What sort of level? If you're going to use a level it needs to be an engineers precision level; DIY levels aren't even close.

There are methods of correcting tapers that don't need levels, but I'll leave those to others to explain as I've never needed to use them. To start with don't try and machine/measure with the tailstock in place. It simply creates two variables (bed and tailstock) to adjust but only one measurement. So it's doomed to failure.

Andrew

That’s a neat looking little level, Steve … but have you checked its sensitivity ?

At that length: If you want to ‘level’ the lathe with it, a piece of cigarette paper needs cause a visible movement of the bubble.

MichaelG.

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Edit: Andrew [predictably enough] beat me to it.

Edited By Michael Gilligan on 02/10/2021 21:05:31

Put the mag base for the dial gauge on the front of the saddle and do your measurement again. That way the dial gauge will be following the path of the tool and should read zero all the way.

That gauge setup is a poor way to check for taper if that's what you're doing Steve. You should be using a micrometer to take measurements at each end of your cylinder. The dial gauge reading can be affected by twist or wear in the bedway.

If it’s any help … I found this statement which presumably originates with Starrett:

Starrett improved machinist level series is a truly American product that is available in varying lengths of 4/6/8/12 inches. The company offers five different models under this series each having a long graduated spirit level that has a sensitivity of 0.42 millimeters/meter or 0.005 inches/foot or 80-90 seconds of arc.

Given that your vial is not graduated, I have to assume that it comes from another range.

Maybe inferior, or maybe just earlier … but certainly worth checking the sensitivity.

MichaelG.

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I agree … so that’s one ticked-off the list

MichaelG.

Not really, it needs to be more than an order of magnitude more sensitive, along with multiple graduations.

Andrew

To be explicit, an ordinary bubble level won't cut the mustard. They're good for putting up shelves and most other purposes but aren't sensitive enough to detect a twisted lathe bed.

You need an Engineers aka Machine Level. They are made to detect tiny deviations from level, as required to set a lathe accurate to a thou or two over several inches. Typically, in a new installation the lathe stand is set up with an ordinary level first, and then the lathe is tested. If not cutting straight a Machine level is used to check for bed twist, which can be corrected by shimming a foot: some machines have screw-adjustable feet.

This example is made by Dasqua and sold by RDG.

In theory new lathes are confirmed to cut straight on a true level surface in the factory, so plonking them down on any decently stiff flat surface should be good enough. In practice, don't expect too much of inexpensive hobby or elderly lathes. Note flat rather than level. It's not necessary for lathes to be level provided the bed is straight: they work perfectly well in storm tossed ships. Levelling is just one way of eliminating twist, and a bent stand is one way of accidentally twisting a machine.

In my book Machine Levels aren't good value for money. Pricey and much too sensitive for ordinary work. Fussy and the bubble takes an age to settle. Good for anyone installing lots of machines, dubious for putting one into a shed! After being used once to set-up the owners lathe, I suspect most Machine Levels end up in a cupboard. As an alternative, Rollie's Dad's Method takes longer and is more complicated to do than detwisting with a good level, but it requires no special equipment.

A word of warning: high-precision measuring is so difficult it's quite easy to lead oneself up the garden path into a deep maze of confusion. A wobbly DTI moving on a slide will cause trouble. When measuring into the 0.02mm / 0.001" region don't rush to adjust anything based on amateur measurements: they're likely to be flawed because taking them properly is a skill you don't have!!! Therefore, keep measuring simple and use the right tools: detect taper with a micrometer, not a DTI. Check everything – it may take several hours practice to get a micrometer to repeatedly read the diameter of a precision rod consistently. Positioning the micrometer correctly is important, and so it applying the same pressure to the screw every time. The ratchet helps, but trained craftsmen rarely use it; they develop a 'feel'. Some are better than others, so find out how good you are by practising. In the meantime, don't jump to conclusions!

Dave

That should be plenty good enough for most bench lathes.

If you have a machine with 2 pedestals like a Bantam, the first thing to do sould be to level the bed and fix the feet to the floor, with shims of required to achieve level. I rebuilt a Bantam and as an exercise I put a dial gauge on the saddle and against a part in the spindle, then I moved it about on my workshop slab – the dial gauge swung all over the place just from the variations in floor level and the lathe stood normally on it, and my floor isn't bad at all. It was quite the eye-opener.

Steve you might well damage your lathe If you keep that up. You don't say what lathe is actually is. It could be that your bed is level but the headstock is not pointing straight down it.