Procedure for centering tailstock?

[cnczoner]

On my G0602 (10x22) lathe, I notice that when I drill a hole using the tailstock, the hole is larger than the bit (I take the bit out of the chuck and insert it into the drilled hole, and I notice there's a noticeably lot of slop). So I started tweaking the left-right adjustment screws on the tailstock, but that's a bit too trial and error.

I've thought about machining a point on two sacrificial pieces of round bar stock, then putting one in the tailstock, and one on the main chuck, and aligning the two points.

Is there a better way to do this?

And what about the height, is there some way to adjust that?

While I'm here, in general, is there some guide to properly setting up/aligning a lathe? I found mini-lathe.com, but that's a bit too specific for the 7x10's.

Thanks,
-Neil.

[Monkey King]

Hi Neil,

You must align the headstock paralel with the bed, before you do anything else.
Put a round bar stock, without tailstock, cut slowly by minimal depth to get perfect finish and measure on headstock side and taper side which one is bigger/ smaller. You must tweaking the front/back adjustment screws on the headstock to get same diameter ( you must cut again after adjusting before re-measuring).

Put live / dead centre on tailstock, put comparator/ dial indicator on headstock. Rotate spindle by hand, measure the dial, you must tweaking the left-right adjustment screws on the tailstock to move front/back.
If too high / low, solution only grinding the tailstock / put sheet metal under tailstock.

[MrWild]

Or...

Center drill the end of a 10" long shaft and chuck the other end into the head stock. Using a center in the tail stock, support the end of the shaft with the center drilled hole.

Take a light cut the entire length of the shaft. Measure the shaft diameter at the tail stock and head stock. Taking your measurements, subtract the smaller diameter from the larger, then divide by two. This is the amount you want to move the tail stock. If larger at the tail stock the tail stock adjustment moves the tail stock to the front, if smaller diameter, you move the tail stock to the back.

Example. After a full length cut, the shaft reading at tail stock is .605 dia. The reading at the head is .591 dia. .605 - .591 = .014 .014 / 2 = .007 Because the shaft is larger at the tail stock, it needs to be moved to the front. .007.

DO NOT use an indicator on the tail stock itself, DO indicate the shaft near your dead or iive center

[Cruiser]

You don't have to cut anything to center your tail stock down to the nut. take a piece of bar stock, mine is 1.25" cold rolled and straight. then put a center in both ends of the bar and true it with a single point tool if necessary to insure that the center is truly dead on center. Now, put a dead center into the spindle throat and live center or dead center into the tail stock and load your new tool. A dial indicator should be able to travel end to end on the bar without deviations. So then set indicator at the headstock end and run travel down to opposite end and then adjust the tail stock as necessary to zero indicator and call it a done deal. With the tool you can offset your tail stock for cutting a taper then quickly re center back to zero easily and repeatably.

[RCaffin]

Originally Posted by Cruiser You don't have to cut anything to center your tail stock down to the nut. take a piece of bar stock, mine is 1.25" cold rolled and straight. then put a center in both ends of the bar and true it with a single point tool if necessary to insure that the center is truly dead on center. Now, put a dead center into the spindle throat and live center or dead center into the tail stock and load your new tool. A dial indicator should be able to travel end to end on the bar without deviations. So then set indicator at the headstock end and run travel down to opposite end and then adjust the tail stock as necessary to zero indicator and call it a done deal. With the tool you can offset your tail stock for cutting a taper then quickly re center back to zero easily and repeatably.

A length of good ground stock is excellent for this. Running between centres is excellent too.

However, while moving the tailstock back and forth will reduce any taper, it may not remove it all. The tailstock may have a height problem. Mind you, if it does, either you have a totally worn-out lathe, a cheap and nasty Chinese copy, or maybe the tailstock was off a different lathe.

Cheers

[M250cnc]

Originally Posted by RCaffin The tailstock may have a height problem. Mind you, if it does, either you have a totally worn-out lathe, a cheap and nasty Chinese copy, or maybe the tailstock was off a different lathe. Cheers

You could test by running the DTI on the top of the test piece to check.

