Using & trusting a brand-new Starrett 98-6 machinist's level

[cazclocker]

I just bought a new Starrett 98-6 machinist's level. I bought it to help level and tram my new mill from Little Machine Shop, and to keep it leveled and trammed in an ongoing basis. I've never owned a level of this quality before. Then again, this is my first milling machine too.

My question is about the adjusting thumbwheels I see on one end of the level. I have NOT touched them or fiddled with them in any way whatsoever. Am I supposed to assume that they came perfectly adjusted from the factory? If they ever go out of whack, how would I know? Seems to me I would never know. If I ever had to adjust it, what would I use as a reference?

I guess these questions show my unfamiliarity with this area of metrology - but there you are. I'm a newbie! )

 

[Harvey Melvin Richards]

Place the level on a reasonably level flat surface. Note the reading, turn the level 180° and the reading should be the same. If the reading isn't the same, adjust until it is.

 

[cazclocker]

Place the level on a reasonably level flat surface. Note the reading, turn the level 180° and the reading should be the same. If the reading isn't the same, adjust until it is.

...........of course. Thanks Harvey, the answer is so SIMPLE! I am embarrassed to say I didn't think of that. But now I know!

 

[RockwellHardness]

I just recently purchased a 98-6 level myself, for my new PM 1236 lathe, and PM 962 Mill.

Using the level has been a great experience, and I have come up with all sorts of uses for it on the Mill, probably known and written about by others, I just have not been able to find anything similar to what I am doing.

Before I go on, the 98-6 was not perfectly flat on the bottom, I could press on one corner sharply and it would tap the plate. About .0002 clearance, and would shift the bubble a bit if you held it down. I took a permanent marker and marked up the bottom, rubbed on the mill table, and the lifted corner was barely touched, and the others about a half inch was cleaned off, though diagonally from the lifted corner it was rubbed off about 3/4s of an inch.

I Called Starrett, and Scott the technician educated me a bit on levels. Machinist level bottoms are slightly bowed, so you have to have a surface longer than the level to place them on, as only the ends touch the surface you are leveling. That was good to know !

Mine was definitely warped, and he said return it. I do not get Starrett, no instruction in the box, no instructions online. I find that odd.

I am still not positive how much to tighten the adjustment screw and nuts. I forgot to ask the technician while I had him on the phone

I have been loosening both nuts, snugging the screw, the adjusting the bottom nut first when matching the bubble, then snugging the top nut slightly, rechecking, and then snugging up just a bit more on the nut that will bring the bubble into the perfect position both sides. Then check again. I do this on a rigid precision flat surface on the mill table, in exactly the same position when reversing. And I give half a minute between adjustments for the bubble to truly settle. I do not breath on it, I do not have hot lamps shining on it, and I make sure the room has been at a steady temperature for many hours.

Anyway, I am thinking that it is not important that the mill table be level in an absolute sense. The level can give a quick check of your table one position relative to another and will reveal any twists, depressions or bows. You will need precision bars to put the level on, that bar length can be whatever you want it to be, depending on what you are checking for. A 6 inch level should be the only level any hobbyist would need ?

The most trick use is to compare the table to the vise. I have not come across any posts that discuss calibrating the vise to the table. It can be done a couple of different ways with a dial test indicator, but the level is quick and easy. I lay the level on the same surface you place the parallels on with the level on the same bar and on the same spot on the bar as when it was on the table., if the bubble is at the same spot as it is on the table, bingo !

This level is so sensitive, that is why it needs to be used on the same bar on the same spot throughout. And they make one even more sensitive !

I am sure if you buy a Kurt or Glacern vise, it is perfectly square to a high precision, but what about used or imported vises ! Assuming the surface the parallels sit on is parallel exactly with the table would be a mistake I am thinking.

I am thinking that lathe owners trying to level their lathes may be laying the level directly on the ways, and this will give a reading that represents the relative difference between the small areas at the ends of the level. I really think the only way to use a level for anything is to lay in on various length precision bars, with the level on the same position on the bar.

But then again, I am not so positive about anything I just wrote, I just noodled it out the other day !

