Alignment issue AL 330

[tbonesmith]

Hi guys, I recently bought a second hand AL 330 in pretty good nick. I have levelled it pretty well, the bed is untwisted, not perfectly level, but parallel and only out by about .003".
Over 18" I'm getting indicted spindle/bed misalignment of .010", so that would be cutting a taper of .020" over that distance, which is pretty major.
I got the relevant Grizzly manual(which seems to be the same machine) but it doesn't go into the details of spindle alignment.
I read the thread on the spindle alignment on the AL960, is it all the same here?
Any one done this on this model?
I've been tinkering on metal lathes for a few years, but am still pretty novice beyond the basics and realize I can quickly go from bad to worse when I start turning screws I'm not sure about.
Any help gratefully accepted and put to use. Will post pics of the process to help future people in my situation.

Other than this the lathe is great, quiet, no vibration, all feeds and controls work smoothly, no real wear to speak of ... I've got a ripper when I fix this.

Cheers guys!

[Stustoys]

Hi tbonesmith,
Welcome,
Congrads on your new lathe
"not perfectly level, but parallel and only out by about .003". Over 18" I'm getting indicted spindle/bed misalignment of .010", so that would be cutting a taper of .020" over that distance"
Can you explain how you came up with these numbers?

Does it look pretty much like this one? http://www.machineryhouse.com.au/L183

Stuart

[pipeclay]

Have you performed a cut over the 18" length.
If so was it supported by the tailstock.
If you did do a cut over this length unsupported what was the diameter of your stock.
If you havent turned over this length what are you using as a sample.

[tbonesmith]

I levelled the lathe at each end with a precision level. with a .003 feeler gauge under one end of the level the level shows "level" at both ends (would have corrected it but my jacking screws are fairly coarse and it's the best I can do) So it's parallel and close to level.

I dialed in a piece of 2' long precision ground 1" bar in the 4 jaw with a dial indicator on the carriage and set it to "0" at the chuck, so I rotate the chuck and the average reading is "0", I then wind the carriage down to the end of the bar 18" towards the tailstock and again rotate the bar, and the average reading is "25" ie. .25mm (there is negligable deflection of the bar from the force from the dial indicator stylus)

Test cuts have shown similar numbers when mic'd over shorter distances I just don't have them specifically noted, but it's of the same order.

[tbonesmith]

Does it look pretty much like this one? L183 | AL-335 Bench Lathe | machineryhouse.com.au (http://www.machineryhouse.com.au/L183)

Stuart[/QUOTE]

Similar, but the feeds are the lever type

[Dave J]

Hi and welcome.:2tsup:
I have a similar lathe so does Stuart and we have ironed out most of the problems with our lathes.
With your lathe both ends need to be pretty well exact for twist wise, level doesn't really matter. You need to place the level on the flat ways themselves, don't go off the V way as it's not finished accurately.
I use parallels on mine to get up over the V ways, but if you don't have them use drill bit shanks or something similar, but remember to use the same ones on the same sides at the other end. You need to aim at 0 each end or as close as you can get it.

For you ground bar it wont tell you anything about your lathe alignment. The jaws on the 4 jaw could be throwing it out on the end, the bar maybe out etc. The only way to properly check it is to machine something. I would use some heavy wall pipe around 100mm diameter and 250-300mm long. Machine it with sharp HSS taking a light cut after you clean it up.
Make sure you lock the compound and the cross slide up, so they don't creep while your doing the final cut as well.

Dave

[pipeclay]

Your dialing in of the bar at only one end of the workpiece is not going to work,you would need to dial both ends in,moving the indicator left then right,you may even have to give the outer end a final tap with a soft hammer to get zero.

[tbonesmith]

Hi and welcome.:2tsup:
I have a similar lathe so does Stuart and we have ironed out most of the problems with our lathes.
With your lathe both ends need to be pretty well exact for twist wise, level doesn't really matter. You need to place the level on the flat ways themselves, don't go off the V way as it's not finished accurately.
I use parallels on mine to get up over the V ways, but if you don't have them use drill bit shanks or something similar, but remember to use the same ones on the same sides at the other end. You need to aim at 0 each end or as close as you can get it.

