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View Full Version : Metric vs English chisels



David Romano
04-04-2009, 7:46 PM
I'm looking at buying some bench chisels and a mortise chisel or two. Does it cause problems when english and metric are mixed? If I want to chop a mortise and I start with a 1/4" drill bit, will I be able to square up the ends with a 6 mm mortise chisel? The difference is a mere 14 mils. Other sizes have bigger discrepencies though.

Thanks
David

glenn bradley
04-04-2009, 8:34 PM
The only times I rely on the chisel width to be my final width is on things that don't show (like mortises). For exposed joints I use a smaller cutter and work up to the outer dimension. This method means I don't really care about exact chisel widths so the 9 mm vs. 3/8" problem is moot for me. HTH.

Wilbur Pan
04-04-2009, 9:07 PM
The only time I've found that a chisel needs to be an exact size is when I need to make a mortise in a groove, in which case I want the mortise chisel to be the same width as the plow plane that I use for the groove.

In your case, you still can square up the ends of your 1/4" drilled mortise with a 6 mm chisel. You could do it with a 1/8" or 3 mm chisel -- it just won't be as convenient as having a true 1/4" chisel.

Mike Henderson
04-04-2009, 10:00 PM
Unless you use modern chisels made by a name company, the sizes are just suggestions. I have a number of older chisels (mostly Swan and Witherby) and none of them are the size they claim to be. I bought a set of Harris Tools chisels (used) a while back (this is a modern set). They are supposed to be metric sizes but none of them were accurate. I have a mixed set of Hirsch and Two Cherries (metric). Some are right on, but a lot are off, especially the smaller chisels.

The only chisels I've found to be accurate are LN and Blue Spruce - but I haven't measured all the manufacturers so I'm sure there are others who are accurate today.

Mike

Mat Ashton
04-05-2009, 3:06 AM
It shouldn't if you keep a "close enough" type of attitude. What I mean is if you chop out a mortice with a 6mm chisel you will be fitting the tenon to that so there shouldn't be a problem. Same wth a rabbit (rebate). If the plane isn't quite the width it should be, fit the piece that slots into the goove so you have a good fit...

Pam Niedermayer
04-05-2009, 3:42 AM
Wilbur's example is a good one; but I've never had occasion to require a chisel to be of a specific measure. When I make a mortise, I make it the same width as the chisel I'm using. When I make a tenon to fit that mortise, I set the marking gauge directly from the chisel. This saves an enormous amount of time and bother.

That said, I much prefer the metric system because a millimeter is a good unit of measure when I need to measure stuff, much smaller than an inch but not too small to be of use in woodworking.

Pam

David Romano
04-05-2009, 9:30 AM
Thanks for the replies everyone, that helps alot in my descision.

David