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View Full Version : Threading a tapered arbor - any reason not to?



Jim Shaper
05-27-2010, 12:00 AM
I use my drill chuck to hold hole saws on my mill, and it's impossible to make it through a job without loosening the taper and dropping the chuck at least a couple times. We're talking 4" hole saws, so there's a bit of torque and a lot of vibration.

Is there any reason not to simply counter bore the body of the chuck and run a socket head cap screw up the middle of it into the arbor?

This is just regular R8 tooling. I tighten the arbor enough to not put undue stress on the index pin, so twisting that off isn't a real concern.

hornluv
05-27-2010, 01:08 AM
I hate using hole saws. They're never concentric and chip clearance is always a problem. Have you tried using annular cutters for your job? They make annular cutter holders with an R8 taper and they do a much better job than a hole saw.

With regard to drilling and tapping the drill chuck and arbor, will that really solve your problem? The drill chuck might still spin on the arbor, it just won't fall immediately and ding up your mill table.

Jim Shaper
05-27-2010, 01:17 AM
These are jobs that don't pay all that well and I already have all the hole saws from the days I was doing this on a drill press. If they were better revenue makers, I'd simply make a fixture and cut them with the cnc mill.

I'm hoping the screw would allow me to apply enough preload on the taper to retain it under the vibration. The real question is will the screw cause some kind of distortion in the chuck body?

chipmaker4130
05-27-2010, 02:22 AM
Sounds like a reasonable solution to me. I had a Milwaukee hammer drill with the chuck fastened to a threaded arbor in that manner. I know that's different, but with regards to creating problems with the chuck, odds are it would be fine.

Jim Shaper
05-27-2010, 02:42 AM
The chuck in question isn't exactly a pillar of precision (it's not even a super chuck, but just a regular plain bearing jacobs), and the arbor isn't anything 30 bucks wouldn't replace either - I just didn't want to do something someone knew would be a bad idea from experience. There used to be more than a couple people I knew who'd get pissy about drilling the pilot hole through the body to drift the arbor off a chuck. Even having Jacobs post the method on their website didn't seem to make them happy. :)

The other option is to loctite it on and see if it holds.

Black_Moons
05-27-2010, 03:46 AM
What is failing here? you mention R8 tooling, so do you have an R8->JT(insert number) adapator going to a standard chuck?

If so, a touch of acid(*) or moisture will rust that taper SOLID in no time at all, requireing destruction of the chuck and/or arbor to get it off again.

Also you can try hammering the chuck onto the R8 adapator after fully retracting the chuck jaws and using wooden blocks to prevent damage. I did this with my first chuck and was near impossable to get off.. Yea.. unfortualy it had really bad runout (Dirt in the taper? Make sure to get those tapers prisene clean)

*- I forget what acid is best for this. I assume anything that rusts steel pertty well would work however. (Not acids that like to remove rust)

Jim Shaper
05-27-2010, 04:10 AM
I'd rather not rust it on, as that sounds like an uncontrolled way to cause runout in a presently rather true set up (it's a decent chuck). This is also why I'm not so hot on the loctite option.

I figure if I drill the holes while the arbor is in the spindle, it'll pull as true as it's going to get when I set the screw in there.

oldtiffie
05-27-2010, 06:49 AM
Here is the OP:


I use my drill chuck to hold hole saws on my mill, and it's impossible to make it through a job without loosening the taper and dropping the chuck at least a couple times. We're talking 4" hole saws, so there's a bit of torque and a lot of vibration.

Is there any reason not to simply counter bore the body of the chuck and run a socket head cap screw up the middle of it into the arbor?

This is just regular R8 tooling. I tighten the arbor enough to not put undue stress on the index pin, so twisting that off isn't a real concern.

The chuck to adaptor taper is useless for all practical purposes as is the taper in the chuck.

Press them together under a load (vise if big enough) and tack-weld (MIG preferred) them together in say three places.

airsmith282
05-27-2010, 08:03 AM
just as an idea perhaps you may have even done this already. try maybe taking more time to do the job, by not pressing so hard into what your cuttting, let the saw do the job. may take longer but it will do a better job and you might not lose the chuck off the taper anymore.. that you if possible mount the saw in a collet if you can, if this is a saw with a hex shaft and if the room is there then turn the shaft round or make a round shaft for it and then put it in a collet and all your problems will be solved..

J Tiers
05-27-2010, 08:30 AM
Here is the OP:



The chuck to adaptor taper is useless for all practical purposes as is the taper in the chuck.

Press them together under a load (vise if big enough) and tack-weld (MIG preferred) them together in say three places.

If the chuck taper is the issue, and it has come off while under power, it needs to hit the scrap bin.

If you split them apart, and then use the Forrest technique of freezing the adaptor and warming the chuck, THEN putting them together..... I suspect the chuck would never again come off..... IF the taper were still good

I have had tapers vibrate out of the spindle, but I have NEVER has the chuck come off its taper.....

I suspect the taper is now damaged, if it wasn't before, and now will never again stay on.... toss it, you are probably beyond the point of worrying about runout (and with a HOLE SAW? Uh-Uh).

JCHannum
05-27-2010, 08:36 AM
The short answer is no, there is no reason not to drilll & tap the JT to retain the chuck. It might work to salvage the chuck and arbor, and is certainly worth a try.

Boucher
05-27-2010, 09:35 AM
Jim
I have been fighting this problem for some time. I had an Albrecht drill chuck that came loose from the Jacobs to R8 arbor while trying to scarf the end of 2 pipe with a 2 3/8 hole saw. This creates a very unbalanced load on the joint. I have probably ruined the arbor but I have tried unsuccessfully to re set them. My hole saw arbor is aprox. Hex. I was thinking about buying a R8 Hex collet. I have a new Glacern drill chuck with integral shank that works. I also tried one of their 2 Index able mills this is close enough fit for my application. If you do the mod that you have addressed please keep us posted on how it works.
Have you ever tried to use a fly cutter?

Bob Ford
05-27-2010, 09:46 AM
Jim,
If you want to use hole saws make a R8 to hole saw adapter. Problem of chuck getting ruined and falling off taper solved.

Bob

Jim Shaper
05-27-2010, 10:57 AM
...

I have had tapers vibrate out of the spindle, but I have NEVER has the chuck come off its taper.....

I suspect the taper is now damaged, if it wasn't before, and now will never again stay on.... toss it, you are probably beyond the point of worrying about runout (and with a HOLE SAW? Uh-Uh).

Yeah Jerry, I never use that chuck for 1/16" drill bits or anything... :rolleyes:

As for having the taper come out of the spindle, wouldn't that mean your spindle is now junk and should be thrown out?


I'm going to try the hot seating method. Hadn't thought of using that with a chuck, but it's worth a go. The chuck taper was slightly galled when I got it 3 years ago (the chuck is probably from the 70's; it came with the mill), but it's still perfectly acceptable when it holds.

I also have multiple different hole saw arbors, so I'd need multiple collets, and that's not something I'm going to invest in here. Turning off the flats would negate their usefulness in cordless drills, so that's also not a good idea.