For you ground bar it wont tell you anything about your lathe alignment. The jaws on the 4 jaw could be throwing it out on the end, the bar maybe out etc. The only way to properly check it is to machine something. I would use some heavy wall pipe around 100mm diameter and 250-300mm long. Machine it with sharp HSS taking a light cut after you clean it up.
Make sure you lock the compound and the cross slide up, so they don't creep while your doing the final cut as well.

Dave

I'll go over it again tonight, getting above the V ways rather than going off them. And I'll buy some suitable pipe or make a 2 collar test bar and post the results.

Thanks for your responses, I just looked and notice I'd joined back in 2009 and havn't posted until now. Talk about lurking!
Cheers Gents.

[simonl]

Hi guys,

I've always leveled my lathe from the top of the v's. Dave you say this is not a critically accurate spot? I have never really thought about it but now you mention it the top of the v is not used for anything of accuracy as the saddle takes up on the sides of the v and the opposing flat. My lathe is dead flat and i really enjoy leveling it to a high degreeof accuracy but it does appear i will have to revisit my methods. Thanks dave, thanks guys!

Simon

[Pete F]

I'll go over it again tonight, getting above the V ways rather than going off them. And I'll buy some suitable pipe or make a 2 collar test bar and post the results.

Thanks for your responses, I just looked and notice I'd joined back in 2009 and havn't posted until now. Talk about lurking!
Cheers Gents.

If you're averaging the readings at the end of the bar what you're doing is quite a legitimate test. The only issue is that the figure you're obtaining will not be an absolute figure due to the droop of the bar. How the bar is chucked and any runout at the end is immaterial, however will make the whole process much more difficult. When it comes time to actually adjust the headstock (if necessary) I would suggest doing it from taking cuts and measuring. I do however think that headstocks are adjusted far more that should be necessary, and wonder if in fact many more times the "fault" is actually a twist in the bed due to improper levelling rather than a misaligned headstock. Having said that, it does assume the lathe was built correctly in the factory, something the Chinese products aren't exactly renowned for.

Pete

Edit: I should add the above is assuming your test bar is otherwise dead-nuts straight and round

[Stustoys]

With the test cuts, which end was the big end?

[.RC.]

I dialed in a piece of 2' long precision ground 1" bar in the 4 jaw with a dial indicator on the carriage and set it to "0" at the chuck, so I rotate the chuck and the average reading is "0", I then wind the carriage down to the end of the bar 18" towards the tailstock and again rotate the bar, and the average reading is "25" ie. .25mm (there is negligable deflection of the bar from the force from the dial indicator stylus)



Do not even consider doing that test as it means not one thing.... 4 jaw chuck jaws even good quality ones will not hold stock parallel to the axis of the lathe when swallowing the work...

As far as the two collar test on a lathe such as this, as far as I am concerned is it not worth a pinch of ####.. Reason being the headstock on the AL330 is adjustable, not so on the lathe this sort of test is designed for, the south bend which is very light and small and the headstock sits on V-ways and is not adjustable....

What I would do is this....

Level the lathe with the precision level, get rid of all twist in the bed.... Then chuck up your stock and test the headstock for alignment..... if it is not aligned, loosen the headstock retaining bolts and align it... Takes a long time to do, but is doable..... Then align the tailstock... Job done... None of this two collars or rollies dad ########...

[Stustoys]

Do not even consider doing that test as it means not one thing.... 4 jaw chuck jaws even good quality ones will not hold stock parallel to the axis of the lathe when swallowing the work...


Hi RC,
If he is taking the average at each end, wont that tell him the axis of rotation of the bar regardless of how out of wack the bar is gripped? In fact I'm not even sure the bar needs to be straight.(though it would need to be round)

Stuart

[Bryan]

.... Then chuck up your stock and test the headstock for alignment.....


Could you elaborate on this please RC? Test how?

[PDW]

Do not even consider doing that test as it means not one thing.... 4 jaw chuck jaws even good quality ones will not hold stock parallel to the axis of the lathe when swallowing the work...


I agree with that (bitter experience confirmed it many times tho my NOS 6" P-B is very close) but the 2 collar test is still fine.

Level the machine, sure, but unless you have a lovely ground precision test bar that is a perfect fit in your machine spindle taper, the best thing you can do is the 2 collar test.

Adjust slew of headstock until both measurements are the same.

I need to do this with my Chipmaster but as I can work around the error, it's a task for when I have nothing better to do.

PDW

[.RC.]

