View Full Version : Levels

10-20-2003, 08:55 PM
Paul Simon once had an album that contained a song about a man who thought too much about writing a song. On the flip side of the album was the same song done a different way. LOL.
I feel that I am also thinking too much about something so simple...Levels:

A water-level is cheaper than a Starrett Machinist's Level, but wouldn't a 6" Starrett be better (or is that too small)? Also, the water-level measures actual height, in a fashion, whereas the Starrett measures only if the level is exactly parallel to the earth. Still, I think the Starrett Machinist's Level would be easier to use and more precise.

Any thoughts?

10-20-2003, 09:58 PM
Unless youíre setting up high end machine tools get yourself a 12Ē carpenterís level, about $10 at the big box store. Or use the one in the tri square base, if you have that. Youíll be fine.

Gary :D

10-20-2003, 11:13 PM
"Unless youíre setting up high end machine tools..."

The beauty of a CadCut machine is that you can make it as high-end as you want. I ain't going to this much trouble unless I go all the way. A 4x8 router is no small task and I don't ever want to have to build another one! Steel frame, THK rails, peak 1500 oz-in servos, and as level as I can possibly make it.

10-20-2003, 11:30 PM
Something to consider before purchasing the level is what quality is the surface that the level is going to be used upon? Machinist levels are meant to be used on a machined surface, but would not do a good job of finding the average level of a long surface, which may be rough and/or bowed slightly.

If you are levelling the table, an ordinary level is likely good enough to get your table in the ballpark. Actually mounting a dial indicator on your gantry and moving it around to test the depths is likely a much better method of setting it up for the conditions that actually exist in your machine.

10-21-2003, 01:08 AM
It has to do with two very long precision machined aluminum rails (tolerence of .005") that go on either side of the machine. The idea is to get them as perfectly parallel and level as possible.
The steel frame on which it sits isn't that big a deal because it has tabs on it which the machined rails sit. Once you get the rails perfectly aligned then you use some kind of epoxy stuff to make it all solid.
Bob (the guy who wrote the plans) wanted mucho accuracy! Incidentally, it was one of the reasons I chose his plans.

"If you need a machine and donít buy it, then you will ultimately find you have paid for It, but donít have it." - Henry Ford.

10-21-2003, 01:14 AM
This is what I addressed my response to.

ďI feel that I am also thinking too much about something so simple...Levels:Ē

I can appreciate the fact that you are concerned about getting your machine level. But a bubble level is just a reference tool and the accuracy is in the operator not the tool. I didnít know you had such a large machine, I would now suggest a 48Ē carpenterís level. I think you could get a nice one for under $20. Please donít think Iím making a joke. I spent some time setting up $500K VMCís, we used carpenters levels. After all was leveled we would check things with the expensive level. I donít recall ever changing anything. Save your money for 1 or 2 good indicators.

Gary :D

I love the H Ford quote.

10-21-2003, 01:41 AM

I don't know about "epoxying it down". One of Murphy's corollaries is this:

"Anything which must be permanently assembled with great difficulty must always be disassembled once more, immediately after the shrink fit forms, the Loctite gets hard or the epoxy sets. Only then may it be assembled permanently" :D

10-21-2003, 09:48 AM
I'd like to butt in here concerning the leveling of your table. I'm just thinking outloud ... so to speak, but I'm looking at your question from a different angle (I tend to do that with most things)

Instead of worrying about the level of your rails in relation to each other, I think it is more important to be concerned with the level of your rails in relation of the z axis spindle to the the table.

An idea would be to build the table (I haven't seen the plans for yours if it's possible) with the ability to adjust the rails from time to time as needed for maintenence. Shims and spacers come to mind here.
Then, run your gantry back and forth across y as you move across x checking for distance from the z (spindle) to the table with a micrometer and adjusting the rails as you go.

In addition an idea is to run a routine to mill the table flat after the machine is finished to get rid of any bumps or imperfections in the surface if accuracy is important.

You can check on the shopbot forum and they have discussed this to great length. I think the shopbot software even has a routine just for this (not sure ... don't have a shopbot either) but you can use their procedures to aid in your project.

