Thread: Squaring my lathe

Frank, I know the lathe you have. The moment you touch the 4 nuts that hold the headstock down, you are in big trouble! Why you may ask? Unlike other lathes, your headstock does not sit on the V-ways. It sits on the way flats. By design, there are a total of 4 grub screws that push sideways onto the 4 studs that the headstock bolts down to. These are for adjusting the headstock parallel to the bedways horizontally. The vertical adjustment is done by "torque shimming" (tightening the front two hold-down nuts slightly more or less than the rear two nuts. But these chinese lathes are not as well made as the Austrian EMCO-C8 they were cloned from, sometimes not all 4 grub screws are installed, and if some or all are installed their threaded holes are often not drilled at a right angle to the studs, sometimes if they had trouble aligning the headstock they are drilled by hand at about 45 degrees downwards into the V-ways. Also, the bottom of the headstock is not ground flat and parallel to the spindle, it is actually not ground at all. They use paper shims between the headstock and the ways to align the spindle parallel to the bedways in the vertical plane. This method of aligning the headstock means, that after every alignment the tailstock height changes. Not a problem at the factory, as the tailstock is simply matched by selection to the headstock height. But at home you do not have a pallet full of new tailstocks to choose from. A tailstock that is high is not a big problem to fix, but a low tailstock takes lots of time to fix.

Now, the lathe comes new from the factory with a properly aligned headstock. They check everything as required by the Schlesinger inspection record, and this inspection record should come with the lathe. If it was not properly aligned, buyers would return the lathe under warranty. As long as you do not disturb this headstock alignment, you can use the "Rollie's Dad Method" RDM to untwist your lathe bed. But the RDM is a shortcut method that can only work if the headstock alignment is correct. Once the headstock to bed alignment is off, you must kiss goodby the RDM. Instead you now must buy or borrow a precision spirit level and an MT3 lathe test bar. First you must level and bolt down your lathe bed, it must be straight and untwisted. Then you use the test bar to align your headstock to be parallel to the bedways horizontally and vertically. Do not even try to at the same time adjust the headstock height to the tailstock - it is virtually impossible to succeed at this, it is hard enough without having to worry about the height. Once you begin to "torque shim" the headstock and see how flexible it all is, you understand what I mean.

Ok, by now you know why with this particular lathe model, I always discourage to even touch the headstock alignment, unless the lathe had an accident and is known to be completely off alignment.


By the way, there is no lathe cheap or expensive, where you can adjust the cross slide to the headstock to face concave. It is NOT POSSIBLE TO ADJUST THIS. This is why "concave facing" always is the last thing (or one of the last things) to be tested in the Schlesinger inspection protocol. The cross slide ways at the top of the saddle are machined at an offset angle to the inverse Vee ways at the bottom of the saddle. DO NOT, UNDER NO CIRCUMSTANCES, TRY TO ADJUST THE HEADSTOCK TO FACE CONCAVE!!!

Good Luck

Wow! So many replies. Thanks guys, I'll try to answer some questions.

As already mentioned, as I've already CNCed the lathe, I'm not too concerned about changing the saddle height. The leadscrew mounts I made are adjustable so hopefully I can shift it when I reset the saddle.

I did get the moglice from http://www.dynaref.com.au/. According to the manufactures website calculator I only needed 20g. I wanted to buy 100g, but they only has 500g locally. That cost $240+GST. I'm told that was a cheap price - I'm assuming because it only has about 2 months left on the shelf life.

I do have a machinist level, and a MT3 test bar (I actually have 2 - when I bought 1, 2 arrived, but it they were packaged in the one box - am I supposed to use 2?). When trying to use RDM, I didn't have any irregularities when spinning the bar so I just ran a DTI along the side and top on the saddle.

When realigning the headstock, I replaced the cheap chinese studs and set screws. I didn't see any paper shims when I removed the headstock, but there was plenty of paint.

I'll try levelling my bed again. I've attached a picture cross section of the ways.

Ways.png

The red parts show the saddle bearing surfaces. The blue is for the tail stock. The green are for the saddle gibbs.

