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Cutting mortises by hand. (Read 16894 times)
Mat Bailie
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Cutting mortises by hand.
Oct 8th, 2009, 12:28pm
 
I've decided to get my handy work skill from from zero to passable.

With my engineering background I over-engineered a bookcase so as to only need screws, but be strong and not wobble, etc.  The only real wood working skill was cutting timber to length and smoothing the ends.

Now I want to join using tenon and mortise.  Using only a tenon saw and chisels as I do not have any cash for tools.  I've got the hang of cutting the tenon and using a chisel to trim to size and shape.  But I'm less succesful with the mortise.

The main problem seems to be that I want to cut the mortise across the grain of the wood.  Every site I read suggests a chisel equal to the width of the mortise, chiselling out along the length of the mortise.  When the mortise is with the grain this seems to work.  But when it is across the grain it splinters horribly.

Am I right that I have to chisel with the grain?  And so have to chisel small pieces across to the mortise, slowly making it longer?  Very slowly.  And it seems near impossible (for me) to keep the sides of the mortise straight enough for a snug fit.

Or is chiselling a mortise across the grain in a plank of wood just a bad idea anyway?


Wood laying flat with location of mortise:

Code:

+--------------------+
|               .-.  |
|   Grain       | |  |
|   ---->       | |  |
|               '-'  |
+--------------------+


The grain goes along the length of the wood.  And the mortise should not go all the way through the wood.  (About 10mm deep in 19mm thick wood?)

I need to acheive the results with just basic chisels and a very basic work bench kindly donated by a friend.  I can't afford a router, etc.  And have no real woodworking experience.

Any advice on how to go about it, what to avoid, tops&tricks that could help, etc Smiley


Cheers,
Mat.
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sparxxxx
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Re: Cutting mortises by hand.
Reply #1 - Oct 8th, 2009, 1:21pm
 
In joinery it is critical that all cutting tools must be very sharp. So you're first lesson is tool sharpening. For your chisels you will need a stone and some oil - to lubricate the stone. You can buy a honing guide that will hold the chisel at the correct angle, unfortunately the guide will also mess up the stone but it will teach you the correct angle.

A properly sharpened chisel will not split the wood, unless you drive it in too deep.
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Mat Bailie
Re: Cutting mortises by hand.
Reply #2 - Oct 8th, 2009, 1:39pm
 
The splintering I'm referring to doesn't appear to be related to the sharpness of the chisel.  It seems to be more a mechanical effect based on the direction of the fibers in the wood and the direction of the chiselling.

As the mortise is perpedicular to the grain, and I'm chiselling along the mortise, the flat of my chisel is entering the wood parrallel to the grain.  This means that rather than cutting through fibers, I'm merely pushing the chisel Between fibers.  When I lift, therefore, the wood on either side of the chisel is also lifted.

When I attempt a mortise along the length of the wood, perpendicular to where I need it, things are much neater, faster, simpler, etc.  This seems to be because the chisel is now at right angels to the grain, and so I am cutting through the fibers.  When I lift the debris, the fibers to the sides of the chisel have not been cut and are not lifted with the debris I'm seeking to extract.



Cheers,
Mat.
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Re: Cutting mortises by hand.
Reply #3 - Oct 8th, 2009, 2:03pm
 
You're trying to take too much out and driving your chisel in too far when you're cutting along the grain (and risking splitting the wood). Use your chisel merely to make a light cut into the surface of the wood along the grain either side of your area, making the deeper cut across the end of the mortice, then take a cut across the grain, probably equal to half the width of the mortice, taking a second cut across the other way. That's the long way.

Mark a centre line along the length of the mortice and drill holes equi-distant along this line or, for the small depth you're talking about, drill a series of small holes around the perimeter of the mortice to just short of your required depth and then chisel out the mortice centre (all of which is called "wasting"), cutting the edges square when the middle is more less done. Then just go around with the chisel to square it all off.

The other way is the most sensible of all...

B&Q sell a smashing little router for just under thirty quid. It's the 1020W machine with the depth adjuster knob. My second one sounds as if it's about to give up the ghost after four years hard work so I bought another last week so that I won't be without. They're that good. I use it for cutting hinge rebates and lock mortices/face plate rebates in both door and frame.

A full set of basic basic 1/4" cutters can also be had for less than a tenner.
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« Last Edit: Oct 8th, 2009, 2:04pm by Joiner »  
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Mat Bailie
Re: Cutting mortises by hand.
Reply #4 - Oct 8th, 2009, 2:43pm
 
Thanks for your post.

As in my original, I have zero funds to do this.  I don't know about you, but I find £40 is Quite a bit more than £0  Embarrassed

For my shelves I borrowed a drill, so I'll have to wait a while before I can try that idea out.  I really am stuck with just:
- an old work bench
- 4 chisels
- a mallet
- a tennon saw

For the chiselling.  the "splintering at the sides" happens even when I don't use a mallet.  I'm confident I'm doing something wrong if you're certain it can be done without this effect.

> Use your chisel merely to make a light cut into the surface of the wood along the grain either side of your area.

Yep, been doing that.

First with a craft knife, which gave me long straight edges, but didn't go deep enough to stop the splintering.

Then with a chisel, which went deeper and so reduced splintering, but not alot.  The inside edges of the mortice became splintered and wider than I wanted them to be.

Next I chiselled the edges of the mortice to maybe 1mm.  Then almost 'planed' a layer out with the chisel.  Then chiselled the edges of the motice maybe another 1 mm.  Then 'planed' again.  Repeating to the right depth.  This stopped the majority of the splintering, but the long edges of the mortice were not particularly straight.  Maybe that's just a practice thing?  But placing a dozen chisel cuts side by side while keeping them vertical and perfectly in line proved extremely hard.  Especially when it was repeated every millimeter.

