shims on PM3520B tailstock...

[Rasmus Petersen]

??? my lathe is level, completely but i have to add to buissnes cards to the tailstock to get alignment (one in each side)??? thats 0,31 mm.. so now how do i go about this, is it to the local smity, or do i try to get the headstok ground down ??

if i am to ad shims would epoxy be enough or ??

[Steve Schlumpf]

Rasmus - before you get shims made - have you taken the lathe 'off' level to see how it impacts the alignment? I want to believe it is adjustable!

[Rasmus Petersen]

Hi steve : no i havent, but i have done the headstock move back and forth and this way and that but its still off. but its funny that it is straight hight wise, the alingnment sideways is spot on...

[Steve Schlumpf]

I know it seems strange - but the bed will flex. Just curious what happens when you play around with the adjustment a little. Wouldn't take to much time and would sure be a lot easier fix than having shims made.

[Jeff Nicol]

Rasmus, I am not sure what type of level you are using, but if it is not a precision gound and calibrated level that are used by people who set up highly sensitive precision machinery, the level could be off. If you put the level on the ways and it reads level, turn the level over and see if the reading is the same. If it is off just a little bit that can cause problems. Also if you are using the leveling feet that came with the 3520B I would get rid of them and find a better way. I could not get mine level at all with the little feet. I made some spanners that go back to front and bolted the lathe to them. They are 3" thick oak and the I leveled the machine with some shims under the wood spanners. The larger surface area to the floor keeps if much more stable and that is important. Also the length of the bed being level on both ways and the bed across the ways front to back has to be level. If one end is off a few thousandths it will twist the whole bed. Like Steve said get it to where it works and see where the level is, uneven floors are tough to work on.

Jeff

[Rasmus Petersen]

steve : No change.. raised it 5cm and no change .

The bed is level, done with 2 different levels, both good qulaty Hultaforce levels turned this way and that way. and ,31 mm is a lot. to deal with throug bed twist.when headstock and tailstok are close to eachother

[Steve Schlumpf]

Rasmus - did your lathe line up when you first got it? If so, I am wondering why the change.

I have to agree - 2.5 cm is a lot of adjustment and if it was going to impact the height issue I would have thought .5 cm would have been enough.

Hopefully we can have someone with a mechanical background jump in with some advice for you!

[tom martin]

Have you checked the bottom of the head stock? A small burr on the bottom of the head stock could cause your problem. I would try rubbing the bottom with a bench stone or diamond stone- especially on the spindle side before shimming.
Tom

[Rasmus Petersen]

Steve i think my lathe sees more hours than most. I do production, lots of it.. lets say the lathe runs on avrage 20-25 hours a week. (running time)

tom it isent long ago i had the head off and wiped it clean. I will try that, but im not convinced that that it.. but will try..

Any one else ??

[Richard Madison]

Check the lathe bed for dents or nicks which may have raised a high spot. If your tail point is lower than headstock point, the high spot might be under the right end of the tailstock at the place where you are measuring.

[Rasmus Petersen]

Richard : done that.. moved the head along the bed and meassured.

Forgot to say that it is the tailstok thats lower than headstock

[Steve Schlumpf]

Then it sounds like you may have a buildup under the headstock. That could easily happen by sliding the headstock on the bed. I know it is heavy - but worth checking!

[Dick Strauss]

Rasmus,
Richard has a good point...if the back of the tailstock is high from a burr under the far end, it will cause the point on the front to tip down regardless of where your tailstock is placed on the bed. Check it just in case...

FYI-0.31mm is only 0.0122" so this may be within spec for the lathe.

[JerHall]

I had a few thousandths of a hump just under the headstock cam mechanism. My theory is that years of hard use "molded" the base, or time relaxed the casting. Anyway I "milled" the hump off with progressive sandpaper glued to a flat mdf block and it has been fine since. Also eliminated minor rocking of the headstock with heavy blanks. Worth a check.