The 2 horizontal surfaces are not in the same plane, so if I use them with parallels to hold the level, I'll need to shim. I tried that the first time round, but it was hard to move the assembly without shifting the shims. That's why it was easier to let the level ride on the saddle. I've read about the King-Way alignment tool - is there a quick way to whip on up for a small bed on my lathe.

When I level/untwist my lathe, I keep the head stock end fixed. I've add a couple of jack screws to the tail stock end so I have a 3 point levelling mechanism.

Originally Posted by ftkalcevic

The 2 horizontal surfaces are not in the same plane, so if I use them with parallels to hold the level, I'll need to shim. I tried that the first time round, but it was hard to move the assembly without shifting the shims. That's why it was easier to let the level ride on the saddle. I've read about the King-Way alignment tool - is there a quick way to whip one up for a small bed on my lathe?

Frank, if you recall on Sunday Phil showed us his bed leveling jigger - a couple of dowels, a length of flat and few bolts. Someone probably took a picture but where it has been filed I don't know. Perhaps search for scrapefest photos and you may see it

Michael

Originally Posted by ftkalcevic

Ways.png

When I level/untwist my lathe, I keep the head stock end fixed. I've add a couple of jack screws to the tail stock end so I have a 3 point levelling mechanism.

I would put the level onto the cross slide table, which is ground flat on this lathe. Simple and easy. Alternatively you can make a jig that on one side rests on the red Vee surfaces, on the other side rests on the red flat surface.

This lathe bolts down with only two screws, one under the headstock and one under the tailstock end, both located at the center of the bed as seen from the narrow sides. You firmly bolt down the headstock end, and you insert metal shims either under the front or rear tailstock end. You then need to tighten the the bolt down screw at the tailstock end, before you can check the level. It usually does not take much, being such a short bed. In many cases it needs no shims at all. Beware, not all Chinese 9x20 have the surfaces at the underside of the bed where it rests on the bench milled flat. And milled or left rough cast, there may be considerable paint thickness there as well.

Originally Posted by Michael G

Frank, if you recall on Sunday Phil showed us his bed leveling jigger - a couple of dowels, a length of flat and few bolts. l

We call it a roller bar.
https://www.woodworkforums.com/showth...85#post1385385

I'm not opossed to a level on the saddle, it will certainly show you twist.

Originally Posted by cba_melbourne

I always discourage to even touch the headstock alignment, unless the lathe had an accident and is known to be completely off alignment.

Which part of this did you, miss?

Originally Posted by ftkalcevic

To turn a parallel bar, I would always have to place the workpiece between centers - I could never just mount it in a chuck, no matter how short it was.

At post number #3 no less. If their interface is so Mickey Mouse / cheasy with paper shims, and dodgy adjustment screws. What makes you think it was ever correct to begin with? And then drop in "Schlesinger". You have to be joking?

Simple matter of fact, the thing can't turn parrallel out of the chuck, and your advise is to not correct it. I'm speachless.

Originally Posted by cba_melbourne

By the way, there is no lathe cheap or expensive, where you can adjust the cross slide to the headstock to face concave. It is NOT POSSIBLE TO ADJUST THIS.

ARE YOU SURE YOU ARE QUALIFIED TO BEING GIVING THIS ADVISE OUT IN CAPS LOCKS? It is absolutly adjustable, it's called scraping.

Phil.

Originally Posted by Machtool

ARE YOU SURE YOU ARE QUALIFIED TO BEING GIVING THIS ADVISE OUT IN CAPS LOCKS? It is absolutly adjustable, it's called scraping.

Phil.

If you choose to call scraping "adjusting" then you are right. To me, if an alignment requires the removal of metal (be it by scraping or lapping/grinding/milling/turning etc), its not something that I would term "adjustable". If metal removal is required, then I would think the term "manufacturing" is more appropriate. Or in the case of a worn out machine, I suggest the term "restoring".

But back to the Chinese 9x20, yes they are badly finished. But they usually really do meet the standards set forth by Schlesinger. I dare say it is rare if a new 9x20 cuts convex, and if it does it is most likely due to an accident in transit having dislodged the headstock alignment. And NOT due to a manufacturing fault of the saddle. And hence the solution will not to be found in scraping the saddle.

> At post number #3 no less. If their interface is so Mickey Mouse / cheasy with paper shims, and dodgy adjustment screws.

