Why Do You Own A Try Square?

[steven c newman]

Thought I posted a little blurb last night.....must have missed the "post" button...

The combo square ( single one, per project) I use is usually set up to mark a depth of cut, like around a mortise. I leave the setting alone.
The Try Square I use is for marking a square line across a board, and to check IF a joint is square.

Both squares will sit on the bench during a project, each has their own jobs to do.
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Usual suspects. There is a small combo square and a small try square in the jumble.....
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Add in a backsaw, and these will appear..
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Other times, other sizes of squares get used. Not the least worried about who made any of them...all I ask is that they do their jobs.
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Even if it is to just check a corner....

[Patrick Chase]

That makes perfect sense. I've tilted my combo square for that exact reason.

The problem with tilting is that the straightness specs for rules as used in combo squares are only valid when used flat.

When you tip them on edge any curvature/bend will contribute additional height errors. You can get a sense of this by tilting both ways and seeing how the apparent flatness of the piece you're evaluating changes (which it almost certainly will unless the workpiece is so far out that its error swamps any contribution from the rule).

Beveled edge master squares don't have that limitation, because you can hold them in the optimal, as-specified orientation and still have a sharp edge in contact with the workpiece.

[lowell holmes]

Do you think that can be seen in normal carpentry? If you square the end of a 2x4 and cut it with an 8 point saw you are not working to precision.

If you want the end to be flat, hit it with a hand plane after the cut. You can scribe the mark with a knife before cutting, but you still need the flat surface.

[Patrick Chase]

Do you think that can be seen in normal carpentry? If you square the end of a 2x4 and cut it with an 8 point saw you are not working to precision.

If you want the end to be flat, hit it with a hand plane after the cut. You can scribe the mark with a knife before cutting, but you still need the flat surface.

Thread view says you're replying to my comment #36 about square-tilting so I'll reply accordingly.

No, that amount of imprecision doesn't matter for something like marking out a crosscut.

With that said, you would only tilt a straightedge or use a beveled master square to begin with if you were trying to detect small flatness deviations, on the order of tenths of mils. For anything larger than that a conventional rule held flat against a backlight is sufficient. I therefore replied to Michael Evan's post under the assumption that he had some underlying requirement that caused him to do what he described.

IMO there are cases that arise in woodworking (more in tool preparation than in marking) where that sort of precision can be handy, though never necessary. As I said in a previous post, flatness specs on the order of tenths of mil are overkill for woodworking.

[george wilson]

For the woodworker or the machinist as an every day square,I'd recommend using a flat edge square rather than a bevel edge square. The bevel edge square is made for a certain application. It is for standing on the beam and checking the squareness of an adjoining vertical surface.(I hope I made that statement understandable). The knife edge of a beveled square is also easier to use for seeing if ANY light is coming from under the blade. You can see as little as .0001" of light coming from under the blade more easily if there is a single line of contact with the blade and the beam.
The bevel edge square is a good INSPECTION instrument. The flat edge square is better for scribing lines against the blade. Its blade is completely in contact with the surface you are scribing. That is what wood or metal workers will be doing most of the time.

Beware of any square, including the bevel edge ones. All of these squares can be made in China. Despite the accuracy that the bevel edge square's appearance implies, it may not be any more accurate than any other Chinese square. If you buy ANY machinist's square,be prepared to spend a bit of money on it if you want an accurate one. Back in the 70's,I paid $50.00 for a 6" Starrett square in new condition. It has proven to be a wise investment. Now that I also have black granite squares and granite
straight edges to check everything with,I can be more sure of myself.

I bought a 3 piece set of SPI machinist's squares from Manhattan Supply Co. for the toolmaker's shop before I retired, and took my squares home. The SPI squares were not horribly expensive, and all 3 have proven to be quite accurate. SPI means "Swiss Precision Instruments". They are no longer made in Switzerland, and Manhattan Supply Co. (MSC) bought the name several years back. SPI instruments may be made in a number of places, including China. But if they are made to the specifications demanded by the supplier, they can be perfectly good. The Chinese CAN make good tools. It is the BUYER, who wants to pay nearly nothing for his tools, etc.,who is responsible for the lack of quality inherent in most Chinese products. An oil can that came with a Chinese lathe I bought for the Toolmaker's Shop revealed the label for a can of Lychee nuts !!! (I have also seen that same sort of thing inside Japanese made Zippo style cigarette lighters back in the 1950's. Now, their tools and instruments command high prices) The Chinese themselves do not use things like table saws and other equipment we commonly use over here, for the most part. Many Chinese factory workers have little idea how the tools they are making actually function.

An American quality control supervisor in Taiwan, for example, saw a small crew of Chinese, do the trim in a new office. These workers had a sort of folding plywood "bench" that they used. With JUST hand tools, they efficiently made all of the panelling on the office walls.