RH

 

[cazclocker]

I just recently purchased a 98-6 level myself, for my new PM 1236 lathe, and PM 962 Mill.

Using the level has been a great experience, and I have come up with all sorts of uses for it on the Mill, probably known and written about by others, I just have not been able to find anything similar to what I am doing.

Before I go on, the 98-6 was not perfectly flat on the bottom, I could press on one corner sharply and it would tap the plate. About .0002 clearance, and would shift the bubble a bit if you held it down. I took a permanent marker and marked up the bottom, rubbed on the mill table, and the lifted corner was barely touched, and the others about a half inch was cleaned off, though diagonally from the lifted corner it was rubbed off about 3/4s of an inch.

I Called Starrett, and Scott the technician educated me a bit on levels. Machinist level bottoms are slightly bowed, so you have to have a surface longer than the level to place them on, as only the ends touch the surface you are leveling. That was good to know !

Mine was definitely warped, and he said return it. I do not get Starrett, no instruction in the box, no instructions online. I find that odd.

I am still not positive how much to tighten the adjustment screw and nuts. I forgot to ask the technician while I had him on the phone

I have been loosening both nuts, snugging the screw, the adjusting the bottom nut first when matching the bubble, then snugging the top nut slightly, rechecking, and then snugging up just a bit more on the nut that will bring the bubble into the perfect position both sides. Then check again. I do this on a rigid precision flat surface on the mill table, in exactly the same position when reversing. And I give half a minute between adjustments for the bubble to truly settle. I do not breath on it, I do not have hot lamps shining on it, and I make sure the room has been at a steady temperature for many hours.

Anyway, I am thinking that it is not important that the mill table be level in an absolute sense. The level can give a quick check of your table one position relative to another and will reveal any twists, depressions or bows. You will need precision bars to put the level on, that bar length can be whatever you want it to be, depending on what you are checking for. A 6 inch level should be the only level any hobbyist would need ?

The most trick use is to compare the table to the vise. I have not come across any posts that discuss calibrating the vise to the table. It can be done a couple of different ways with a dial test indicator, but the level is quick and easy. I lay the level on the same surface you place the parallels on with the level on the same bar and on the same spot on the bar as when it was on the table., if the bubble is at the same spot as it is on the table, bingo !

This level is so sensitive, that is why it needs to be used on the same bar on the same spot throughout. And they make one even more sensitive !

I am sure if you buy a Kurt or Glacern vise, it is perfectly square to a high precision, but what about used or imported vises ! Assuming the surface the parallels sit on is parallel exactly with the table would be a mistake I am thinking.

I am thinking that lathe owners trying to level their lathes may be laying the level directly on the ways, and this will give a reading that represents the relative difference between the small areas at the ends of the level. I really think the only way to use a level for anything is to lay in on various length precision bars, with the level on the same position on the bar.

But then again, I am not so positive about anything I just wrote, I just noodled it out the other day !

RH

Thank you for the musing, RH. I had no idea that a machinist's level was meant to be slightly bowed on the bottom - I have a surface plate, so I plan on checking my 98-6 with some Prussian blue later on this afternoon. I bought my 98-6 brand-new from Little Machine Shop, and it came with minimal documentation - just a standard certification slip, and a very small slip of paper explaining that each division on the glass vial represents .005" per foot deviance. The slip is very small, so I would guess yours got lost in the outer wrap that the level comes in.

As far as adjusting the level, once I understood the principle outlined by Harvey (below), I found it easy to verify that my level was just fine as it was from the factory - so I didn't adjust it at all. But if you've been tweaking yours, I suspect you now need to return it to the factory setting. The two nuts on the threaded post are meant to act like jam nuts - you need two wrenches to perform the final locking move. With the nuts loose, once you've found your perfect setting for your level, you need to put one wrench around one nut and the other wrench around the OTHER nut, and jam them together with light force...just enough to secure them together.
Hope that helps.

 

[Bill C.]

I just recently purchased a 98-6 level myself, for my new PM 1236 lathe, and PM 962 Mill.