[Rasmus Petersen]

Now had tha lathe head and tailstock disassembled.. and cleand and filed the edges (fine key file) and the result is the same. Still off so that 2 buisnesscards fixes the problem.. beginning to sound like shimms..

im willing to try any good ideas..so keep them comming..

0.3 mm might be within some tolerance, but that doesn't solve my issues. Try turning pens in large numbers using the penturnerproducts bushhings.. the .03 mm is a lot.. and with 200 stil to go on the big order ...

Also im wondering if anybody out there have seen the same issu before wth the jet 4224 or the pm/jet 3520B..

[Rasmus Petersen]

jerhall : will do. i think i have to get my friend the maschine engenire to have a go at it...

[Tony Wheeler]

I would want to know what reference point are you measuring from as center of headstock spindle and the center of the tail stock spindle. the amount the you are giving is a big difference to appear over night. are you matching the point of a inserted drive center in the headstock to the point of a live center in the tail stock. maybe you have a bent live center. put the drive center in the headstock and measure the distamce from the bed and point on the drive center and then take the same drive center and place it in the tail stock and see if it the same, of course mark one of the spurs of the drive center and put it a 12 oclock each time after that try your live center and see if you get the same heights. then see which has the diffence in measurement. If I have read your post right this has appeared while turning 200 pens

[Jeff Nicol]

Rasmus, I wonder how many times you have had the tailstock on and off the lathe? I wonder if you have not worn the base of the tailstock off enough in the front end so that when you tighten it, down it tips the center down the difference you are seeing. If you can get something to see if the line of the base is still parallel with tailstock taper. If for some reason they are not parallel to one another that is a problem. Also if anything in the tail stock is getting worn and there is some wobble or flex in something that will cause it also. One last thing, I had a live center that had lots of use and at some point it got bent. Get a nice clean #2 taper solid center and make sure the tailstock reciever and the headstock taper are both clean and with no build up. Check the center line up with the headstock and see how it looks. This will cause your problem in a heart beat

Good luck,

Jeff

[Bob Haverstock]

Rasmas,

I'm thinking you have a wear issue. Is there any measureable tipping movement left to right or right to left in the tailstock body while it is setting on the lathe? This would mean that the base of the tailstock is no longer flat. The base may have wear that is dead flat or it may have worn rocker shaped, check and see.

I'm a retired machinist / toolmaker and have seen many engine lathes that were damaged by abrasive materials. If you are touching up your turnings with sandpaper, abrasive materials are falling onto the bed of the lathe. Some of the abrasive grit will get (mothered) into the bed and tailstock and it is very difficult to remove. 20 hours of use per week is a lot, so you are moving the tailstock many, many times per week. Each move abrades the base of the tailstock and it wears away much more quickly than the bed.

If shimming the tailstock negates the problem, go for it. I would find a sheet of material that is of acceptable thickness and fit it to the bottom of the tailstock.

If I had the space, I would do only large work on the large lathe and do the small work on a dedicated midi.


My opinions and three dollars will get you a cup of coffee some places.
Bob

[Dick Sowa]

You've gotten some good advice already. My 3520b is spot on, but I don't do production turning. Has it always been off? Or did you only just discover it?

One thing I thought about, but it sounds like you already tried, was to slide the head and tailstock to different parts of the bed, and do the same checks. If it is off the same amount at one end of the bed as at the other end, then it's got to be a problem with the head or tailstock.

[Bob Haverstock]

Rasmus,

Did you solve the tailstock problem?

Bob

[Rasmus Petersen]

as posted elsewhere it's still work in progress.. will get back when i have news :)

[Allen Neighbors]

Rasmus, I don't have any idea how to help you, because I don't have the problem. But if it were me, and it's off enough, vertically, to cause problems, I would have the head machined down enough to take out the necessary amount. Always shimming under the tailstock, or trying to have the right amount added to the tailstock would seemingly be harder to do. Just my thoughts on it.