Machinist squares

[Johnny chaos]

I recently bought a set of cheap machinist squares from Amazon, I understand that “cheap” and “machinist” are polar opposites. Three of the four appear to be square but the fourth (largest) of the set is almost ridiculous. Any recommendations on a set that is reasonably priced with relative value? I am not planning on using these for anything overly critical at the moment, just set up for welding, woodworking etc. I would love to see a metal lathe or mill in my future so if it’s a buy once, cry once situation I understand. I do a lot of automotive work and have purchased many snap-on tools that at the time made me question my sanity. What say you? I appreciate any input given.

 

[cvairwerks]

You would be better off starting with a high quality combination square, with various length blades and a couple of Fireball Tool welding squares instead of machinist precision squares. I've got Starrett squares in 4" and 6" heads with 6", 12" and 18" blades in 16R graduations. I also have a Mitutoyo set with the square, v head and the protractor. The machinist squares I have are relegated to being used for precision layout work, for the mill.

For welding, I've got several of Jason's squares, but haven't had a chance to use them yet. Everyone that I know of that has used them, loves them.

Starrett heads and blades can be found on evilbay relatively inexpensive, but be sure to look close at the blade photos for wear and damage.

 

[Dave455]

First off - I can‘t think of any occasion where I have ever needed a “set” of engineers squares.

Sure, I’ve picked up a couple over the years, but I could probably do 90% of everything I have ever done with just a 3” or 4”.

Some companies are desperate to sell you “sets” but that’s just a way to get more money out you per purchase.

So just buy what you need, but buy decent quality.

Secondly, understand the different “grades”. In the U.K. we have “Grade A” (sometimes called “inspection grade“) and “Grade B” (workshop grade). The U.S. uses different terms, but the principle is the same.

It’s easy to think “I want the best” but even a grade B will be far more accurate than most folks need, and a grade A will probably be 5 times the price.

So, if you want a 4 inch square, grade B, have a look at what’s available from the known makers. I’m talking Starrett, Mitutoyo, Moore and Wright etc. Anything from one of these makers should be fine. Avoid like the plague any shite with an unknown (probably made up) makers name or other dubious provenance.

 

[shawhite]

PEC, IGaging on the cheap side. Starrett if you have money to burn.

 

[Johnny chaos]

Thanks for the replies, I will look into the high quality combination square, that seems to make the most sense for my needs. I have a few combination squares I have acquired over the years but never really considered there may be a higher quality one out there? I assumed the design less accurate but that is using home center or used units as a reference.

 

[PBCampbell]

I'll second that a combination square setup will be way more useful. Brown & sharp, Mitutoyo will probably be less expensive than Starrett on the secondary market. PEC blemished used to be sold through Harry Epstein's and have a good reputation here.

 

[neophyte]

As has been mentioned, Combination squares tend to give you a better return on your money, and might be better to start out with.
Starrett is considered the standard by which combination squares are evaluated.
Starrett manufactures their square in both cast iron heads, and forged steel heads.
Forged steel is the high end option, but both will work.
The head material type on the Starretts can be determined by the finish.
Cast iron heads use a crinkle finish.
Forged steel heads use a shiny black enameled finish.
Starrett manufactures the square in a 4”, 6”, 12”, and 24”, sizes.
The “size” is really based on the nominal rule length designed to go with the square.
The rules for the square have markings on both sides, that are reversible.
Metric versions of the rules use different blade lengths to correspond with a standard metric length.
In some cases, such as the “ 12” rules” there are longer blades you can get, such as 24”, although the 24” “jumbo” combination square, is a different model, with a larger head.
The rules are, or were, available in mat chrome, as well as bare steel.
Most people prefer the mat chrome.

There are also “double squares” which function like a combination square, but with have a straight head that reads 90 degrees on both sides.
These are available in the 4” and 6” sizes above, like the Starrett combination squares, and in a 2-1/2” size, for more precise work.

While Starett is the “gold” standard, PEC tools, also in the USA, makes a decent combination square, and likely supplied other major metrology companies, like Mitutoyo and Browne & Sharpe with combination squares.
PEC also manufactures double squares.
Epstein tools had some deals on “seconds” on the PEC squares if you need to save some money.
Most combination squares, at least the quality ones, are usually somewhat interchangeable parts wise for the heads and rules, in similar sizes, so you can buy a square, and update parts later, adding longer rules, or metric rules, etc.

I might recommend a double square as well as a combination square.

Another advantage to combination squares, is that the fit of the rule to the head can be adjusted if it goes out of accuracy.
Something that is way harder on a fixed square.

For fixed machinist squares, I usually prefer the European designs that are made from a single block of steel.
A small high precision “00” grade one can be used to check combination squares for accuracy.

