Thread: Lathe alignment question

Congrats to the new lathe.

How do you level a lathe "with a digital protractor"? I only ever seen this done with a spirit level. You need something able to resolve close to about 0.1mm/m

Please do NOT touch the headstock bolts, before you are 100% sure what you are doing and what the consequences are. On some lathes, touching the headtock adjustment opens a can of worms.

Hi

Congrads on your new lathe.

Originally Posted by bowseruni

using a 400mm length of 38mm hydraulic cylinder rod which ran out even in v blocks.

If you're adjusting the headstock its not RDM(though the list what "RDM"s is seems to be growing daily). Anyway*, RDM isn't for lathe alignment, its for accurate misalignment. RDM assumes certain things, If you've moved the headstock you no longer have one of those things. So you have to start over with a level bed. Level in the 0.1mm(or better) per meter sense. What your digital protractor? 0.1 degree? thats (I think) 1.7mm per meter

Though just how fussy you need to be depends on just what you are going to be making and how accurate that needs to be?


Stuart

*As I understand the what I believe to be the original purpose of RDM to be

thanks guys, it got the better of me, made some adjustable bolt down feet today and bolted it to the floor and got it perfectly level with the digital angle finder (across and along the ways).

Adjusted the head stock so the bar gets -4/+4 thou near end and -10/+10 thou at far end 10" out which from my understanding of RDM means it's true.

plan on ordering a 3MT test bar to fit in the tail stock and align it.

is not perfect but i'm not planning on turning bits for NASA just yet, will get the tail stock aligned then spend the money on a precision level and get it fully dialled in.

Congratulations on the new lathe. Since you are reasonably happy with your alignment job, Put a piece of 2" bar in the 3 jaw and take some very light cuts along about 100 - 150mm length. Then measure the diameter at each end. If it's parallel then you have done well.

Simon

using the tail stock Simoni?

i ordered a test bar last night and still have to align the tail stock as i'm guessing its now out with the headstock changes made

Originally Posted by bowseruni

using the tail stock Simoni?

i ordered a test bar last night and still have to align the tail stock as i'm guessing its now out with the headstock changes made

That was not a good idea to undo the headstock alignment. The headstock only needs alignment if the lathe had some sort of accident, was dropped in transit or the like. Especially on a brand new lathe, there is absolutely no reason to undo the headstock alignment. I wolud go as far as to say, if the Headsock on a brand new bench lathe is off, return it to the seller for a warranty exchange.

Now that you have misaligned the headstock, you will need some tools to get it right again. The first thing that you need, is probably to read a good book like Georg Schlesinger's "testing machine tools". Then you need to borrow or buy a reasonably accurate "machinist's level" to level the lathe bed to at least better than 0.02mm/m, that is an absolute pre requisition to put the headstock alignment bach where it was when new. Next you need a test bar to fit directly into the spindle taper, do not use a sleeve. And a magnetic stand with a reasonably responsive (not gunked up) DTI.

The Rollie dad's method is NOT suitable for headstock alignment, it is only intended as a shortcut method to untwist the bed when no accurate level is available. The RDM method relies on the headstock being already properly aligned. It actually uses the headstock alignment as the reference to untwist the bed. Also forget your "digital protractor" - I assume its one of these alarm clock sized things with only half a degree resolution. You need something 50 times more accurate than that for lathe alignment.

Do you intend to look for the mentioned book or a machinists level?

I take it you have some type of dial indicator,do you also have a micrometer?

Seeing that you have already adjusted the Headstock it may need to be re adjusted.

With your piece of rod in the chuck was there any great variation when traversing in the horizontal with your indicator mounted on the top of your bar,if not you could say that the Headstock is sitting flat on the lathe bed.

If there was a significant amount over your test piece then there may be crap under the Headstock,if no crap you may need to shim it to get it running parallel to the bed.

If it is all good I would suggest putting a piece in your chuck as suggested and turn the OD for the suggested length and then measure and see if there is any taper.

If there is a taper then you will need to adjust the Headstock to remove it , by using the pushme/pullme screws.

If this is the case just crack the Headstock hold down screws and then adjust.

After you get the Headstock cutting reasonably well without to much taper or none at all,mount your bar between centres and do a test cut.

If there is a taper present then adjust your tail stock to reduce or eliminate it.

Originally Posted by pipeclay

Do you intend to look for the mentioned book or a machinists level?

I take it you have some type of dial indicator,do you also have a micrometer?

Seeing that you have already adjusted the Headstock it may need to be re adjusted.

With your piece of rod in the chuck was there any great variation when traversing in the horizontal with your indicator mounted on the top of your bar,if not you could say that the Headstock is sitting flat on the lathe bed.

If there was a significant amount over your test piece then there may be crap under the Headstock,if no crap you may need to shim it to get it running parallel to the bed.

If it is all good I would suggest putting a piece in your chuck as suggested and turn the OD for the suggested length and then measure and see if there is any taper.

If there is a taper then you will need to adjust the Headstock to remove it , by using the pushme/pullme screws.

If this is the case just crack the Headstock hold down screws and then adjust.

After you get the Headstock cutting reasonably well without to much taper or none at all,mount your bar between centres and do a test cut.

If there is a taper present then adjust your tail stock to reduce or eliminate it.

Basically, what PC said. Don't worry about your tail stock, it's neither here or there, for now. Any adjustment on the head stock is a complete waste of time unless you have your bed levelled to a degree of precision achieved using a precision level.

I agree with CBA, you probably shouldn't have loosened your head stock, but it's done now so you need to align it anyway.

