# 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

Harvey Melvin Richards said:


> 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

RockwellHardness said:


> 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.

RockwellHardness said:


> 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

cazclocker said:


> 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

cazclocker said:


> ...........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.


----------



## astjp2

I should have you check my level, its pretty old but I think its in good shape.  Tim


----------



## cazclocker

illillill said:


> 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.



illillill, thanks for your input. It's been extremely enlightening to me to learn that the bottom surfaces of these fine levels are just slightly concave. I have a Starrett 98-6 which is longer than the width of my milling machine table, so I see that my 98-6 can be applied to the table lengthwise, but not widthwise. Luckily, I just acquired an extremely sensitive Chinese-made level that was made for Chinese army's artillery - and I got it for just $12.00. It's only 4" long so I use it for leveling my table's width. Also, I can understand just why it would be ideal to calibrate a level under steady temperatures - I wish it was possible in my home shop, but unfortunately it just isn't! I live in northern Arizona, so we have some pretty wild temperature swings. I guess we homeshop type guys just have to do the best we can do with what we have.


----------



## illillill

I don't think that the temperature differential is that big of a deal for the kind of work that most people will do in the shop & probably could be ignored for the all but the most exacting work.  When you calibrate your level take your level & a surface plate in the house, & leave the heat set at the same temperature all night.  The next day everything should be at the same temperature, & you will be fine.  Even the concavity of the base of the level might not matter if you don't need that kind of accuracy.  The concavity on the Starrett 199 is something like < .00005" iirc, so it's not much.  So using a precision level on a part shorter than the level will still be much more accurate than eyeballing it or using a framing level.  You could probably calculate a worst case using some trigonometry, & it would still be only a few arc seconds difference. Always make sure to look straight down at your bubble using your good eye, to minimize any parallax & line up the bubble on the lines the same every time.  All of the precision levels I have used have a surface that is not perfectly flat, but even a brand new framing level is awful in comparison. But make sure the level & what your putting it on is clean & free of burrs that could scratch the surface.

I only mentioned the temperature thing because it's part of every  calibration we do at work.  We wear cotton gloves to prevent the heat  from our hands to cause the material to expand possibly affecting our  measurements.  One thing I teach the guys at work is heat causes stuff  to grow, & cold causes it to shrink.  Think about your anatomy, to  remember this.  A cold swimming pool causes shrinkage & a hot girl can cause a swelling in your pants.   You'll never forget it if you think of it like that.

To get a little deeper into it you can find out the coefficient of linear expansion, for the material you have & see that a few degree temperature change affects it a little, but not that much. It's probably not enough to measure, unless it's a big temperature change from 68ºF (20ºC), or you have some really expensive & accurate equipment.  The Coefficient of Linear Expansion for a given type of steel is something like .000012" per degree C away from nominal of 68ºF (20ºC).  So say it's freezing in you shop, @ 32ºF (0ºC) that's only .00024" that the item has shrunk (20ºC temperature change x .000012 =.00024".  It's unlikely that anyone would try to perform any precision work at that temperature.  Also if your measuring instruments have also been in that freezing environment they would also have contracted or shrunk a bit depending on the material, so the true difference in size would be even harder to measure.

Not to get too off topic, but in case all this talk about temperature has caused some confusion let me state that a temperature change can cause a size change that will be noticeable to most people. Like when machining a part to a specific size, because the temperature difference is much greater when that part you are machining gets hot.  Say the part got hot during machining & is now 212ºF (100ºC).  That's 144ºF (80ºC) difference from the nominal of 68ºF (20ºC).  That much of a temperature swing will cause a noticeable affect on you measurements.  Again using steel for our example; .000012" x 80ºC = .00096"  Almost .001" is a measurable difference in size & could cause a part to not fit.  This would be more measurable than the previous example because your micrometer or other measuring instrument would not be at the same temperature as the part you are measuring.

That explanation is over simplified of course, the part size, & material type/quality will affect it as will other feature such as a hole, & probably a bunch other things.

 I'm not an engineer, but I think my simplified math is correct.


----------



## cazclocker

illillill, thank you for the elucidation. You're my kind of engineer!
...Doug


----------



## coolidge

I used a machinist level to level my new lathe last week, turns out I had leveled it with my Home Depot level to within .002 of the machinist level end to end


----------



## tripletap3

RockwellHardness said:


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



Thank you! Thank you! Thank you x100! I have a pristine older Starrett 98-8 that I bought off Ebay a few years ago. This thing drove me bonkers while trying to level my lathe until I figured out it had a bow in the middle. I thought it was warped and just threw it in the tool box and have been meaning to mill the bottom flat to try and save it I just haven't got around to it yet.


----------



## cazclocker

*Re: Using &amp; trusting a brand-new Starrett 98-6 machinist's level*



coolidge said:


> I used a machinist level to level my new lathe last week, turns out I had leveled it with my Home Depot level to within .002 of the machinist level end to end



Dang! Yer good! Way ta go...!!! :tiphat:

- - - Updated - - -



tripletap3 said:


> Thank you! Thank you! Thank you x100! I have a pristine older Starrett 98-8 that I bought off Ebay a few years ago. This thing drove me bonkers while trying to level my lathe until I figured out it had a bow in the middle. I thought it was warped and just threw it in the tool box and have been meaning to mill the bottom flat to try and save it I just haven't got around to it yet.



Yeah, I know what you mean...that was a revelation to me too. I wouldn't have figured they were supposed to have a bow in them.


----------

