Working Towards 1/64's Accuracy

[Jeff Wright]

I have a question about measureing long things over 3 feet. If you dont use a tape, then how will you measure it then? I am fairly new and have yet to tackle anything of great style. Still trying to get all the basics down.

Being a self-confessed sucker for woodworking gadgets (and boating and flying gadgets as well), I use the gauges shown here. They can be adapted for almost any reasonable length:

http://www.leevalley.com/wood/page.a...,43553&p=32585

[Mark Singer]

I use a tape to rough out. Then as I crosscut to length , I use the first piece cut as the "story stick" and measure all from that. Drawing and drafting most of my life is an advantage in layout. Some tings I measure with a digital caliper such as distance from blade to fence and heigh of blade at the cabinet saw for ripping rabbets...etc. Some things I just eyeball....you need to know when. My main marking/measuring tools are combination square, double square, marking gauge, bar gauge for inside and outside measurements, marking knife, hard and soft pencils, I also use colored pencils for general marking, like matching boards, "planed face,",jointed edge" etc..... The best measurements come from the piece that is already cut. Cutting techniques are critical or marking accuracy doesn't matter. Cross cut sled....transfer mark with a square to the leading edge and set the blade right next to the line.
Joinery...scribe from one part to another as with dovetails then saw accurately. The properly tuned bandsaw and fence is a great place to make joints and templates.....you can just move the fence a touch and trial and error if need be. You can set stops to limit each cut consistently.
It is far easier to make a tight joint the first time then it is to try to fix it and it always shows.

[josh bjork]

I'm a hack but my stuff got a bit better when I started checking my framer's square for square every day. Also checking things for square after they come off if the saw. My equipment isn't elaborate by any means and there is a lot of user deviation.

[Pete Bradley]

I have a question about measureing long things over 3 feet. If you dont use a tape, then how will you measure it then?

A lot of times, the exact length is not as important as having it match other parts. For example, if you're cutting aprons for a table, hold the two pieces together and cut them to length. If you marked and cut the two pieces separately, it would be very difficult to achieve the same level of accuracy.

Pete

[pat warner]

A connection like this will not tolerate a .003" error.
The parts just jam on assembly. The T&G runs along the entire glue line
A 1/64th is a mile. Keep it tight.

[lou sansone]

it depends on what you are building. story sticks work for a lot of things, but in the case of sash, you better be within 1/64 or you will see it when you assemble it. Although I have not built any yet, the gallery in a decent secretary would also need some pretty close measurements.

Lou

[Al Killian]

Thanks for explaining it to me. I am still working on getting a decent set of measureing tools to make life easer.

[Steven Wilson]

Accuracy and precision start with machine setup. It's hard to make a square box when you can't cut square! I was using story sticks, a knife for marking dovetails, Starret rules, a single tape measure (there is only one tape measure in my shop), well tuned planes, very sharp paring chisels for making things fit, stops for repeatability, and all the other usual things and was fairly happy with the results although sometimes a glueup would take a bit more force than it should. Well the next step up in accuracy occured when I replaced my American style tablesaw and got my sliding table saw dialed in. All of a sudden glueups went smoother, boxes were square without clamping the diagonal, and things just went smoother. What was the change? I'm now cutting square stock. It's very hard with the limited crosscut capability of a standard tablesaw (or a cutoff saw you make) to make square cuts with great precision. It may measure square but still isn't quite square. This inaccuracy doesn't show up in smaller pieces but is very noticeable with larger assemblies. The large cutoff carridge of a sliding table saw makes it fairly easy to dial it in so that square cuts are really, really square. Life is good when it's square.

[Matt Lentzner]

So if one is shooting for 1/64ths by length, what is the equivalent accuracy of an angle? 1 minute, or less?

Just curious,

Matt

[frank shic]

jeff, if you want 1/64 accuracy, you may want to consider investing in a digi-fence - although it's not cheap! i bought one last year and it's made my woodworking much more accurate and repeatable.

[Steven Wilson]

what is the equivalent accuracy of an angle? 1 minute, or less?

It depends over what distance. I was always able to get things square on my PM66 to well under a minute as measured with a Starrett protractor, however that isn't good enough for an 8' bookshelf. For an example, I use pieces of MDF roughly 2'x2' to align the crosscut carrige on my slider. Performing a 5 sided cut (cut, rotate, repeat) I can get the maximum difference in parallel between the 1st and 5th cut to be .003" or less. That mean's over roughly 8' I'm off .003" from being square. That's a whole lot less than 1 minute of arc and probably less than a second (I should calculate that sometime).

[Jeff Wright]

Accuracy and precision start with machine setup. It's hard to make a square box when you can't cut square! .... Life is good when it's square.

Steve . . . AMEN!!

[Jeff Wright]

jeff, if you want 1/64 accuracy, you may want to consider investing in a digi-fence - although it's not cheap! i bought one last year and it's made my woodworking much more accurate and repeatable.

Frank . . . a friend of mine recently installed the digi-fence system on his Euro combo machine. That will be "second semester" work for me!!

[Michael Cody]

I've always treated accuracy as a goal but precision is a must. If you cut 4 pieces of wood all the same length and miter all the corners so the angles total 90dg at the corner and 360dg for the entire square -- it will be square.

If the table legs are 27.75 inches or 27.57 inches, it doesn't normally matter as long as "ALL" of them are the same. I strive for ok accuracy --- but always for repetable precision. For me it's story sticks and blocks. Measure the first one close, make all the rest the same.

[Jeff Wright]

. . . For me it's story sticks and blocks.

Mike, I am familiar with story sticks, but can you clarify what BLOCKS are? Thanks.

EDIT: Ahhh, you are referring to SET-UP blocks!