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Leveling lathe - how to level the v-ways

SteveM

Diamond
Joined
Sep 22, 2005
Location
Wisconsin
I don't want to open the can of works of "they couldn't level lathes on a ship", so please don't take the thread there.

A friend has a South Bend 13" lathe that is cutting a taper. He wants me to take a look. I haven't gone to his shop yet.

I have an Atlas, and leveling the bed when you flat ways is pretty straightforward.

With prismatic ways, how do you level the bed? Wouldn't putting the level across the tops of the V's be like trying to measure a thread by measuring the outside diameter instead of the pitch diameter with thread wires?

Can I remove the compound, lay the level on the flat machined surface and move the carriage back and forth to see how the level bubble moves?

Steve
 
Before I would get excited about leveling the lathe, I would want to fully understand how the lathe is exactly cutting a taper. That means by direction and amount in a given distance.

It is also very important to understand how the owner is setting up the part and if that is part of the problem.

After you have a handle on that, then I would want to verify the amount of wear that is present.

After you have this information, then you can start to consider "leveling" the lathe.

Since you mentioned a forbidden lathe name and I'm assuming that is your frame of reference for experience, I would caution you about "leveling" the lathe.

The goal is not necessarily to make the lathe level but to to make the lathe geometry correct. That means the the axis of spindle rotation needs to be parallel with the bed ways. This also means that you would not want to have any twist in the lathe bed if everything is perfect but sometimes a slight amount of twist can be your friend in compensating for wear.

Now to answer your real question about putting a level on the saddle. Yes you can do that but you need to keep in perspective what the end goal is to cut a straight part. It is very likely that the saddle will indicate that there is wear. That means the level will being indicating that the lathe is going down hill and up hill depending on which side of the low spot you are on.

What is more important is using an indicator to measure how much the head alignment varies with the lathe bed. Many times the lathe bed is fine, all of the problem will be in the head alignment and if they are turning between centers, in the tail stock adjustment.

Again, I cannot emphasize the importance of correcting geometry and not going just for "level". Being level will get you nothing except parallel to the earth.
 
Here are a couple pages out of South Bend's "How to Run a Lathe" on leveling a lathe:

HTRAL_P15.jpg


HTRAL_P16.jpg


The picture came out a little rough but you can still make out how the level is set across the ways of the lathe.

Hope this helps,

-Ron
 
There have been so many threads on this subject, the archive is your friend. However, troubleshooting the fault is what you need to be concentrating on. This is a multi-step process and sequence is important, First, make certain the spindle line is parallel to the bed. Do not use a chuck or collet. Use the internal spindle taper as the spindle reference line. If you don't have a test bar, get one. The two collar test will only tell you that an error exists. It will not tell you where the fault is. A parallelism fault could be skew to the left, the right or up and down. Without a test bar, you don't know. If one is detected, shim or otherwise correct the headstock mounting. Then do the bed and lastly, the TS.
 
I don't want to open the can of works of "they couldn't level lathes on a ship", so please don't take the thread there.

A friend has a South Bend 13" lathe that is cutting a taper. He wants me to take a look. I haven't gone to his shop yet.

I have an Atlas, and leveling the bed when you flat ways is pretty straightforward.

With prismatic ways, how do you level the bed? Wouldn't putting the level across the tops of the V's be like trying to measure a thread by measuring the outside diameter instead of the pitch diameter with thread wires?

Can I remove the compound, lay the level on the flat machined surface and move the carriage back and forth to see how the level bubble moves?

Steve

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put blocks of metal on each side of compound rest and a piece to bridge across on the 2 blocks with level on the bridge
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professionals often use a 6 foot bridge with holes in it so its not so heavy to span across 2 sole plates on floor that are 5 foot apart. the 6 foot long ones are hard to find now a days
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the bridge dont need to be flat use .001" (what ever thickness needed) or so feeler gage strips on under each end of level so level dont rock
.
i had a device i made to clamp on most anything with a rotary table and precision level sat on shelf attached to rotary table so i could turn to make level within one second. used on printing press but you dont need anything that elaborate
 
The picture came out a little rough but you can still make out how the level is set across the ways of the lathe.

Well, that certainly says that South Bend thinks the tops of the ways are sufficient to level it.

If he has a bench top lathe on a chunk of wood, or on a sheet metal cabinet....it won't happen.

It's a 13, so it's probably on the cast iron bell stand. I'll see it later this week when I stop by.