 

[dutchgray]

Those two piece precision squares, no matter how good quality you buy, tend to go out of square if they get dropped, the one piece type of precision square tend to break if dropped.
Unless you're doing precision work, you're better off with combination squares or roofing speed squares.

 

[Dave455]

Thanks for the replies, I will look into the high quality combination square, that seems to make the most sense for my needs. I have a few combination squares I have acquired over the years but never really considered there may be a higher quality one out there? I assumed the design less accurate but that is using home center or used units as a reference.

The good quality ones are very accurate indeed.

Pretty much a standard marking out tool in some shops.

Starrett offer a small one. It doesn’t accept all the different heads that are available for the bigger squares, but I think they are a popular tool, and surprisingly reasonably priced.


Maybe keep an eye open for used examples too?

 

[AEAdam]

One of my favorite subjects!

My problem was I bought a Chinese mill and Chinese or second hand tooling and had trouble producing accuracy.

So it was back to basics. Flat, straight, and square.

Here’s what you need to know: when you are setting up machines, or checking measuring equipment, especially second stuff, it’s really REALLY helpful to have a master square. What you want is a Starrett #20, made in Athol Mass. Starrett makes #20 squares in China and sells them on Amazon. DONT BUY THOSE. A real USA #20 is square to .0001“/6”.

Step 1. Go look at Starretts website and see what a 6” #20 costs new.

Step 2 Go surf eBay for 6 months and buy a #20 you believe looks like a US made one ( should say made in Athol on it). Don’t buy a shiny one. Buffers can wreck the accuracy of these. A few rust pits are acceptable. Be prepared to pay more than you think you should. But rest assured. Pros buy these, and generally treat them well.

Step 3 buy at least 2 so you can inspect one against the other.

Step 4, buy and learn to use a machinists hard Arkansas hone and carefully deburr your used squares.

Step 5, once cleaned and de-burred, slather in Vaseline, wrap in vapor paper, place in a zip lock bag and put them away!

Step 6 buy whatever square you want to use for woodworking. I like the double squares @neophyte mentioned above. I like the 4” Starrett best. Combination squares are okay, but not as helpful in my shop. I like the little 6” combo tho.

Step 7 check whatever you buy against that master square. You can get lucky with used or China and you will always know you didnt get ripped off because you have the S#20

 

[AEAdam]

Just looked this up for you guys:

Starrett #20 .0001”/6”
PEC .0005-6/6”

Starrett combos and doubles: Starrett doesn’t provide squareness specs for their combos. They have to be clean, adjusted correctly and they are subject to wear. My experience with them is they are more than good enough for woodworking, but I’m not sure I’d set up a precision machine with one.

Starrett combo blades are thicker than others’. This means you can buy a Starrett 12” combo and put 18” or 24” PEC blades in it, but you can’t put Starrett combo blades (rules) in others’ heads.

 

[larry_g]

I recently bought a set of cheap machinist squares from Amazon, I understand that “cheap” and “machinist” are polar opposites. Three of the four appear to be square but the fourth (largest) of the set is almost ridiculous. Any recommendations on a set that is reasonably priced with relative value? I am not planning on using these for anything overly critical at the moment, just set up for welding, woodworking etc. I would love to see a metal lathe or mill in my future so if it’s a buy once, cry once situation I understand. I do a lot of automotive work and have purchased many snap-on tools that at the time made me question my sanity. What say you? I appreciate any input given.

You may have a third option here. Consider this an opportunity to take a marginal tool and make it a good one. Figure out just what is wrong and then go about fixing it. Search out how squares are derived with the 3 square method and then go about testing yours and improving what you have. If you can't get them to work you will get educated in what it takes and be able to confirm the better tools you may buy in the future.

lg
no neat sig line

 

[slowtwitch73]

I have a Starrett combo square that is really a pos.. I would not buy again. Only thing Starrett I have that isn't high quality.

 

[RTM]

I have a few tiny (2 & 3"?) machinist squares that I use for chisel sharpening, getting them squared up in the jig. The combo or double squares are too big to do this easily.

I have a 4" double square from PEC that I like way more than I expected to.

I have 4, 6, 9, 12, 18 , & 24" combo squares, from Starrett, Lufkin, B & S, and a few others that all hold square enough for woodworking. I tossed a cheap Stanley that was out, rule was too crappy to keep.

 

[AEAdam]

I have a few tiny (2 & 3"?) machinist squares that I use for chisel sharpening, getting them squared up in the jig. The combo or double squares are too big to do this easily.

I have a 4" double square from PEC that I like way more than I expected to.

I have 4, 6, 9, 12, 18 , & 24" combo squares, from Starrett, Lufkin, B & S, and a few others that all hold square enough for woodworking. I tossed a cheap Stanley that was out, rule was too crappy to keep.