I agree with that (bitter experience confirmed it many times tho my NOS 6" P-B is very close) but the 2 collar test is still fine.



I thought the two collar test involved twisting the bed to make the headstock turn parallel not moving the headstock?

Yes turning two sections 300mm apart of a sufficiently stout bar and adjusting the headstock so a taper of no more then 0.02mm is the way to go... But I would not call that the two collar test...

I am probably a pretty ordinary machinist but when I did the above to reassemble one of my lathes years and years ago I had hell getting it right.. took hours to get it to be repeatable due to the bar being deflected when turning the sections from incorrect tool geometry and too slender a bar....

[.RC.]

Hi RC,
If he is taking the average at each end, wont that tell him the axis of rotation of the bar regardless of how out of wack the bar is gripped?

Stuart

Don't ask be that @ 2:30pm on a Friday afternoon.... I am down to two syllable words at this time of the week.. :D

[Pete F]

Stuart is quite right, as I suggested above, the OP's test is quite valid.

Stuart I think the bar would still need to be straight (of course as I said, in fact it's not "straight" as it will droop), but like you I'm also not convinced that this is a requirement. I was trying to imagine a radical situation where the geometry of the bar was truly bizarre but even then, as long as it was round it would still give valid indications as far as I can tell, but maybe I just need to imagine a more radical set of bends. :D

When aligning a lathe in this regard the principle is quite simple; you either start with a bar of fixed diameter and indicate off it, or you turn a bar and measure the diameter. Both ways have their disadvantages, with the "test bar" it will droop and introduce an error (however that can be calculated). With the latter, deflection of the work is a major consideration. Personally I favour turning and measuring as I figure at the end of the day you're looking for the lathe to turn accurately, so why not do the measurements by turning. They're not however done this way in the factory, possibly partly because they're only half assembled at the time!

Pete

[.RC.]

Hi RC,
If he is taking the average at each end, wont that tell him the axis of rotation of the bar regardless of how out of wack the bar is gripped? In fact I'm not even sure the bar needs to be straight.(though it would need to be round)

Stuart

I am not sure what he means by taking the average at each end...

I assume it means total indicated runout.. But the problem is four jaw chucks do not hold work parallel with the spindle axis...

What someone might think of doing next is zeroing the error... So that you rotate the workpiece at the free end to exactly halfway between the TIR for example the TIR measures +12 then goes to -12 on the indicator, so you turn the workpiece until is indicates the 0 point....

You think then volia the bar is now parallel to the lathe axis.... But again that is incorrect as the indicator is not reading at the same point in the horizontal axis on the bar at the two positions... Say if you set the indicator at perfect halfway on the bar at the chuck, then down the other end when you set the bar to read zero, the indicator position on the bar could be 1mm high or low...

This is the same situation that when setting the cross slide for taper turning with an indicator using a known standard in the chuck as a guide to set the angle.... The indicator must be set perfectly on centre height otherwise it draws the wrong taper.. Been there done that.... Learnt the hard way...

[PDW]

I thought the two collar test involved twisting the bed to make the headstock turn parallel not moving the headstock?

Yes turning two sections 300mm apart of a sufficiently stout bar and adjusting the headstock so a taper of no more then 0.02mm is the way to go... But I would not call that the two collar test...

I am probably a pretty ordinary machinist but when I did the above to reassemble one of my lathes years and years ago I had hell getting it right.. took hours to get it to be repeatable due to the bar being deflected when turning the sections from incorrect tool geometry and too slender a bar....

OK, difference in terminology/definitions, we both mean the same thing. Tweak the headstock alignment, not twist the bed, based on cutting a bar in the chuck.

Agree WRT the bar - been there, too (and I am *definitely* a poor machinist, as one of my ex-staff took delight in reminding me when I insisted on using *his* lathe bought from *my* budget). Best is to use thick walled aluminium pipe IMO as you get stiffness, free machining and light weight all at the same time. Then grind a tool with a lot of rake and sharpen the edge on a stone, diamond hone etc.

Then measure, move, cut, curse, recurse....

PDW

[PDW]

I am not sure what he means by taking the average at each end...

I assume it means total indicated runout.. But the problem is four jaw chucks do not hold work parallel with the spindle axis...

