Dialing in Set Tru Chucks??

[hwingo]

Hi Guys,

With the first two sentences, I am making an effort to reduce the need for some individuals to bring to question my abilities or sanity. I freely admit that the following may be a stupid question thus, with that being said, let's move on to the question at hand.

I have a Bison Set-Tru 6-jaw chuck and a Bison Set-Tru 5C collet chuck. Attempting to dial in either, using manufacturer's instructions, is time consuming, hence, a pain in the butt. It's my understanding that when changing sizes of stock material, it's necessary to redial-in either otherwise neither will run true. It's also my understanding that once a piece of stock is dialed-in, it can be removed from the chuck and returned to the chuck without the need for dialing in provided that stock size does not change.

Manufacturers provide instructions for a reason. Sometimes I happen upon a method that seemingly circumvents manufacturer's instructions and I wonder *why* instructions were made so difficult. A case in point follows.

To dial in either of the above mentioned, one needs to *slightly* loosen the bolts that hold the chuck to the back plate and use 4 unevenly spaced set-screws to dial in the work piece. When finally dialed in, the bolts holding the chuck to the back plate are tightened. Attempting to utilize the 4 unevenly spaced set-screws is time intensive and a pain in the butt. Still, that is the suggested method for dialing in the work material.

Rather than using this awkward, hit-and-miss time consuming method, as of late I have chosen to freely loosen the 4 set-screws and slightly loosen the bolts holding the chuck to the back plate. When the dial indicator is in place, and bolts holding the chuck to the back plate are ever-so-slightly-loosened, the chuck can be lightly tapped, turned and tapped again until the work piece is quickly dialed in. Chuck bolts are secured and the dial indicator utilized a final time to insure that nothing has moved. With the bolts that hold the chuck to the back plate firmly secured, I tighten the 4 unevenly spaced set-screws and indicate one last time.

This is such a quick, easy method. In fact, it's so easy and quick that it causes me to question if my method is seriously flawed.

Why is this alternate method not preferred or suggested by the manufacturer? Why would my method be considered wrong and what problems would this alternate method pose?

Harold

[macona]

It doesn't matter how you do it. All that matters are the results.

[Black_Moons]

Your using the method people use with cheapo chucks that have been 'converted' to set true

You paid good money for those unevenly spaced set screws, Now use em!

(It likey makes a much bigger diffrence for larger chucks where the weight of the chuck would make hammer adjustment hard with the bolts tight enough to keep the chuck from sliping under its own weight)

[Ron of Va]

I used the manufacturer suggested set up method to true up my new Bison 6 jaw. Every time I tried to fully tighten the bolts that hold the chuck to the back plate, the chuck would move one or two thousandths. I spent several hours messing around, gently tightening in a star pattern, and eighth of a turn here an eighth of a turn there, a little here a little there. No luck at all, it really pissed me off. I am feeling like I just wasted $800.

I finally gave up. I tightened her up as close as I could and let it sit overnight.

I came back the next day and started over. I found that something had settled in, the bolts had stretched, or something relaxed in the set up. I don’t know but it dialed right in, and didn’t move when I tightened the bolts.

[JCHannum]

I am familiar with Buck A/T chucks, and the adjusting screws are evenly spaced. They is simple enough to adjust, but I can see that if the screws are not evenly spaced that adjusting could be problematical. If bumping works for you, go for it. Snugging the screws after tightening the mounting bolts will preclude the chuck being knocked out of adjustment.

It is not absolutely necessary to readjust after every change of stock size unless you are working to very close tolerances or doing repeat work. The Bison chucks are good quality, and without readjusting are as accurate as any good scroll chuck or collet chuck.

[J Tiers]

With no picture, the screws are all perfectly and evenly spaced......... Lets see this crazy chuck. Bison products are normally very good, and unevenly spaced screws would be reason for return, not something normal to be dealt with.

That said, probably it is too late to return them, etc.... so you get to deal with them.

IF the "uneven screws" are at least opposite each other, and not TOO far out, no problem.

If they are NOT, well, I can see the issue. It depends on how bad they are.

You may have to adjust the best pair first, then the worse pair, letting the worse pair be loose for the first adjustment so that the chuck is "freer" for the first adjustment, and still moveable for the second.

Of course you know that an adjust-true works exactly opposite to a 4 jaw, right?