Die makers squares! Very handy little devils.

 

[RTM]

Die makers squares! Very handy little devils.

I have two or three of those too. They come out for the really weird stuff, like changing to the skinny or offset rule to get the setup. Never tried the off square setup.

 

[Fixr]

Used precision machinist's tools are worth squat these days, so instead of automatically buying whatever import **** is cheap on Amazon, or even PEC and similar mid-grade stuff, consider looking for used Starrett, OLD Browne & Sharpe, Mitutoyo, etc. on CL, Marketplace, eBay, and such. The old manual machinists are all dying off, and CNC does not need more than a small fraction of the manual measuring tools that were needed a couple of generations ago. For the purposes described, the simple flip and scribe test for a square should be quite adequate to determine if it's FUBARed. You can get the really sweet classic stuff for pennies on the dollar if you have time to devote to the search.

 

[AEAdam]

Used precision machinist's tools are worth squat these days,….

So true, and kinda sad too. I’ve bought really high quality, well made tools for pennies.

 

[rancherbill]

FIX THEM. It's a good project. Lots of skill building if you try to do it accurately.

 

[Fixr]

So true, and kinda sad too. I’ve bought really high quality, well made tools for pennies.

Yeah. I've got a set of Mitutoyo micrometers that were obviously well used and immaculately cared for by a meticulous person. Always make me feel a bit guilty using them for my decidedly low-precision projects. I am not worthy! (But I do handle them carefully and wipe them down properly before putting them back in their cases.)

 

[Fixr]

FIX THEM. It's a good project. Lots of skill building if you try to do it accurately.

I might argue that in the OP's case, "Lipstick on a Pig" might apply. Just look at that first photo. And not everyone wants to, needs to, or should become an instrument maker.

 

[dscheidt]

I have a few tiny (2 & 3"?) machinist squares that I use for chisel sharpening, getting them squared up in the jig. The combo or double squares are too big to do this easily.

I have a 4" double square from PEC that I like way more than I expected to.

I use a 1-2-3 block to square up chisels before grinding them.

the pec stuff is very nice. I had a four piece combo square, adn a 6" double square. I loved the six inch square, but
then I used a 4" cheapie double square in a class. So I bought the pec one, and use it much more than the 6". I also bought some pec scales (seconds from HJE), so I could keep a center finder and protractor head mounted all the time. I never used them, because it's too mu h work to put them on.

 

[AEAdam]

I use a 1-2-3 block to square up chisels before grinding them.

the pec stuff is very nice. I had a four piece combo square, adn a 6" double square. I loved the six inch square, but
then I used a 4" cheapie double square in a class. So I bought the pec one, and use it much more than the 6". I also bought some pec scales (seconds from HJE), so I could keep a center finder and protractor head mounted all the time. I never used them, because it's too mu h work to put them on.

I bought a Chinese set of 123 blocks. They didn’t measure 1”x2”x3”, but I guess that’s okay…..ish. What I didn’t realize was, while the sides were all perfectly parallel, they weren’t square to each other. Not sure why. So,…trust but verify.

For grinding a chisel or….a few thousandths out of square is imperceptible. But you might need tools better than that for some things. Don’t let these really small numbers throw you.

 

[jar944]

MSc has the spi set for $150.

 

[dutchgray]

I bought a Chinese set of 123 blocks. They didn’t measure 1”x2”x3”, but I guess that’s okay…..ish. What I didn’t realize was, while the sides were all perfectly parallel, they weren’t square to each other. Not sure why. So,…trust but verify.

For grinding a chisel or….a few thousandths out of square is imperceptible. But you might need tools better than that for some things. Don’t let these really small numbers throw you.

25, 50, 75mm by any chance?

I know you have to check all the Chinese stuff, the parallel sets are often only parallel top to bottom.

 

[RTM]

For grinding a chisel or….a few thousandths out of square is imperceptible. But you might need tools better than that for some things. Don’t let these really small numbers throw you.

good point. I’m not counting on my chisels to be “that” square. I’m eyeballing square, sometimes scribing a line to work towards. But the tiny squares let me get in to my jig to set perpendicular, and measure progress without taking it out of the jig mid sharpening.

It’s really just the small size that’s important.

 

[AEAdam]

MSc has the spi set for $150.

For 123s? I bought suburban tools 123s on eBay way cheaper than that and you can actually bolt them together. Hell I bought Starretts on eBay that are like gage blocks for less. They had a rust spot and couldn’t be sold as new.

@Fixr said the truth above. Machinist tools are worth very little. People use grind vises on their mini Chinese mills. I had a Hermann Schmidt V0-4 I paid $125 for. They are like $1000 new. I thought $125 wasn’t too much to pay for a decent vise.

