Leveling a lathe, can't get it perfect???
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  1. #1
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    Default Leveling a lathe, can't get it perfect???

    First of all I do know how to level lathe and have all the tools to do it. I just moved my lathe to a new building and in it's past location as the floor was cracked and sinking a little bit over time, getting it level was a lost cause.

    Now that it is moved to a new 8" thick reinforced slab, I am trying to get it perfect. The lathe is 16" x 40" about 4,600 lbs. After many hours I am stuck and can't get it perfect unless I think I bolt it to the floor. From one end to the other on my Starrett master precision level the best I can achieve is three divisions which would be .0015" to a foot. I see no other option but to bolt the feet to the floor to take out the twist. So the first question is this good enough? The lathe is 43 years old and has a small amount of wear so will never cut perfect anyway. And no, I have not taken a test cut yet to see how good or bad it is at the moment. Am I wasting my time trying to achieve better? Is it ever possible to achieve a perfectly level lathe when it is just sitting on the floor?

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    What is this thing you call "perfect"? Never met this... ;-)

    (And yes, bolt it to the ground amd sneak up on level slowly)

    Lucky7

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    I know lathes will wear funny if used un level for long enough, but the casting may also have settled to match the old floor. Might need to let it rest on 3 feet for awhile until it flattens out, or bolt it down like you say.

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    It is very rare to get a used lathe perfect. Set up the headstock as best you can, and try to minimize the bed twist as you move the carriage to the tailstock. Don't worry to much about changes in level along the length of the bed. A little saddle wear can make the level move surprisingly large amounts as you move from one end to the other.

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    A lathe of that weight but being so short is likely very rigid and suffers the same issue as many smaller lathes, that is it's own weight is not enough to twist/un-twist the bed. As has been suggested you could let it sit on three feet on the TS end and it may settle out over time. Bolting the floor would would help you do it (much) more quickly, and definitely has been done.

    With a used lathe it's important to evaluate the wear and determine what the best path forward is. 0.0015"/ft isn't much but if it were mine I'd do some more evaluation and if it made sense bolt it down to pull the twist out for sure.

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    You could bolt a long piece of heavy flat iron under the tail end of the lathe to serve as a lever. On the floor, place a fulcrum under the center (directly under spindle centerline) as the 'third leg'. Then apply some weight to the bar to 'correct' the twist. This might be a lot of trouble but then you wouldn't have to drill any holes in the floor until you're quite convinced of the value of getting this bed theoretically level. It is conceivable that you might have to twist the bed a little out of perfectly level in order to make it turn a long straight cylinder or bore a long hole. I prefer to test by boring a long hole because I don't have to factor out the effects of the tailstock on the work. If you can bore a 6" long hole perfectly straight, that's what you want.

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    We used to " bend lathe beds straight " in the past when they were bolted down. However I'm talking longish bed lathes not 40" long machines. What configuration is the lathe holding down bolt wise ? 4 holes at the headstock and 2 at the tailstock ?


    Regards Tyrone.

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    The never ending subject of lathe leveling

    Be nice to see what sort of machine it is and how you were taking your readings, tops of the V ways? 0.0015" over 12" over 40" doesnt sound like much at all, unless its some huge single bed casting should be able to easy lose that if you bolted it down.
    Cheers D

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    I'd do the turning tests before anything else, …….(you may well be very pleasantly surprised ) ………….. and at the end of the day that's the only test that matters!

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    Quote Originally Posted by Limy Sami View Post
    I'd do the turning tests before anything else, …….(you may well be very pleasantly surprised ) ………….. and at the end of the day that's the only test that matters!
    Trouble maker!

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    Quote Originally Posted by Demon73 View Post
    Trouble maker!
    I prefer realist

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    I'd just wait for a few weeks to let the lathe settle better and then make corrections if needed. Meanwhile do some testing.

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    A 16" x 40" is a fair sized machine. You do not say, but I am assuming that it has it's own METAL bench or cabinet or legs. If it is on a wood bench, you will never get it "perfect" as it will change with the moisture in the air and even as you lean on that table.

