Help with a stubborn double through mortise and tenon

[SteL]

I've been building my first workbench using only hand tools and posting my progress here ...

https://www.ukworkshop.co.uk/threads/yet-another-english-style-workbench-build.124501/
I'm a complete beginner, but things have gone quite well up until building the face vice. This is my second attempt at it and I don't want to cock another one up! Basically, the mortise and tenon will not hammer flush on one side. It is supposed to be a tight fit because it'll experience quite a bit of racking force, so I don't want to keep taking tiny shavings off until it just slides in and out by hand. I've already tried taking slithers off the tenon that won't go flush but it didn't seem to help. I thought I'd cracked it when I realised the surface where the tenon sits wasn't 100% square. That helped a bit but that is square now and the gap is still there (slightly). I can sort of press it (using a lot of force) so it all goes nice and tight but when I let go it comes out on that side again.

Some images to better explain...

Mortise cut by hand so a bit scruffy inside (I don't have a mortise chisel)

Tenon...

Problem...

It's actually not as much as that now after I worked out the surface was not square (even though I spent ages getting it square yesterday)...

But it is still there. I'd say 0.5mm - 1mm...

(Not the best picture but it is there)

From the front...

(nice and tight)

Do any good folks have any advice on what might be causing it? I've been taking shavings off and it persists. It's still a nice hammer fit but I know I'm a few shavings off making it too loose now. The shoulders are all square - one definitely isn't slightly higher. I've been on it for the past hour and got nowhere. Any help will be greatly appreciated!

Cheers

 

[SteL]

I meant to say this is literally the second time ( the first one went belly up) I've ever done a mortise and tenon so don't think I've thought of the obvious... I won't have.

 

[Droogs]

Pick 3 there is a bit of "fluff" on the should of the tenon - is that still attached and stopping it going in flush

Is the mortice slightly too shallow - tennon a little too long/not quite square on the end ie on side longer than the other even by a couple of mm? Leading it to sit askew.

top not totally square take a couple of shavings off the back half of the mortice

 

[Ttrees]

Hello
Youre half way there by getting a nice fitting double tenon, now comes the shoulders. Presuming you don't have a shoulder plane so a chisel will have to do .
I recommend squaring an accurate line all round with mechanical pencil to pair or compare to. Another thing might be useful is a accurate block with graphite to highlight high spots to get the permiter of the tenon stock proud all round so no gaps show. Make sure your face is ninety to the mortices as the walls of this is the reference now.

Also make sure there is no lump in between tenons

 

[SteL]

Pick 3 there is a bit of "fluff" on the should of the tenon - is that still attached and stopping it going in flush

Is the mortice slightly too shallow - tennon a little too long/not quite square on the end ie on side longer than the other even by a couple of mm? Leading it to sit askew.

top not totally square take a couple of shavings off the back half of the mortice

Thanks. Definitely no fluff and it is a through tenon so it doesn't matter how long they are. I think maybe a couple more shavings might do it in that area. I'll try that tomorrow. Cheers.

 

[thetyreman]

watch out for high spots in the mortise hole, I recon it's the top of the tenon being very slighly too wide for the hole, take off a tiny tiny amount and try re-fitting, repeat until it goes all the way in, using a flat file can be useful for this because it takes off such a tiny amount of wood, also bear in mind (presuming you're gluing this) that the glue may freeze the joint if it's too tight, PVA will expand the wood slightly so it can be very slightly loose but not too much.

 

[SteL]

Hello
Youre half way there by getting a nice fitting double tenon, now comes the shoulders. Presuming you don't have a shoulder plane so a chisel will have to do .
I recommend squaring an accurate line all round with mechanical pencil to pair or compare to. Another thing might be useful is a accurate block with graphite to highlight high spots to get the permiter of the tenon stock proud all round so no gaps show. Make sure your face is ninety to the tenons as this is the reference now.
Also make sure there is no lump in between tenons

Thanks. I do have one shoulder plane but it's a bit big for them shoulders. I have tried to see any high spots and used my square to check. I got them straight off the saw and they seemed dead on. I did the line all of the way around and they are identical. Actually, I did that by using the face and edge marks. Am I right in assuming that wouldn't guarantee the shoulders are actually level with each other if the other two faces are not square? I'll check that out tomorrow.

Cheers.

 

[Peter Sefton]

I would say it pretty clean, are the tenons parallel to the timber, are the mortices going through square? If the morticed timber has moved out of square and a mortice gauge was used to mark the joints then the mortices will be on the skew.

