Framing Squares

Date 09-24-2003 19:26

John,

Have you checked out a Master Precision Square? Starrett makes them with squareness accuracy of .0001". Blade length ranges from about 2" to 36" and beam length ranges from 2" to 20". These have no graduations. The model series is Starrett No. 20. But get your checkbook out!

In the old days, squares would be proven by the 3,4,5; 6,8,10; 12,16,20 method.

Hope this helps

By jwright650 (*****)

Date 09-24-2003 19:47

Thanks for your reply,
I used to use the old 3,4,5 (& multiples) rule as well, but found it easy to align the square being checked with one known to be true. I just want to use an "industry standard" to avoid any confrontations with the auditors over our methods of madness. I've checked our tape lines against a calibrated Lufkin with the proper pull tension handle, but the squares I was in doubt as to the method most accepted. Cost is always a concern, but I'd rather have the right equipment than to argue with an auditor over the method. I'll give Starrett a call and see what they have to offer. Thanks for the suggestion, I had let the Starrett Company completely slip my mind as a resource to use.
John Wright

By JTMcC

Date 09-24-2003 20:33

Can you ask the auditors what they will and won't accept? Do they have any written standard?

JTMcC.

By jwright650 (*****)

Date 09-25-2003 12:51

JTMcC,
I may give Quality Managment a call and ask what they would recommend or what they would accept as "good enough" for the type work we do. They ultimately will be the one to say yea or ney come audit time.
John Wright

By CHGuilford (****)

Date 09-24-2003 21:38

If you have a precision straight edge about 4' long, you can lay that on a board or plate. Draw a fine line 90 degrees to the straight edge with the square. Then turn the square over the other direction and see if the line is parallel to the square. It should be very close, but if not, your square is out by 1/2 the difference of your lines. You could do this informally on any surface that you know is flat and true and long enough but a certified straight edge is not terribly expensive for your AISC certification purposes.

Chet Guilford

By CHGuilford (****)

Date 09-24-2003 23:11

Actually John, you don't even have to have a certified straight edge to satisfy the requirements. You can use something like and extruded aluminum flat bar, and use the same method as I mentioned for checking the square. Just draw a fine line and flip the bar over so the same side is compared from a different direction. As long as you can incorporate geometric principles into your procedure nothing more needs to be done (I think.) (I just returned from "boot camp" too)
Chet Guilford

By jwright650 (*****)

Date 09-25-2003 11:23

Hi CHG,
How did your "Boot Camp" go? Did it meet your expectations? The one I attended was taught by Anna Petroski and Terry Logan. Mine was cut short by the sudden death of our Company's founder and we missed the last day of the seminar. I enjoyed it and wished for better circumstances at that time, it was hard to concentrate on the subject at hand with all that going on back here at the shop. I had worked for that guy for 19 years and it was a great loss to us. Anyway, I hope you learned something so I can bounce more questions off of you before I finalize our "new" manual.
The way we had been doing this may have been OK, but I really didn't know if there was a "Standard" that the industry uses that was widely acceptable or not.
John Wright

By TimGary (****)

Date 09-25-2003 12:49

Hi guys,
The procedure I wrote for verifying accuracy of our squares and tape measures consists of checking the tools against a machined angle plate. (see McMaster Carr item # 23525A69)
This angle plate is machined square and is 6" tall by 6" wide (dimensions are within .002" in 6")
Tools are checked against this reference on a daily basis and documented using a check off sheet.
Do you guys think this would be sufficient, or is it over-kill?
Thanks,
Tim

By jwright650 (*****)

Date 09-25-2003 13:00

Hi Tim,
I was wondering if I must have a square that came with cert. papers to check these squares with. My tape line came with papers and gives the accuracy at several tensions and temps. Maybe I'm making mountain out of a mole hill, I don't know. I just want to avoid problems in the audit, if possible. I check our squares annually and rarely find one out by very much. If I find one that is out, I use a center punch and punch the inside or outside of the intersection of the beam and blade, depending whether it needs to be opened up or closed, to match my "known true" square. I've not found anything in the ASTM's book of standards, but I could have overlooked it. When you have to put your procedures on paper, it makes you look at them too hard.
John Wright

By jwright650 (*****)

