PDA

View Full Version : Tailstock Alignment Question



Wrongway
05-27-2010, 05:36 AM
I have a novice question I guess. How to go about aligning the tailstock? I put centers in it and the headstock and matched the points but the ram must be not parallel with the centerline of the headstock. A 1/4 " drill will get extremely noisy in a very short time as the ram is traveled toward the headstock. I'm guessing the ram is not parallel and centered on the headstock axis. How to check this just won't pop into my head. Thanks.

beanbag
05-27-2010, 05:42 AM
Mount a round object into the tailstock e.g live or dead center. Mount indicator to headstock/chuck and spin that around to check if the object in the tailstock is centered. Then slide the tailstock body back along the ways and extend the ram. Indicate again.

oldtiffie
05-27-2010, 06:24 AM
Rotating an indicator in the head-stock will cause a "nodding" error due to the gravity effect reversal on the indicator and the flexibility of the indicator and its support.

"Good enough" option is to take the Jacobs chuck out of the tail-stock, put the Jacobs chuck MT adaptor into the head-stock spindle MT. Put the round and straight test piece into the Jacobs chuck and with a good test dial indicator on the test piece, rotate the chuck/head-stock spindle by hand and (TDI) record the Total Indicator Run-out (TIR) of the test piece both at the chuck and at the projecting end of the test piece. Not use a bit of patience and pack/shim, "tap-in" etc. and repeat until the TIT is no more than 0.001" on both test points. Tighten the Jacobs chuck and re-check the TIR and re-adjust if required. The test piece and the MT are are aligned to the head-stock MT.

Remove the Jacobs chuck and its MT adaptor - carefully - and put it back into the tail-stock quill MT.

Mount a good TDI onto the cross-slide and set it onto the test piece. Zero the TDI.

Run the saddle back and forth and note the deflection of the TDI on the test piece.

Any deflection of the TDI is the alignment error of the tail-stock quill MT axis with regard to the head-stock MT axis as measured over the length of the test piece.

That sorts the horizontal plane out, but it is wise to check the vertical (top and bottom) of the test piece as well as the error may be either all horizontal, all vertical or a combination of both.

Testing both horizontal and vertical will soon identify any angular alignment error.

Test for axial alignment by using a good round, straight bit of anything at all - say 10" long. Centre it in a four-jawed chuck and centre-drill it. Repeat for the other end. Put the part between centres, put a TDI on the cross-slide and check for any deflection. Adjust the tail-stock until there is as near zero deflection as you can get. Tighten the tail-stock. RE-check. RE-adjust if required.

If all is OK - job done.

You should now have minimal problems from the tail-stock as regards drilling in the lathe.

It sounds a lot and difficult.

It is neither, as it is quite simple, easy, quick and effective.

Ian B
05-27-2010, 06:41 AM
It would be very unusual for the axis of the ram not to be parallel with the headstock spindle's axis.

First, take the tailstock off the bed, slide the tailstock back, wind the barrel almost all the way out, move the centres towards each other - do they still line up?

If they do, the axes are the same.

If this is all ok, the problem is more likely to lie with the drill, the material you're drilling, feeds & speeds etc.

Ian

beanbag
05-27-2010, 07:04 AM
Rotating an indicator in the head-stock will cause a "nodding" error due to the gravity effect reversal on the indicator and the flexibility of the indicator and its support.


So stick a long rod out from the headstock and put the indicator to that. Rotate the chuck - the indicator is always measuring the same spot - and observe the droop.

airsmith282
05-27-2010, 07:42 AM
take the sleeve out of the tail stock and mount it in the chuckhave the taper facing out then do the same with the back end facing out and check to see if it maybe the problem i had a tail stock sleeve once that was a problem, i had the alignemnt dead on but then when i mounted the sleeve in the chuck to check it thats when the damage was seen so i got a new sleeve and never had a problem sence..

ace
05-27-2010, 12:21 PM
I made a similar mount as in the video, but out of scrap delrin and the indicator is held in with set screws as opposed to friction. I also used a test indicator.

http://www.youtube.com/watch?v=1EZh8SUoA4o

Wrongway
05-27-2010, 12:28 PM
Well I think I got it...good 'nuff for me at this point. It was running downhill towards the headstock by .015 and away from the front towards the back by .012. Now running parallel and true to .002 over 2.5 inches of travel in the ram. I chased the last .002 for a couple hours and just couldn't track it down. I chalk it up to wear and tear on a 40 year old machine that wasn't tool room quality to begin with. Thanks for the help. Now I need to go make something.:cool:

dp
05-27-2010, 01:08 PM
Try Frank Ford's trick: http://www.frets.com/HomeShopTech/QuickTricks/TailstockAlignment/tailstockalignment.html

Do this with the ram at various degrees of extension.