What someone might think of doing next is zeroing the error... So that you rotate the workpiece at the free end to exactly halfway between the TIR for example the TIR measures +12 then goes to -12 on the indicator, so you turn the workpiece until is indicates the 0 point....

You think then volia the bar is now parallel to the lathe axis.... But again that is incorrect as the indicator is not reading at the same point in the horizontal axis on the bar at the two positions... Say if you set the indicator at perfect halfway on the bar at the chuck, then down the other end when you set the bar to read zero, the indicator position on the bar could be 1mm high or low...

This is the same situation that when setting the cross slide for taper turning with an indicator using a known standard in the chuck as a guide to set the angle.... The indicator must be set perfectly on centre height otherwise it draws the wrong taper.. Been there done that.... Learnt the hard way...

You can get a bar in a 4 jaw exactly concentric with the spindle axis - I've done it - but it is a major PITA.

Assuming the bar is actually straight in the first place....

You need to hold the bar in a ring of soft metal in the 4 jaw - I used 3mm brazing rod IIRC. This allows the bar to move but provides enough grip if you're sensible with your cuts. Tedious measurements and judicious taps (with lots of swearing when it moves too far) can get it true.

Which is all fine & good but totally useless for this thread because to keep that alignment, you need to use a tailstock centre and a travelling steady, so no use at all for setting headstock alignment!!!

The reason for going to the trouble of dialing in as above is, if you have a long slender rod and it is not concentric with the bore, even with the far end constrained by a centre and a travelling steady it may end up barrel shaped, or with a waist, from movement, or even worse, climb out of the travelling steady and totally screw the job. No guesses as to how I found *that* out. I was cutting a new leadscrew for my old lathe many years ago. The 2nd one was acceptable. Bad, but better than the one that came with the lathe.

PDW

[PDW]

Don't ask be that @ 2:30pm on a Friday afternoon.... I am down to two syllable words at this time of the week.. :D

Aaaaaand, it's beer o'clock in Rocky!

PDW

[tbonesmith]

Okay, there is no twist in the bed, and there wasn't to begin with. My bar is dead straight and there is no discernible deflection due to the pressure of the DI stylus. Cuts on a test bar confirm the machine is cutting a taper of approximately .001' per inch.
So... any more details on the course of action other that "adjust the headstock..." which I have no idea how to do. As I mentioned I don't have the original manual and could use some advice on exactly how to do it, from someone who knows the ins and outs of it on this model.

[Stustoys]

This is the same situation that when setting the cross slide for taper turning with an indicator using a known standard in the chuck as a guide to set the angle.... The indicator must be set perfectly on centre height otherwise it draws the wrong taper.. Been there done that.... Learnt the hard way...
Not exactly, setting up a taper you want a known difference between your two readings. So yes you have to be dead on centre height.
Measuring the axial alignment you want 0 difference so the height of the reading doesnt matter(within reason)

I'm not so sure about the bent bar anymore, I'll have to think about that some more.

I think, its even later on Friday now :)

Stuart

tbonesmith Which end is big?

p.s. I'm starting to think RC is correct but am struggling to prove it either way

[tbonesmith]

Not exactly, setting up a taper you want a known difference between your two readings. So yes you have to be dead on centre height.
Measuring the axial alignment you want 0 difference so the height of the reading doesnt matter(within reason)

I'm not so sure about the bent bar anymore, I'll have to think about that some more.

I think, its even later on Friday now :)

Stuart

tbonesmith Which end is big?


Growing towards the headstock

[Dave J]

With getting the lathe perfectly leveled (for twist) etc is just eliminating any other cause, as moving the head stock is the last thing to do and only done if you really have to.
Saying that it sounds like you have been through everything. I noticed my lathe was turning a taper after moving it and it never did before, then I remembered I hadn't re-leveled it and that fixed my problem. It just showed me how a little twist could put it out so much.

You will need to undo your bolts that hold down the head stock. There are bolts at the back of the head stock for adjustment like shown in thread from Eskimo. When you undo the bolts only undo them a bit, not loose, the adjusting bolts will pull it over.

It is just a case of adjust it a bit, then do a cut to see how it's going, then repeat until your happy with it. As said in the other thread you where reading, it wont take much of a turn of the bolt to move it over.

As said above it is time consuming, but if it's out it needs to be done.

Dave
PS
I never noticed you had joined back then, just thought you where a new member.

