How close is close nough

[Bill Dufour]

realize that you should be able to estimate to 1/10 of the smallest division on your measuring equipment. All measurements are more accurate then the ability to make the item. Measuring and squaring to a great deal of precision is kind of a waste of time in wood.
Do a little study about precision metal measurement and you soon realize wood workers ignore almost all the rules. Biggest one I see is temperature control. I have never seen wood measuring tools with thermal insulation pads. No instructions say wear gloves to hold the tool or the work. In metal the measurements really should state at what humidity and temperature.
How do you compensate for gravitational sag of your work and the measuring tool.
Bill D.

[Robert Willing]

First I would like to thank all of you for your comments. I originally posted this as a question to the group was that I needed to check my TS. It was pushing the wood away from the fence, but than I saw a YouTube video stating how to put pressure on the fence to correct the fence Parnellism. So, I tried that process and it appears to work based on my measurements with a dial indicator relative to the miter slot. I have not checked the actual operation so far due to other projects tying up the saw. By the way this is a SS TS Contractor saw, which has a very poor fence to start with. So, other reviewers tell me.

[Simon MacGowen]

First I would like to thank all of you for your comments. I originally posted this as a question to the group was that I needed to check my TS. It was pushing the wood away from the fence, but than I saw a YouTube video stating how to put pressure on the fence to correct the fence Parnellism. So, I tried that process and it appears to work based on my measurements with a dial indicator relative to the miter slot. I have not checked the actual operation so far due to other projects tying up the saw. By the way this is a SS TS Contractor saw, which has a very poor fence to start with. So, other reviewers tell me.

Interestingly (coincidentally?) enough, a blogger has covered this topic in his post today: http://www.rpwoodwork.com/blog/2018/...come-accuracy/

Simon

[Robert Willing]

Great article.

[Phil Mueller]

Hmmm. I didn’t think someone would actually take a straight edge to their fine furniture, but thanks for doing that Simon. It got me curious and I checked a few of our finer mahogany antique pieces...inside drawer frames and case outside corners with a Woodpecker mini square and Starret square. I may have to eat a little crow, because I have to admit, they were pretty darn square

[Simon MacGowen]

Hmmm. I didn’t think someone would actually take a straight edge to their fine furniture, but thanks for doing that Simon. It got me curious and I checked a few of our finer mahogany antique pieces...inside drawer frames and case outside corners with a Woodpecker mini square and Starret square. I may have to eat a little crow, because I have to admit, they were pretty darn square

Flatness over a large surface is harder to achieve than squareness (esp. when the assembly is small because we can clamp/force it to square -- just align the clamps till the diagonals meet). On the other hand, large hardwood boards react to seasonal changes and there is only so much you could do to keep them flat in a carcase. At least that's my experience.

I have various tops that were machined flat (taking alternate passes on both sides) checked against my 50" straight edge. But they can be "less" flat depending on the season.

Simon