My best success was taking the motice all the way to the edges and cutting the sides with a tenon saw.  Then chiselling the waste out.  The bottom of the mortice was very hard to get flat and regular.  it normally sloped slightly and 'rippled' as I was hitting the grain.  Does this matter though?  When I glue the pieces together, what is more important, flat sides for good bonding area, or flat base of the mortice for good bonding area?  Or do I need to achieve both?

I'm hopeing to make your other ideas work, as using the saw doesn't give any where near the cleanness I'm hoping to achieve.


Thanks,
Mat.
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Re: Cutting mortises by hand.
Reply #5 - Oct 8th, 2009, 3:18pm
 
If you take the mortice all the way to the edge then it's no longer a mortice.

I think you're worrying too much about the appearance of the mortice for the reasons you're aware of. Once glued the joint will be as strong as a depth of 10mm will allow. I wouldn't depend on such a shallow joint without reinforcing it in some way, unless it was just to stop sideways movement in the tenoned piece, certainly not in tension.

You'd probably achieve the same result by (2 or 3 x 6mm) dowelling the joint, which would actually be much stronger in all directions.
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Mat Bailie
Re: Cutting mortises by hand.
Reply #6 - Oct 8th, 2009, 4:00pm
 
I think I'm going with Joiner on this.  The solution to my woes it to find a different solution.  I'll stick to easier mortices (where the grain aint a pain), where they get harder I'd instead use Dowel or Screws or whatever.  Then when I have some skills (as opposed to nearly no skills) think about it again.


Other than aestethics, is there any benefit of using dowel over screws?


Thanks for all your help.

Mat.
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« Last Edit: Oct 8th, 2009, 4:01pm by MatBailie »  
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Re: Cutting mortises by hand.
Reply #7 - Oct 8th, 2009, 5:19pm
 
A handy bodge tip...

Drill one side of the joint to take a screw. Glue the two sections together and drive the screws through into the other piece. When the glue is dry remove the screws and take a drill (6 or 8mm, depending on the size of the section) through the screw holes to their full depth. Drop a touch of glue into the hole and knock home the dowels, wipe away excess glue and sand to smooth.

The screws act a clamp on the two pieces!

Don't tell anyone I told you. Wink

As for the aesthetics... dowels look neater and don't rust, quite apart from being stronger, actually.
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« Last Edit: Oct 8th, 2009, 5:20pm by Joiner »  
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Re: Cutting mortises by hand.
Reply #8 - Oct 8th, 2009, 7:27pm
 
My dad - cabinet maker and joiner - will be spinning in his grave.
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Re: Cutting mortises by hand.
Reply #9 - Oct 8th, 2009, 7:53pm
 
Which sneaky person told you what I'd said?
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Re: Cutting mortises by hand.
Reply #10 - Oct 8th, 2009, 8:11pm
 
The smoothness of the sides of the mortise are what counts, the bottom doesn't matter at all.

You may well find it easier to cut a bridle joint, especially as you say you have no problems cutting the tenon.

http://rabbitwoodworks.com/images/Joinery/corner-bridle-joint.jpg

The joint is almost as strong as a mortise and tenon, but relies mainly on the glue, whereas a m&t joint has a lot of mechanical strength on its own. Use a quality PVA adhesive and you will be fine.
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Re: Cutting mortises by hand.
Reply #11 - Oct 8th, 2009, 9:56pm
 
From the drawing, his problem will be the location of the joint. Inset as it appears, I assumed the morticed piece overhung the tenon piece. Otherwise, on such thin section, he'd be better off with a dovetail. Even stronger.

Any advance on that?
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Re: Cutting mortises by hand.
Reply #12 - Oct 9th, 2009, 7:43am
 
Joiner wrote on Oct 8th, 2009, 9:56pm:
From the drawing, his problem will be the location of the joint. Inset as it appears, I assumed the morticed piece overhung the tenon piece. Otherwise, on such thin section, he'd be better off with a dovetail. Even stronger.

Any advance on that?


Cut a slot in each piece and slide  a piece of ply in Grin
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Re: Cutting mortises by hand.
Reply #13 - Oct 9th, 2009, 8:28am
 
Slip tenon. Even better!! Grin Grin
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Re: Cutting mortises by hand.
Reply #14 - Oct 9th, 2009, 8:31am
 
Or a couple of two inch nails and then smother it in VARNISH! Wink Grin Smiley = Wolfie Grin Grin Grin
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Mat Bailie
Re: Cutting mortises by hand.
Reply #15 - Oct 9th, 2009, 12:00pm
 
It's me playing with how to make a side unit.  The plank with the mortise will the the side of the unit.  The plank with the tenon will be the top of the unit.  The sides and back, however, will extend about an inch (maybe a little more) above the unit top, creating a 'fence' on three sides.

There is obviously more to the unit than just that, but I haven't got that far in my playing around yet Smiley
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Re: Cutting mortises by hand.
Reply #16 - Oct 9th, 2009, 7:35pm
 
As a relative beginner to wood work I'd say the problem Mat describes with cutting mortices is possibly down to the wood he's using. DIY store timber is mostly fast grown softwood and can easily crush when you try to cut it cross the grain.  I was amazed how much easier it was to cut them in green oak when I did that for the first time some months back. You can take wafer thin shavings off the end grain. Try that with softwood and it crushes and bits tear out.

http://img154.imageshack.us/img154/7985/img1902.jpg
http://img505.imageshack.us/img505/5725/img1900.jpg

However as someone pointed out, when it's all thogether you can't see it so it's not that much of a problem..

http://i586.photobucket.com/albums/ss303/CWattersUK/IMG_1934.jpg
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« Last Edit: Oct 9th, 2009, 7:39pm by CWatters »  
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