Cheers,

Simon

thanks guys, will get a machinist level and get it levelled before worrying about the tail stock. I was planning on doing this just not straight away.

also, it's not a new lathe, it's a secondhand 2002 (from memory) Hafco AL340A (no longer sold), I have no idea of its history. I'm not too worried about adjusting the headstock, yes i haven't done it before but with the right tools and information i'm more than competent at getting it sorted. For what I plan on using it for I'm not too worried if it's not the most precise lathe in history, i'd be happy to get it back to OEM spec or slightly better.

Yes i have a micrometer and a DTI. The bar I was using didn't change over the 10" in the vertical plane indicating the headstock is parallel to the ways in the vertical plane (not much bed wear).

I have also been stripping and cleaning it up as there was excessive backlash in the cross feed and very sticky in the cross feed and tailstock, these are heaps better now

I'll go into a little more detail of the process used so far.

bolted the lathe to the floor

levelled to 0.00 deg across and along the ways (yes it's not a machinist level but best I had in the shed at the time - plan on getting a machinist level and getting it spot on)

installed 38mm polished hydraulic cylinder rod in the 3 jaw chuck, tightened it evenly. measured diameter to be even using digital verniers (yes not the best but didn't have micrometer big enough yet), set the DTI to dead centre of rod at jaws. tested runout as close to jaws as i could, was 4 thou at two opposing spots (ref them zero spot 1 and 2) on the bar indicating it had a slight bend, adjusted it even +2/-2 at point 1 zero spot, traversed 10" up the bed taking note of variance to point 1 zero on the DTI, checked runout again taking note of +/-, added them together to get a reference for how many thou it varied from the chuck measurement.

repeated for the second zero point on the bar, averaged the two measurements. adjured the headstock adjustment bolts to give equal +/- at 10".

repeated many times. Now when I set the chuck DTI reading at 0, traverse along 10" at point 1 zero the DTI doesn't change, and for point 2 zero it also doesn't hang from 0 and both have equal +/- runout of 10 thou.

repeated the same for vertical and got the same runout at chuck and 10"

besides not using a machinist level to get it level, is there any problems with this process of headstock alignment?

The lathe only came with a 3MT dead centre and no 5MT-3MT collar for the head (3MT tail, 5MT head) and I currently don't have a 5MT dead centre so have no way of mounting the test bar between centres until I get one.

Not sure what you mean about checking at opposing jaws ( it is a 3 jaw ) or do you mean at opposing points.

How much runout is there in the 3 jaw chuck.

Are you able to use a 4 jaw chuck ?

May be with your aligning of the headstock you have centred your 3 jaw chuck.

Are you able to put another piece of round material in the chuck and re check it ( not the same piece you already used.)

You can place a piece of material in your 3 or 4 jaw chuck and turn a 60 degree point on that and use that as your Headstock centre and run the drive dog for your work piece off the chuck jaws.

Have you machined along the length of a piece of material yet to see if there is a taper.

Originally Posted by bowseruni

I'll go into a little more detail of the process used so far.

bolted the lathe to the floor

levelled to 0.00 deg across and along the ways (yes it's not a machinist level but best I had in the shed at the time - plan on getting a machinist level and getting it spot on)

installed 38mm polished hydraulic cylinder rod in the 3 jaw chuck, tightened it evenly. measured diameter to be even using digital verniers (yes not the best but didn't have micrometer big enough yet), set the DTI to dead centre of rod at jaws. tested runout as close to jaws as i could, was 4 thou at two opposing spots (ref them zero spot 1 and 2) on the bar indicating it had a slight bend, adjusted it even +2/-2 at point 1 zero spot, traversed 10" up the bed taking note of variance to point 1 zero on the DTI, checked runout again taking note of +/-, added them together to get a reference for how many thou it varied from the chuck measurement.

repeated for the second zero point on the bar, averaged the two measurements. adjured the headstock adjustment bolts to give equal +/- at 10".

repeated many times. Now when I set the chuck DTI reading at 0, traverse along 10" at point 1 zero the DTI doesn't change, and for point 2 zero it also doesn't hang from 0 and both have equal +/- runout of 10 thou.

repeated the same for vertical and got the same runout at chuck and 10"

besides not using a machinist level to get it level, is there any problems with this process of headstock alignment?

The lathe only came with a 3MT dead centre and no 5MT-3MT collar for the head (3MT tail, 5MT head) and I currently don't have a 5MT dead centre so have no way of mounting the test bar between centres until I get one.

HI,
Just one thing when you say you are Levelling across the Ways of the Lathe Bed. Make sure that your Level is not touching the 'V' of the Bed. A good way to avoid this is to use two 1-2-3 blocks and sit them on the flats of the Lathe Bed and Level across them. Good luck with it.

Originally Posted by cba_melbourne

The Rollie dad's method is NOT suitable for headstock alignment

No argument there.

Originally Posted by cba_melbourne

it is only intended as a shortcut method to untwist the bed when no accurate level is available.

Not as I understood it. RDM method is for making a worn but level lathe cut parallel by twisting the bed. The name has since be applied(or misapplied) to just about every lathe alignment technique I have seen, including the "two collar method" which has been around since year dot.

Stuart

been in the car all day so haven't had a chance to cut a test piece yet and thanks for the tip on not being on the bed V when levelling, will keep that in mind when I source a precision level.

a couple of questions (may seem basic but i'm learning)

what is the best way to test chuck run out?
good source of online lathe accessories (chasing a 5MT dead centre and precision level amongst other things)?
and a loaded question, what is the best way to align a headstock assuming it is levelled?