Using the level has been a great experience, and I have come up with all sorts of uses for it on the Mill, probably known and written about by others, I just have not been able to find anything similar to what I am doing.

Before I go on, the 98-6 was not perfectly flat on the bottom, I could press on one corner sharply and it would tap the plate. About .0002 clearance, and would shift the bubble a bit if you held it down. I took a permanent marker and marked up the bottom, rubbed on the mill table, and the lifted corner was barely touched, and the others about a half inch was cleaned off, though diagonally from the lifted corner it was rubbed off about 3/4s of an inch.

I Called Starrett, and Scott the technician educated me a bit on levels. Machinist level bottoms are slightly bowed, so you have to have a surface longer than the level to place them on, as only the ends touch the surface you are leveling. That was good to know !

Mine was definitely warped, and he said return it. I do not get Starrett, no instruction in the box, no instructions online. I find that odd.

I am still not positive how much to tighten the adjustment screw and nuts. I forgot to ask the technician while I had him on the phone

I have been loosening both nuts, snugging the screw, the adjusting the bottom nut first when matching the bubble, then snugging the top nut slightly, rechecking, and then snugging up just a bit more on the nut that will bring the bubble into the perfect position both sides. Then check again. I do this on a rigid precision flat surface on the mill table, in exactly the same position when reversing. And I give half a minute between adjustments for the bubble to truly settle. I do not breath on it, I do not have hot lamps shining on it, and I make sure the room has been at a steady temperature for many hours.

Anyway, I am thinking that it is not important that the mill table be level in an absolute sense. The level can give a quick check of your table one position relative to another and will reveal any twists, depressions or bows. You will need precision bars to put the level on, that bar length can be whatever you want it to be, depending on what you are checking for. A 6 inch level should be the only level any hobbyist would need ?

The most trick use is to compare the table to the vise. I have not come across any posts that discuss calibrating the vise to the table. It can be done a couple of different ways with a dial test indicator, but the level is quick and easy. I lay the level on the same surface you place the parallels on with the level on the same bar and on the same spot on the bar as when it was on the table., if the bubble is at the same spot as it is on the table, bingo !

This level is so sensitive, that is why it needs to be used on the same bar on the same spot throughout. And they make one even more sensitive !

I am sure if you buy a Kurt or Glacern vise, it is perfectly square to a high precision, but what about used or imported vises ! Assuming the surface the parallels sit on is parallel exactly with the table would be a mistake I am thinking.

I am thinking that lathe owners trying to level their lathes may be laying the level directly on the ways, and this will give a reading that represents the relative difference between the small areas at the ends of the level. I really think the only way to use a level for anything is to lay in on various length precision bars, with the level on the same position on the bar.

But then again, I am not so positive about anything I just wrote, I just noodled it out the other day !

RH

When I mount a vise on a table I clean both the bottom of the vise and surface of the table. I usually double check if the vise is level by running a indicator over the ways. I have used precision level to check to see if a lathe bed is level maybe once or twice since I never moved machinery. My Dad was a plant maintenance man who would have used levels to build production lines.

 

[RockwellHardness]

Thank you for the musing, RH. I had no idea that a machinist's level was meant to be slightly bowed on the bottom - I have a surface plate, so I plan on checking my 98-6 with some Prussian blue later on this afternoon. I bought my 98-6 brand-new from Little Machine Shop, and it came with minimal documentation - just a standard certification slip, and a very small slip of paper explaining that each division on the glass vial represents .005" per foot deviance. The slip is very small, so I would guess yours got lost in the outer wrap that the level comes in.

As far as adjusting the level, once I understood the principle outlined by Harvey (below), I found it easy to verify that my level was just fine as it was from the factory - so I didn't adjust it at all. But if you've been tweaking yours, I suspect you now need to return it to the factory setting. The two nuts on the threaded post are meant to act like jam nuts - you need two wrenches to perform the final locking move. With the nuts loose, once you've found your perfect setting for your level, you need to put one wrench around one nut and the other wrench around the OTHER nut, and jam them together with light force...just enough to secure them together.
Hope that helps.