[Stustoys]

Hi tbonesmith


"Growing towards the headstock "
I guess that rules out deflection from the tooling.


I see Dave's been typing while I've been looking for threads :)
A flick through this thread should help you get started, assuming your lathe is something close(which I'm guessing it is.)
http://www.woodworkforums.com/f65/my-new-al960-cutting-taper-147402/ (http://www.woodworkforums.com/f65/my-new-al960-cutting-taper-147402/)

Stuart

[.RC.]

I know the AL1000C had the headstock adjusting bolts tucked in next to where the motor was.. It was crude, but worked....

[pipeclay]

It would appear that you would need to move the chuck end of the headstock to wards the carriage hand wheels.
Set your indicator up at the tailstock end of your bar and move the headstock adjusting screw untill the indicator is showing the amount your taper is.
Lock the headstock bolts and see if the indicator reading is still the same,if it moved more than .002" or .003" reset it.
Take a cut and see what the taper is.
If you are lucky and dont try and chase too much accuracy you should be able to get it down to around a .001" to .0015" pretty quickly.
Once your happy with your setup lock the headstock bolts down and then nip the adjusting screws up and lock any lock nuts that may be there.
If by some chance the movement of the headstock increased your taper just move it the other way.
The tailstock side screwwill push towards the carriage and the change gear side screw will push to wards the splash guard.
If you try and chase the PERFECT some on here seem to achieve you will be chasing your ar-e for a long time.

[slhouetteV8]

I thought the two collar test involved twisting the bed to make the headstock turn parallel not moving the headstock?

I thought the whole idea was to NOT put a twist in the bed. So when you're bolting your lathe to a surface that may not be flat or level you don't impart a twist in the bed. On the occasions where a lathe already has a twist in the bed you can follow the same procedure to remove it?

Just to add... Doesn't the method assume your headstock is already aligned to the ways? If the headstock is not aligned then you need to align it not twist the bed.

[Bryan]

I thought the whole idea was to NOT put a twist in the bed. So when you're bolting your lathe to a surface that may not be flat or level you don't impart a twist in the bed. On the occasions where a lathe already has a twist in the bed you can follow the same procedure to remove it?

Just to add... Doesn't the method assume your headstock is already aligned to the ways? If the headstock is not aligned then you need to align it not twist the bed.

Neither test cuts nor indicating will tell you why there's an error. It could be bed twist or headstock adjustment. You need to eliminate twist by levelling; any remaining error is headstock. That's my take anyway.

[slhouetteV8]

Okay I think I'm with you now. So what you're saying is that if the bed is level then the headstock must be out?

[tbonesmith]

So I mucked around a bit more and ran a few more test cuts on some thicker bar, 36mm round hollow bar, medium carbon steel, and got some funny results. I had it protruding 9" from the 3 jaw, and took some very light cuts with very sharp HSS, and got a taper of .0005" per inch for the section 4"-9" away from the chuck, and no taper for the section 1"-4" away from the chuck.
So it isn't as bad as I thought, but that seems a bit odd doesn't it?
Anyway I'll play with it some more before moving anything. Hopefully it's just me somehow.

[.RC.]

That is correct.... The idea is not to twist the bed... From what I understand the two collars/rollies dad test is for when you have no level and have a small lathe like a Hercus..

As the headstock sits on V ways it should* be parallel to the ways as good as when it was new... it is not adjustable by any easy method..

So when doing the parallel turning test if there is any deviation you can assume it is caused by a twisted bed, so you adjust the bed bolts to untwist it and get it turning parallel.....

From what I understand most US designed lathes the headstock sits on the tailstock V ways...

In lathes designed in the UK and elsewhere like China, the headstock sits on flat ways (cheaper to manufacture) and are adjustable... I have had to adjust the headstock on an old geared head Nuttall, an AL1000C and a medium sized Purcell.... All had the headstock sitting on flat pads...

[Stustoys]

Hi tbonesmith,
Still big at the chuck end?
Stuart

[tbonesmith]

Still bigger at the chuck end.

[tbonesmith]

I could almost live with it. But as usual, I'll be better off getting to the bottom of it now, rather than having an issue on a job down the track.

[Pete F]

I am not sure what he means by taking the average at each end...