Date 09-25-2003 13:10

Tim,
What page is that item on in their catalog? I was looking at the Precision Series 20 squares on page 2028.
John Wright
PS. thirdeye is right, big $'s for something with papers

By TimGary (****)

Date 09-25-2003 14:04

Hi John,
McMaster Carr page #2087 Item #23525A69.
This item does not come with a cert paper, but does have a riveted on serial number for traceability. I was not able to find one with a cert.
I was hoping the the catalog information would be enough to appease the auditor. If not, I guess I could send it out to a calibration lab to get "certified".
I thought the old code said that tapes had to be checked daily and squares weekly. Has this changed with the new standard?
Maybe I was just paranoid that an auditor would find a square out of square and would want us to go back and check everything that had been fit up with it since the last calibration check.

Thanks,
Tim

By CHGuilford (****)

Date 09-25-2003 14:43

Hi John and Tim,
The boot camp went very well. Terry and Anna are quite a comedy team aren't they? They did a great job, I thought. I had anticipated much of what they covered but i did learn a lot. Boy have we got some work ahead of us!

To be honest, Tim, you might be overkilling it. I don't think all that is necessary but then again it isn't for me to say. Maybe you could send an email to QMC for an auditor's opinion?

Something covered on the last day might help both of you out. As far a your measuring equipment being calibrated, it was explained that this is required only for equipment used in final inspections. It is nice to have every tape or square in the building calibrated, but it is not required.

You don't have to have machine shop levels of precision. Many calibrated tapes can be purchased without the printout of how far off each inch mark was. Instead they can be verified not to exceed an error of 1/16", or 1/32", or whatever you need. Tapes used in structural steel production only need 1/32" to 3/16" accuracy depending on overall length, so why pay for precision finer that that?

You probably already know this, you can check your own tapes against a certified instrument, just assign them some kind of ID and log it. Your master calibrated tapes and other instruments can be sent out for checking at whatever interval YOU decide to write your procedure for. If your masters don't see heavy use they can go for years, despite what Starret, or whoever says. Just define your criteria and methodology.

Keep in mind that you can use known scientific facts for your calibration checking or other standards. For example, thermometer accuracy could be verified with boiling water (allow corrections for altitude). Paint thickness shims can be checked with a micrometer that was verified with a calibrated "joe block". Calibrate the "joe block" only, and it also doesn't get much wear and tear.
The 3-4-5 triangle standard can verify squareness as was mentioned above, or you can try the straight edge method as I highlighted. Any method that reliably demonstrates the accuracy is within YOUR written procedure will work.

My goal is to keep our procedures as simple as possible. I think the most important aspect of all this is to document what was checked and how.

Chet Guilford

By jwright650 (*****)

Date 09-25-2003 13:19

For those of you that are involved with the AISC certification I am referring to the Element #14 from the new Standard.
John Wright

By thcqci

Date 09-25-2003 14:46

I managed a calibration lab for 10+ years. In our lab we had a granite certified flat surface within 0.000005" in 3'. We had a certified granite square within 0.00001" in 2'. Electronic equipment with resolution of 0.000001". VERY expensive toys. I've verified precision machinist squares and cylindrical squares. Can be tricky at those levels of precision. What you need is no where that precise.

3-4-5 or the straight edge/draw a line/flip it over methods should satisfy any auditor for the level of work we do in the steel fabrication industry. Comparing against a known square off of a straight edge (flat surface)also works. Also, if you have a straight edge (flat surface) and 3 squares, you can intercompare the squares (a-b, b-c, a-c) and if they all are square to each other, they are all square. We drilled holes in our "master" steel framing square first and then compared it. Then we put it on a board on a wall in the shop where anyone can check their squares any time.

Tapes with temperature and tensions incorporated into the verification certificate should be valid. Tapes should be verified at a known temperature. The coefficient of expansion should be stated on your certificate so you can calculate actual length at ambient conditions other than laboratory conditions (68°F ±1°F, >50% RH). I am sure your shop is not that temperature very often. Assuming your tape is steel, it expands at the rate of 0.000036"/in./°F. In other words, your tape expands almost 0.001"/in. if it was verified at 68°F and you use it at 95°F in your shop. That may not seem much, but at 100' (1200"), that calculates to about 1 1/8"!!! A NOTE OF CAUTION, THIS IS FOR YOUR OWN INFORMATION. DO NOT TELL THE AUDITOR ANY OF THIS. THEY WILL BE ARMED WITH A NEW THING FOR US TO MONITOR. IT WILL JUST MAKE IT HARDER ON ALL OF US!!!

