What size machinist level do I need?

Pcmaker

Pcmaker

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I ordered a Precision Matthews 1127 lathe. I made enough overtime money this Christmas to buy 2 machinist levels from Amazon.

What size machinist levels should I buy? I plan on putting a level on each end of the ways to level the lathe. Will a 6" be long enough? Will I need to use 123 blocks?
 
A 6 inch would proabaly do it. You may need 123 blocks, depends on the design of the ways. You need a set(s) of 123 blocks anyway.

You only need one level and move it end to end as needed. Trying to calibrate 2 levels to read exactly the same would not be fun. Don't assume that the level is calibrated out of the box. You need to check the level by rotating 180° and adjusting it to read exactly the same in both positions. This does not require a perfectly level surface to adjust. I calibrated my level as I was leveling my mill, check, rotate, adjust, check again.
 
Good machinist levels are not cheap and don't get used very often. I own two and haven't used either of them in quite some time. My recommendation would be to borrow one from someone nearby and return it with a six pack of good beer. Then you can spend that money on tooling that you will actually get some use out of.
It really isn't necessary to have your lathe perfectly level anyway. It is a nice place to start from when you begin the important tasks such as tail stock alignment and performing a two-collar test. On some lathes it actually becomes necessary to shim/jack them slightly out of level to remove or induce twist in the bed. This will become apparent during the two-collar test.
Just my two cents worth and worth every penny you've paid for it.

Ted
 
I have 3 machinist levels, 6-12-15 inch that have served all my needs for 45 years, if you only get one I would get a 12 inch,
 
An 8" would be a better size, unless you have a bigger lathe with a 9" or larger bed. You would want a precision level, so something with a sensitivity of 0.0005" over 12" or better. As others mentioned, use two 123 blocks and move them down the bed with the level. It isn't as much as having the bed absolutely level in both directions, what you are looking for is that the lathe bed measures the same as you move down the bed, i.e. minimize bed twist. Also recheck the bed in a day or two after leveling, and then periodically after that. You can get some settling and shifting, also the precision levels are very sensitive to temperature. Metal feet are typically preferred as they are more stable vs. isolation feet, it also depends on the rigidity of the stand/base you are using.
 
I used to think that two levels were needed to do a direct side-by-side comparison, but in leveling my 14x40 Logan recently, I found I only used one level (a 12"). When you have to move from one end of a long(ish) bed to another, having only a single level is not much of a handicap, as you are going to forget the reading regardless and end up writing down the bubble position (interpolating between the 0.0005" marks) or taking a photo.

In regards to size, the larger the level the larger the bubble, and therefore the easier it is to interpolate between gradations. But keep in mind the cost-benefit analysis also: you're going to use this level once or twice a year, and even then you're going to have to do test cuts on a bar in order to really fine-tune things.

Something to keep in mind, if you're planning to use shims, get a proper shim pack (for example McMaster-Carr 18-8 SS shim stock set).
 
Two levels are a PIA. With one level it doesn't even have to be calibrated just consistant. I have a mark on mine that I line up with the edge of the rear bedway so that it's alway oriented the saw way both end for end and along it's length. I have a 12 inch good for .0005" over 10 inches. It's so sensitive I have to be careful how I hold it. The heat of my hand will move the bubble in about 10 seconds. I think it was just over $100.
 
Hi Pcmaker, Hoping I don't start a flame war here, but I recently acquired my first lathe (Boxford VSL) and was also struggling with what level to buy, how much to spend etc. When I finally picked up the lathe I had not bought a level yet, but now had a lathe that just had to be used. So I launched into Rollies Dad's Method, figuring I had nothing to loose. I started by making sure the lathe solid on its table, and table legs were all stable on a part of the floor with no concrete cracks between the legs. I used a 1.5" aluminum round extending about 8" from the 3-jaw and made very light passes (i.e. .002") with a sharp HSS tool to minimize deflection. I recall the diameter varied by about .015" after the first passes.

I started adjusting the feet, but found that the Boxford table was too rigid for gross adjustments. Instead I started shimming between the lathe and the table until the aluminum bar diameter varied by about .001" to .002" over 8 inches. Let the lathe sit for couple days, then checked again, iterated on the shims a bit, then let sit a day. Then moved on to adjusting the feet for final trim. Got down to about 0.0004" over 8". Checking again a few weeks later the lath had shifted to about 0.001" over 8", but was easy to re-adjust back to 0.0004. I spent a lot of time staring at that lathe during those initial adjustments! I am satisfied, and now know how to adjust again as things shift.

If I ever determine that I need truly level rather than simply a lack of twist, I can always buy the level and redo. In the mean time, I saved $100 to $200, which was very easy to spend on other tooling! Anyway, don't let the lack of a level keep you from getting started.

John
 
John, you don't have a machinist's level that is sensitive to 1 micron over 2 miles? And you call yourself a hobby machinist? Shame on you! ;)

I think many hobbyists think that if you don't have a level then you cannot level the bed or get the twist out of it but you definitely can. It just takes a lot of fiddling and messing around to do it. A good level just gets you there much, much, much faster. You still should do a 2-collar test to fine tune it but what took you a week to do, I can do in a few minutes to an hour depending on the wind direction and the phase of the moon.

Thing is, you have to do this whole leveling thing periodically. I check level twice a year or if I do some particularly heavy turning so that level saves me a lot of time. My lathe has adjustment bolts under the feet so I can adjust things quickly. The last time I checked a 2-collar test it took me 3 minutes to dial out 0.0002" of difference over an 11" run. End result was zero over that span. Doesn't make me a better machinist; nothing will do that but at least I don't have tapered work pieces unless I want them tapered.
 
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