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2ManyHobbies
02-04-2008, 02:52 PM
Some tinkering this weekend left me scratching my head and wondering where I went wrong. I turned down a 3/4" x 6" piece of steel this weekend to build a small spindle sander for a little project, chucked up on the accessory shaft of the arm saw, flicked the switch and could see wobble. Re-chucked it thinking maybe I had a chunk of something in there, same wobble. Well, I wasn't turning it at 3450 rpm in the lathe, so maybe that little bump on the bottom is doing it. I reset the lathe speed, drop it in the lathe chuck, face both ends, and do another very light pass just to test for concentric problems. One long piece of metal about as thick as a human hair, so everything looks good. Back to the drill chuck on the saw and the wobble is still there. Not enough to look like it will tear anything apart, but about what it looks like when you have a wheel on a bench grinder slightly skewed -- just a little shadowy indication that it is wider running than not running, complete with that low hum that isn't there with nothing in the chuck.

Now for giggles, I decide to stick it in the drill/mill head on the 3-in-1 (which I've only used for a circle cutter on wood and plastics) and see what happens. Same issue, so of course, I've got something really wrong on the lathe part right? Not exactly, I drop the speed back down and chuck up a cutting disk from the pencil grinder. Yep, that wobbles, but it could be bent, so back in the grinder, and clean past 10k and smooth as silk.

So I've got a pair of chucks that are off center and a couple of hour I'm not getting back. Is there a way to true those up, or do I throw them in the scrap pile and order new ones? I've read enough that I could probably true up a 3-jaw chuck in a lathe if I had to, but I don't know that the jaws on a drill chuck would massive enough to use the same method...

SGW
02-04-2008, 07:54 PM
? My apologies for my inability to comprehend, but I've read your post 3 times and I still don't have a clear idea of what you did, what you're trying to do, or what the problem is. Would you be willing to try again?

In general, any chuck jaws are going to have some amount of runout; if by chance there happens to be no runout when they are holding a piece of diameter A, there will almost certainly be runout when they're holding work of diameter B. It's just the nature of the things. If you want assured concentricity, everything has to be machined in one setting.

As far as truing chuck jaws: they need to be loaded as they would be when holding work. You can't just open them up, grind the jaw surfaces, and expect them to be true when you apply a clamping load with them.

Does any of that address any of your problem?

TECHSHOP
02-04-2008, 08:36 PM
Me thinks he is using a "Jacobs" gear type chuck (5/8-11?) as part of an attachment to a radial arm saw and it don't run "true".

If that is the case then there is quite a bit of "stacking" possible, and the thus the "wobble". Most "drill chucks" are not considered to be the paragon of precision. Holding a "drill chuck" in a lathe by the "outside" would most likely not achieve the desired "true up" of the inside (work holding) jaws.

Depending on the size and brand of the chuck, they can be "rebuilt". But you may be asking "more" from the set up than is "realistically" possible.

Pherdie
02-04-2008, 09:13 PM
Two years ago I purchased three of what I thought were quality chucks (Jacobs 5/8 ball-bearing). All three proved to have problems with jaws cocking after light tightening. Increasing tightening pressure further aggravated the issue until the bit appeared to be emulating some sort of carnival ride. Smaller bits were worse than larger bits.

I returned one for an exchange and received another not much better. All three now hold an important position in my junk bin and have been replaced by Albrechts, which have been exemplary.

As a further note, I recently completed drilling approximately an 1/8" hole in some steel stock using my Bridgeport. I raised the quill about four to six inches to remove the bit and began to loosen the Albrecht. Before i realized what had happened, the bit slid out of the chuck and neatly dropped back into the hole it had just drilled. I thought to myself I couldn't do that again in a hundred years. WRONG! On every consecutive try the bit dropped the full distance straight back into hole. Try that with a cheaper chuck!

2ManyHobbies
02-05-2008, 12:24 AM
Both are Jacobs style, one is a 1/2-20 mount and the other is unknown though I suspect something like a hot fit on a JT-1 maybe?

Both chucks appear to run smooth with nothing in them but they seem to turn anything they are holding into an orchestra conductor's wand. I'm not sure what the runout is, but I don't need a dial indicator to see it, and quite frankly, I'm afraid to be near either under power...

It hasn't bugged me before because chucking a 3/8" bit and putting holes in wood with a 1/4" accuracy is acceptable for what I've been doing. A spindle sander or shaper though have different opinions on what is "good enough".

Is there any way to correct runout on a Jacobs chuck, or is it even worth the time?

Paul Alciatore
02-05-2008, 01:01 AM
As stated above, drill chucks can and do vary in quality and specifically in run out. Even Jacobs itself has a number of lines of chucks. The cheapest is their Multi-Craft line. I have a couple of these and I can tell you they are at least 0.005" off. I use one as a hand held chuck for the occasions when I want to use a drill or countersink by hand.

http://www.jacobschuck.com/products.asp

Other Jacobs lines and other brands can vary in quality and run out. They all will have some and it will not get better with use.

Then there is the mount it is used on. Most high quality machines use a tapered mount and the most common tapers used are "Jacobs Tapers". Even my $50, imported, bench top drill press has a chuck mounted on a Jacobs taper. And I have MT to Jacobs taper adapters for the chucks on my lathe. This is the best in terms of run out. But chucks are also made with screw thread mounts. These are easier to interchange and are also quite common. They are also commonly used on hand held drills, both manual and electric models. They can also be quite accurate but in some cases they are not.

As for improving the run out of a drill chuck, probably the only good thing is a rebuild with a set of new jaws. The major manufacturers like Jacobs offer rebuild kits with al the parts necessary. But if the body or tightening ring is damaged they may not do much good.