Keep your tape aside as the standard only (mine labeled not for shop use!!!) and then just compare your working tapes to it as often as you feel comfortable comparing. Of course AISC wants you to set a time period when you WILL verify tapes. We verify and document verifications only on tapes and squares used for QC checks. With careful observation, your QC personnel and their instruments should be able to identify working tapes and squares when they are not correct. Another note, your standard tape certificate should give you a formula to use when your tape is not fully supported on a surface. The sag in 1 or multiple catenary suspension(s) can be calculated with the formula.

Gotta get back to work.

Plan to attend the boot camp in Orlando in November. Hope to learn as much there as I have been hearing others talk about. Looking forward to it.

By pipewelder_1999 (****)

Date 09-25-2003 17:10

That amount of expansion seems pretty great. I had thought that the coefficient of thermal expansion was on the order of 6.6x10^-5 inches per in deg f increase. I found a chart by weldbend that indicates a 30 degree rise to equal .23 inches in growth over 100 ft.

Another thing to consider is that if you are building steel products, they have usually expanded with the temp increase.

The 3/4/5 or any variation of the pythagoreom thereom (Spelling may be off) will always work regardless of how much your tape has expanded provided the temperature has not varied significantly while checking the various legs of the triangle.

On large items tape tension may be a factor using this method but I think that is more related to pulling the sag out of the tape and NOT stretching the tape.

Have a nice day

Gerald Austin

By jwright650 (*****)

Date 09-25-2003 18:52

Hi Gerald,
I have a book (Manual for Steel Construction) that gives the coefficient for expansion for 100 degrees F as .00065, in other words if a beam is exactly 40 feet long at 60F, and the temp rose 30F, the new length would be 40.0078feet long at 90F. [.00065 x 30F x 40ft divided by 100 = 0.0078ft] or 100' beam w/ a 30F rise would be .0195ft of growth.
Your formula may work out to be about the same thing, I didn't try it.
I guess you would have to factor the coeffient in if the tape line was in a 90F office and the steel to be measured was outside in 60F or visa versa. or maybe the building was fab'd in our 20F shop in Feb. and erected in July at 100F. I have been on jobs where the steel in the morning had camber in the beams going the wrong way and the sun heat it up by 3:00pm and change the direction of the camber. Rails on train tracks suffer from the heat as well, making them buckle and then at night cool off and loosen the spikes. I thought maybe his decimal might have been typed in the wrong place, it did seem like alot (1200" at 100'). The tape (according to the certs with the tape) has to be supported for the entire length and tensioned to 10# at 68F. I use 68F divided by actual ambient F x 10 to achieve the correct tension if ambient is not 68F. I rigged up a way to clamp the tape to the floor at the free end (out beyond 100') and hook my pull handle to the 0 end and tighten a bolt that is welded to a column base plate right at the floor until the correct tension is read on the handle for the tempF. It used to take two people to check tape lines and now I can handle it by myself.
John Wright

By jwright650 (*****)

Date 09-25-2003 19:06

Yep, your formula worked out the same....0195ft or .23in (1/4"roughly)
John Wright
BTW, if you had a 40' beam fixed at both ends and the tempF rose 30F the change in unit stress would be 5655 lbs/sq.in.[29,000,000(mild steel is 29ksi) x .00065 x 30F divided by 100 = 5655lbs/sq.in.]

By thcqci

Date 09-25-2003 20:36

See, there you go. I got my one mistake for this year out of my system. That is why you are supposed to look it up instead of accessing the old hard drive. I knew 1 1/8" seemed awful large, but thought I had rechecked my math and guess I made the same mistake twice. Don't have my metrology reference books at my welding office so can not look up the number I really wanted. Probably did have the decimal point off in my CoE value. I will go get my Manual of Steel Construction out and start learning again. Will check closer next time so I don't embarrass myself so badly also. Sorry all.