Black_Moons
05-27-2010, 02:01 PM
Try Frank Ford's trick: http://www.frets.com/HomeShopTech/QuickTricks/TailstockAlignment/tailstockalignment.html

Do this with the ram at various degrees of extension.

Another vote for Frank's trick. I was gonna post it but you beat me too it.

Forrest Addy
05-27-2010, 04:14 PM
Think your tailstock is out of whack? There are simple standard tests you can make to determine the out of whack-ed-ness in real numbers. From this you can scrape. shim or plain ignore. Otherwise you're lost in a mytery. Mystery belongs in tacky novels not in a precision machine shop where everything is known and verifiable, open to challenge and honet to a fault.

Check the tailtock ram for parallelism? There are some simple tests. Extend the quill. Mount a dial indicaor on the carriage to register on the side of the quill and set a zero. Slide the tailstock back and forth on it bedways. Note readings.

While you are at it, apply several lb of manual force (less for a small lathe) twisting the tailstock casting as it sits unclamped on the bed: first one way note reading relax, then the other, note reading, relax. Do the same in the vertical plane but instead rock the casting on the bedways.

Clamp the tailtock, note reading. reset zero. Extend quill, register a dial indicator on the end and set a zero. Wiggle the quill by hand with the quill clamed snug and then when released. Note readings in both horizontal plane and vertical.

Keep careful notes. All readings should be 0.001" or less. More would indicate wear in proportion to the reading. To verify the quill alignment to the spindle, measure quill dia and turn a short length of material that diameter and leave it in the chuck. Register a dial indicator on top of the diameter in the headstock. Move the carriage back slightly to clear the chucked piece and without moving the indicator take a reading on the quill note the reading. Move back and check for a repeat zero on the piece in the headstock. Do the same in the horizontal plane.

The plug in the head stock method almost eliminates the gravity error Tiffie mentioned.

Go through your notes repeating tests as you need to verify and detemine the individual errors present in your lathe. Make ketches. You now have quantitive data on the magnitude and direction of the errors in your tailstock. This is called a partial survey.

Ideally machine tools are surveyed evewry few years to track condition and eventually assist in reconditionng/replacement decisions. The information is stored in the machine inventory package along with the machine's manuals, procurement records, maintenence notes, and original inspection card (sometes called a "run-off card"). "Worn out" is not qualtitive data. It's an opinion or rather a denunciation. "Worn beyond factory specs" is no better becuase there's no informaton on how much wear and to what part of the machine it applies. A survey is a process where the results of standard tests for every precision attribute of the machine are recorded. It consist of quantitive information - hard data - from which decisions can be made. These inventory and survey records are as helpful in running a home shop a they are in a 600 man shop. That's why you keep a library in your shop with a couple of pockered binders for your machine records.

doctor demo
05-27-2010, 05:42 PM
Mount a good TDI onto the cross-slide and set it onto the test piece. Zero the TDI.
Run the saddle back and forth and note the deflection of the TDI on the test piece.
Any deflection of the TDI is the alignment error of the tail-stock quill MT axis with regard to the head-stock MT axis as measured over the length of the test piece.
it is quite simple, easy, quick and effective.
Tiffie,This test works as long as it has already been confirmed that the lathe bed is not twisted or worn and that the saddle is bearing properly on the bed ways.
Any time You add extra equipment (the saddle) to the equation You increase the chances of adding error.

Steve

The Artful Bodger
05-27-2010, 06:06 PM
Did anyone mention taking off the tailstock and checking for chip or crud stuck underneath?

aboard_epsilon
05-27-2010, 06:15 PM
Sounds like you have tailstock barrel wear ..


