Lathe Headstock Alignment

[colin james]

Does anyone know how to adjust the Headstock Alignment on an Optimum TU2807V Lathe

 

[dnalot]

What is the machine doing that you think the headstock needs alignment?

Mark T

 

[SmithDoor]

Does anyone know how to adjust the Headstock Alignment on an Optimum TU2807V Lathe

Most head stock can not be adjusted.
Is it a old lathe?

Dave

 

[colin james]

The machine is cutting a .11mm (.0043") taper in 34mm (1.339")
The Machine is an Optimum TU2807V which I bought brand new 4 years ago,
but have only just set it up, and have just started using it.
There is no twist in the bed.

Colin.

 

[dnalot]

There is no twist in the bed.

Sorry but you do have a little twist in your bed. This link will show you how to fix that.

Mark T

 

[SmithDoor]

The machine is cutting a .11mm (.0043") taper in 34mm (1.339")
The Machine is an Optimum TU2807V which I bought brand new 4 years ago,
but have only just set it up, and have just started using it.
There is no twist in the bed.

Colin.

It could be the lathe casting has warp.
This does happen when the casting are machined green.

American manufacturers would let the casting age a year before machining.

Check the bed and see if it is straight.

Dave

 

[petertha]

@colin james
I found this link to what I think is the operating manual.
https://www.manualslib.com/manual/1378971/Optimum-Optiturn-Tu-2506.html?page=186#manual
I only gave it a cursory look but I did not see the headstock adjustment screws shown. This topic is of particular interest to me because my '97 vintage Taiwan 14x40 lathe manual also does not show adjustment screws, but I can assure you they exist. Very hard to photograph but maybe these pics will help.

Most well meaning folks will tell you to start jacking the lathe feet in order to alter the lathe bed twist in order to correct taper cutting. This is often called 'lathe levelling' which is also a potentially confusing choice of words. If by levelling we are talking about using a precision level across the ways incrementally down the length of the bed in order to get a sense of current twist condition, that's fine. But the lathe does not have to be level left to right.

I suspect the reason people recommend to start altering bed twist right away is out of tradition because older vintage lathes had their headstock integrally cast with the lathe bed. There was nothing to adjust, the spindle axis was a function of the HS line bore & bearings. However, what many seem to miss (maybe including Blondihacks) is that most Asian lathes are constructed differently & have their headstock bolted to the ways as my manual shows. I have heard that some manufacturers 'key' the HS & bed together but I don't know to what extent or class of machine that may pertain to.

Anyways, for Asian lathes including my 14x40, which is actually quite ordinary, it has micro-adjusting set screws to tweak the HS rotation viewed from the top. This is done at factory. But if the HS has become misaligned relative to the ways, then this effect will also cut a taper even if the bed twist is 100% perfect. The best way to test for this is with a cylindrical test bar which has MT taper on one end to match your HS spindle socket. I bought a 24" made in India off Ebay for very reasonable cost. I was apprehensive but it is good value. They say cylindrically ground within 0.0001". I have no good means to validate that other than mic-ing down the length, but seems plenty accurate for hobby class machine HS & TS alignment work. Now with test bar inserted & cantilevered from the spindle, you can traverse an indicator down the length & this will tell you what's going on with regards to HS alignment - yawing in/out and/or pointing up/down. I have to caution you though, that breathing on the set screws can have a dramatic effect so proceed very carefully & only if you have a repeatable test bar. Maybe the factory omits mention of these adjustment screws so people don't start messing around, but that's pure speculation. With the spindle aligned to bed, then proceed to lathe twist (not the other way around).

I've read all the articles about cutting test bars & such. Nothing wrong with that & it has its place near the end of the procedure. Its just another means of verifying taper. You can save a lot of material & false readings by doing your best to initially validate geometry with test bar & indicator.

 

[colin james]

Sorry but you do have a little twist in your bed. This link will show you how to fix that.

Mark T

There was no twist in the bed when I set up my machine up as per blondihacks, I've just rechecked it today with a machinist level and it still not twisted.

 

[colin james]

@colin james
I found this link to what I think is the operating manual.
https://www.manualslib.com/manual/1378971/Optimum-Optiturn-Tu-2506.html?page=186#manual
I only gave it a cursory look but I did not see the headstock adjustment screws shown. This topic is of particular interest to me because my '97 vintage Taiwan 14x40 lathe manual also does not show adjustment screws, but I can assure you they exist. Very hard to photograph but maybe these pics will help.

Most well meaning folks will tell you to start jacking the lathe feet in order to alter the lathe bed twist in order to correct taper cutting. This is often called 'lathe levelling' which is also a potentially confusing choice of words. If by levelling we are talking about using a precision level across the ways incrementally down the length of the bed in order to get a sense of current twist condition, that's fine. But the lathe does not have to be level left to right.