By CHGuilford (****)

Date 09-25-2003 20:51

You did very well to have your annual mistake show up so late in the year. I think mine was used up by Jan. 1 @ 12:01 and now I'm credited into the next millenium.
Chet

By jwright650 (*****)

Date 09-25-2003 22:18

I did like Chet and got mine out of the way early in the year as well. Just wish I could limit it to just one a year, but I'll try harder next year.

thcqci,
Don't be so hard on yourself, we are all entitled to a few mis-quotes from memory every now and then. :)

John Wright

Funny how heat, or the lack of it, effects something hard like steel.

By thirdeye (***)

Date 09-25-2003 23:24

Once again science comes to the rescue. I’ve always gotten a chuckle about the “Brass Monkey” story and the fact that the different coefficients of thermal expansion between the brass tray and the iron cannonballs was responsible for that famous nautical expression. But it sounds like the numbers don’t lie. Anyway, it’s a great story…..And a great discussion on this topic.

By jwright650 (*****)

Date 09-26-2003 00:46

thcqci,
You mentioned you bet our shop isn't 68F very often, I'm here to to tell you that it is 68F "at least" twice a year, once in the spring and once in the fall. :)
John Wright

By ssbn727 (*****)

Date 09-26-2003 02:41

Hello Thcqci!!!
Interesting thread!!! Hi JW and CHG!!!
Thcqci, I noticed that you mentioned you once managed a calibration lab... I had the opportunity once (for only a year) to calibrate and resurface (only if necessary) those Lab grade (within millionths of an inch in overall flatness!) granite surface plates you mentioned... I'll tell you, that was one hell of a back-breaking job!!!
I had a great time though doing that type of work until my woman decided that it was more important to spend more time at home than to galavant up and down the east coast for most of each month...
Of course as the newbie, I was given some of the jobs that required more resurfacing than the more senior techs but, I really liked the work so, I really did'nt mind!!! My favorite granite was the pink and Blue-gray plates because, they did'nt wear out as much so if I had to resurface the plate, the job did'nt take so long with the exception of those custom size plates I always found in the inspection labs used by some military contractors... Those black "granite" plates were always being used so much that they constantly required resurfacing (breathed in too much granite dust, and 5 to 30 micron diamond powder!) but, since they were cheaper, I guess that's why most customers had them, besides most customers did'nt have to meet lab grade specs., anyway so, that was probably another factor also... What I loved most about that job was using the laser autocollimator to plot eight planes when inspecting the surface... Everybody in a shop would come over, and ask all kinds of questions about what I was doing, and that gave me the excuse to take a break now and then (enhancing customer relations)... Anywho, I guess I got a little carried away, and off the subject a bit but, hey-it's been awhile!!! I still love welding and everything related to it so, I do'nt think I'll be doing any of that work again...
That guy Pythagorus came up with some nifty theorum!!!
My students always ask why is it so important for them to know the Pythagorean Theorum and, here's another example I can use also to explain to them besides all of the other examples I use!!!
Thanks for a very informative and nostalgic thread gentlemen, and I hope I did'nt stray off the topic too much...

Respectfully,

SSBN727 Run Silent... Run Deep!!!

By jwright650 (*****)

Date 09-27-2003 12:28

To anyone interested in a calibrated Starrett Series 20 24" precision square w/ papers, they run about 795 buckaroos and another 90 for the case. I checked with a local supplier here in town and this was his catalog price, so you might could work a deal and get a few bucks knocked off of that price tag.
I think I'll pass and write my own calibration procedure and check our final inspection squares against one that I've proven true. After all "most" structural steel is fit within a sixteenth of an inch which is not all that tight of a tolerance compared to other trades.
Thanks to all for their input and ideas,
John Wright

By TimGary (****)

Date 09-27-2003 14:32

Thanks for bringing up the topic John!
Tim

By Wildturkey (**)

Date 10-16-2003 15:21

John,
I have not seen anyone post what to do if the square is out. When i worked in the shop if the square needed to be opened up I would take a punch and start punching on a 45 degree angle where the two legs meet to open it up. If it needed to come in, i just clamped down on it a little. I prefer the straight edge method for checking squareness because i believe it is more accurate than measuring with the tape.

By jwright650 (*****)

Date 10-16-2003 16:01

That's the method of opening and closing squares that I use too. See my post of Sept 25 06:00. Never knew if that was the (w)right way or if it was the correct way to straighten out a square that was not truely square.
John Wright