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jeremy13
11-11-2009, 11:02 PM
I want to re-level my lathe it's a 16X60 5000# . It has fore leveling legs under the head stock and two at the tail stock. So if I level the fore out side legs and use a torque wrench to find out how much force it took to level the lathe. Then use the same amount of torque on the two in side legs of the head stock would it be loaded evenly?:confused:

mechanicalmagic
11-11-2009, 11:11 PM
Maybe, depends on the weight distribution of the castings.

Why do you care about even weight distribution?

The thing that matters is insuring the bed does not have a twist. This can be measured in several ways, but most use a master level, on the bed ways.

jeremy13
11-11-2009, 11:29 PM
I'm just assuming that the two inner legs of the head stock would be there to take (maybe) sagging out of the lathe bed at the weekend cut for the gap bed.

barts
11-11-2009, 11:55 PM
This is a good question; I've wondered the same myself. My 15x30 is really heavy, and w/ 6 leveling bolts it wasn't at all clear when things were right.
My lathe balances on the center two very nicely.

- Bart

doctor demo
11-12-2009, 12:25 AM
You can't rely on bolt torque or weight per bolt, what is important is that the lathe is twist and sag free. The best way to do that is with a precision level.
My big lathe has four bolts at the headstock end and four bolts at the tailend, and all do not have the same weight or torque on them...but the machine is level and in plane.

Steve

whitis
11-12-2009, 02:19 AM
I want to re-level my lathe it's a 16X60 5000# . It has fore leveling legs under the head stock and two at the tail stock. So if I level the fore out side legs and use a torque wrench to find out how much force it took to level the lathe. Then use the same amount of torque on the two in side legs of the head stock would it be loaded evenly?:confused:

I can't tell you what the right answer is, but I will tell you that probably isn't it. If you did that, you would be picking up the lathe on the middle two feet and taking the weight off the other two at that end. Half the torque used for the two outer feet on the headstock end (the torque on the two at the other end is irrelevent) would probably be closer (at the same time, you would be reducing the weight on the outer feet by half). Four feet level the lathe, the other two would minimize curvature, vibration, etc. Or you could adjust the headstock end (all 4) level front to back, then adjust the tailstock end to match, but that will probably undo the balancing at the headstock end.

The two middle feet would probably be closer to the airy point of the bed but there is a lot of extra weight at the headstock end. In theory, a long beam such as a lathe bed (with evenly distributed weight) will be flatter if supported at the Airy points. The cantilevered weight on the ends helps counteract the sag in the middle. If you have enough weight on the headstock end, it might even cause the middle to "sag" upwards.

Here is how someone else did it, but that didn't sound right.
http://bbs.homeshopmachinist.net/showpost.php?p=394422&postcount=7

As far as leveling the bed is concerned, I might try extending the middle feet first, then adjust the tailstock end to match, then crank the outer feet on the headstock end to take about a 1/3 of the load at the headstock end, then use the level to check level again and curvature of the bed and tweak.
But with 5000lb, this could put much of the weight on the center to start with and could put a lot of stress on the stand and the floor which needs to at least be considered. If the weight on the headstock end equaled the weight of the rest of the bed, you would basically have the whole lathe balanced see-saw like on the middle feet. Given the length of the bed, you probably don't have half the weight on the headstock end. When you tighten the outer feet, though, you will probably have to readjust the tailstock because as you reduce the load on the middle feet, the stand will flex less there, raising the headstock end. With six feet, an extra levelling pass or passes is inevitable. Also, with extra degrees of adjustment, you need extra degrees of measurement, such as curvature along length of bed, and the extra degrees are likely to mean extra iterations.

If your lathe does balance on the middle feet, then you probably want to shift some weight to the outer feet. You don't want a tippie canoe. Unless you are in a mood to play Wally Wallington (http://en.wikipedia.org/wiki/Wally_Wallington).

Supports near the spindle nose vs the back end of the tailstock may make a significant difference in rigidity. If there was 2' of bed to the left of the spindle nose vs 6' on the right (with the tailstock support at the far end), beam deflection of a 6' beam is less than half of the deflection of an 8' beam with everything else being equal. For this reason and the reasons given above, I would think of the feet under the spindle as the primary supports and the ones on the back side of the spindle as the extra. However, a lot depends on how the lathe was supported (and how much weight was on the headstock end) when the bed was ground, as well as any stress shifts which have occurred since. And how the bed was aligned (or misaligned) when the headstock was aligned to the bed.

And remember that your primary goal is to make the lathe bed coplanar, not level or evenly distributed weight. Level is just easier to measure and if it is level to high accuracy across the entire bed it should also be coplanar.

