Thread: Jacked Feet or Shims to level a lathe ?

Hi Bill,
Definitely jacked feet. But mine are on the base of the cabinet and the lathe is bolted down to the cabinet hard. Saves lots of stuffing around when leveling.....which leads me to another subject. Rollies dads method (RDM) is not the be all and end all of tests....you are better off either leveling the lathe with a precision level (something that costs money and unless you are going to be reconditioning machines will not be used very often) or taking test cuts on a bar around 4" long, unsupported by the T/S and jacking the bed so the test bar is parallel. Once its cutting parallel you can then cut a test bar between centers to ensure the T/S is in alignment. Be sure to freshly machine your dead center before you do this, and mark your T/S barrel and live center so your results should be repeatable.
As for test cuts, take it slow with a really sharp HSS tool, make sure there is no heat build up in the bar and only take tiny cuts. You made need a decent feed per rev to keep chatter away, well at least i do on the mars when cutting unsupported bar that long.

There is a book called Lathework, a complete course by Harold Hall that includes making cylindrical squares and it takes you through test cuts etc. Lathework A Complete Course BY Harold Hall Paperback 2003 1854862308 | eBay
Actually i didn't get the mics away yesterday, i'll find my copy and put it in with them.

Cheers,
Ew

I think the jacked feet pictured might be a little difficult to adjust in increments afforded by shims. After roughly levelling with similar jack feet on the stand, I used shims between the stand and lathe bed in the order of .05 to .15 mm. I don't think you could get that sort of accuracy just using jack bolts.

Originally Posted by Ueee

Hi Bill,

Actually i didn't get the mics away yesterday, i'll find my copy and put it in with them.

Cheers,
Ew

G'day Ueee,

Thanks for offer of book but have already got it ..........

I've got the 2012 version of that Harold Hall book called "Metal Lathe For Home Machinists" goes through the cylinder/square and the test bar and a heap of other things, and I've got access to most of the Workshop Practice Series at local library.

Was messing about with Rollies Dad prior to micrometers getting here for measuring the cylinder.


Bill

No worries Bill.
The point th62 brings up is relevant if the bolts are close together. As mine are on the base of the stand they would be around 500mm apart, and even though the bolts are 5/8 x...10? there is plenty of fine adjustment to be had. If they were only on each side of the bed though it may be a different story.

Ew

I used the method Hercus said to use in their manual....

I tried using the precision level and levelling by adjusting the screws on the bottom of the sheet metal base but it was a waste of time..

Seems getting small lathes like the Hercus level does not mean they will not turn stock supported only by the chuck, parallel...

I found the bed has to be adjusted where it bolts onto the base, just like the manual says... Testing with test cuts until it turns parallel...

Originally Posted by th62

I think the jacked feet pictured might be a little difficult to adjust in increments afforded by shims. After roughly levelling with similar jack feet on the stand, I used shims between the stand and lathe bed in the order of .05 to .15 mm. I don't think you could get that sort of accuracy just using jack bolts.

How about if finer threaded bolts were to be used ?

Will check down local bolt shop or even make my own. Good learning.

Chicken and egg - how well set up does my lathe have to be to cut usable threads ?

Rollies Dad currently telling me I am 0.025" out of alignment over 15" ...... to my Weekend Woodworker mentality that's nothing, but to an experienced machinist that must be heaps ?

Bill

Yep its may as well be miles.....(well maybe not that bad)

As someone once said on this forum, There is a whole nother family of measurements to be found lurking under the millimeter.

You could thread cut with it as is, but really an m12 bolt , 1.75 thread and a long spanner will give you pretty fine adjustments, you can also "torque shim" the lock nuts to get it really close. A dial gauge would be really handy to see how far you are moving if you have one.

My lathe stand is welded SHS not pressed so i guess i can get away with the bolts at floor level.

