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Mortise width question

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Mortise width question

#1

Mortise width question

Stephen in Ottawa

>This is a follow up to my mortise chisel question yesterday, which turned into quite an interesting thread about the virtues of the different techniques for cutting a mortise!

Since I can only afford one mortise chisel, I need help deciding the width. I'd initally intended to get a 3/8" chisel since it seems to be the most versatile for the stock thicknesses I use. I typically use 3/4" stock for face frames, cabinet doors or table aprons and the like. In the past I've used 1/4" wide mortises when joining 3/4" rails and stiles. Ian Kirby suggests using a 3/8" mortise with 3/16" cheeks, while other authors advocate dividing the thickness of the stock into thirds which would imply a 1/4" wide mortise. For wider stock a 3/8" wide mortise would definately be desireable, but is it okay to use a 3/8" wide mortise ( actually 10mm if I end up getting the Two Cherries chisel ) in 3/4" thick stock? I know there isn't a real right or wrong answer, but does anyone know of any concrete disadvantages to doing this, considering this will be a situation that would arise when building face frames or cabinet doors.

I am leaning towards getting the 10mm ( ~3/8") chisel for starters.

Thanks again for the help.

- Stephen

Re: Mortise width question

#2

Re: Mortise width question

GolfSteve in Calgary

>10 mm is an excellent choice. This is my most commonly used size. If you need a 6 mm mortise, you can always fall back on the drill and pare method.

Re: Mortise width question

#3

Re: Mortise width question

Adam Cherubini, NJ

>Stephen,

You are (once again) exposing an interesting problem. IMHO, 3/8 is too big for 4/4 stock. 10mm is even bigger than 3/8�. The problem isn�t so much the thin cheeks, but lack of a robust shoulder on the tenon (other engineers may disagree).

Unfortunately, that�s not the only problem. If you are doing frame and panel work, there is an advantage to plowing the groove first, then mortising. You certainly don�t want a 3/8� groove. The resulting cheeks WOULD be too thin and you�d have no chance for molding.

Having a mortiser the exact width of the plow iron (or vice versa) is yet another advantage. The mortiser can then index on the sides of the groove allowing you to skip a step in the mortise creation. Also, the tenons can be produced to the plow plane setting (or vice versa), so all your tools start working together, which is what you want.

The problem as I see it with 2 Cherries is the metric sizing. 10mm is too big for 4/4 stock. It�s a monster chisel. 6mm is less than 1/4 and IMHO that presents a problem (since raised panels get really thin and tenons pretty wimpy). So my advice would be to choose the 8mm as a compromise.

Theoretically you really need 1/4" chisel, for 4/4 stock, 5/16" for 5/4 and 3/8" for 6/4. But I find 90% of the time I use 4/4 stock and the 1/4 chisel. When I�m making a big table I use the 3/8� mortiser. For mortises bigger than that, (like workbench legs) I use an auger and a framing chisel! Workbenches are carpentry IMHO.

I haven�t gotten rid of my 6 other mortisers though, since they look so pretty in my toolchest. But some really observant guys (Like John Aniano) have noticed that only a few are actually sharpened!

Adam

Re: Mortise width question

#5

Re: Mortise width question

Stephen in Ottawa

>Adam,

You raised a good and very important point that I'd overlooked, namely, the size of the groove matching the mortise width in frame&panel work. Since I have some frame and panel doors in an upcoming project, this is partucularly relevant. It looks like the 8mm chisel is almost exactly 5/16th. inch and I have a 5/16th. inch iron for my plow plane.

- Stephen

Re: Mortise width question

#6

Re: Mortise width question

Alan Hamilton

>Stephan,

The traditional, time-honored ideal-size mortises and tenons are: more than a third, and less than a half.

So to comply to the rule with 3/4 stock, mortises and tenons should be more than 1/4" and less than 3/8"; which means you'd need to find a mortising chisel somewhere around 5/16" or so.

My dear family just got me a set of Two Cherries mortising chisels (stealth gloat!). Their metric sizes look like they'll fit the bill more closely than trying to find an English measure chisel that's the right size.

You'll have great fun chopping mortises. It's fast, relatively easy, and a great way to get rid of frustrations, unfocused anger, and nervous energy.

Alan

Re: Mortise width question

#7

But, ...

Clay C. in Miami

>Isn't Adam recommending the 8mm for 4/4 stock, while you are using mostly 3/4? Maybe for 3/4 the 6mm is a better choice?

Just making sure y'all are on the same page ... maybe I'm missing something ...

Clay

Re: Mortise width question

#8

TERMINOLOGY

Adam Cherubini, NJ

>I'm not sure I understand Clay's question, but I can see how someone could get confused. I suggest we all add the inches symbol when we are refering to real measurements (or use decimals) to distinguish between lumber stock sizes and actual thicknesses.

Example:

"Modern, surfaced 4/4 lumber is 3/4" thick."

We should never write:

"I scrub planed my stock to 4/4" (or 5/4" or 6/4", etc) thick".

Clay, Was that your question? I think we were all talking about the same thickness of material-4/4 stock (which is 3/4" thick).

Adam

Re: Mortise width question

#9

Sorry for the caps above

Adam Cherubini, NJ

>

Re: Mortise width question

#10

Re: TERMINOLOGY

Bill Houghton, Sebastopol, CA

>Or, we could use one of the traditional, if fussy, methods, and talk about "nominal" 4/4 stock.

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