Phil, you are probably not familiar with this machine. This is a light duty 9"x20" hobbylathe. Less than 100kg with accessories. It costs only some AU$ 1,100 including both chucks and both rests and norton gearbox and life and dead center etc. Please step forward if you think you can make a lathe with a less mickey mouse cheese headstock interface for that sort of mickey mouse money. The last to try in Australia to make a 9x20 was Hercus, and it would cost at least $10,000 to make such a machine here today, without any accessories. See, appels with apples...



> What makes you think it was ever correct to begin with? And then drop in "Schlesinger". You have to be joking?

Yes, most Chinese 9x20 out of the box will meet Sclesingers standards for lathes below 250mm swing - not bad for a brand new $1,100 lathe. Most 9x20's will actually come with a filled in Schlesinger inspection record. And if you set out to verify the alignments, they will be within spec or very close unless you get one that had an accident. The 920 is a mass produced in China. Many factories make this model. The dealers get what they pay for, so some 920 are ordered for cheaper without the inspection record. If you buy a 920 without inspection record, you should not expect that thame amount of time has been spent assembling and adjusting it.



> Simple matter of fact, the thing can't turn parrallel out of the chuck, and your advise is to not correct it. I'm speachless.

Actually, I thought he said it faces convex. Anyway.

- If it cannot turn parallel out of the chuck by a few 0.01mm over 100mm, then most likely the bed is twisted. It would not be a good idea to start adjusting the headstock.

- If it cannot turn parallel out of the chuck by more than 0.05mm over 100mm, then most likely because it had a transport accident and the headstock alignment is off. Then you have no other choice than readjust the headstock, have you?

- But there have also been cases where it cannot turn parallel, because the headstock casting had a crack. These are not nicely made castings you know, how could they for that money. In this case its better not to mess around and return in warranty.

- And a too loose preload for the taper roller spindle bearings has also been known to lead to it turning taper. An inexperienced user easily confuses this with a misaligned headstock. The preload can be fixed fairly quickly. The headstock alignment on this lathe can take several hours with a level and a test bar, and days without. You must understand, the owners of these lathes usually cannot afford a precision level.

[QUOTE=cba_melbourne;1786690]
Now, the lathe comes new from the factory with a properly aligned headstock. They check everything as required by the Schlesinger inspection record, and this inspection record should come with the lathe. If it was not properly aligned, buyers would return the lathe under warranty.


CBA, do you honestly believe that all the low quality lathes coming out of China are tested for and conform to Schlesinger limits?

Just to be certain I would be doing another skim of the faceplate with the saddle "locked" just to make sure it didnt move while you skimmed it the first time. Had that problem with my 6123.

Roger

[QUOTE=Techo1;1786815]

Originally Posted by cba_melbourne

CBA, do you honestly believe that all the low quality lathes coming out of China are tested for and conform to Schlesinger limits?

That is not what I said, is it?

But those lathes that come out of China with a Schlesinger inspection record that matches the serial number, are assembled to Schlesinger limits, and conform to Schlesinger limits - at least when they leave the factory.

That excludes of course fakes. There are no doubt backyard operations that assemble machine tools and provide fake inspection records. They even fake the brand names of other Chinese makers. You can buy in China fake "Sieg" minimills and minilathes for example. And you can import them to Australia. But you would be suspicious if offered a Rolex watch with guaranteed 18KT massive gold housing for $50, would you? What about if you were offered a 10" Sieg lathe brand new for $800, would you assume you had a bargain or would you assume you got a fake?

Originally Posted by ftkalcevic

I do have a machinist level, and a MT3 test bar (I actually have 2 - when I bought 1, 2 arrived, but it they were packaged in the one box - am I supposed to use 2?). When trying to use RDM, I didn't have any irregularities when spinning the bar so I just ran a DTI along the side and top on the saddle.

After you level the bed, put one of your test bars in the headstock spindle taper, and stick the indicator base on either the tailstock or the saddle and the DTI on the bar in a horizontal position then firstly zero out the runout.. By that I mean put the indicator on the end of the bar, spin the spindle and say the run out is 0.1mm, you have the spindle in a position so the dti would read half of the runout..