    So, YES, DO BOLT IT TO THE FLOOR. You did say that is a concrete floor. For concrete work, "level" means +/- 1/4" or perhaps MORE. When leveling a lathe you are talking about split thousandths. A concrete floor will change by more than that with changes in position of less than a half inch: the lathe MUST stay in ONE and ONLY ONE spot. Otherwise you are just "whistling Dixie". Oh, and concrete "powders" so if it is moved and then put back in the same place, it will not be the same height. It must STAY in that one place at all times therefore it MUST be tied down. Also the pads on the feet that rest on that concrete are a concern. Common rubber and most plastics are not a good choice: you need something more stable. For smaller lathes I have used metal strips (1/8" thick and 1.5 to 2" wide) that extend across two legs: this distributes the load over a larger area of the concrete. You may need something heavier. Each leg can then have a steel foot resting on that strip. The strip is fixed to the floor so it can not move around and each leg is fixed in one place on the strip. This seems to work well.

    If it is sitting on a bench or table, getting the bench level is not a necessity. But it must be locked down so it can not move. And that includes not moving UP. You don't want the lathe bed pulling the bench up, off of the leg. That would mean that it is not resting on a stable platform and then it WILL MOVE around.

    Also, if your bench or table or legs provide four point support, you should try to have the load approximately even on each of them. This may mean that the bench/table/legs are not perfectly level. This is OK. They are there for support, not to establish level.

    You should need to insert shims between the lathe bed and the bench/table/legs to get it "level". And they should be at least partially torqued down before you take any readings. This is true because your final level may depend on holding one corner DOWN while one or two others are raised. The bed will bend and flex as you tighten the support points. After the legs/bench/table are finalized, the "drill" is something like this:

    1. Torque the bed down.
    2. Take readings with level.
    3. Calculate the needed shims.
    4. Loosen the bolts and insert new shims.
    5. Repeat until you reach the desired level of level.

    The final adjustment may well be the amount of torque on the individual fasteners. A tip: Common aluminum foil is about 0.0007" thick. That is only 0.0003" different from a 0.001" shim. Also two layers of aluminum foil will give you about 0.0015" for another, different, fine increment. Using it for one or more of the final shims can provide both a finer adjustment and a layer that can be crushed with more torque on the bolt for a final tweak.

    As to weather or not your present level of level is adequate, I don't know. Only you can answer that.

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    Flat part of bed-ways stoned and cleaned. 12" long granite parallels put on bed to get level over V ways. It is a Victor made in 1976 and taken care of by the original owner so has no crashes or abuse. It replaced a Monarch. The base is also cast iron so along with it and the bed it does not bend easy so I see my only option to get it perfect is to bolt it to the floor. Unfortunately I don't want to drill in to my new concrete with epoxy coating.

    victor-1640.jpg

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    You'd be surprised how much cast iron will bend. When I was trueing up columns on Hor bores I'd have a 4ft square on the table with a DTI touching it. You could give the holding down bolts a wallop with a ring spanner and big hide hammer and watch the plunger on the DTI move dramatically.

    Regards Tyrone.

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    Quote Originally Posted by Laverda View Post
    Flat part of bed-ways stoned and cleaned. 12" long granite parallels put on bed to get level over V ways. It is a Victor made in 1976 and taken care of by the original owner so has no crashes or abuse. It replaced a Monarch. The base is also cast iron so along with it and the bed it does not bend easy so I see my only option to get it perfect is to bolt it to the floor. Unfortunately I don't want to drill in to my new concrete with epoxy coating.

    victor-1640.jpg
    Once again ! ………do the turning tests.

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    Don't know why you're reluctant to drill your concrete floor? If you're in part of California that occasionaly shakes rattle amd rolls as per Mr Richter, I'd bolt it down just for that reason. Pulling the bed into level, if needed, is a bonus. You have a shop, not an art gallery, yes?

    L7

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    Your floor is pretty nice, but here is another thought- has anyone ever been able to zero out the level before? Could just be that it has always been like that. Sounds like you need to just go make some chips with it and see how it does.

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    Quote Originally Posted by Limy Sami View Post
    Once again ! ………do the turning tests.
    Exactly. If your Machine is at a 45° Angle, but cuts Straight-fuck it.

    R

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    I'll add another "leave it alone if it's cutting straight." If not, first thing you should do is make sure there are no worn spots on the ways. If there are, leveling the machine better probably won't be of benefit. If the ways don't have any worn areas and pulling the machine straight would make it cut straighter I wouldn't hesitate a bit to do so. I agree with Tyrone that cast iron (and steel) are not nearly as stiff as most people think. It's very easy to move small amounts like we're talking here. I've set up and leveled machines from lathes the size being discussed here to floor bars (HBMs) with ways 40+ feet in length. When bolted to a solid floor it's no problemo to move them wherever you need them for the most part.


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