Just a measurement rambling

[Zachary Hoyt]

When I'm measuring to cut slots in a fretboard I have inches measured to three decimal places, but in reality I round the last digit, and the fret slot is .023" wide. I have a ruler marked in hundredths (actually there's a line every 2/100) and now I use an old magnifying lamp I bought at a yard sale last year to see the marks better. For some other things I have to be accurate to a 32nd or less, but a lot of the details are flexible.

[Robert Hazelwood]

I am usually making my own plans, and unless the piece is very simple I'm not sure how you avoid having fractions smaller than 1/16. This is usually driven by a desired reveal, or clearance between sliding components, the need to center one part upon another, to evenly space items, etc. I don't set out to make a part be 39 23/32" or whatever but it's just what ends up happening, especially with multiple doors or drawer openings.

I find 32nds ok to work with and sufficient for most nominal design dimensions. I don't bother much with 64ths. At that point I switch to decimal inches, and it wouldn't be noted on plans, just left to fit in the shop.

[Myk Rian]

Interesting question Phil.

I think 1/32” is a bit fine for woodworking dimensions, that said I design in metric for the most part and use 1mm increments as the smallest design measurement, however I often find myself using design dimensions in 2mm increments to simplify everything.

Regards, Rod

P.S. For example a leg in Imperial might be 2” square, so I make it 50 mm, likewise 3/4” thick material becomes 20mm. For accuracy I normally use +/- 0.1mm for furniture, a lot more for a fence��

Too bad we didn't fully convert to metric way back in the 80s I believe.

[Maurice Mcmurry]

Metric certainly has advantages. I have always enjoyed Bicycles and working on Bicycles. I started out on USA one piece crank bikes and old school USA BMX bikes. Our son got the bike bug and is making a career of it. He will not allow me to talk Imperial at all regarding bikes.

[mike stenson]

Yea, there's nothing left that's imperial on bicycles. Thankfully.

[Maurice Mcmurry]

Most Ball bearings are Imperial even on Italian and French bikes. Ball bearings are also becoming a thing of the past.

[mike stenson]

Most Ball bearings are Imperial even on Italian and French bikes. Ball bearings are also becoming a thing of the past.

I haven't used a hub or bottom bracket that's used them in over a decade now.

I'm assuming you're talking loose ball bearings. Not sealed unit bearings.
name a single imperial tool used though. Last one I threw away was a 9/16" pedal wrench.

[Maurice Mcmurry]

I haven't used a hub or bottom bracket that's used them in over a decade now.

I'm assuming you're talking loose ball bearings. Not sealed unit bearings.
name a single imperial tool used though. Last one I threw away was a 9/16" pedal wrench.

Yes, loose balls or the ones in cage retainers. My language and bikes continue to be antiquated. It is helpful to be getting a handle on Metric in the auto parts store too.

[Rob Luter]

For thickness I think it has as much to do with material yield as anything. Any lumber I buy to a nominal size is usually on the low side of the allowable tolerance. For example If I need an actual 1/2" thickness I have to buy 3/4" and mill it down. If I resaw 4/4 wood I still have to mill it and wind up with less than 1/2". Usually 15/32" or 7/16". That being the case I always design for 1/32" to 1/16" under nominal for a finished thickness.

If you're using S4s or S2S lumber the same can hold true for widths. In Phil's example above I suspected the table width started out 17 3/4" after glue up and lost 1/16" from edge planing.

Sometimes lengths wind up to be odd sizes too. An example would be when you're trying to hold the outside dimensions of a box or case to an even 1/8" increment but you have to fit pieces in the interior and the thickness of the exterior parts is undersize per the first example above.

Or, the guy/gal drawing the plans is showing off.

[Scott Winners]

Boat plans are often out to 1/32 or 1/64 inch. My next boat is going to be metric. I don't mind converting quarters and eighths and sixteenths in my head, but that is my limit. One millimeter, about 1/25 of an inch, no fractions, ought to be a fine looking boat when it is finished.

[Maurice Mcmurry]

Scott Winners, I hope you post about your boat project.