View Full Version : What size Machinists' Level for leveling a lathe
04-08-2010, 01:49 AM
I am looking for a Precision Machinists' Level for leveling my 12x36 lathe
Considering that price for longer levels is much higher I don't want to buy a level any longer than I really need.
What is the min size level I can use?
04-08-2010, 02:08 AM
Length is less important than than accuracy. I have two - one at 10 inches and 0.0005" divsions and per foot; the other 12 inches and 0.01mm per meter, or, 0.00013" divisions and per foot. I can spend all day chasing the 12 inch levels' bubble around:rolleyes:
04-08-2010, 06:10 AM
Here is the Starrett catalogue page (pdf) for their 199 precision level which is 15" long and has an accuracy of 0.0005"/foot ie "half a thou per foot" = 0.0005/12 ~ 0.00004"/" (~ 0.4 tenths per inch) ~ 0.04mm/metre = 0.04/1,000 = 1/25,000.
It will drive you nuts unless used only at the very end of the leveling process. Its so slow-w-w-w-w
And its too bloody long as it gets in the way and won't get into small spaces.
I'd rather settle a 6" long level and sit it on good parallel strips anywhere where 6" is not long enough.
I use a 0.5mm/metre = 0.5/1,000 = 1/2,000 = 0.0286* = 1.72 minutes = 103 seconds. It is also 1/2,000 = 0.5/1,000 0.0005"/" (half a thou per inch). I get that from a good extruded and machined aluminium carpenter's level - at any good tool shop. It is a good compromise between accuracy, size and cost and is easy and quick to use.
My 6" long 0.02mm/metre levels hardly ever get out of the box.
I checked and re-set my 0.02mm/metre level on my surface plate recently - spot on. I checked the builders levels that I have and they too were spot on.
04-08-2010, 08:16 AM
Waste of time and money. Use a decent off the shelf level. Use it across the ways at the headstock and tailstock end. Take as much twist out as you can. Cut a test bar and finish the job. Spend the money saved on needed tooling.
Ever wonder how lathes are kept level on a destroyer???:)
04-08-2010, 10:40 AM
Level isn't important - but "true" is. For practical purposes, that means getting the lathe "level" a least once, for nothing more then a starting point.
I have a lathe that is cutting with a taper. I needed to get the lathe bed "perfectly level" to diagnose the exact issue. In this case it has nothing to do with the bed. If I'd just made a test cut and twisted the bed to get it cutting correct, I'd be chasing my tail. Oh.. and as I found out, I can't "twist" this big bed materially - I'd need hold-downs as well as the level adjusters.
Be careful with using very high precision levels - Typical wear in the bed is not symmetrical, and trying to level to a worn bed is frustrating at best. For most purposes, a 0.0005 per inch level is just fine. You'll likely need 1-2-3 blocks and maybe some other precision pieces to make bed bridges.
Machine levels are rarely used. I figure one per town is all we need. I'm the one around here with them, and they spend more time with trusted friends than in my shop.;)
04-08-2010, 11:27 AM
FWIW: I have a 13x40 lathe, and an 8 inch .0005/ reading level works fine. I bought a European-made one a decade ago from MSC, use it about every 3 months as preventive maintenance...now Grizzly has one in their new catalogue for around $60 iirc, no idea where it's made. The MSC one was about $100 then, nice piece of work. Amazing how things can shift and how flexible cast iron really is, I keep my lathe, mill, surface grinder and surface plate leveled with it and I almost always find that small changes have crept in since the last levelling....
04-08-2010, 11:33 AM
Alex, think about this, you have a 36" span and you want to level it. The 6" model 98 Starrett level is more than adequate to level your lathe. If you have a good eye and patience you can get any twist out of the bed easily. It's more important to get the twist out than to have it near perfect end to end.
If you had a lathe that is 8' or 10' between centers you may want to use a longer level or put it on a long wide parallel.
04-08-2010, 07:36 PM
I'd get whichever level you can find that is cheap and at least long enough to span your ways front to back. Obviously you'll need to rest it on parallels or 1-2-3 blocks to get it above any inverted vee ways.
"Level" for its own sake is not important, hence the use of machine tools on ships. What IS important is removing twist in the ways. Since the only cheaply available external reference available is the earth's gravity we use levels. In whatever precision grade you feel like embracing. The tool of choice as used by generations of machinists/millwrights is the master precision level in 0.0005"/ft variety Sarrett 199, B & S, Tumico. 15" is the most common length I've seen in these.