 

[jar944]

For 123s? I bought suburban tools 123s on eBay way cheaper than that and you can actually bolt them together. Hell I bought Starretts on eBay that are like gage blocks for less. They had a rust spot and couldn’t be sold as new.

Squares.

https://www.mscdirect.com/product/details/79268058?cid=ppc-google-&mkwid=%7Cdm&pcrid=&rd=k&product_id=79268058&gad_source=1&gclid=CjwKCAiAtt2tBhBDEiwALZuhAP-g8lpDeWQSvrZCVL7co4Ai5mlcIIApix4H8lzBGuDm6MdWABZ0ChoCY1IQAvD_BwE&gclsrc=aw.ds

 

[AEAdam]

not exactly shouting about their squareness specs. Note the laser marking. That’s the kiss of death for me with impact sockets. Pass.

 

[RustyRelicRevival]

When I'm running my press brake, my parts have to be perfect. I have two 4" adjustable Starrett squares. One of those tools I put alot of trust in. Buy off marketplace, Craigslist or new. Worth every penny.

 

[pfaustus]

In my [very limited] experience, machinists squares get banged out of square easily. So, I've never bought one. In fact, I've passed on a number of them over the years. It would be overkill for my mostly woodworking anyways. On the other hand, I would be curious to learn how the old timers maintained and checked theirs.

 

[PittsburghTim]

I've purchased some machinist's squares made by Groz that are very good quality and some v-blocks also. Reasonably priced for home shop use.

 

[AEAdam]

In my [very limited] experience, machinists squares get banged out of square easily. So, I've never bought one. In fact, I've passed on a number of them over the years. It would be overkill for my mostly woodworking anyways. On the other hand, I would be curious to learn how the old timers maintained and checked theirs.

Not my experience. If you drop a solid square, I’ve found they mostly just get dented or dinged which can be honed out. Actually losing square takes abuse.

When you are shopping, I mentioned never buying one that’s been polished. You should also watch for dings and dents. Almost impossible to hide a ding from a drop.

 

[rancherbill]

I might argue that in the OP's case, "Lipstick on a Pig" might apply. Just look at that first photo. And not everyone wants to, needs to, or should become an instrument maker.

He says in the future to get a lathe etc. I know I had to learn skills as I went along and getting this into service again is a good project, along with checking and perhaps tweaking the other three.

A carpenter checks by putting it up against a piece of plywood.
A machinist is at an entirely different level.

 

[Fixr]

He says in the future to get a lathe etc. I know I had to learn skills as I went along and getting this into service again is a good project, along with checking and perhaps tweaking the other three.

A carpenter checks by putting it up against a piece of plywood.
A machinist is at an entirely different level.

I see fixing that junk square as an appropriate exercise for an aspiring apprentice manual machinist/toolmaker (if such is even a realistic career path any more). From the OP's description, I didn't get the impression at all that there is any such career intent, but as stated, welding and woodworking to start is the goal, with maybe a lathe and mill eventually. Seems to me that starting with reliable basic measurement tooling would be a better fit in this case. As and if more precision is needed, build suitable skills and acquire/build further tooling to fit the situation.

 

[dscheidt]

I bought a Chinese set of 123 blocks. They didn’t measure 1”x2”x3”, but I guess that’s okay…..ish. What I didn’t realize was, while the sides were all perfectly parallel, they weren’t square to each other. Not sure why. So,…trust but verify.

For grinding a chisel or….a few thousandths out of square is imperceptible. But you might need tools better than that for some things. Don’t let these really small numbers throw you.

All of the 123 blocks I have, all cheap imports, are as square as anything I have. I did get one that wasn't square, one edge was not parallel to its opposite. still square enough to build a house, not good enough to set up a saw or something.

 

[Wamsutta]

I wouldn't call their squares cheap.

 

[HenryAZ]

My PEC double square locks up perfectly square, as verified with a machinists' square

 

[AEAdam]

I find Starrett rulers MUCH easier to read. It’s not just the depth of the engravings but also the difference in height of the markings.

The SPi, PEC, even Mitutoyo markings all look like they were printEd on and are an unintelligible blur. Just look at the pictures above. The 64ths will always be tricky, but even the 32nds are harder to read than Starretts.

In addition, I’ve owned both PEC combination squares and Mitutoyo and found them both cheap feeling, I think the locking knobs were plastic, the rulers were thinner than Starrett as I said before. So many used Starretts on the market, I’ve never felt attracted to these other brands.

The PEC double square has quite a lot of material removed from the handle and it throws the balance off.

 

[bpwoodworking]

Older made in Japan Mitutoyo is high quality. Nothing plastic, new stuff is fine too.

That said, I definitely prefer Starrett’s rulers, they’re excellent.

For squares I prefer Starrett, I check them using a scraped in master square and a granite surface plate or on a scraped in box beam.