought my first ever machine tool, a small mill, the importers used to fit a captive drawbar themselves. Took me a while to figure it out as there was no documentation, but eventually I got the hang of it. About a year later the importer stopped doing the mod to the mill. When I was on the phone to them I asked why they had discontinued what I thought was the most useful ever mod to the mill. They said that hardly anyone bothered to use it!! Reading between the lines they didn't, like me initially, realise what it was for. Captive drawbars are a great idea and should be standard on all mills, particularly those with MT tapers. As you can see I'm a bit of an enthusiast!

David

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Author Topic: Air powered Draw Bolt (Read 33332 times)

bogstandard

bogstandard