Headstock / bed alignment.

[YouraT]

Hi all.

I'm giving my new (to me!) machine (TDS 1/1 GB) a good strip-down and clean.

One thing I'm wondering about is whether to take the headstock off entirely - on other machines (a Boxford, for example) I wouldn't have hesitated, but in this case I can't immediately see how the spindle and bed axis are aligned - I don't want to do anything that will doom me to weeks of pain trying to re-align things....

Same sort of question for removing the bed from the stand - that's easier to understand, but what's the procedure for re-installing with correct alignment/lack of bed twist?

Both desires to disassemble are cleaning related - a previous owner clearly had great faith in the cleaning ability of compressed air, and there's muck where you wouldn't believe...

Any hints/advice ?

Thanks,

Youra.

[Bogus105]

Hi YouraT,

I bought TDS 1/1GBL last weekend and it seems that it has a slight headstock/bed misalignment... I turned test steel round bar and there is 0.03mm difference in diameter over about 5cm bar lenght (i used short stock bar not supported with tailstock)... So there is a headstock re-alignment need in front of me:(

I got some ideas about it: if you look at the picture below you can see that there is rectangular bar screw on to the bed and headstock by 4 capscrews. Two vertical screws (shown by red arrows) and V prisms of the bed secure this bar against movement. The 2 horizontal screws (yellow arrows) goes into the headstock. So if you loosen 4 capscrews located inside of the headstock (the screws that hold the headstock down to the bed marked red here: viewtopic.php?f=50&t=3808&p=14529&hilit ... ent#p14529 in Thu 19 Jul post ) you can align headstock by inserting shims between that rectangular bar and headstock. Then thightening all screws and making test cut, measuring and... re-alignment again until you get a perfect alignment. What you guys think about this? Does that make any sense?

[dazz]

Hi
Unless the lathe has been abused, the headstock alignment should be fixed. I would suggest checking for any twist in the bed before touching the headstock alignment. A twist on the bed will cause a tapered workpiece.

There are four bolts holding the bed to the cabinet accessible through the doors. These are bolts inside bolts. The procedure I follow is to:
level the lathe by shimming the three feet that sit on the floor.
Move the carriage to one end of the bed.
Use a laser level placed on the top slide or carriage aimed at a distant point. I use my boundary fence that is about 20m in front of the lathe.
I mark (horizontal line) where the laser dot hits the fence.
Move the carriage to the other end of the bed and aim the laser dot at the mark. Try to minimize movement of the laser level. If the bed is straight, the dot will be on the mark. If the bed is twisted, the dot will be above/below the mark.
Pick one adjustment bolt for adjustment. I always use the right front one (but it doesn’t matter).
Do not rely on the peaks of the bed Vees being accurate (ask me how I know that).

The vials or digital display on builders laser level is not accurate enough for aligning a lathe. The method above relies on the relative fixed relationship between the laser and the surface of the level. Using a fence 20m away gives a resolution of about 0.006 degrees. Professionals use engineers levels with senstive and precision vials. If you don’t have a lot of space in front of your lathe, you should use one as well.

If you have a straight (no twist) bed, you can then start testing for alignment of other parts of the lathe, including the headstock. You should also buy/make a test bar. I made one as part of the process of aligning and testing my lathe.

[Bogus105]

Thank you Dazz for your ideal. You're right. I'll not detach headstock from lathe bed. Instead i'll try to figure out if my bed is twisted. Unfortunatelly i can't use your laser method. I purchased a precission machine level (i hope it is a proper name) of class 0,02/1000mm. It means that level will indicate 0,02mm difference in level over the distance of 1 meter. I think that should be enough to check bed twist. I'll put the level on the cross slide and move carriage from head stock to tail stock and check if there are any differences in measurement. Does this approach ok?

[dazz]

Hi
I am no expert. I just make it up as I go.
Your approach seems reasonable to me.

Do not rely on the top of the vees being "right". Put your level on the carriage and move it along the bed.
Pick one (any one) adjusting screw on the bed and make all adjustments on that one only.


Good luck

Dazz

[Bogus105]

Putting my level on a carriage was something I was planning to do.
Thanks Dazz, i'll act on your advice during adjustment.