Richard, you compare the average reading at the headstock end (which can be made to be zero with a 4 jaw) to the average reading at the other end. It doesn't matter that the bar isn't parallel to the spindle axis. Imagine the bar in crazy bad jaws that are 10 degrees off axis, but an otherwise perfect lathe. At the headstock end the indicator would be zero, rotate the chuck 180 degrees and measure again it would still be zero. Now go to the other end of the bar and rotate the bar so it reads the minimum, call it -10 units, rotate the chuck to find the maximum and it should both be +10 units and at 180 degrees; the average is still 0.

Now assume either the lathe bed is twisted (most likely) or headstock alignment is out (less likely), the readings at the headstock end will still be zero/zero, but at the other end they may be +12/-8. The maximum to minimum readings are averaged and then that average is compared to the average at the headstock end. I think this is quite different to what you're suggesting.

Pete

Edit: I should add that I don't for a moment advocate this approach, simply that's how it works.

Edit #2: Incidentally, before moving the headstock have you checked to see if the lathe faces accurately?

[rusty steel]

Hello tbonesmith,
My understanding is that you need to first remove any twist from the bed. Then you need to get the spindle axis parallel to the ways ("Rolle's Dad's Method" will do this), when viewed from the side (standing at the controls). This adjustment can be achieved by raising or lowering the tailstock end of the lathe or shimming under the headstock bolts. The aim is to keep both the lathe bed and spindle axis horizontal according to your spirit level if possible.
Next you need to get the spindle axis in alignment with the ways when viewed from above (looking down from the ceiling). Rolle's Dad's Method will show this as will the Two Collar method. If any taper shows up it can be removed by imparting a twist to the bed or adjusting the Headstock (preferred) by loosening the four bolts (I think your lathe has 2 bolts and 2 capscrews) and adjusting the four capscrews at the back of the head,above the motor.
Regards,
Russell

[rusty steel]

Me again,
I made a test bar by turning up two 60mm dia. aluminiun rings from 10mm plate and locktiting them onto a piece of 25mm dia.solid steel spaced about 200mm apart with the first ring 50mm from one end to hold in the chuck. I have a centre in both ends of the bar so that I can also check the tailstock alignment.
Russell

[pipeclay]

When you set your test piece up were you using the 3 jaw chuck?

[tbonesmith]

When you set your test piece up were you using the 3 jaw chuck?

Yes.

[pipeclay]

If possable do another test cut with the material set up in a 4 jaw.
Is the 3 jaw chuck your using a Set True chuck?
The amount of taper that you mention after turning could possably be caused by the 3 jaw.
The 3 jaw is not the most ridgid (firm holding) chuck to use for your testing.

[Pete F]

Why should it be a set-tru chuck, once cuts are made it's completely immaterial how the work is held. The only time this is a factor is if the work is re-chucked, not at all relevant in this case.

[.RC.]

Richard, you compare the average reading at the headstock end (which can be made to be zero with a 4 jaw) to the average reading at the other end. It doesn't matter that the bar isn't parallel to the spindle axis. Imagine the bar in crazy bad jaws that are 10 degrees off axis, but an otherwise perfect lathe. At the headstock end the indicator would be zero, rotate the chuck 180 degrees and measure again it would still be zero. Now go to the other end of the bar and rotate the bar so it reads the minimum, call it -10 units, rotate the chuck to find the maximum and it should both be +10 units and at 180 degrees; the average is still 0.

Now assume either the lathe bed is twisted (most likely) or headstock alignment is out (less likely), the readings at the headstock end will still be zero/zero, but at the other end they may be +12/-8. The maximum to minimum readings are averaged and then that average is compared to the average at the headstock end. I think this is quite different to what you're suggesting.

Pete

Edit: I should add that I don't for a moment advocate this approach, simply that's how it works.

Edit #2: Incidentally, before moving the headstock have you checked to see if the lathe faces accurately?

The bit I do not get is the average.... An average is readings divided by number of readings.. TIR is just a single figure..

I just did a test on my lathe where I know the headstock is pretty damn good... I found using the precision bar in the four jaw chuck, zero it at the headstock end... And rotate the spindle until you get halfway between the high and low TIR points on the free end you can get it close, but it was simply way too easy to put an error in there and get the wrong figure... Also you get the small error of the indicator point not being in the same horizontal position at either end, as the free is pointing either up or down..

[Bryan]

Also you get the small error of the indicator point not being in the same horizontal position at either end, as the free is pointing either up or down..

