How many mortice chisels......

[whybob71]

do I need??? maybe just four size are OK.........6, 8, 12 and 15 mm....
I have some firmer chisel I use for making mortices, but I want some dedicated chisels.....

many thanks
Bob

 

[woodbloke]

Bob - depends really on what you're doing. If you want to make canal lock gates :lol: then small sizes ain't going to be allot of use. For general furniture making I use a 6, 8 and 10mm tho' a 12mm would be useful on occasions - Rob

 

[bugbear]

do I need??? maybe just four size are OK.........6, 8, 12 and 15 mm....
I have some firmer chisel I use for making mortices, but I want some dedicated chisels.....

many thanks
Bob

Depends pretty much absolutely on how many stock sizes you'll be working with, since it's usual to make mortices roughly(*) 1/3 the stock size.

BugBear

(*) This is the rule for imperial; it may be different in mm

 

[whybob71]

Thanks a lot for the replays.
Actually the size of the board I use is very variable, ranging from 20 up to 50 mm depending on the type of project i'm working on.

My major question can be: do I really need one mortice chisel for that specific width or can I use 2-3 mortice chisel for different size of mortices?
If I have to make a 30 mm wide mortice I will not use for sure a 30 mm chisel!

 

[woodbloke]

The problem here as I see it is that if a wider mortice is cut with a narrower chisel (say a 16mm wide mortice cut with a 12mm chisel) the first part cut out (12mm wide) will be fine as both sides of the blade are supported by the timber. When you then go on to cut the remaining 4mm only one side of the chisel is supported and the danger then is that the mortice will not be square as you chop deeper into the timber...a sort of a wedge shaped mortice may develop, narrower at the bottom than the top, which will need additional paring with a normal chisel to make square....so to answer your question, in my view, a 16mm mortice will require a 16mm mortice chisel etc - Rob

 

[ike]

On the rare occasions I have needed to chop large mortices (1") I auger out the meat of it first (brace and bit, but a mains drill on low gear is quicker), then it's much easier to use the correct width chisel.

Ike