Lacking better advice (or even with it), let your level be your guide. Because nobody else can tell you the idiosyncrasies of your particular lathe. Good advice might help you converge on a solution quicker, though.

rbjscott
11-12-2009, 07:52 AM
The spindle center line needs to be level to start with and then you bring the bed to it. The head stock pads and bed pads need to be as sold as possible.

dlsinak
11-12-2009, 02:55 PM
Let me see if I read all this right. As the starting point, the lathe spindle should be absolutely level. Then the entire bed should be leveled in reference to the spindle, beginning with the headstock end?

I went to level my Jet 1340 lathe and am using a 0.0005/10" level I bought from Shars. The level seems ok in that I get the same bubble indication when I swap the level end for end. What I found is that I cannot get the entire lathe level end for end or front to back in the same level plane. It is close, but not perfect. I am wondering how close is close enough or if I should bolt the machine to the floor. I am very reluctant to bolt it to the floor as we have to deal with a certain amount of heaving during the winter and we get the occasional earthquake which, although it hasn't happened in a few years, can "adjust" the level of my house, and rearrange a few things.

I didn't mean to hijack the OP's thread, but I thought the question was relevant.

Dennis

smalltime
11-12-2009, 05:37 PM
The spindle center line needs to be level to start with and then you bring the bed to it. The head stock pads and bed pads need to be as sold as possible.

This method is as close as I've seen so far.

Think of the lathe as two pieces: The gearbox/headstock, and the bed. the bed can "sag" or droop as I call it, but not as much as you think. The main thing to worry about is twist. This can greatly effect the accuracy of your machine. This is how I adjust twist:

Get the headstock dead level in X and Y, or as close as you can.
then dial down the bed levelers to get the bed level at the rightmost point in the Y direction (crossways)
Here it gets interesting:
find a peice of scrap, say 3/4" that is as long as you can turn, within reason.
Take a cut up next to the collet and set a zero, then move all the way to the right, and take a cut at the same zero. Measure the two. This difference will tell you the twist in the bed.A larger dia at the right will tell you that the bed is tilting down towards you a smaller number means the twist is away from you. then simply use your level to make SMALL changes in the twist and dial it in.
Now you may need to relevel the headstock to gain enough travel to level the bed, but that's part of the fun.

tattoomike68
11-12-2009, 05:51 PM
I want to re-level my lathe it's a 16X60 5000# . It has fore leveling legs under the head stock and two at the tail stock. So if I level the fore out side legs and use a torque wrench to find out how much force it took to level the lathe. Then use the same amount of torque on the two in side legs of the head stock would it be loaded evenly?:confused:

dude you need help, get a pro to help you, its real that you dont have a clue.

Im being nice saying you dont have a clue.

Davo J
11-12-2009, 09:21 PM
Would it be posible to talk to a rigger or machine installer, even if it's on the phone they may give you some info on the way they do it.
Dave

doctor demo
11-12-2009, 10:51 PM
Here it gets interesting:
find a peice of scrap, say 3/4" that is as long as you can turn, within reason.
Take a cut up next to the collet and set a zero, then move all the way to the right, and take a cut at the same zero. Measure the two. This difference will tell you the twist in the bed.A larger dia at the right will tell you that the bed is tilting down towards you a smaller number means the twist is away from you..
Or it means that the tailstock is not adjusted properly.

Steve

jeremy13
11-12-2009, 11:17 PM
I'm looking at the torque on the screws as a way of seeing how much force is on the leg. Right now I do not have the leveling pads and screws in place. I set the lathe on the remarkably flat concrete flour and just shimmed under the base. But now I'm afraid that the thick coat of paint and the drips of paint are crushing and changing the level of the lathe. I'm not trying to replace the precision level. Just trying to make sure the weight of the machine is distributed evenly.

doctor demo
11-12-2009, 11:31 PM
An important element is missing from this thread that would clear this up easy.
Ping Forrest Addy

doctor demo
11-12-2009, 11:38 PM
Just trying to make sure the weight of the machine is distributed evenly.
You can't distribute the weight of the machine evenly , if the machine 's weight is not designed evenly over the bolt placement.
For instance: the weight on the front headstock bolts could be less because the motor hangs off the back.

Steve

jeremy13
11-12-2009, 11:47 PM
That's true as evenly as possible.

JoeLee
11-13-2009, 08:41 AM
Just use a precision level. Thats the way it's done. (periiod...) This is getting rediculous, torque wrench.

JL....................

dlsinak
11-13-2009, 04:14 PM
Just use a precision level. Thats the way it's done. (periiod...) This is getting rediculous, torque wrench.

JL....................

Why use a torque wrench? Are you saying the lathe should be bolted to the floor and leveled by the amount of torque applied so as to remove any twist or sag?

smalltime
11-13-2009, 04:31 PM
Or it means that the tailstock is not adjusted properly.

Steve

Maybe I got confused.......
I thought I said DO NOT use the tailstock. Machine the workpiece with no center.