Steve
 
It's a 13, so it's probably on the cast iron bell stand. I'll see it later this week when I stop by.
Steve

1) how much taper? 1/8 of an inch over two inches, or three thou over a foot?

2) two collar test as detailed above - that's the first thing to do. Don't bother bringing any kind of bubble level.

3) what is the wear state on the bed? That factor sets how well you can trim the bed to turn and bore a constant
diameter.

Unless somebody's taken an angle grinder or somthing to the ways, or unless there's some gigantic piece of swarf
between the headstock and the ways, the machine is probably fine.

Be sure the cast iron base under the headstock has contact to the ground on front and rear. If needed put some hard
shim under there if the concrete floor is rough. Steel, aluminum, brass. Not wood or plastic. Then check the front and
rear legs on the right hand side. They should both be more or less in contact wtih the floor. Nothing floating above.

Then take the tailstock off the machine. Set it aside.

Chuck up some stock and turn a diameter. The diameter near the headstock needs to match the diameter farther out.

If it does not, then put hard shim under the front, or the rear leg. Re-check. If it's better, keep going. If worse, then
swap the leg the shim was under.

Basically the system is a three point suspension. The headstock end is one point, the two legs are the other two points.

If you can put a 1-1/2 inch diameter aluminum part in the chuck, and turn a diameter for say, 8 inches that is within a thou,
I'd say it's done.

On edit: bring a box of various types of shim with you. I tend to shear sheet aluminum in varying thicknesses, about three
inch square. Thicknesses ranging from 1/8 down to 1/32. If the floor is real rough then a few 1/4 inch pieces.
 
On edit: bring a box of various types of shim with you. I tend to shear sheet aluminum in varying thicknesses, about three
inch square. Thicknesses ranging from 1/8 down to 1/32. If the floor is real rough then a few 1/4 inch pieces.

I'll have to remember to bring some shims. Don't know how good the floor is, so a wide variety.

All I know at this point is that it cuts a taper, so I just want to be prepared and have everything I might need when I show up. I don't even know how much taper it is at this point.

The owner does vintage car restorations, and while he's not a full-time machinist, he's been restoring cars probably since he could walk, has a bachelors degree with honors in automotive restoration (yes, there is such a thing) and worked at with an established restoration shop before buying the business out when the owner retired. He's smart, a quick learner and has a good eye for detail.

I have test bars for cutting with and without the tailstock and a large flat round for checking the perpendicularity of the cross slide.

Steve
 
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Not a SB but I use a matched pair of parallels on the flat ways to set the level on. SB 13" may have 3 V ways and the tips of those V's may be the ideal spot. Another thing that works to get close on some later model lathes is setting the level on the cross slide, only works if it is one of those lathes with all ground surfaces.
Dan
 
I'll have to remember to bring some shims. Don't know how good the floor is, so a wide variety.

All I know at this point is that it cuts a taper, so I just want to be prepared and have everything I might need when I show up. I don't even know how much taper it is at this point.

The owner does vintage car restorations, and while he's not a full-time machinist, he's been restoring cars probably since he could walk, has a bachelors degree with honors in automotive restoration (yes, there is such a thing) and worked at with an established restoration shop before buying the business out when the owner retired. He's smart, a quick learner and has a good eye for detail.

I have test bars for cutting with and without the tailstock and a large flat round for checking the perpendicularity of the cross slide.

Steve

Steve
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HF sells box of slotted shims i believe called fender or body shims in auto section
.
144 Piece Body Shim Assortment
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feeler gage or thickness gage material used for smaller and finer increments
 
Keep it simple, because its a simple thing.

Use a level mounted to the carriage pointing across the ways, it doesnt matter where or how you do it as long as its mounted stable and the readings repeatable. Crank the carriage to each end and shim the bed to take out any twist as best you can with the wear that you have. You want the bed as untwisted as you can, being a lightweight machine itd pay you to bolt it to the floor.
Chuck a piece of 2" whatever youve got, turn two collars of equal diameter over 6". Using it as test bar indicate from the carriage, ideally you want the head pointing up 0-.001" in 12" and 0-.001" in 12" towards the operator, but you can be a country mile away from these numbers and still cut well.
The cross slide you want heading a smidge towards the chuck so as it faces flat to a touch concave.

Try not to get too caught up in the numbers and if you get weird readings keep an eye out for things jacking off of bits they shouldnt. Bottom line is if the machine does what you need then great, doesnt need to be A1 Schlesinger perfect :)
 








 
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