Thanks cazclocker, I think you are right about the two wrenches at the same time.

I do not think there is a factory setting per say, just a proper procedure to calibrate. I just wish Starrett would have some instructions in the box and on there website so we would know exactly how to to it correctly instead of guessing.

RH

 

[itsme_Bernie]

...........of course. Thanks Harvey, the answer is so SIMPLE! I am embarrassed to say I didn't think of that. But now I know!

Make sure you leave it sit for 10 minutes or so before you move it.

With the .0005 #199 level you need to leave it even longer each way, and keep lights off of it an everything.

 

[RockwellHardness]

Hi Cazclocker,

Looks like you have had some more good advice, I am learning as well.

I have been working with may 98-6 some more. When the bottom is covered with a permanent marker, and rubbed back and forth on a perfectly flat surface, in this case the side of my side of my screwless vice, the wear pattern is very revealing. I did not press down when rubbing, just even pressure from the ends.

One corner has the marker worn away about an inch, it's diagonal partner about 1/2 an inch, it's side partner about 3/8ths of an inch, and its opposite end partner barely 1/4 of an inch, this corner is the one that will bend down and move the bubble if pressed when on a perfectly flat surface.

I was still thinking this was no good, I am taking it back, but then with more fooling around, I learned a few things.

Since I now know that I must place the level on know perfectly flat surface such as a precision 2x4x6 block or my screwless vice, ( at least almost perfectly flat, and my blocks and vice are with 1/10000 flat and parallel) to check a surface over a large area, the level will always repeat itself, and it does rest on that high corner a bit.

And then I found that I could use the level for another purpose because of knowing the condition of the corners. On my mill bed, I was able to find the high and low spots. Not that It matters that my mill bed is not perfect, but maybe if I had a granite surface plate I could use this concept to calibrate it, or other similar machine or test bed surface.

RH

 

[illillill]

My day job is as a metrologist, so I have calibrated many precision levels, like the Starrett #199. When I calibrate these levels at work we need to make sure that the temperature hasn't changed more than 2 degrees in the past 8 hours & that the level has been in the same environment for that 8 hours. We try for 68F (20C). The first check is for flatness. This is the hardest part of the calibration & requires some skill & practice. But for you guys at home long as it doesn't rock move when you push on any one corner, & then you are probably flat enough. Yes the levels are made slightly concave & you shouldn't use them on anything that is shorter than the level.

Clean the level & the surface plate, checking the level for any burrs or other damage. Level the surface plate (using the level you are calibrating) & let the level sit for a few minutes, re-check level & readjust as needed. Then rotate the level end for end putting back up against your reference point. I use two 2x6 granite parallel bars with 1 perpendicular to the other, & held in place to the surface plate with modeling clay, to maintain a reference point. A few minutes later after the level settles it should indicate the same level reading. If not double check your first reading, rechecking to ensure that everything is clean before adjusting the level. Screws & jam nuts type adjustments are very touchy, & it may take some time to get it spot on, the only to find that when you tighten down the jam nuts you throw the level out of whack again. A light touch is needed & always allow time to let it settle. Sometime I'm not even be sure I moved it at all when adjusting it, that how light of a touch you need, unless it's way out already, probably from moving the adjustment to much in the first place.

At work we also check the level sensitivity to ensure that each division on the level equals a certain amount of angle. With the Starrett 199 one division equals 1/2 thousandth (0.0005) of an inch per foot. When I check the 199 it's typically about 8 arc seconds per division. So figure 4 arc seconds if you are only off half a division when you use it. To calibrate the sensitivity we use a Brunson 470 small angle generator. It's basically a granite sine plate with a big micrometer head to adjust the angle down to 0.1 arc seconds per division. I move the bubble exactly 1 division then record the reading, move it another record, etc... then at the end average the readings. The factory usually specs levels as a certain amount per distance, such as .0005" per 12".

It usually comes down to the person eyeballing the bubble to determine the sensitivity. The biggest error we encounter is the person looking at the level isn't looking at the bubble dead on the same way, using the same eye, each time they make a measurement.

Hope this was helpful.