can anyone tell me how to square up a combination square. mine is alittle off.
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Replies
Buy a Starrett!
Napie
I have 5 Starrett squares in my toolbox. 1 4" double, 1 6"double, 1 9" combination (no longer made) and 2 12" combination. All of these were bought new. The only one I did not have to fettle to make square was the 9". All the rest got the treatment that roc explanes. Also have a Brown and Sharp 6" combination that was dead on right out of the box. I still prefer Starrett tools though.
Rich
ps. You need to go real easy with the filing as a little makes a big difference. I prefer 600grit wet-dry paper.
The Professional Termite
Edited 12/6/2008 9:57 am ET by trialnut
I have a quite number of them myself and NONE of them required any work to true them. For the price they get for them if one was not correct I'd send it back. Like L-N planes Starrett tools are not kits like a Stanley or Record would be. The premium price equals a tool good to go out of the box.
Napie
It may also be a matter of what degree of accuracy a person is after. Had one of them not been a 64th off I probably would not have checked the rest. One bad apple prompted me to put them all on the CMM and fiddle with them untill they were all within a thou. But I have a tendency to get obsesive sometimes.<g> These are the tools I used daily as a patternmaker so I wanted to know I could grab any of them and get the same results.
I have a couple of cheapos I use with welding projects that I know are out nearly a 32nd but use them anyway without taking the time to adjust them. There close enough for what I use them for.
RichThe Professional Termite
I would like to thank you all for your advice. Have a Marry Christmas.
Square square,
It is possible and customary procedure (or as Pooh says "Crustimony proseed cake"), to tune the combination square. There are little "lands" inside the square's body that you can touch a bit with a file and bring the ruler back into square with the casting. Make sure the ruler is straight first.
Slide the ruler out of the casting and look in the bottom of the slot. You will see a raised area down the middle of the bottom of the slot. These get worn from use and one can file the one on the opposite side to compensate . I forget where I read this but was probably in one of these magazines:
http://www.homeshopmachinist.net/
I really like Starrett tools and recommend them but for the most precise work and for some of their tools to work smoothly ( clamp and release the ruler on my 150mm for example) I find I need to tune them a bit. Hard to find perfection on a factory produced tool for under hundreds of dollars.
Worth getting their little book The Starrett Story.
As I always say a tool is a kit. Take it home and make something usefull to you out of it.
roc
No matter how much you spend for a device, you still don't know if it is square. I ran a large tool and die shop and we purchased a number of Brown & Sharp and Starrett devices and some of them were not "square". We had "standards" that our quality department periodically had validated by an outside service that we then used to verify the worker's tools.
One day, one of our designers brought in two plastic drawing triangles he had purchased at a local art supply store. He had them compared to our standards and they were as accurate as the tools could measure. The triangle cost a couple of dollars each. They would certainly serve very well as the "standard" in any woodworking shop to validate and/or adjust other devices.
An excellent way to validate the accuracy of the plastic squares is to use two squares on a flat surface. Get a $10-12 plastic 30-60-90 drafting square. To prove it's exactly 90°, take two to a glass counter, put the shorter legs on the counter and face the longer legs away from each other and butt them together (like a teepee). If the legs exactly butt, you can assume you have two perfect 90° angles. Using one of the plastic squares, do the same thing using your other tools. Any that mismatch, means that the tool is not square. You can also take the plastic square with you whenever you go to purchase another tool. Keep your "standard" somewhere where it doesn't get banged up.
Finally, remember that the wood you are using will expand and contract a couple of thousands from one day to the other. Does't pay to get too uptight.
While we are at it, I also only purchase the cheapest of adjustable squares. I square them with a drafting triangle and an auger file until they are square across 10". And I own a Bridge City square that isn't that accurate. Stainless steel machinist's squares are only square until you drop them. I have had several over the years and each has found a away to drop to the floor.
The key is to NEVER use your best square on for day to day measuring. Use it only as a reference tool to verify your other day to day tools.
In a comparison test reported in Fine Woodworking Magazine a couple of years ago, the Stanley 46-123 square was awarded the best value. It's much less expensive than a Starrett and just as accurate.
Howie,
You are so right about the Stanley 46-123. Great $$ value.
-Jerry
howie,Using the method you describe to test the "squareness" of 2 squares is the correct way to do it, but is only 2/3 of the machine shop procedure to check for accuracy. If the two "mate up" exactly there are actually 3 possible conclusions:1. They are both perfectly square.2. Square A is less than 90 and square B is greater than 90 (by the same amount).3. Square A is greater than 90 and square B is less than 90 (by the same amount).Each possibility is equally probable.There is no way to resolve the uncertainty without using a third test square. If all three instruments perfectly "mate," then all three are perfectly square. There is NO other possibility, they ALL must be exactly 90 degrees for that to happen.There is no combination of any being greater, equal to or less than 90 that will work. Two of them may line up, but one of them will not match the third.So, with three instruments lining up, one knows that each is an absolute reference tool. It's not necessary to own all three, just to have access to them to do the test.The first step, however, before even trying to line up one against another is to use each as a reference against ITSELF, otherwise one is just chasing one's tail. The base of the square is held to a straight edge or flat surface and a line is scribed against the leg. The square is flipped over so the base is still against the same reference and the leg is brought to the line. One of 3 conditions will result. It will either line up perfectly, or will meet first at the base or meet first at the end.If, and only if, the leg lines up perfectly with the line, the square is exactly 90 degrees (There is always a degree of error to any measuring method. This method "magnifies" the possible out-of-square condition of the test square by a factor of 2 and results in a degree of accuracy twice any that could be encountered in normal use.)The same process can be used to test for straightness of a straight edge. If one has a quantity of straight edges from which to choose, it's possible, by finding 3 that perfectly match, to be absolutely sure of getting a reference tool.I have bought (very) inexpensive straight edges and squares from Big Box stores, knowing I had an absolutely accurate tool when I left the store. It's not unusual for there to be a dozen or more from which to choose. The possibility that 3 out of that number is accurate is high enough. A few minutes spent finding three that "pass the test" is all that's needed. Of course, none might pass, in which case I know not to waste my money, or that I'll need to do some fine tuning with the "self reference" method later.Rich
"can anyone tell me how to square up a combination square...." Trade it in for a drafting square. Unless you can afford a Starrett.
Look for a brown and sharpe on ebay
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