Ew

Hi all,

I have only used jacking feet. My limited experience tells me that shimming may well get you spot on with a lot of stuffing around but if you check your levels in a years time you may find yourself looking for another set of shims. I check the level on my lathe probably once a year just to see how much things move. it's more out of general interest than anything else but it also justifies me having the level! Anyway, what I have found is that it is not unusual to find that it needs tweaking to get it spot on again. No big deal with jacking feet, just a bit here and a bit there and it's all good again. If I had the lathe on shims I would be pulling my hair out..... Actually, I probably just wouldn't bother checking it. Ignorance is bliss!

As for not being able to perform fine adjustments, I have found a way that suites me well. For the "course" adjustment I take a spanner to the nuts (underneath, the ones that support the lathe) until I get it to less than a graduation on the level. Then for the fine adjustment, I use the sandwiching pressure from the top nuts. I nip here and a nip there and I get it pretty good. Hope I have explained my method.

Cheers,

Simon

Gee that looks familiar.
What diameter bar are you using?
I thought RDM didnt use tailstock?
You're turning 15" from the chuck unsupported?

Originally Posted by th62

I think the jacked feet pictured might be a little difficult to adjust in increments afforded by shims. After roughly levelling with similar jack feet on the stand, I used shims between the stand and lathe bed in the order of .05 to .15 mm. I don't think you could get that sort of accuracy just using jack bolts.

Nope you can, using a level thats 0.02mm/m, say the bolts are 200mm apart front to back, that means to move one division you need a shim 0.004mm thick thats about half the thickness of Alum foil. Its a nightmare..... I tried shims before "inventing" the jacks. With a 300mm spanner and a 1.75mm pitch thread .004mm is about 5mm of rotation.
So leveling is fine........... not how rigid the result is, thats another question.

Stuart

When you have no accurate level and no ground test bar, AND you are confident that your headstock alignment is fine, then Rollie Dad's method (RDM) can work fine albeit a little slow. You need be fully aware that RDM is a shorcut method that assumes the headstock-to-bed alignment is correct to begin with. It is usually safe to assume correct headstock alignment, if you know the full history of your lathe (like if you bought it new, or know and trust the previous owner) and you did not fiddle with this adjustment and the lathe did not suffer in a transport accident.

Otherwise, use a good egineer level of better than 0.5mm/m per division to level the lathe bed. Then finally check with the spool cutting test to verify headstock alignment is fine too.

Well designed(!!) leveling screws are quicker to setup than shims. But that is just the secondary bonus. The main benefit on a bench lathe is in my opinion another one. In most cases a perfectly aligned lathe does not remain that way forever. There are constantly changes due to movement of the floor with the seasons (even on a concrete shed floor), and in case of a wooden bench this wood also moves with the seasons and humidity. All causing small taper errors. On the rare occasions when you need all the accuracy your lathe can give you, turn your workpiece slightly oversize, check for any taper error with the micrometer, then correct for this error by very finely altering the setting of one leveling screw (always use the same leveling screw for this fine tweaking). Edit: look at it like a trim wheel in an aircraft to correct for pitch changes as the center of gravity of the plane changes whilst burning fuel. With the levelling screw you can trim your lathe to keep cutting straight "on the fly".

Chris

Hello Stu,

Some answers to your comments below.

Originally Posted by Stustoys

Gee that looks familiar.
Stuart

Yes it probably does, as is clearly seen in the link text, its a link to a photograph in another thread on this forum. If I have somehow transgressed forum etiquette by doing this I apologise. Simply wanted to refer to an image of the jacked feet.

Originally Posted by Stustoys

What diameter bar are you using?

Stuart

0.750" diameter bar

Originally Posted by Stustoys

I thought RDM didnt use tailstock?
Stuart

Not sure what you are referring to here, I havent mentioned anything about a tailstock.

Originally Posted by Stustoys

You're turning 15" from the chuck unsupported?
Stuart

No I'm not, perhaps my inexperience is shining through here, I did the RDM test on a point 15" from the headstock. Then, perhaps in error, assumed that the results indicated that over a distance of 15" any cylinder that I tried to turn would be out by 0.025" or alternately 0.0016" per inch. Complete and total newbie speaking here.