 

[SteL]

watch out for high spots in the mortise hole, I recon it's the top of the tenon being very slighly too wide for the hole, take off a tiny tiny amount and try re-fitting, repeat until it goes all the way in, using a flat file can be useful for this because it takes off such a tiny amount of wood, also bear in mind (presuming you're gluing this) that the glue may freeze the joint if it's too tight, PVA will expand the wood slightly so it can be very slightly loose but not too much.

I have taken slight shavings off the tenon and the mortise but the gap persists. The worry is I'm missing something else and I'll make it too loose once I discover what that other thing is! I was thinking maybe the top tenon is at an angle somehow or something I hadn't thought of. You may be right, though and I just need to keep going. I'm not sure what freeze the joint is - I'll look it up. I've got PVA some tightbond and hide glue.

 

[Steliz]

Have you checked the other side of the top to see if it still square? The end grain on your board shows the centre of the tree so it could be that the wood is moving and opening up that gap.

 

[SteL]

I would say it pretty clean, are the tenons parallel to the timber, are the mortices going through square? If the morticed timber has moved out of square and a mortice gauge was used to mark the joints then the mortices will be on the skew.

Thanks. That was my worry but I have no idea how I can check if the mortise is running through square. They're too small to get my square in to check. I didn't use a mortise gauge, just a marking gauge off the same edge. That was squared at another - time yesterday I think. I wonder if it has moved since and I've marked it up off dodgy face and edge marks. Note to self -- check before marking up or do it all at the same time! Cheers

 

[SteL]

Have you checked the other side of the top to see if it still square? The end grain on your board shows the centre of the tree so it could be that the wood is moving and opening up that gap.

I bet it has moved. I squared it, left it then marked it without double-checking it was still square. D'oh! I wish I had a tiny square to fit in those mortise holes to check. Cheers

 

[Droogs]

try rubbing a bit of blue chalk on on the tenon and shoulder. fit it and see where they rub off

 

[SteL]

My first attempt yesterday was an ordeal. I went past my lines slightly on the mortise so I made a new bar to fit the holes. Then after doing all that, I hammered it home and It was tight... too tight! It went in all nice and was lovely and square. Then I realised why it suddenly went in with my heavy-handed blows...

If you look close you can see a split from the bottom tenon all the way to the edge. So I knew I didn't have time to redo it because I'm as slow as a glacier. So I thought I'll just choose another face for the vice and square it, then crack on some other time. I suppose that was a bad idea now!

 

[Peter Sefton]

My guess would be timber movement issues, can you put a rule in the mortice held up against the side and see if its square to the face, or plane a piece of timber the thickness of the tenon and put it in the check for squareness of the face of your timber.

 

[SteL]

try rubbing a bit of blue chalk on on the tenon and shoulder. fit it and see where they rub off

I'll give it a go. I am confident there are no high spots, though - but I'd love to be wrong! I could always lower the shoulder that fits tight and then square the bar to the face. Actually, someone might have suggested that before but I've only just realised what they meant. Cheers

 

[SteL]

My guess would be timber movement issues, can you put a rule in the mortice held up against the side and see if its square to the face, or plane a piece of timber the thickness of the tenon and put it in the check for squareness of the face of your timber.

Ha, yes. Why didn't I think of that! I was scratching my head thinking there's got to be a way to do something so simple. I'm on that tomorrow! I have a sturdy thick rule that'll fit through then use my small set square against the face to see how square it is inside.... I'm betting not very! Cheers.

 

[samhay]

Does the tenon pull up square in the other side?
Either way, is the guide piece square to the chop in both axes? If so, I'd be inclined to call it good enough and glue it up. It's tidy on the face and that gap isn't going to cause it to fail.

 

[SteL]

Does the tenon pull up square in the other side?
Either way, is the guide piece square to the chop in both axes? If so, I'd be inclined to call it good enough and glue it up. It's tidy on the face and that gap isn't going to cause it to fail.

I like your thinking! That's what I was thinking but not admitting to myself! It's not square, it is slightly off and if It'd just sit flush I think it'd be close to right - it'd be better than it is anyway. I have thought about calling it good enough because the vice guide underneath is able to be adjusted so I think it would be fine. I just want to get it as good as I can. I can actually get the thing together with the strength of a bear, so I have thought about clamping it in position. I'd sooner it fit in, though but that may become the outcome if I can't get it flush.

 

[samhay]

It depends on how much and which way it's out of square. It could work in your favour - much like we fit vice chops to toe in to prevent racking - but it could also stop you pulling the vice chop hard against the bench at the screw end. Perhaps you could drill the hole for the screw and see how it looks once dry fitted?