How square is square enough?

[Brad Shipton]

I think at some of the figures being suggested one needs to consider the reality of their machine. I cannot produce parts nearly as accurate as a supersurfacer on my Hammer J/P, nor will my shaper produce the same results as a Martin. Why? Bearings, and the accuracy of the parts that are assembled to make the machines. I know Mark and Brian can measure this, but some of us cannot. I aim for the best I can with the setup tools/equipment I have, and am constantly improving as I learn from others. If it fits, and I happy, good day. I have to put down the 24" calipers many days.

[Kevin Jenness]

Without questioning the importance of accuracy and precision in general, let's go back to the original post. The parts in question are the horizontal elements of a bench base trestle which are going to be mortised to accept the legs. They have two parallel surfaces, one square edge and one that is slightly out of square, No matter what process is used for mortising the fourth edge can be ignored and a mortise square to the faces/ parallel to the good edge can be produced within the capabilities of the mortising equipment. So yes, the pieces are "square enough" for use.

[Bill Dufour]

I just finished getting the top on my tablesaw. I have the blade aligned parallel to the mitre slot within about .001" in the diameter of the blade Should I break out the .0005 DI and fight it down smaller? How much is too much as to be unsafe. It was within .01 just by luck at first.
Bil lD

[Robert Hazelwood]

I just finished getting the top on my tablesaw. I have the blade aligned parallel to the mitre slot within about .001" in the diameter of the blade Should I break out the .0005 DI and fight it down smaller? How much is to omuch as to be unsafe. It was within .01 just by luck at first.
Bil lD

I will defend working to thousandths, but ten thousandths are getting silly for woodworking

[Jim Becker]

I will defend working to thousandths, but ten thousandths are getting silly for woodworking

I will agree that there may be limited practical benefit based on the material being processed, but there's absolutely nothing wrong with someone dialing things in even more precise if they want to. There's zero negative to that other than time and, perhaps, a few bad words being uttered from time to time.

[Osvaldo Cristo]

For practical reasons in woodworking (I am an Engineer with microelectronics background so I am comfortable to work at very high precision) my smallest reliable measurement with my steel rules is 0.5 mm. I consider my squares "bull´s eye" precise if on 300 mm lenght I have 0.5 mm error or less. It means 0.1 degree error (1:600).

Your propose is equivament to 1:1,500 - thoughter than mine!

[Jared Sankovich]

The entire set is cheaper than a 12" woodpecker square, and inherently more accurate than a combination square.

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20200515_141814.jpg

[Andrew Seemann]

Anyone else here remember the 1970s when the most accurate tool 90% of woodworkers owned was a Craftsman combo square and most had never heard of a thousandth?

I suppose you could say the same about 1770, when the the most accurate tool a professional woodworker owned was an ivory rule and no one had ever heard of a metal plane.

How ever did they get work done?

[Brian Holcombe]

That is a bit a strawman, given that if we’re using machinery it can very well be made accurate. I’m not sure who 90% of woodworkers refers to when you can clearly see very stout and precisely made machinery and measuring tools from US, Europe and Japan from that era and prior and presumably many professional woodworkers used those tools.

Finally, when one works by hand one uses hand method of fitting individual parts.

[Bill Dufour]

What I find very imprecise is when a woodworker will say my fence is out of parallel by 2/1000. But no mention of in what distance.
Reminds me when I complained to the city that there was hump in the gutter in front of my house. Some engineer type responded with a letter that it was within tolerance. Some thing like 6 inches in 1000 feet so they would not do any repair. I suppose the average slope was good but it humped up so there was a 2" deep lake in the gutter unless the sprinklers were off for a few weeks in summer.
I put a little oil on it every few weeks to kill mosquitos.
Bil lD

[Mark Hennebury]

I remember the 70's well, i have been woodworking since then. Most of my machines are from the 50's, Robinson and Wadkin, i do have a few more modern machines from the 70's, like Marunaka supersurfacers, Balestrini mortise and tenoners, Maka Mortisers (All designed and produced in the fifties and sixties.}

This is an old 70's machine that i rebuilt last year. Craftsman table.....oh no actually a Dinky little Martin table saw, and a mickey mouse jointer from Japan. Last photo has a little 20"Wadkin Jointer from the 50's, a hobby shop 30" Robinson Bandsaw from 1951, a Dean Smith and Grace lathe from 1959. a Wadkin LQ mill/ router type thing, from the 50's. I could go on for quite a while.

i think you need to broaden your horizons.
Woodworking is a wide world. Room for everyone. Lots to learn
Share what you know and how you do it.



SAM_5704-001.jpgSAM_2801.jpgBandsaw.jpg

Anyone else here remember the 1970s when the most accurate tool 90% of woodworkers owned was a Craftsman combo square and most had never heard of a thousandth?

I suppose you could say the same about 1770, when the the most accurate tool a professional woodworker owned was an ivory rule and no one had ever heard of a metal plane.

How ever did they get work done?

[Ryan Yeaglin]

Standard unspecified machine shop tolerance is +/- .005" (A machine shop that sees an untoleranced diameter, without knowing the design intent, may apply a standard tolerance for three-decimal-place untoleranced dimensions, ±0.005 in). Not saying that there aren't tighter tolerances, just stating the standard.

[Ron Citerone]

I layout all of the boards that I am going to glue into a panel, put the cabinet makers triangle on them, and mark each edge of the joints alternately out/in. I go to the jointer and run each edge away from the fence or toward the fence. This cancels any error that my jointer fence is not exactly 90 degrees.

Yes, what Frank said!!

[Brian Holcombe]

Standard unspecified machine shop tolerance is +/- .005" (A machine shop that sees an untoleranced diameter, without knowing the design intent, may apply a standard tolerance for three-decimal-place untoleranced dimensions, ±0.005 in). Not saying that there aren't tighter tolerances, just stating the standard.

You can appreciate that length and size tolerances are much different than tolerances for squareness and parallelism.

It has been my experience that tenon shoulders being out by .002” over 3” or similar would show minor but visible gaps which would require some kind of filler. Completely different than a part size tolerance of .002”.

Not to say I’ve never made a gap, but the goal is basically to reduce them to zero.

Practically speaking that means the error must be smaller than the woods ability to crush under clamping pressure to disappear the gap. That can at times be fairly generous and with harder and lighter colored woods it can be quite small.

[Patrick Walsh]

Mark,

You just became my second hero of the day next to Howard Stern.

Go take a listen. Hopefully o don’t make a mortal enemy after you do but if I do so be it lol..

Oh and by the way that jointer!

And why Im on a roll you really do some crap work.....

I remember the 70's well, i have been woodworking since then. Most of my machines are from the 50's, Robinson and Wadkin, i do have a few more modern machines from the 70's, like Marunaka supersurfacers, Balestrini mortise and tenoners, Maka Mortisers (All designed and produced in the fifties and sixties.}

This is an old 70's machine that i rebuilt last year. Craftsman table.....oh no actually a Dinky little Martin table saw, and a mickey mouse jointer from Japan. Last photo has a little 20"Wadkin Jointer from the 50's, a hobby shop 30" Robinson Bandsaw from 1951, a Dean Smith and Grace lathe from 1959. a Wadkin LQ mill/ router type thing, from the 50's. I could go on for quite a while.

i think you need to broaden your horizons.
Woodworking is a wide world. Room for everyone. Lots to learn
Share what you know and how you do it.



SAM_5704-001.jpgSAM_2801.jpgBandsaw.jpg