I just don't see where having the parallel rails level to each other in relation to earth is as important as it is to being level to your work surface and the rails being true to themselves to prevent binding of your linear bearings.

10-21-2003, 01:12 PM
Good ideas, but not what the plans call for. The reason you must get the two machined rails exactly parallel and level is because the gantry sits on them. If the rails are perfect then the gantry will be perfectly aligned. It's so well aligned that a single finger-push can cause the gantry to travel the length of the table. I'm hoping mine is that accurate.

Once this table is built there is no disassembly. Heavy steel frame that is welded together, machined rails that are epoxied to the frame, and a pretty heavy gantry mean you arn't moving it much either. The guy who wrote the plans looked at all the commercial machines and tried to figure out why they built them the way they did. He then incorporated all those ideas into this machine. Its more of a business machine than a hobby machine. In other words, this ain't your Mama's router! LOL.

But, we digress:
Has anyone here ever used a water-level vs a Starrett Machinist Level? Which did you think was better and why?

10-21-2003, 03:41 PM
I have had numerous level gauges in the past. Expensive ones, cheap ones. When i had to put something against a wall wich needed to be level i tried my very best every time.

Then, one time i used a level, and the mounted object still looked "not-level". Then i figured out that when i turned the level gauge around, it would show a different measurement than the way i first started out with.

This can mean only two things. 1) I have an el-cheapo level gauge wich needs to be thrown in the garbage can, or 2) No level gauge in the world is exactly LEVEL. (wich i doubt).

The thing i learned : I'll never trust a level-gauge just like that.

Lately, for rough measurement i used a long hose filled with water, holding both ends near the measured object. That seemed to work well, but a lot of hassle.

Good luck, get level :D


10-21-2003, 05:47 PM
I relocated and installed equipment for about 10 years, we used Starrett Precision levels 12" long .0005" per foot accuracy. I have also used water levels for fences and such, and there is no comparison to a precision level. Mills and toolroom lathes get only a torpedo level job, precision Grinders and large machining centers got the Starrett levels. I am building a router table but only using a 2' level for the frame, the rest will be dial in with indicators. There is no use in buying a 500 dollar level when the surface you are leveling is rougher than the level tolerances. A good practice when using a level is to check it by flipping it over and also turning it around, if the bubble moves, the level is no good.

10-21-2003, 09:25 PM
You can get a reasonably accurate precision level from Grizzly for $80. Thats what I did. It comes with adjusting screws and a booklet to explain how to zero the level in. It is calibrated to .0005" per foot. I set up my rails with it. Took all day but was worth it and the money spent. Finish hooking up my first axis Sunday and when my friend wanted to see how much slop was in my ball screw he moved the whole table; there was so little friction from the rails that he back-drove the screw with about 5 lbs. of pressure! I'm sold. In the end, I'd have to say its all about what you're after, how much time and money you're willing to spend....

10-21-2003, 10:56 PM
I went to www.grizzly.com but couln't find that level. Got a URL?

In my frantic, fevered, and somewhat delusional buying frenzy I just bought an unused Starrett 8" Machinist Level #98 for $68 (including shipping) on ebay. 'main level vials have graduations that are approximately 80-90 seconds or .005" per foot (0.42 mm per meter). There are five, six, or seven lines on each side of the bubble, depending on the base length.'

I get the feeling I'll be selling these tools when the thing is built so I can afford to finish the project. Maybe I'll find a way to keep them, I really hate letting go of good tools.

10-22-2003, 02:03 AM
Hey, that is a smart way to work, Samualt: buy used, use it and then sell it when done :)

10-22-2003, 03:57 AM
Hmmm, the plans also call for a 4 foot "Contractors Level". I can't find much on ebay for that. Anyone know what that is, what its used for, and how accurate it is?