[Geof]

Originally Posted by cnczoner On my G0602 (10x22) lathe, I notice that when I drill a hole using the tailstock, the hole is larger than the bit (I take the bit out of the chuck and insert it into the drilled hole, and I notice there's a noticeably lot of slop). So I started tweaking the left-right adjustment screws on the tailstock, but that's a bit too trial and error.... Thanks, -Neil.

Not only too triall and error too premature.

(take the bit out of the chuck....)

Your tailstock may be perfectly aligned (as perfect as is practical) but your chuck may be off.

Check that the tailstock is true by the proceudres already mentioned. Or do a quick check by using a center in the tailstock and a DTI in the spindle running around the body of the center.

Then check the drill chuck by gripping a short piece of good round bar and running the DTI around this. It will be surprising if the drill chuck is 'perfect.

Even if everything is 'perfect' a drilled hole may be oversize simply due to the drill running out slightly or because it has been sharpened slightly unevenly. The uneven sharpening can sometimes be noticed because one cutting edge will produce a bigger chip than the other.

[zavateandu]

hi all

u all are complicated with a lot of stuff and cutting.

let me show u how easy u cn adjust the tailstock position.

take a piece of metal and make a excentric hole on 1 face of it .
in the hole put a dial gauge and tie it with a screw to saty fixed.

than clamp the piece on the chuck and than put the dial gauge meserment needle in the interior of the tailstock.

adjust the clock to show 0 and than rotate easy the chuck and read the dial gauge.
u will see a deviation of the 2 circles that are not concentric.

u have to adjust the tailstock untill this 2 circles described by the spindle and tailstock will be concentric and u will see the dialgauge will be around 0.

when is wrong the dial gauge indicate 4 values around 0 cause the circles are not in the middle of the line described by the center of the spindle and the tailstock

EASY ? VERY EASY MY FREINDS.

i attached a simple scheme to understand what i mean

GOOD LUCK!

[cnczoner]

Thanks for the replies everyone. I can't see any way to align the headstock on my lathe, but I will run a test cut tomorrow and see where it's at.

I'm confused about one thing... If I spin a piece of round stock between 2 centers in the spindle and tailstock, there must be a *live* center in the tailstock, correct? Otherwise, wouldn't the spindle-side slip rather than the tailstock side?

FWIW, I found the manual for this lathe online, and it has a basic procedure for aligning the tailstock, but theirs involves a lathe dog, which I don't have.

[cnczoner]

Originally Posted by Geof ... Even if everything is 'perfect' a drilled hole may be oversize simply due to the drill running out slightly or because it has been sharpened slightly unevenly. The uneven sharpening can sometimes be noticed because one cutting edge will produce a bigger chip than the other.

Here's what I'm trying to do... I need to drill an accurate 4mm hole, so the piece I'm making fits snug over a stepper-motor shaft. Because I'll have another concentric cuts on this piece, I want to do this on the lathe. Now, 4mm is 0.1575". However, 5/32" is 0.1563", and I'm wondering if I can use a 5/32" drill bit for this, then "tweak" the left-right adjustment on the tailstock until the drilled hole is where I need it to be. This would compensate for any chuck (and other) errors, including tolerances of the stepper shaft.

Alternately, is it acceptable if I chuck a 1/8" endmill in the tailstock and use that to drill the hole, opening it up incrementally in a similar manner?

Cheers,
-Neil.

[lancut]

Go ahead and rill the hole with the drill 5/32 bit. Did you miked the drill bit? some are bit smaller or larger by thou or so. Thru my experience the hole machined with higher speed and some sort of oil as lubricant will produce bit larger dia hole. Make test cur and measure. Really, what I like to do is drill the hole 1/64 under and ream to size. Hope this helps.

[photomankc]

Maybe a reamer following up the slightly undersized drill to get that dimension really close. I've never had much luck getting a drill bit to do much besides bugger up the sides of things by pushing it over a little. I think you should be able to find a reamer in that size.