Help an idiot fix an 'upside down' mitre joint

[Stickmangumby]

In this project, I have a very small margin for error. I didn't get any surplus wood, I don't have any money, and I have six days to finish it.

Given the above, I was very (very!) careful in deciding on dimensions. I got it just right, so that I wouldn't waste more than a couple of cm of wood.

I was incredibly careful to follow the measure twice, cut once (aka the measure at least 8 times so I don't screw it up) principal.

However, I still messed it up... I accidentally cut one board with the two mitres parallel (ie both 45 degrees, rather than one 45 and the other 135)!

So now I am in a pickle. I've been making cuts with a circular saw, and I don't trust myself to handsaw it straight, so the kerf of the blade is about 3mm. The side lengths of the mitre are 25mm, so I figure if I cut it off and flip it over the length of the board may be too short compared to the opposite side (which I already cut :( ). I have enough wood to make another mitred section, but I need to know how to fix it to the end of the board once I saw off the current botched part. I will be routing into the board, so I don't want to put any screws or nails into it. I'm unsure whether PVA wood glue will be strong enough to hold it together while I'm routing a groove into it...


What do you reckon? Thanks for the help :)

[silentC]

Bit hard to say without knowing more about what you are making. Is it a frame part or a carcase side? Can you reduce the overall size of the whatever it is and cut the opposite side down to suit?

[Stickmangumby]

I'm making a four sided rectangular box, with each of the four corners mitered. I can't change the side length to make it possible to just cut the correct angle into the board. It seems like my only option is to cut off the dodgey part and fix on a replacement, the right way around, but I'm not sure how the best way is to do this.

[silentC]

There are a few splice joints you could use. Is it possible to arrange it so that the dodgey part isn't seen? It will be hard to join to bits together end to end without it being obvious. A splice might be your best bet. Can you change the height?

[echnidna]

You may be able to glue the offcut back on, but the only glue I would use for this is expoxy.

[Stickmangumby]

To clarify:

http://img517.imageshack.us/img517/3510/miter8oi.jpg

A is the birds eye view of the box, showing the miter joints that will join the sides.

B is what each side should look like.

C is what the side I cut wrong looks like.

D is my proposed solution; cut off the wrong part, glue on another one.

[Stickmangumby]

There are a few splice joints you could use. Is it possible to arrange it so that the dodgey part isn't seen? It will be hard to join to bits together end to end without it being obvious. A splice might be your best bet. Can you change the height?

I'll arrange it so this joint is at the back of the box. Can anyone offer a second opinion on the epoxy suggestions by echidna?

Thanks for the help so far silentC and echidna.

[silentC]

If you were prepared to make the box shorter, there is a way of fixing it using a scarf joint that is more or less invisible if the grain is not highly figured. You could retain the length and depth but the height would be slightly less. Let me know if you want to know how.

If you don't want to change any of the box dimensions (and don't want to pay for any more wood), then you'll need to glue a new bit on. I would use some kind of scarf joint or a splice. I don't think butt joining is going to be very successful. It will stand out. To splice it, just cut an opposing 45 deg mitre on a scrap bit and glue it on, then cut your new mitre.

[TassieKiwi]

You could:

1)Make a feature of the corners with a vertical 'post' in different timber, and a 2mm detail line. Might look a bit fussy though.

2)Cut off the offending northern hemisphere mitre with the thinnest blade you have. BS? Drive over to Lignum's place, and have him domino the cut piece on again. He'd love it!

Commiserations my friend, we've all done it.

[TassieKiwi]

Serendipity, I love. This is what I mean (thanks John):

http://www.woodworkforums.ubeaut.com.au/showthread.php?t=34145

[Stickmangumby]

http://img132.imageshack.us/img132/7797/scarf8fw.jpg

To confirm, does this diagram illustrate the process of using a scarf joint to fix it without changing the box dimensions silentC? If so, would you be using epoxy as echidna suggested, or do you reckon wood PVA will hold up ok?

Thanks for the suggestions TassieKiwi :) I'm in a real hurry though because I've gotta finish this asap for a present, so it looks like the above method is pretty much all stations go.