At max and min readings the bar should be horizontal I think.

[pipeclay]

Why should it be a set-tru chuck, once cuts are made it's completely immaterial how the work is held. The only time this is a factor is if the work is re-chucked, not at all relevant in this case.
I dont know why should it be a Set True chuck,can you provide a clue?

[Pete F]

The bit I do not get is the average.... An average is readings divided by number of readings.. TIR is just a single figure..

I just did a test on my lathe where I know the headstock is pretty damn good... I found using the precision bar in the four jaw chuck, zero it at the headstock end... And rotate the spindle until you get halfway between the high and low TIR points on the free end you can get it close, but it was simply way too easy to put an error in there and get the wrong figure... Also you get the small error of the indicator point not being in the same horizontal position at either end, as the free is pointing either up or down..

Richard I'm not following you. The end of the bar will sweep a cone shape, at one point the cone will be closest to the indicator, at 180 degrees it will be furthest from the indicator (except you will be measuring on the opposite side of the bar, hence why it needs to be consistently round). Add those two reading together and divide by two, that's the average reading. Now do the same at the headstock. Compare those two averages with each other, that's the taper.

Ok, forget lathes for a moment. Think of milling with a properly trammed head (which is just a lathe tipped on end for a vertical mill). Now recall how you dial in a bore. You chuck a DTI any way you like, it doesn't need to be concentric, nor as we all know, does the indicator holder need to be straight (I must admit that one got me thinking), now sweep the bore. Imagine that the X axis is off, the DTI will read more on one side of the bore and less on the other side of the bore. In the case of the mill we can adjust the table so the DTI sweeps around the bore with the same reading. Note how the DTI and its supporting arm form a cone as it sweeps around, a small cone at the collet that gradually gets bigger as it goes down the supporting arm, then typically gets a little smaller at the DTI (at least the way I use mine anyway). So once that's done, now knock the head out of tram, imagine the cone now getting tilted off vertical, it won't indicate the bore the same way.

If you can exchange the words "tram" for "headstock alignment" and picture the mill laying on its side I'm hoping it will either make perfect sense ... or I've just completely confused a bunch of people :D


I dont know why should it be a Set True chuck,can you provide a clue?

Peter, as I have shown above, there is no need for a "set-true" chuck, now would you like to re-ask the question sans attitude?

Hope that makes some form of sense and helps in some small way.

Pete

[slhouetteV8]

Hmmmm... And I thought I was clever using the level app on my phone:o

Better head back to the drawing board:doh:

[Dave J]

Hmmmm... And I thought I was clever using the level app on my phone:o

Better head back to the drawing board:doh:


A carpenters level is good enough for most home shops, but if your chasing low numbers you will need a precision level to start off with, as the first thing you need to do, is to truly level the lathe for twist. I used a carpenters level for many years on both my Hercus and my current lathe and made all sorts, including shafts where a press fit bearing was needed, and they all turned out fine.

Dave

[slhouetteV8]

Lol, Im not serious Dave. Although the level on the phone would probably be better than a carpenters level.

[Dave J]

LOL, you never know these days, my son seems to use his for everything. These days they have more gadgets than mister gadget ever had.

Dave

[slhouetteV8]

That's funny. Im old enough to remember not having mobiles and computers but my kids are out of control. To be honest I didn't know they existed until my daughter showed me a couple of days ago.

[Dave J]

That's funny. Im old enough to remember not having mobiles and computers but my kids are out of control. To be honest I didn't know they existed until my daughter showed me a couple of days ago.

Same here, and I still don't own a mobile. as far as computers go, I have only owned one for around 8 years with the first 2-4 years being mostly self taught learning, LOL.

When I was young we used to just ride our bikes around and go home at the time mum told us to, these days mums ring there kids on there mobiles to come home or find out where they are.
I can see the good in them, but I can also see the bad as some are totally addicted to them and are on face book, messages etc where ever they go.

We are getting a bit of track here so we better get back on topic, sorry Tbonesmith. :2tsup:

How is your alignment going, are you getting any closer to correcting it?

Dave

[tbonesmith]

Same here, and I still don't own a mobile. as far as computers go, I have only owned one for around 8 years with the first 2-4 years being mostly self taught learning, LOL.

