CENTERING TO CHUCK USING INDICATOR

[INTERPOLATE]

Greetings group.
Can someone explain the technique to center tools to the chuck like a drill bit mounted on the carriage or tailstock for that matter.
I have heard of using a dial indicator on the face of the chuck. But how does this determine the true center????
I am trying to precisely align a drill bit mounted on the carriage for some drilling. I have a 8" chuck on the spindle and a drill chuck mounted on a arbor to a QC holder on the carriage.
Thanks guys,
JD

[BillH]

Why dont you use the 2 sharp points with a 6" steel ruler sandwich between method? Same method I use for setting tool height and tailstock. The ruler will tell you how your off by how it gets tilted

[lynnl]

Sounds like a good job for a wiggler. There's probably more accurate methods. But that's what I'd use. Especially since a drill doesn't produce a perfect hole anyway.

Mounted in the tailstock it ought to be centered automatically, unless the tailstock is needing adjustment.

[This message has been edited by lynnl (edited 01-13-2005).]

[Rustystud]

Why don't you use a test bar and indicators? That is if your lathe is not warped or in a bind to begin with. How else are you going to get the Tail stock accurately aligned with the bore of the spindle. Points just get them adjusted to the same height.
Rustystud

[BillH]

no, Points also get left and right adjusted, AND if you do the test with the tailstock ram all the way in, and all the way out, you can see the 3 dimensional error. Besides, he is talking about a drill bit mounted into his QCTP on the crosslide. Yeh, your going to have to figure a way to get the drill bit perfectly perpendicular to the face of the workpiece. I would face the workpiece, then move the toolpost right up against it, still not 100% accurate though. If you need more accuracy, use a boring bit.

[This message has been edited by BillH (edited 01-13-2005).]

[J Tiers]

Well, when it looks hard, turn the problem on its head........


assuming you have your QCTP block set so the tool would be parallel to the spindle axis...how about....

Grip a piece of rod of same diameter as drill etc in the 4 jaw chuck. Center it up.

Remove drill from QCTP block temporarily.

Bring the crosslide and carriage etc over and adjust crosslide and QCTP block until the rod enters the QCTP block hole, or until the drill chuck will close evenly on it.

At that point you should be correctly alined with in a thou or two.

For regular use with a drill chuck, a piece of accurate rod and a close-fitting matching sleeve with OD and ID concentric would allow doing it easily.

Rod goes in chuck, sleeve in 4 jaw. Center sleeve, then adjust QCTP and crosslide until rod enters sleeve.

If you need it done to fractional tenths, this probably won't be good enough. But it will be as good as your centering job and the fit of rod and sleeve allow it to be.

The drill in tailstock should be automatically centered, or else you have some shimming and scraping work to do.

[Joel]

As was said, no alignment should be needed when using the tailstock. For the quick drill jobs in the QCTP, just chuck a piece of drill rod in the lathe chuck. Leave the clamp nut and locking lever on the QCTP loose, and chuck the other end of the rod in the drill chuck. Tighten everything and start drilling.

This generally gets you plenty close for drilling. If you want to check your alignment, just chuck up an indicator and sweep the rod. If you need an accurate hole, bore it.

[ERBenoit]

As others have stated, drilling is the least accurate method of hole production. When I set up for drilling in the lathe using the QCTP, I proceed as follows. 1. Center drill the work. 2. Square tool block to the work. 3.Use the conical point of an edge finder in the drill chuck to the center drilled hole. Using the cross slide on the lathe, and the height adjustment screw on the tool block, adjust X axis and tool block height until you feel no transition between the conical point and finder body. 4. Secure tool block. That should be centered accurately enough for drilling. If the conical point shifts slightly, in relation to the body, when you secure the tool block, repeat steps 3 and 4 until you are satisfied with the result. Securing the tool block, depending upon how loosely you have it to be able to adjust, may shift when tool block is locked in place. Takes longer to type how to than actually do. Again, if you need very accurate holes, bore them. Are you using a wedge or piston type QCTP? I use the above method with a wedge type.

[pete913]

the only way i've ever lined up a tailstock is to indicate on the bore of the ram with a chuck mounted test indicator. I never saw any use for test bars except to check headstock alignment, and even at that, the bar has to be machined in place on the machine each and every time.