Center-finding tape measure

Jul 23, 2008 10 Replies

An interesting low-tech gadget. It has two scales, one on each edge. They are both labelled in inches, but the second scale is actually 50% the size of the first one. To find the center of what you are measuring, read the true scale, then find the corresponding number on the other edge. That is the center.


I have a center-finding two-foot steel rule I got from Lee Valley that has proven one of the most useful gadgets I've bought in years, I use it all the time. Whoever invented this thing deserved a big raise.

Been around forever.

Find an old time drafting machine that still has the scales on it.

Engineering scales have full size along one edge, 1/2 size on the other edge.

Very helpful when doing layouts around centerlines.

A little tip to find the centerline of a large piece.

Eyeball the piece, then estimate total length.

Divide that estimate in half, the add 6".

Layout that value from the left and mark, then from right and mark.

Measure between the marks, divide in half, layout and mark from each side and mark.

You now have the center.

Laying out twice is usually enough.

Lew

As a carpenter's tape measure?

I've been around long enough that I took drafting as a shop class in high school. Same principle, different application.

Do they come in 16' lengths?

Or just use the nifty 16' tape I just described.

A cheap roll of drywall paper tape comes in handy to divide a line segment into any number of equal sections, plus it's easy to pencil in marks.

I saw that Lee Valley has a Golden Mean version as well.

It's pretty easy to find centers if you're using a metric tape measure: just measure the width and divide by two -- which is much easier using a whole number of millimeters than when using fractional inches. (Quick -- what's half of 55 13/16 inches?)

My metric tapes don't indicate fractional millimeters. Dunno about yours.

You have a tape measure that shows 8th's of a millimetre?

You have eyes that can see an 8th of a mm?

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