Marking mortices (Part I)

[derekcohen]

Whenever I see photos of someone checking a stretcher for square, it looks like this ...

http://i13.photobucket.com/albums/a262/Derek50/Marking%20mortices/4_zps5fcf47be.jpg

It looks square, even when you hold it up to the light ...

http://i13.photobucket.com/albums/a262/Derek50/Marking%20mortices/5_zps0ed2c2f8.jpg

However, if you reverse the square and measure across the wide side, any error present is magnified and is easier to see ...

http://i13.photobucket.com/albums/a262/Derek50/Marking%20mortices/6_zps5fa14473.jpg

http://i13.photobucket.com/albums/a262/Derek50/Marking%20mortices/7_zps0974e6dd.jpg

Is this degree of accuracy necessary? Well, errors can be additive, and door/panel frames need all the help to end up flat. Anyway, it is better practice to measure for square across the wide side than across the narrow end.

Regards from Perth

Derek

[IanW]

Derek, this is one of the times I don't entirely agree with you. OK, I will admit straight up front that part of my objection is a purely reactionary response to the thought of reversing a habit maintained for 55 years! :U

Your logic is fine, but in practice, it's less easy to ensure the stock of a square is truly registering the average surface on a narrow edge - a bit of grot or a small high spot will throw it off by a larger % of the distance. So while any out of square deviation may be magnified on the longer side, the benefit may be negated by a false 'reading' of the narrow side. I think it's a case of just doing the checking carefully, whichever way you go about it, and of course, checking at several points along the board, particularly if it's a critical piece.

And don't forget to check on a regular basis that your trysquare is actually square - I'm ashamed to admit, there have been a few occasions in my woodworking career that I neglected this bit of advice, and paid the price..... :C

Cheers,

[ian]

:whs:

for the reasons given

[yowie]

I do seem to find myself checking both ways quite often, just to be sure.

[Berlin]

Derek, this is the sort of arcane
detail that makes this sub-forum so interesting. :)

If we were to check our workpiece and find it out of square as you show, would we true the face or edge to correct the error?

Cheers
Matt

[derekcohen]

Hi Matt

What would I do?

I'd begin using this square ... :)

Magic Square - YouTube (http://www.youtube.com/watch?v=dB0MBGiX8TQ)

Regards from Perth

Derek

[IanW]

Hi Matt

What would I do?

I'd begin using this square ... :)

Magic Square - YouTube (http://www.youtube.com/watch?v=dB0MBGiX8TQ)

Regards from Perth

Derek

:U :U

Was it you, or someone else who drew our attention to that video a while back? It's a goodie, & strikes few chords - some of my early woodworking was very much in that spirit - plumb & square were rather vague concepts, but getting joints to close up was no problem, just a matter of applying enough clamps. Sometimes they even remained closed after the clamps came off...

Cheers,

[derekcohen]

Hi Ian

It was I. I do love the logic therein. :)

Regards from Perth

Derek

[RayG]

I must get one of those magic squares, and a bigger hammer... :)


Regards
Ray