Headstock not perfectly square to the lathe bed

[robo hippy]

I have a Jet 12 inch lathe, vs, forward/reverse, and in the course of making my 3 to 5 second drop boxes, as in pick it up by the lid and it takes 3 to 5 seconds for the bottom to drop off, I discovered that the headstock is not perfectly square to the lathe bed. This is essential for making sure the tenon and recess/mortice are spot on parallel for that "perfect" fit. There are some set screws under the headstock, but I haven't really experimented with that yet, so that may or may not be the problem/solution. I did have a "jig" made so I can line cutters up for supposedly being able to make the fit perfect, but no matter what I do, it is always just a tiny bit off. It was off in the direction of the lathe bed being slightly out of square to the chuck jaws. Oh, I put a 12 inch straight edge in the chuck jaws, then eyeballed with a square, well a couple of different squares and the bed is slightly off, maybe 1/16 in 10 or so inches. That is just enough to make the whole set up out of whack. Anyone know, or have suggestions? I did watch Eric Lofstrom and his box demo where he uses a 1 inch tenon, and the recess tenon on the lid he cuts with a scraper where the cutting edge is parallel to the lathe bed, and eyeballs that to get a spot on parallel cut for the recess. The tenon he makes the cut spot on parallel and then takes a tiny bit off the top and bottom of the tenon so it will move. I did see Soren Berger do a similar box years ago.

robo hippy

 

[John Grace]

Have the same issue on the vertical axis for my relatively new Nebula...it's on my winter to do list. Bad news...I 'thought' I fixed this issue several times now.

 

[John K Jordan]

I discovered that the headstock is not perfectly square to the lathe bed.

It would be nice to verify how much it's off. 1/16 over 10 inches sounds WAY too much!

I use a laser center finder in my metal working but I'm wondering if a laser pointer could be mounted in the chuck and shimmed so the dot doesn't move when rotated, then use that to measure over a longer distance to check. Or if handy, a length of straight round metal rod, steel or aluminum, also mounted and checked to be sure it's exactly aligned with the lathe rotation then check near the end with the square.

If it's off just a little, maybe there's some play in the headstock bolt holes, enough for alignment.

But one question: if centers with points are mounted in the headstock and tailstock and brought close together so they almost touch, are they in perfect alignment? If off a bit when viewed from above the bed may be twisted and might be adjusted using the leg leveling method. Cast iron bed? It's amazing how easily they can flex and twist. I check and adjust if I move a lathe even a little on what seems like a smooth concrete floor. (If the lathe doesn't have leg levelers, a shim will work.)

I'd verify that alignment first before messing with the headstock.

I put some alignment steps in this thread, post #9

Post in thread 'Powermatic 3520c'

Apr 4, 2025

Does anyone do anything besides set their powermatic 3520 lathe on a concrete floor? I have it pretty much leveled, but still get some vibration with larger bowls and til they are trued up. Or maybe this is just the norm?

Don't know if this was mentioned, but every time I move a lathe I check the alignment of the headstock with the tail stock. Even if the bed is level, uneven pressure on a foot can actually twist the cast iron bed. This can create various problem, especially when doing small and precision work.

Procedure:

• Clean the morse tapers on both the headstock...

• John K Jordan

• 

JKJ

 

[robo hippy]

Well, I messed with it yesterday, mostly trying to see which, if any of the lines I use to eyeball spot on parallel were good. I did use a micrometer to check the gap in the bed, and it was off by a tiny bit. I do use a 6 inch machinist's ruler to see where that "perfect" spot is. Funny thing, I get different readings for both sides of the bed, as well as for the outside of the lathe bed. Harumpfh! I did set up a square and scribe lines in the bed and they seem to be pretty close. I chucked up a 12 inch ruler, then put several squares on it to get the "perfect" measure spot on parallel. It seemed to be the closest one. More playing with it today.

robo hippy