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Cutting M&Ts at 45-degrees

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JakeS

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I'm in the middle of making a right-angle-triangular table to go in a corner, and as such, I need to have my back two apron rails and stretchers at 45 degrees to the front ones. I'm keeping the front two legs perpendicular to the front of the table, so the two back aprons and stretchers are going to need to be mounted on the square-section legs at 45 degrees.

I know I could cut a 45-degree slice off the back of the leg and then just cut the mortise normally, but I don't like the idea so much. Plus it's cheating! ;-)


I had a practice go on a spare piece with the most-obvious-to-me approach, which was to clamp the workpiece at 45-degrees using a set of blocks to hold it, chisel a flat into the corner to cut the joint into, and then mortise into that flat. Which mostly went well:

45a.jpg

45b.jpg


Unfortunately, I fell at the last hurdle - while cutting the mortise, I couldn't help but mar the corner at the top. I think I squished it with the back (face? I don't know) of the chisel when I was paring out the waste from the bottom of the hole. I tried leaving some un-trimmed waste at the corner at first, but it became quickly apparent that it'd get in the way of the mortise itself. :/

Anyone got any tips for cutting the mortise out of here without damaging that corner (and without buying a mortiser ;-) ) ? I suspect I could get away with it on this one, since it's just a table to stand some plants on in the hall, but I'd know. There's already some hidden mistakes on this project, and obviously I'd like to learn to do stuff like this more cleanly!

45c.jpg



A related question, of course, is: is this kind of joint likely to be a problem with movement over time? The apron will obviously only be enclosed on one side - I'm planning some of those little L-shaped blocks to hold the tabletop on, don't know what they're called - but the stretchers would have the end enclosed on two sides with the triangular section of the leg...
 

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flounder

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I don't know the correct way of doing it but you could take one of those spare v-blocks in the top picture and clamp it on the leg so it is flush with the top of the notch thereby protecting the top corner??
 

JakeS

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flounder":26g9hp4t said:
I don't know the correct way of doing it but you could take one of those spare v-blocks in the top picture and clamp it on the leg so it is flush with the top of the notch thereby protecting the top corner??
Not a bad idea - I can give it a go, but I worry that it'll just make it impossible to get the angle on the chisel to clear out the bottom of the mortise! That said, I did dig the flattened-off recess too deep in this test case (as can be seen, there's a couple of millimetres of 'spare' flat either side of the tenoned-in bit of wood) so maybe the extra clearance afforded by a shallower recess will give enough space for something like that to be held in place...
 

AndyT

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Interesting question - one idea - proceed as you are doing, but make your initial cut shorter. Cut your mortice. Then clean up the vulnerable corners by making two new cuts, slightly further apart, ie cutting off the bits that may have got squashed. Arrange things so that the dimension you now reach is the width of your stretcher.
Cut the tenons with shoulders on top and bottom, equal to the amount removed in this extra cut.
 

Argus

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If you have compressed the wood in the corner, without severing any fibres, it is sometimes possible to get most, if not all, of the ding out with heat and steam.

I admit that the arris on an angled corner may be tricky, and I don't know if you know this trick, but here goes......but it's worth a try.

You need some clean water, a clean cloth and an electric iron.

1 Heat the iron up on it's hottest setting (cotton, usually).
2 Soak the imediate area of the knock and the cloth.
3 Place the cloth over the area that is damaged and press the hot iron on the cloth for half a minute or so. There should be a lot of steam. (The pointed end of the iron works best for this).

You may need to repeat the exercise, but it usually works.


Hope this helps.


.
 

RogerP

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I tried this for the first time a week or two back on a nasty dent and .... it worked like magic! :)
 

JakeS

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Argus":2a73g2e7 said:
If you have compressed the wood in the corner, without severing any fibres, it is sometimes possible to get most, if not all, of the ding out with heat and steam.

I admit that the arris on an angled corner may be tricky, and I don't know if you know this trick, but here goes......but it's worth a try.
You know, I had heard it in passing, but never really understood how the steam is applied to the wood... but I just gave it a go on the test piece, based on your instructions, and the initial result looks perfect! I'll leave it a while to dry out again before I'm confident in the success, but it looks great at the moment - thanks!



I did have a look at what could be done with the spare angle blocks atop the corners, but there simply isn't enough space left to get the chisel in to clear out the mortice, at least not the way I'm used to cutting my mortises. I'll try leaving a bit of spare waste while cutting the mortise as Andy suggested, and hopefully between that and this it'll all turn out OK in the end... thanks for the tips, guys!
 

woodbloke

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JakeS":2rcgiynu said:
You know, I had heard it in passing, but never really understood how the steam is applied to the wood... but I just gave it a go on the test piece, based on your instructions, and the initial result looks perfect! I'll leave it a while to dry out again before I'm confident in the success, but it looks great at the moment - thanks!
A useful trick and an old electric iron (make sure it's not SWIMBO's best one :shock: ) should be part of the power tools arsenal. It works by forcing hot steam into the fibres of the wood which then swell back to their original size, but note, it will only work on timber that's bruised...if the fibres have been cut then that's something that either needs to be lived with or repaired in a different way - Rob
 
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