I attempted to mount a Jacobs Multi-Craft chuck on my Unimat lathe spindle. I carefully centered the body of the chuck in a four jaw and bored the mounting hole dead accurate - I thought. After threading it and mounting it on the spindle, I measured about 0.010" run out. It's a cheap chuck and it shows. You get what you pay for.

radish1us
02-05-2008, 01:30 AM
Is there a way to true those up, or do I throw them in the scrap pile and order new ones?



Being very blunt and unkind, toss the rubbish and go buy a decent brand, something like an Albrecht, or Rohm, anything but an el-cheapo Jacobs junk, oops, chuck.
If you really want to use a Jacobs, then go have a good look at the highest priced chucks that they sell, then compare that with a good middle priced Albrecht.

radish1us
02-05-2008, 01:39 AM
I attempted to mount a Jacobs Multi-Craft chuck on my Unimat lathe spindle. I carefully centered the body of the chuck in a four jaw and bored the mounting hole dead accurate - I thought. After threading it and mounting it on the spindle, I measured about 0.010" run out. It's a cheap chuck and it shows. You get what you pay for.
Hey Paul, tried the same thing myself, even for the U3 as well.
First attempt hit the bin.
Second attempt was much, much better than the first go in the four jaw, used a short length of 8 mm silver steel/ drill rod and held it in the 3 jaw, then attached the el-cheapo jacobs junk to the drill rod. Very, very carefully bored it out to 13 mm and then set up my home brew thread cutter and started the thread, finished it of with a 14 x 1 mm tap.
Run-out is very minimal, possibly a couple of thou at the most, I just use in in the tail-stock, as it is a keyless chuck, does the job quite nicely and NO searching for that bloody key.

darryl
02-05-2008, 02:05 AM
I checked out several chucks when I was building my lathe drill press accessory. I definitely wanted the bits, etc to run true, and since there would be all sizes being used, I had to test them at a few different diameters at least. For the most part I found that runout was consistent, in other words it didn't change much over differing diameters of bits. It was mostly wobble and not parallel axial displacement, and it did vary a lot. The best chuck I had, and the one I used, came off a cordless drill, and is a keyless. I wouldn't normally expect such a thing to be a cut above other, more expensive chucks.

I have a Rohm, which cost quite a bit more than my Yamawa, and the Rohm is good, but the Yamawa is better in terms of runout. The one that came with the Unimat was quite good, but I killed it. The replacement isn't very good.

I think it's largely luck of the draw, at least it appears that way to me. I once trued one up by tightening it onto a stub that I had trued in the lathe, then machined the back and inside for a short distance. I turned an arbor to match the new inside diameter, bored that out for a short distance, then pinned in a short section of bolt that had the same threads as the chuck. I figured that the chuck, once seated, would tend to align the bolt to some extent. I used epoxy to secure this bolt into the new arbor, and still used the cross pin. Making sure that no epoxy got on the threads, I snugged the chuck on and waited while the epoxy set. That worked, and I could remove and remount it and it would stay true, but as I opened and closed the jaws on something, I got a random runout. Not much but still there.

I think for the most part that if a chuck is well used and is displaying runout and/or wobble, it should be, well- chucked. Before tossing it though, it would be a good excercise to learn how to take it apart.

mark61
02-05-2008, 07:26 AM
The sanding drums and arbors that came with my radial arm saw are threaded and screw right onto the motor shaft. This does a way with run out problems. Make them to fit the saw!

mark61

Paul Alciatore
02-05-2008, 09:40 AM
Interesting that others have done the same thing for the Unimat. I also wanted a larger chuck for the tailstock, which has the same thread and taper as the headstock. Mine does work fairly well in use there so I keep it. And it was worth the $12 or so I paid for it for the experience.

If I can find a good buy on a quality chuck with enough metal on the back end to try again, I will. I am not sure if I should once again center the body in the four jaw or use a piece of 1/2" drill rod in a collet and grab that in the jaws. Oh well, I don't have the victim yet.

pcarpenter
02-05-2008, 11:13 AM
Be careful using your radial-arm saw with a sanding arbor. You will make lots of fine powdery dust (moreso than sawdust) that the motor will promptly try to suck inside if its not a TEFC motor.

I figure threaded arbors and threaded chucks make for two places for lots of error even if the chuck was otherwise in good shape. Effectively, you have a threaded shaft and a threaded bore defining how concentric the whole thing will run....something you don't have with precise machine tools. Even a threaded chuck on a lathe has a register surface that can or should keep it square. Additionally lathe spindle threads are likely cut a whole lot more precisely than the threaded rod arbor for a stick-on-the-back-of-your saw drill chuck.

Grinder shafts are probably the most similar in construction..and there you have the luxury of truing the wheel mounted on the threaded shaft.

Paul

2ManyHobbies
02-05-2008, 12:24 PM
Long term for the RAS, I'll probably build or buy a collet for shaper bits and I am somewhere in the middle of working out the details a spindle sander that threads directly onto the accessory shaft. My preference is to wrap my own spindles and not buy sleeves to save money.

As far as the chuck on the 3-in-1, I guess I throw another MT3 spindle chuck on the list. I'm not even sure that I used it for anything more than spotting for centers prior to last weekend...

Mcgyver
02-05-2008, 01:26 PM
you may be asking too much of a drill chuck,.....think of how much run out there is on a good three jaw, you can't expect a drill chuck to act like a collet.

the cheap Jacobs have .014 runout, the good ones .004 according to the web site.....but that's not how accurate they'll drill....a drill cuts accurately because of the grind not because its perfectly aligned to the spindle's axis and a good grind will do better better than .004...point being for use as a drill chuck there's not a lot of benefit to making it better than .004 and not doubt it would cost a lot to do....albrecht & rohm don't say the runout, but I'd guess they'd be about the same?