As for slacking the bolts.... on my Buck, I ended up just letting them stay snug, but not reefed down. There are 6 of them, and they enter from the face of the chuck.

If your chuck uses rear screws, I'd probably suggest the nut or bolthead have a belleville washer on top of a flat washer. Select the belleville to be pretty darn snug force-wise, and tighten down for somewhat past half compression. Should give good holding, but still allow sliding when the set screws are adjusted.

[Rich Carlstedt]

I have a Buck 6 inch 6 jaw chuck and like J, I do not re-tighten the clamp screws. They are snug, and yet the adjusting screws can move the C/L when needed. I find I do not need to adjust them even when changing diameters.
having the adjusting screws fully engaged helps to maintain the stabillity of the setting. It is important, that all have the same torque application !

As good as Bison may be, if you find that adjustment is needed when diameters are revised , I suspect the scroll is not as good as it should be.

If you have crashed a Set True chuck, then of course all bets are off.
This is the case I have seen in many used chucks on eBay
Rich

[cuemaker]

I need help in this area too.....I have been messing with a Buck Adjust Tru AT model... 6" 3 jaw...

I have a piece of drill rod in....

My questions...

Where do I indicate to set the chuck? close to the jaws? 6" out ? Do I put the mag base on the saddle (as I have been doing) or on the lathe bed>

I can get it to a hair less than .001 about 2 inches out.. but if I move the indicator in, I get like 2-3 thou off.. got out to about 6" I get 10thou off...

I have flipped my drill rod on both ends and get the same basic results...

Edit for new results.............

I put the dial indicator on the lathe bed.... I went 5 inches out.... I am able to get the needle to bounce no more than the width of a line marking... I am astounded how quickly I got there versus having the indicator on my cross slide..... My indicator is a .001, so I am less that .0005 at 5 inches out.. do I stop, call it good?


2nd edit... .GAAAERRRRRRR!////

I move the dial indicator to about 2 inches from the chuck (a hair less) and the indicator bounces 6 thou... I move it to 6 inches out and I am moving about a half thousandths again...

[hwingo]

With no picture, the screws are all perfectly and evenly spaced......... Lets see this crazy chuck. Bison products are normally very good, and unevenly spaced screws would be reason for return, not something normal to be dealt with.

Ok, here are 2 (two) images. As you can see, set-screws are not evenly spaced around the chuck. Set-screws on my 6-jaw are arranged like this as well as are my friend's Bison chucks. They are made this way. I don't know anything about Buck products. Bucks may be different. We are talking about a Bison product so the two should not be confused.

[Lew Hartswick]

Frankly that looks like a piss poor design.
...lew...

[Ron of Va]

My 6 jaw Bison shows the layout of the adjust-tru bolts indicated by the orange tape.

[JoeLee]

I found it pretty touchy to zero my 6 jaw in also. To start off you need a precision gound piece of round stock. Preferably something of gage pin quality. I have found discrepancies even with ground shafting and once you get it zeroed in with say a 1" dia test piece and then jump to a larger dia test piece you may find a difference. repeatability doesn't seem to be an issue as long as you remember to mark your piece and put it back in the chuck the same way you took it out while indicating. I would be against your method of tapping the chuck around to obtain zero, locking it down and then tightening up the adjusting set screws as that method causes forces in unknown directions which could eventually move the chuck with temp. change and work force. Eventually as fine particles work thier way into the scroll gear you will start to notice a change, and loose or improperly adjusted spindle bearings can leave you chasing that chuck all over the place. Been there...................

JL......................

[duckman]

Just take the chuck off and drill and tap 2 new holes where they are supposed to be, they should be at 90° each other, not being at 90° you will be forever trying to get it aligned.

[Peter N]

I'm surprised that Airsmith hasn't chimed in on this one with some advice.
Apparently with his method, all you need to do is use your eyes to get it running true to half a thou'......

[Carld]

hwingo, the way your doing it is ok. The mistake many make is to over tighten the side adjusting screws. If you do that you will burr up the ends of them and make burred indentations in the chuck body. When that happens you will limit the adjustable movement of the body.

I have had to take the back plate off a few Buck type chucks and clean up the surfaces and replace some or all of the adjusting screws. It helps to cut the thread off the last 3/16" of the adjusting screws so they don't burr over.

The only bolts that need to be tight are the back bolts, the adjusting screws just have to be snugged up.