Then run it along the test bar... and note the error... It should be something like 0.01mm over 300mm with the error at the unsupported end pointing towards the tool pressure, or in layman terms, pointing towards the operator...

In my opinion I would put about as much value in the paper entitled "Inspection Record" of a lathe such as this, as I did the paper I used this morning for my usual morning routine about 30 minutes after finishing my coffee. Sorry, maybe I'm just overly sceptical ... or have been around the block a few times

Originally Posted by Pete F

In my opinion I would put about as much value in the paper entitled "Inspection Record" of a lathe such as this, as I did the paper I used this morning for my usual morning routine about 30 minutes after finishing my coffee. Sorry, maybe I'm just overly sceptical ... or have been around the block a few times

It is only 40 tears ago, that like minded people had the same views about Japanese machine tools. They certainly must fake their inspection records, as they cannot even read or write English. How very wrong they were.
10 years ago, Hyundai cars were belittled as low quality. Today Great Wall cars are belittled... meanwhile drivers vote with their feet.

Georg Schlesinger set out his standards for ordinary production lathes in 1927. With the manufacturing machinery available back them, his tolerances were demanding. But his tolerances are still the same today as they were in 1927. They are actually not anymore that hard to achieve. No scraping is required at all. Do not confuse these with tolerances for toolroom lathes, which easily halve and quarter the basic Schlesinger toerances. If you do not believe, buy yourself such a cheap Chinese 9x20 hobbylathe, its only $1000 when on special at Machineryhouse. If you subtract the 10% GST and the 40% dealer margin, the factory in China only gets paid about $600 for it. Then put it honestly and fairly through the full Schlesinger test. I think you would be very surprised (unless you get a Monday lemon, I would guess 1 in 20 is a lemon, but hey that is what the warranty is for).

Also, you need to realize that meeting the Schlesinger standards says absolutely nothing about the rigidity of the lathe. Nor does it say anything about the quality of materials used to build the lathe, or the quality of fit and finish, or how long it will last. A lathe may perfectly meet the standards, yet self destruct in a matter of a few operating hours. A lathe may meet Schlesinger standards, yet the crap chuck may have half a millimeter runout.

Not everybody can afford to spend two months wages on a "good" new lathe. And not everybody wants to restore an old worn out lathe. They sell lots of these cheap 7 and 9" Chinese lathes. But strangely they do not turn up en masse on our tips or scrapyards. Not many are for sale used, and when they actually sell quickly and for good money. So they cannot be THAT bad. Many could not justify lathe ownership, if it was not for the Chinese.

I'm sorry, but one thing that really gets on my goat is when people hold up Japan as an example of manufacturing standards and progression and presume that every other country in the region will naturally follow suit, after all it's all "Asia", and all "Asians" are the same right The Japanese and Chinese are completely different cultures, as any Japanese person will inform you, albeit very politely, and they're about as different as two cultures can get, particularly as it relates to quality control and pride in one's work. That's not to say that China won't indeed move to higher quality exports, and I expect it will, but I'd respectfully suggest that presuming it will follow the Japanese model demonstrates an extraordinary lack of cultural understanding.

As far as presuming a cheap lathe will pass these standard tests, I have no idea if it would or would not. My money is on the latter. Having seen quite a few Chinese "test certificates" and seen them to be quite clearly a work of fiction (either that or a remarkable number of surface plates made in China seem to have identical maps, just for example).

I have precisely zero interest in discussing the merits, or otherwise, of buying Cheap Chinese machine tools, you guys seem to raise that point regularly and can argue about that amongst yourselves. I will however suggest the math is highly dubious, and believe the amount received by the manufacturer is nothing like the figure quoted.

But that's just my opinion, and I have no intention of laying down a grand of my hard earned to prove that a lathe is indeed crap. I'm quite honest in stating this is just my opinion, for what it's worth, but you write of examples with great authority Chris so wonder how many if these lathes you've actually tested yourself? It sound as if it's quite a few, in which case I bow to your greater experience in this area. Otherwise if you think a lathe that is manufactured, shipped, taxes paid, and retailed for under a thousand dollars is put through careful testing and a Schlesinger test sheet produced for it, knock yourself out. My kids believe in Santa, no point in spoiling it for them either.