I suspect the reason people recommend to start altering bed twist right away is out of tradition because older vintage lathes had their headstock integrally cast with the lathe bed. There was nothing to adjust, the spindle axis was a function of the HS line bore & bearings. However, what many seem to miss (maybe including Blondihacks) is that most Asian lathes are constructed differently & have their headstock bolted to the ways as my manual shows. I have heard that some manufacturers 'key' the HS & bed together but I don't know to what extent or class of machine that may pertain to.

Anyways, for Asian lathes including my 14x40, which is actually quite ordinary, it has micro-adjusting set screws to tweak the HS rotation viewed from the top. This is done at factory. But if the HS has become misaligned relative to the ways, then this effect will also cut a taper even if the bed twist is 100% perfect. The best way to test for this is with a cylindrical test bar which has MT taper on one end to match your HS spindle socket. I bought a 24" made in India off Ebay for very reasonable cost. I was apprehensive but it is good value. They say cylindrically ground within 0.0001". I have no good means to validate that other than mic-ing down the length, but seems plenty accurate for hobby class machine HS & TS alignment work. Now with test bar inserted & cantilevered from the spindle, you can traverse an indicator down the length & this will tell you what's going on with regards to HS alignment - yawing in/out and/or pointing up/down. I have to caution you though, that breathing on the set screws can have a dramatic effect so proceed very carefully & only if you have a repeatable test bar. Maybe the factory omits mention of these adjustment screws so people don't start messing around, but that's pure speculation. With the spindle aligned to bed, then proceed to lathe twist (not the other way around).

I've read all the articles about cutting test bars & such. Nothing wrong with that & it has its place near the end of the procedure. Its just another means of verifying taper. You can save a lot of material & false readings by doing your best to initially validate geometry with test bar & indicator.

 

[colin james]

I had a look at the same page in the Manual yesterday, I can only see the screws inside the casting at the front,
I will have to see if I can find the clearance holes that appear on the drawing at the back of the bed at the headstock end.
The machine is not far from the wall, so I will have to remove the splash guard at the back to see if I can see the screws,
as I can see nothing at the headstock end, as the pulley mounting plate blocks the vision of these at the headstock end.
This will have to wait until Monday as I have a very busy weekend ahead of me.

 

[SmithDoor]

There was no twist in the bed when I set up my machine up as per blondihacks, I've just rechecked it today with a machinist level and it still not twisted.

It does need to be twisted.
It can be bending .
But good news is if not bending or twisted and manufacturer machine the head stock wrong that can be fixed.

Dave

 

[Steamchick]

Cast iron lathe beds for small hobby lathes are not very stiff. EVERY good machine will have been properly installed onto a proper levelled and true foundation and stiff support frame. But most hobby lathes (like mine) are simply dumped onto something, (in my case an angle frame sitting on untrue concrete) which probable has moved with time. The only remedy is to reset the lathe as explained in the various posts.
I need to order a test bar to do mine. But I am currently living with it where the tailstock centre is 0.004" off of centre. No good for drilling 0.010"holes!
Face a piece of bar with the tool a couple of thou low, to develop a centre pip, when only 1/2" out of the chuck. The face a long (maybe 1 in dia?) Bar at a long distance from the chuck, with the same tool height setting. You'll easily see the height difference between the 2 positions. You are just looking at taper, but you must also study height as well.
Enjoy!
K2

 

[GregNixon]

Google Rollie's Dad's Method.

 

[petertha]

Here, I'll save you the search. RDM has nothing to say about a headstock that is able to rotate relative to the bed ways, which may be the case of the OP's lathe and is in fact common among many Asian hobby lathes. RDM presumes lathe types where the headstock is integral with the ways; the spindle is bored at factory & essentially un-alterable. So RDM describes altering lathe twist & confirming progress by cutting a test bar. But as I mentioned in prior post, if the HS was either incorrectly set or has shifted, and is pointing at an angle relative to the bed ways viewed from the top, it will cut a taper even if lathe twist is 100% perfect. So HS alignment must be checked first. This supersedes RDM. If you fail to confirm HS angle & go straight to lathe twist, more than likely you now have 2 mislaignment issues essentially competing with one another.

http://neme-s.org/Rollie's_Dad's_Method.pdf

 

[GregNixon]

Rotate relative to the bed ways, was that yaw or roll? RDM does not require cutting a test bar. "RDM presumes lathe types where the headstock is integral with the ways; the spindle is bored at factory & essentially un-alterable?" I don't see this as a requirement. RDM does correct pitch
(vertical) and yaw (horizontal).