When I was young we used to just ride our bikes around and go home at the time mum told us to, these days mums ring there kids on there mobiles to come home or find out where they are.
I can see the good in them, but I can also see the bad as some are totally addicted to them and are on face book, messages etc where ever they go.

We are getting a bit of track here so we better get back on topic, sorry Tbonesmith. :2tsup:

How is your alignment going, are you getting any closer to correcting it?



Dave

No I've just been using it as is while I do some other jobs, but now they're done I need to sort this, because I have to do some precise work. Over 9 inches I'm turning a taper of about 0.006".
There is a lot of runout in the chuck too, and the spindle alignment is even worse in the vertical axis.
Today I chucked up some 1.5" stock in the 4 jaw and turned it unsupported over 9" with a very slow feed at 200 RPM taking very light cuts and got the .006" taper over 9" (large at headstock end).
Then I setup a dial indicator on the carriage and ran it along the top of the bar, and it went from nominally 0" at the headstock to 0.007" at the unsupported tailstock end of the bar (ie. headstock at the top of the hill).
Anyway it won't do for my upcoming work so now's the time...
Any suggestions, I'm considering paying someone to do it for me/ hold my hand through it as it might just be too time consuming for me to duff about with it, and spend weeks working it out...

[pipeclay]

What part of Sydney are you in?

[tbonesmith]

I'm in Coogee.

[tbonesmith]

So I made some progress, finally. Just thought I'd give it a crack, removed the splash guard at rear, undid the bolts at the end of the bed and adjusted the slew at the bed side a bit with the DI on the tailstock end of a test bar until I could run the DI on the carriage down the bar with no change in the reading.
Then did everything up and took a test cut over 9", adjusted things more etc, anyway I now have only .0002-.0003" of taper over 9" which I can live with for now.
I still have a coupe of thou spindle misalignment in the vertical axis, so when I run the DI along the top of the test bar, it indicates .0025 run out from one end to the other of my 9" bar.
I think I can do the jobs I need to with this level of accuracy, and I'll come back to it later.
Now to try to get the chucks to run a bit truer...

[Stustoys]

You didn't slip in an extra 0 there did you? 0.0002" is the amount 1.5" of steel would expand when heated 10C. Still either way, if its close enough for what you want that's all that matters, good job.

I wouldn't think you'll find a standard chuck to run that true, even Bison set tru chucks claim 0.0004" TIR repeatability. The price I'm looking at for a 5" 3 jaw is $897+$250ish for the backplate.
How big is the work you are doing? Maybe ER collets are the way to go?


Stuart

[tbonesmith]

You didn't slip in an extra 0 there did you? 0.0002" is the amount 1.5" of steel would expand when heated 10C. Still either way, if its close enough for what you want that's all that matters, good job.

I wouldn't think you'll find a standard chuck to run that true, even Bison set tru chucks claim 0.0004" TIR repeatability. The price I'm looking at for a 5" 3 jaw is $897+$250ish for the backplate.
How big is the work you are doing? Maybe ER collets are the way to go?


Stuart

No extra zero's. Chuck runout is big on this though, anyway I can work on that, and I don't think it will be insurmountable, as the spindle nose and face are spot on. Chuck looks in good nick, I'll hit the bearing surfaces with bearing blue and see if I've got a bruise or burr somewhere.
I'm going to profile, thread and chamber rifle barrels on it, so the max diameter will be 30mm give or take at the chamber.

[Dave J]

The way I check a lathe is to chuck up a heavy wall pie around 75-100mm diameter, then take a clean up pass, then a fine finishing pass with a honed HSS tool. This will tell you what your lathe is aligned like taking out any inaccuracies in anything.like the chuck and bar, etc.

Dave

[tbonesmith]

The way I check a lathe is to chuck up a heavy wall pie around 75-100mm diameter, then take a clean up pass, then a fine finishing pass with a honed HSS tool. This will tell you what your lathe is aligned like taking out any inaccuracies in anything.like the chuck and bar, etc.

Dave

Mmmmmm... heavy wall pie...:rolleyes:

[Dave J]

OOPS, LOL, honestly some of the pies you get around would do the job well.
I have been busy down the shed and only getting on the forum quickly while I am up here, thats my excuse anyway.
I was going to edit it, but then it will make your post look funny.

You would be better off with steel pipe, often your local steel place will have off cuts if you don't have any laying around, even a bit off a gal fence posts will do.

Dave