Originally Posted by Stustoys

Nope you can, using a level thats 0.02mm/m, say the bolts are 200mm apart front to back, that means to move one division you need a shim 0.004mm thick thats about half the thickness of Alum foil. Its a nightmare..... I tried shims before "inventing" the jacks. With a 300mm spanner and a 1.75mm pitch thread .004mm is about 5mm of rotation.
So leveling is fine........... not how rigid the result is, thats another question.

Stuart

Thanks, thats interesting about the rigidity, that is what I was trying to get at when I made reference above to putting the lathe on stilts, rather than sitting on shims on a solid surface.

Originally Posted by cba_melbourne

When you have no accurate level and no ground test bar, AND you are confident that your headstock alignment is fine, then Rollie Dad's method (RDM) can work fine albeit a little slow. You need be fully aware that RDM is a shorcut method that assumes the headstock-to-bed alignment is correct to begin with. It is usually safe to assume correct headstock alignment, if you know the full history of your lathe (like if you bought it new, or know and trust the previous owner) and you did not fiddle with this adjustment and the lathe did not suffer in a transport accident.

Otherwise, use a good egineer level of better than 0.5mm/m per division to level the lathe bed. Then finally check with the spool cutting test to verify headstock alignment is fine too.


Chris

Thanks Chris,

Have seen people arguing for and against this test in my google searches. Thats the clearest explanation I've seen so far that helps me understand why there are some negative comments out there.

Bill

Hi Bill,

Originally Posted by steamingbill

If I have somehow transgressed forum etiquette by doing this I apologise.

No no not at all.........it looks familiar because it happens to be my lathe... thats all.

Originally Posted by steamingbill

0.750" diameter bar

thats not very big

Originally Posted by steamingbill

Not sure what you are referring to here, I havent mentioned anything about a tailstock.

no, but 15" from the chuck with no tailstock support on 0.75" bar isnt such a great idea.... so I was just checking

Originally Posted by steamingbill

No I'm not, perhaps my inexperience is shining through here, I did the RDM test on a point 15" from the headstock. Then, perhaps in error, assumed that the results indicated that over a distance of 15" any cylinder that I tried to turn would be out by 0.025" or alternately 0.0016" per inch. Complete and total newbie speaking here.

You'd need to give the distance between measurements and what they were before I could comment on taper BUT if I'm picturing your setup correctly deflection is going to be a huge issue. Are you using HSS or carbide?

Originally Posted by steamingbill

Thanks, thats interesting about the rigidity, that is what I was trying to get at when I made reference above to putting the lathe on stilts, rather than sitting on shims on a solid surface.

In a perfect world you would use jack screws then fill the gap with grout........... I dont live in a perfect world.

Originally Posted by steamingbill

Have seen people arguing for and against this test in my google searches. Thats the clearest explanation I've seen so far that helps me understand why there are some negative comments out there.

RDM is "missused" all the time.
"As I understand it" RDM was all about making a worn lathe cut straight..... nothing more nothing less.
Now sure there is a test(two collar method) pretty much the same used to check how well your lathe is setup and maybe even "tweak" it a little this way and that. but its not a starting point for the reasons cba listed.

Firstly you want to be sure you dont have to much deflection and then try and twist the bed to make up for it.

Stuart

Originally Posted by cba_melbourne

In most cases a perfectly aligned lathe does not remain that way forever. There are constantly changes due to movement of the floor with the seasons (even on a concrete shed floor).

Industrially if you are doing things properly machine tools/ equipment are installed on a concrete pad that is a minimum of 6" thick. It gets thicker as the machine gets bigger. I think for a average size top of the line CNC machine you are talking 12 to 24". In that respect RC and I are lucky as the lathes we have are designed for 3 point support - the bed will not twist due to the floor.

Michael