Also on some lathes there is a tailstock barrel lock ..this can be used to take up any slack on the barrel by loosely clamping it .

Should stop the slop wobbling the drill as you drill.

Sometimes the morse taper sleeve can be a bit worn..this can be overcome temporarily by inserting a bit of silver foil in the taper.

Drill bits can be slightly bent.

or you could be drill reaming a hole that is off centre because you've replaced your workpiece into the three jaw in a different orientation.

You could have barrelled jaws in your lathe chuck ..or your chuck in the tailstock........or your chuck in the tailstock is buggered .

There are lots of options to check before you do any measuring .

Check these first...if still no go...then comeback and the guys here will explain how to correct your tailstock alignment.

all the best.markj

oldtiffie
05-27-2010, 06:33 PM
Originally Posted by oldtiffie

Mount a good TDI onto the cross-slide and set it onto the test piece. Zero the TDI.
Run the saddle back and forth and note the deflection of the TDI on the test piece.
Any deflection of the TDI is the alignment error of the tail-stock quill MT axis with regard to the head-stock MT axis as measured over the length of the test piece.
it is quite simple, easy, quick and effective.


Tiffie,This test works as long as it has already been confirmed that the lathe bed is not twisted or worn and that the saddle is bearing properly on the bed ways.
Any time You add extra equipment (the saddle) to the equation You increase the chances of adding error.

Steve


You are correct Steve so far as over-all measuring of the lathe to its limits of accuracy.

The OP's concern was only to do with his tails-stock quill MT as a check for a way to improve drilling from the tail-stock.

Here is the OT:


I have a novice question I guess. How to go about aligning the tailstock? I put centers in it and the headstock and matched the points but the ram must be not parallel with the centerline of the headstock. A 1/4 " drill will get extremely noisy in a very short time as the ram is traveled toward the headstock. I'm guessing the ram is not parallel and centered on the headstock axis. How to check this just won't pop into my head. Thanks.

As he is drilling with a Jacobs chuck - not exactly noted for high precision concentricity and axial alignment - as well as a drill which may not be as straight as it might be as well, a lot of precision is not required in this instance.

Frankly, I just have my quill extended a fair bit as well as having the drills extend out from the chuck as far as is reasonable. I let the whole assembly "float" as a centre drill is pretty good at self-centreing in a lathe but as it has zero rake and there is no web thinning of a fairly wide chisel edge, the "pilot" is pretty flimsy and is likely to snap if forced "off line" by the drill chuck and/or the quill itself.

If you get small drill (less than say 1/16") and a bit of round brass rod (say 1/4">3/8" and put the brass into the lathe chuck and face it off and run it at high speed, hold the drill in a small drill (pin) chuck in your hand and centre the drill to start (peck drilling) it you will find that the drill will not only self-centre but can drill quite a deep and true hole quite a fair depth if you use a "pecking" technique with the drill.

See if alignment and sag matters much here:
http://www.youtube.com/watch?v=bh4L65V1SqQ

http://www.youtube.com/watch?v=TxrfqXs25G0

http://www.youtube.com/watch?v=MxYzn519zQs&feature=related

I'd be more worried if the tail-stock MT was out of alignment and the set up was too "stiff" and could not "float".

RB211
05-27-2010, 06:39 PM
I've never owned a lathe, used or new where the tail stock to spindle were parallel and concentric at any position of the ram.
No, wait... I take that back, my Taig lathe is.

Wrongway
05-27-2010, 09:28 PM
All points are valid and well taken. I was given this lathe by my father-in-law some 25 years ago. He salvaged it from an equipment rebuilding and reclamation yard. It has 2 broke handles but over the years I've had it almost completely dissassembled and have been "restoring" it along the way. I've finally got to the point where it is ready to use again and that was the last "adjustment" to make where it sits now. I'm certainly no expert but I was in on rebuilding an old LaBlond, 42" x about 12 feet or better. It was a bear as the smallest parts were pretty good sized. At any rate, I've cut a few steps in a rod and it seems to do exactly what I ask it too. It will be used for hobby type work and the occasional odd piece to save friends and family money on replacement parts for farm equipment. I appreciate the replys and I've been lurking and learning from this forum for over a year now. Friendly and a great knowledge base. Thanks again.