[Scissors]

A scarf joint should be a much shallower angle than 45 degrees, but since it's a box and therefore won't be under to much stress you could probably get away with that. Definitely use epoxy however.

[silentC]

Yes, although a scarf joint is normally much longer, usually something like 8 times the thickness of the material. There's not a lot of long grain gluing surface there. If you use a good strong epoxy as Bob suggests, it should be OK. It's only a box and not subject to a lot of stress. I don't think I would trust PVA.

[Lignum]

Tassi got it. Although im a fair drive away, i would (if i was in this position) just but it and put four 5mm dominos and PVA then re miter. It would be super strong, and the slight end-end glue line will just go to the back where the hinge will be.

[Bob38S]

Would it be possible to add a feature eg different coloured wood in the centre if the offending piece? [It would basically turn each side you do this to into 3 pieces].
You would also have to add one to the parallel side or all sides if you choose. What I'm suggesting is either a rectangle/ diamond shape in the centre of the side[s] - this would be fiddly sure, but would move the ends out far enough to fix the problem.
Just a thought, hope you get it solved,
regards,
Bob

[echnidna]

By gluing the scrap back on the inside half of the new mitre is still part of the original stock. The only part glued on is the outside half of the new mitre so the joint should still have good strength

[banksiaman]

my 2.2c worth,

A scarf joint would be strong enough for a box, but the join line would be obvious no matter how careful you are. Even if you put it at the back, boxes get picked up and admired, so it would be seen. :(
If it were me, I would put an extra piece as a feature in the middle or at a third or two thirds the length, whatever suits the design. The cross section of the extra piece could be bigger than the sides thickness and the side pieces housed into this - making the glued up side stronger. Assuming the lid design could allow for a thicker bit???

Sorry, I don't have a way of doing a drawing to illustrate at present.

This is what makes woodworking exciting - or is it just me???

Good luck regardless.

Chris

[echnidna]

mmm. halving and rejoining the side with a contrasting timber could look like a design highlight. The perfect solution, if you can't hide it make it stand out!!

[banksiaman]

What BoB38S said, I spent too long composing my reply...

Chris

[Gumby]

Way too hard in my view and any movement of the timber creates a gap.
Do what I did. Buy a Gifkins jig and forget about mitre corners on boxes.

[Lignum]

Mitered corners look heaps more classy on quality boxes. A gap only appears with miters if the sides are backsawn, and rarely if qtr sawn is used :)

[Gumby]

Mitered corners look heaps more classy on quality boxes.

Not when I cut them they don't :rolleyes:

[Lignum]

Not when I cut them they don't :rolleyes:

:D

I must admit though, i seen the Gifkins at the last wood show and was mightily impressed. Makes very nice and clean joins:)

[Auld Bassoon]

:D

I must admit though, i seen the Gifkins at the last wood show and was mightily impressed. Makes very nice and clean joins:)

:D :D Can "she" make 2mm domino joints? :D :D

Just teasing mate!

[Gumby]

:D

I must admit though, i seen the Gifkins at the last wood show and was mightily impressed. Makes very nice and clean joins:)

Exactly. Any jig which makes it look like you've been practicing hand cut dovetails for 20 years gets my vote. :D

[echnidna]

So Gumby,
what CAN your forum do for you ???? :p

[Two-Words]

So Gumby,
what CAN your forum do for you ???? :p

No Comment :cool:

[echnidna]

What else??

[scooter]

My 2c.

I reckon if you're going to glue a piece on, then cut the mitre the right way, the best way would be to butt joint it, drill through the end of the now-longer side & glue in dowels that will span the butt joint. The mitre could then be cut the correct way, and the ends of the dowels will be hidden inside the mitred corner.

This way would be no more or less obvious that the short "scarf" joint, but wouldn't require epoxy and would be simpler to align & glue up.


Cheers...................Sean

[Stickmangumby]

Thanks for all the help guys. I didn't have any nice wood to put a panel in the middle of it, and I was in a rush, so I expoxy'ed it, and it worked fine. I routed the sides yesterday and the joint is holding up fine, it's a bit ugly but not a big deal.

Thanks again :)