10-22-2003, 07:00 AM
There's an old carpentars trick for testing a level to see if it's accurate.
Place the level on a relatively flat surface (no dirt or bumps to induce error) and mark the table where the four corners of the level is sitting.
Note where the bubble is in relation to the reference lines in the glass. say it's just touching the reference line on the left. It doesn't need to be centered better if it isn't.
You could shim (with a feeler ga) one end until the bubble is just bearly touching one of the reference lines. Tape the shims down so they don't move. It is easier to test the level this way rather then having the bubble in the exact center and having to estimate its position.
Then rotate the level 180 deg and align the level back on the corner marks.
Keep the same side up, as the shape of the glass can effect the results.
Again note where the bubble ligns up in the glass. If the level is accurate, it will be just touching the reference line on the left as it was before.
If it isn't, then the level is not accurate, to an unknown amount.
Flip the level ove and repeat the process, you may find that one side is better than the other.
I heard this method years ago, and I have tested levels using this method and was supprised at the ones in the store that weren't reading properly.
Your run of the mill levels aren't adjustable. The buble vial is glued in place.
You could calculate the inaccuracy be using a feeler gage and the know length of the level.
Anyway, give your level a try and see what you come up with.

10-22-2003, 09:00 AM

That link:

Good idea about selling it afterward. Thought about that with the one I bought but decided to hold on to it, just in case. Maybe one could be rented?


Your method was described in the booklet that came with the level I purcased. Except, there are 2 screws (one for each vial) that you adjust until the bubble reads exactly the same when turned end for end. Pretty easy to set up, too.


10-22-2003, 09:16 AM

Use a normal level to set up the steel frame - as i stated, a contractors level is fine. (be sure and check it though)

As I discuss in the plans, use a machinists level to level your aluminum pieces that assemble for the linear rails and rack......

Trust me - It works good.......

HU - The epoxy is used not to glue anything together - but to help bed the aluminum down that the aluminum sits on - more a gap filler than anything. The whole assembly is bolted THROUGH the epoxy after it sets. The epoxy is an industrial grade epoxy that is actually machinable on a mill or lather ( I tried it too) and is a steel filled epoxy - cool stuff... I played with it a lot. Its really good stuff.......and worked wonderfully for the use I had, and thats basically what its made for - repoairing and leveling equipment.....

10-22-2003, 10:14 AM
Having been in the trades where being on the level is important, I question the ability to accurately level an 8' rail with a 12" level. I would tend to think that level is helpful but parallel is of most importance. One long rail set close with a long carpenters level (8'), allow the epoxy to cure, then level across with your Starret on a good straight edge to the other rail, there again checking for parralel over dead nuts level. After completion of the machine, re-leveling using the gantry traveling back and forth and shimming as needed. There again level is good, parallel is a must.
This is why precision machinery is bolted to the floor, because even the highest quality and heaviest machines need to be racked in order to cut to the utmost accuracy.
One final note, I set all our machinery with a Starret level. Don't keep flipping it around end for end and freaking yourself out that the bubble is not the same, as long as it is close. Pick one direction the level sits on the machine and stick with it. Mike

10-22-2003, 11:28 AM
Good advice, MikeA

Anyone considered a string level yet? A person needs to be able to tighten the string up good and taught, but at least you would be able to get a more absolute level of the whole machine.

Place a sturdy post in the center of the table area to pull the line against. Perhaps you would want to use a monofilament fishing line rather than a fuzzy chalk line.

This method should help reduce errors due to poor surfaces, rough surfaces or "curved straightedges", misaligned bubbles or whatever.

10-22-2003, 12:28 PM
I agree - Good points Mike.

I wouldnt personally suggest a string level......except to rough check your frame if you wish. A 4' level is easier to use though - and much more accurate.

04-21-2004, 12:31 PM
All, many good tips concerning levels, parallel and such. I have just put together a 3x4 bed/table and had the opportunity to set it all up on a surface plate a friend of mine has. God, what a treat. The plate kept the Igus rails dead parallel to each other (in the vertical plane) and a faced-off piece of 1/2 drill rod was used to set the width. Then I placed the support rails/legs assembly on top of the Igus rails and bolted it all together with Brownell's gun bedding epoxy mixed with their metal powder acting as compressible shims. When I took it off the surface plate, the gantry (after I mounted it on the Y shuttles) slid from one end to the other with one TINY push. Hope you find a surface plate big enough to do your big table. Even one that is long enough to set the X rails on while letting them hang over a little on each end would work, I think.