Lathe leveling, AKA exercise in masochism...

[daved20319b]

So I have an 80's vintage Grizzly 12x24 belt drive lathe. I've had it about 15 years, circumstances were such that it hasn't seen much use in the last 10 or so. But circumstances have changed, and now I'm really focused on getting more serious about my machining hobby. In that vein, I recently installed a 3 phase motor and VFD, that went well other than needing new headstock bearings. After quite a bit of aggravation, I think I've finally got the bearings sorted out, it's now producing better results than it has for years. But it's been moved several times since I bought it, and it hasn't been leveled or aligned in a long time, so I figured it was overdue. Which brings me to today.

I've attempted to level this lathe several times since its last move, all to no avail. I end up chasing myself around in circles, finally giving up and putting my precision level back in its box and settling for "good enough" with my carpenter's level. Today was no different, other than the realization that I really have no idea of where to even start. Using the precision (.0005"/10") level, I get wildly inconsistent numbers between end to end, front to back, and carriage to ways. I think my problem is I don't have a clue as to what should be my initial reference point. I'm reasonably certain I'm dealing with both twist and wear in the ways, but with no idea of where to start, I'm just chasing my tail, and my puppy is far better at that than I am . I strongly suspect I'm missing something obvious here, I'm good at that, but if someone could point me in the direction of a good starting point, I'd sure appreciate it, thanks!

Dave

 

[Ulma Doctor]

Start with the carpenters level to get you close, then use the machinist level to verify your findings.
OR
The ends of the bed are the least worn, especially the tailstock end and right in front of the headstock.
You could indicate the ways longitudinally, using the areas right in front of the headstock as the zero. Any ware would be apparent.
You can use a thick parallel to straddle the ways and indicate the parallel, anywhere along the ways transverse to the bed, also using the area of least bed wear as a zero.
Make a map as you go, or write the indications on the bed or ,whatever you wish, with a sharpie to help you see what is going on

 

[tq60]

Lathe does not need to be level, it needs to all be in same plane.

The bed is cast iron, and it is likely TWISTED!

There are many ways to do this.

If you have inverted V on the bed, never use those as the tops are not a reference point.

NEXT to the V is a good spot as nothing rides there.

The tailstock usually has one v and one flat. Try for a machined surface at opposite sides of the bed.

Use parallels or a stack of HSS blanks to raise those flat spots above the V.

Use equal height for both front and rear.

Most tailstock end of lathes only have 2 feet while many have 4 at the headstock end.

Getting the 4 in plane can be a challenge.

We will start with tailstock.

Put a piece of tape on top of one end of the level, with sharpie, mark FRONT.

This ensures the same direction, so if the level is not perfect, your measurements will all be in the same plane.

With level front to back, adjust the feet to get it level.

If base near the floor, turn screws one turn for some extra.

Headstock if 2 feet, repeat moves at tailstock.

If 4 feet, you need to do 2 directions at the same time.

Look for a few sets of reference points. A machined top cover is one example.

The bed likely goes to the end of the headstock with a base under the bed.

Both feet on the front or rear support the bed, but if not all the same, it can be twisting.

Others may have a better process, but here is a start.

Slowly adjust the 2 feet on the same side of the headstock until both have the same effect on the level.

One may instantly affect the level while the other may not change at all or as much.

Alternately, adjust the 2 until both move the level the same amount with equal rotation.

Repeat on opposite side.

This should get the 4 feet in plane.

Now level front to back same as tailstock, be sure to turn both feet on same side same amount, and it takes both to change, so turn each 1/4 turn at a time.

Do not worry bout the tailstock.

The lathe may rock on the floor.

Leave it until next weekend and repeat all of the above, and wait another week.

When you come out and nothing has changed, now to level end to end, place level lengthwise in the middle and adjust tailstock to level.

Depending on which way you went, the end screws on headstock need to go opposite a smaller amount, repeat the 4 feet adjustment above, and let it sit for a week.

The reason for the waiting is to allow the bed to settle.

If you do not do this, the lathe may appear to not level so you adjust more, chasing your tail.



Sent from my SM-G781V using Tapatalk

 

[Illinoyance]

Up and down, repeat may times during levelling. I did it alone. Knees protested vigorously. I should have had a helper to turn then levelling screws while I read the level.

 

[WobblyHand]

Up and down, repeat may times during levelling. I did it alone. Knees protested vigorously. I should have had a helper to turn then levelling screws while I read the level.

That was the hard part, going from hands and knees, doing an adjustment to getting up and waiting for the readings to settle. Had sore legs that day. I got close enough and am happy with the results.

 

[daved20319b]

Thanks for the responses, guys. I ended up doing what I always do, stopped a heartbeat away from taking a sledge hammer to the precision level, stuck it back in its box, and just called it good enough with my Stabila carpenter's level. I did map out where and how much it's off, IF I'm interpreting the results correctly, I have both twist and bed wear. I have no good way to quantify the wear, but I tried shimming for the twist, that had almost no effect, I suspect partly due to the stand it sits on. It's not bolted to the floor, and I don't think it's stiff enough to take out the twist. Maybe if I had the patience to follow tq60's method I could make some headway, but I can chase my tail around for just so long before I start getting destructive. As it is, it's good enough for my use, and I'll probably take another swing at abusing myself sometime down the road. Later, and thanks again.

Dave

 

[RJSakowski]

First of all, I see that this is apparently a bench mount lathe. In that regard, the rigidity of the bench or stand will enter into the discussion. Making adjustment to remove bed twist will also introduce stress in the stand and can cause unanticipated results. In my case, I elected to use a three point mounting for the stand. This eliminates any twisting of the stand that can arise with a four point mount. There are two feet at the headstock end but I have a single foot located at the tailstock. There are also two outside feet to prevent rocking of the lathe but they are adjusted to just barely touch and don't contribute to any twisting. Now, any adjustment bed twist is strictly between the lathe and the stand.

In regard to leveling the bed, I place the level on the cross slide. The idea is that any tilt in the cross slide at the tailstock end vs. the headstock end is what causes the cutting of a taper which is what we are trying to correct. Whether it is due to bed twist or to uneven wear, the effect is the same. A second reason is that it provides a stable and reproducible platform for mounting the level.

As mentioned above, leveling the bed isn't required. To that end, we may purposely introduce a twist in the bed to prevent cutting a taper. The last word in adjustment should be the two collar test. My preference is to level the lathe as a preliminary step and the check for headstock alignment. My preferred method is to check alignment of the cross slide to the spindle axis using a modified RDM method (Rollie's Dad's Method). When I am satisfied with that alignment, I move on to using the RDM method for checking for taper, adjusting the tailstock with shims as required.

The RDM method can also be used to check for vertical misalignment. This is particularly true for four bolt headstock mounting but can also be affected by a one or two headstock mount if the stand is a non flat surface. To run the vertical test, the DTI is set up to measure displacement at the top of the test bar rather than the front.

When I am satisfied with the RDM results, I move on to the two collar test to verify my adjustments. If the previous work was done correctly, I should be gold. If a minor tweak is required, I add or remove shims at that point.

 

[JPMacG]

I have a similar experience with my Atlas lathe. The bed has a twist and when I shim to take it out the twist just moves to another place. I suspect that the bed lacks rigidity. An Atlas is not meant to be a precision lathe. But it is good enough for everything that I want to do. Facing cuts are slightly convex, which is sometimes a problem when I do an assembly of parts. I think that problem is caused by the head being very slightly out of alignment with the bed. Some day I will look into that but for now it is plenty good enough.

I resisted smashing my Starret level. It is just too pretty to smash.