PROPER METHOD OF ALIGNMENT

[INTERPOLATE]

A couple alignment issues I have are:

Aligning the tailstock to center of spindle.

Aligning a drill bit held by the carriage (via QC holder.) to center of spindle. (quickly, if there is such a thing!)

What is the proper way to do this?
Someone said with a dial indicator mounted to the chuck. Didn't go into detail. Made it sound obvious. I couldn't figure how it would work! Could someone please explain or point me to a source.
Thanks group!
DJ

[Ian B]

Aligning the tailstock to the headstock - quick method:

Put centres in the head & tailstock, bring them almost together. Hold a thin steel rule or a piece of shim stock between them, screw the tailstock barrel forwards until the shim is pinched between the centres. If it's at right angles to the bed, the centres are pretty much in line.

Using a dial gauge:
Rig the dial gauge so that the plunger is pointing towards the centre of the lathe's spindle axis, set outwards by half the tailstock barrel's diameter. Move he tailstock forward until the plunger touches the barrel. Swing the headstock spindle by hand, the plunger should be in contact with the barrel all the way around (watch out for keyways). If the needle doesn't move, you're concentric.

Best way's not to offset the tailstock in the first place - if you have one, use a boring head in the tailstock, fit a centre to it and adjust it to give the offset you need.

hth,

Ian

[Evan]

Align tailstock by putting dead centers in both tailstock and spindle. Suck tailstock quill all the way in. Bring tailstock up to spindle and visual align till points seem aligned. Back off tailstock a few mm. Place a piece of feeler stock between the points and gently crank the quill until the feeler stock is trapped between the points. If they are aligned then it will be held perpendicular to the spindle axis. Then do the same checks with the tailstock quill nearly all the way extended.

For the drill, drill a hole in some round stock in the chuck with the drill in a tailstock chuck. Leave the stock in the chuck and the drill in the stock. Then use the appropriate packing and shims to clamp it in the tool holder.

[This message has been edited by Evan (edited 01-27-2004).]

[metal mite]

Inter,

Most lathes have an alignment mark on the rear of the tailstock.
That will get you within a couple thou.

Than use an indicator mounted in the spindle chuck.
Tram, or sweep the tailstock with the indicator by rotating the spindle by hand.

I never had to do this except in a turret lathe.

Too much overhang of the indicator will allow gravity to confuse things.

Another way of alignment is to machine a test bar between centers.

Machine the bar and adjust till both ends are the same.

Undercut the center of the bar so your test cuts are only on the ends of the bar.

Remember heat and tool wear can confuse you here.

For precision shaft turning you'll likely have to test cut and adjust the tailstock for each job.

They never seem to cut closer than a couple thou, except the Hardinge at work which repeats within .0003 no matter where you set the tailstock.

Locking and unlocking the tailstock spindle may change things a tad too.

For a qc holder,
Indicate the side of the holder straight with the spindle.

Than tram the hole with the setup above.


On old machinery,
Sometimes the carriage is low in the front (facing spindle) and further shimming of the qc block level is required.

No easy way....

All in a machinists daily work.

Roleydad has some method of alignment that might be easier. Someone here has a site about it.

That razor blade, or scale, may get you close but you're not going to hold tenths, or a thousanth with it. Like using a level to align parts on a mill.

mite


[This message has been edited by metal mite (edited 01-27-2004).]

[ERBenoit]

In regards to aligning drill to spindle center, a method I use is as follows. I am guessing you have a DRO or some type of CNC lathe. I am also guessing you are using a tool holder with a drill chuck for your QC tool post. I use this method in my everyday job and it seems to work well. First, I use the edge of the drill to align drill parallel to edge of work. I put a piece of white paper underneath everything to see where the margin aligns along the work. Adjust QC tool post until parallel. Then using tailstock, drill work with a center drill, and follow with a drill equal to c'drill point dia. to drill beyond the bottom of the center drill hole. This will avoid having conical point "bottom out" rather than contacting the angle. Then chuck a conical point edge finder in the QC drill chuck. The lathe I am using has servo drive motors, no feel of when the conical point actually "bottoms out". I hold the point in the center hole while slowly traversing Z axis until edge finder body and point are in contact, then using X axis and height adjustment on tool holder, set height and centerin relation to X axis. Enter your X axis value as required. I have not set up morse taper drill holders for QC tool posts, I cannot offer you any assistance there.

[This message has been edited by ERBenoit (edited 01-28-2004).]

[Rich Carlstedt]

Quickest on a manual lathe.
Bring the tool post up against the tailstock quill for squaring.
Bring the drill up to the work and touch it.
The tip will deflect and by moving the crosslide, you can get it right by watching the movement. As you start to drill, turn the crosslide in and out ..you will feel the "center" and "ends" of the load and set your position at midpoint.(watch the dials)
You can also watch the chips on a NEW drill bit because,when centered, the chips are even.
I start a larger drill like this, then go back to smaller bits once I have the position.