 

[petertha]

Sorry I meat to say 'equivalent to cutting a test bar'. And maybe that's a stretch because ultimately its trying to determine spindle axis relative to lathe bed axis.
Because RDM doesn't mention anything about 'adjusting' HS headstock relative to bed ways & proceeds straight to altering lathe twist, its just an assumption on my part that it presumes the spindle axis to be fixed. I didn't write it so its only speculation.

What I'm trying to convey is really quite simple. Upper sketch shows aligned lathe viewed from top. Zero bed twist. Lower picture shows the type of lathe where HS is mounted to bed & has the ability to be misaligned. It shows exaggerated HS angled toward rear of lathe, again zero bed twist. Would you concur the lower sketch would cut a tapered coupon?

 

[GregNixon]

Yes I would agree that the setup shown would cut tapers. The one and only time that I have used RDM has been on a mini-lathe with a bolted on headstock. To correct the problem shown in your diagram I would have just turned the headstock until both the near end and far end were the same. Likewise for the vertical adjustment. I would have shimmed headstock to correct the error. A more robust lathe like my Hercus (Southbend) with its fixed spindle will need to be levelled and adjusted.

 

[Steamchick]

Noting that "the draughtsman always draws straight lines, and doesn't compensate for curves".... all the setting guides assume the bed of your lathe is straight and true. I am on my 5th lathe in 30 years... and all have had some bend or twist, I now understand because my base frame is NG. You can't align the head to a bent bed... But all the lathes I have used (school and later in a machine shop - where the lathe had a 2ft swing, 6ft long headstock with motor, 15 ft long bed about 18" wide... and wasn't true, so for long shafts turned between centres, I had to adjust the cut a thou at a time at appropriate intervals... every 2 inches or so on a 5 ft long roller!). Perhaps I should caution that the feet of the lathe need to be on a STIFF and LEVELLED base, as otherwise you will bend the precision (but not very stiff) lathe bed when torsional loads from cutting are applied. - That is my experience anyway... (My stand is NOT STIFF ENOUGH!, nor TRUE and levelled - hence I have a bent lathe, which was good "as new"....).
You should "live and learn", not like me, live and "fail to learn"....
K2

 

[Outback]

I purchased a test bar (25mm x 300mm) a lot cheaper than a level and useful for tailstock alignment as well. make sure to check horizontal and vertical alignment with a dial gauge on the cross slide. as others have mentioned set screws are available on the head stock to adjust lateral alignment but watch the vertical as well mine was out of wack which meant I had to remove the head and use brown paper to shim it up. Then you need to check the tailstock again in case it is out on vertical as well now the head has moved. Two days later my lathe was good over the 30 cm of the test bar which is the best one can hope for. (I had already done the RDM before purchasing the test bar and bed twist did not help as much as lauded.
Brian

 

[petertha]

Yes I would agree that the setup shown would cut tapers. The one and only time that I have used RDM has been on a mini-lathe with a bolted on headstock. To correct the problem shown in your diagram I would have just turned the headstock until both the near end and far end were the same.

I kind of chuckled when you use the word 'just'. This entire post is actually quite typical of many similar 'lathe levelling' posts one encounters on hobbyist forums. Its a familiar script. Someone notices they have taper cutting issue & the immediate solution offered is to jack the feet & twist the bed. The lathe type often does not even come up in in discussion as a qualifier. Or if it does, few people recognize that the HS is bolted to the ways & any misalignment there may well be the dominant if not entire source of taper cutting discrepancy. Then there is mysterious absence of the operator/parts manual even mentioning adjustment screws being there. If one has a larger lathe, say in 14" range, pulling the HS off & shimming is not exactly a trivial job although I recognize hobbyist skill sets vary. I'd certainly want to be sure before embarking down that path. Which is is exactly why a MT test bar is a valuable asset.

Just a guess on my part but maybe 20-30 years ago the chance of a hobbyist lathe being of the 'integrated' type (where no spindle alignment correction is possible) was certainly much higher than today. And yes, in that case you are stuck with what you have. Lathe twist is the only option & this presumes other factors like wear are good or minimal. But I would venture to guess a much higher percentage of hobby lathes in shops today are of the bolt-on style. Here is a popular vendor, quite typical of others including say Grizzly or other Asian importers. I count a dozen lathes from the smallest up to and including 14" swing which are bolt-on HS. Now if the factory did their job 100% and/or we have verified ourselves that HS is perfectly aligned in both vertical & horizontal plane, then we have arrived at the equivalent point of an 'integrated' lathe and hopefully relatively minor bed twist alteration may remedy remaining slight taper cutting. But if you have HS alignment problem & ignore it, and proceed to lathe twist, you are possibly attempting to fix the wrong problem or overcompensating which isn't the best solution. Of course this is a hobby so everyone is welcome to proceed as they see best. I'm just offering another perspective to the discussion.

https://www.precisionmatthews.com/product-category/lathes/12-14-swing/