I am also aware of a father and son working in a single car garage in Taiwan. These poor guys repeatedly dig 8' deep holes in the casting sand floor of the garage. They manage to pour 1000# castings for milling machines into this hole, which they have prepared the pouring cavity in. Their furnace is behind the garage, and is very large, indeed, but a very simple type of furnace which the two of them can rebuild, and re line after several castings have been made with it. I'd love to hang out there and see how they do this amazing effort !! Those guys have great personal skill! This is how cannon makers several hundred years ago made cannon. They were hired by the owner of a castle to make cannon to defend the castle with. They worked in the courtyard of the castle. There, they made a furnace out of bricks (which they may also have made!). The metal, iron or bronze, would be poured in a groove in the ground after a plug in the bottom of the furnace had been knocked out. When I was in England, at the Tower of London, I saw a huge bronze cannon made by the Turks. It must have been over 12' long, and was in 2 pieces which ACCURATELY screwed together with very large threads(about 1 thread per inch, if I recall correctly). They unscrewed the thread to load the gun. One half of the gun was the breech. I looked that thread over very carefully, and could not see any tool marks on it. It was probably chiseled out. The gun, being made in 2 parts, made it easier to transport. It fired LARGE stone balls. I think they must have been about 18" in diameter, but my memory is hazy on that. The gun is now kept indoors, but for hundreds of years it was left outside. This gun would fire these large stone balls at the same spot many times, till the wall crumbled. I'll add that the gunner had to mix his own powder on site, as it was dangerous to transport over bad roads that constantly jarred the powder. Static electricity could be generated and the whole shebang could have gone up!

As a final note, do not forget that properly trained Chinese can build rockets and satellites that work just fine. And, that is no mean trick !! I predict that eventually the Chinese will perfect their quality control efforts, and get their manufacturing other problems in line. Then, their goods will become as prized as Japanese products now are, and will also be as expensive.

[michael langman]

When I bought my bevel edged master square from Starrett it was with the intention of also checking cylindrical things, like the posts on a die set.
With a regular flat faced square it is harder to see the deviations in the surface being inspected.
A lot of times I would use a piece of .0002 onion skin to inspect or setup something because the light could not be seen in place.
Using onion skin with a bevel edged square is also much easier and more accurate in most cases.

[Patrick Chase]

For the woodworker or the machinist as an every day square,I'd recommend using a flat edge square rather than a bevel edge square. The bevel edge square is made for a certain application. It is for standing on the beam and checking the squareness of an adjoining vertical surface.(I hope I made that statement understandable). The knife edge of a beveled square is also easier to use for seeing if ANY light is coming from under the blade. You can see as little as .0001" of light coming from under the blade more easily if there is a single line of contact with the blade and the beam.
The bevel edge square is a good INSPECTION instrument. The flat edge square is better for scribing lines against the blade. Its blade is completely in contact with the surface you are scribing. That is what wood or metal workers will be doing most of the time.

<snip>

Indeed. With that said, my bevel-edge master square is also the best tool I have for evaluating critical flatness, which is after all a component of squareness inasmuch as flatness deviations contribute to angular deviations. I therefore tend to use it for that as well. Sorry I was unclear about that.

w.r.t. Chinese products and quality, I think that the stuff we import from China tends to often be cheap and of low quality because that's what we (specifically the Western-based transnational corporations that outsource to China) want and are willing to pay for.

EDIT: Obviously a bevel-edged straightedge like the Starrett 385 would work just as well (the flatness spec is basically the same). I just don't happen to have one of those.

[Frederick Skelly]

w.r.t. Chinese products and quality, I think that the stuff we import from China tends to often be cheap and of low quality because that's what we (specifically the Western-based transnational corporations that outsource to China) want and are willing to pay for.

Sure, we've had that conversation before and guys who work with chinese companies have agreed that they build what we want to pay for. Plus, IIRC, they stressed the need for Customers to regularly perform QC onsite, at the factory.

[John K Jordan]

Sure, we've had that conversation before and guys who work with chinese companies have agreed that they build what we want to pay for. Plus, IIRC, they stressed the need for Customers to regularly perform QC onsite, at the factory.

A number of things I've bought through Amazon have come directly from China. Yesterday I received an adjustable reamer (with free shipping). It was a disaster. The sent me one that someone else had apparently abused and destroyed. It was nicely wrapped and sealed in new packaging materials. The Amazon return process wanted me to pay the postage. We'll see how it works out.

On a previous order a different company substituted a very cheap and worthless item for the one advertised and that I had bought before. I had to argue with them for days before they refunded the money. Another Chinese company sent me a 400nm UV light when they advertised a 365nm light. Useless to me.

In all three cases the correct or undamaged product would have been usable but the people supplying it were either not careful or dishonest. Maybe they will learn to change their methods. Someday I will learn to pay more attention to where the item is coming from.

JKJ

[Patrick Chase]

Sure, we've had that conversation before and guys who work with chinese companies have agreed that they build what we want to pay for. Plus, IIRC, they stressed the need for Customers to regularly perform QC onsite, at the factory.

Yep. That's true of any manufacturing environment.

When I started out as an ME new R&D engineers were expected to rotate down through manufacturing with and be on-call to support the products they had designed. When my employer outsourced manufacturing they severed that link, and it took years to rebuild post-manufacturing-release support back to an adequate level. Unsurprisingly this involved a lot of travel, continuous on-manufacturing-site presence, etc.

I'm sure none of that was accounted for in the cost projections that drove the decision to outsource, though.