Mitre joints/accuracy - thoughts/help required!

[J4m3sg]

Hi all,

I think I know the answer to these 2 questions, but I thought I’d ask people far wiser than me in case anyone has any bright ideas…

I’m building some cabinets. I’d like a long mitred edge. I’m using birch play and I’d like to keep the edges exposed cos I kinda like them. It means I need to somehow join these long edges, and I’d LIKE to do it without using any hardwear or any additional battens where I screw both sides to it. Does anyone have any bright idea how I might achieve this? (see Pic1 below)

Second question – I’m REALLY struggling to get accurate cuts for these mitres with my circular saw. I’m using guide clamps and a few jigs I’ve made but the tolerances seem so small I’m actually wondering if it’s possible with the tools I have. Has anyone done something like this with a circ saw or are there any tips/tricks that I’m missing which might make this easier/hide my inaccuracies?

Couple of pics (Pic2 & pic 3 below) below to illustrate the point…

 

[novocaine]

cut them then shoot them to 45 with a decent plane and a guide jig (top and bottom batten that lets the plane rest at 45 degrees is easy enough to make)

mitreing a long edge like that isn't likely to come off perfect from the cut. impossible to set your fence to the required tolerances.

 

[novocaine]

example attached.

http://www.theunpluggedwoodshop.com/mit ... board.html

 

[dzj]

A circular saw isn't the ideal tool for the job. A proper table saw or router table would be much better.
You might eventually get your circular saw to make these cuts, but there'll be a lot of tinkering involved, a lot of
practice cuts on scraps of ply.
Unless you're going to paint it, I'm not aware of any tips/tricks that might hide your inaccuracies.

 

[custard]

Getting it absolutely perfect straight off a circular saw is tricky and needs both decent kit and a fair bit of operator experience; but the fact is you can get way, way closer than you're doing in those photos!

The trick is to unplug the saw, fully plunge it, then use a 45 degree mitre template to set the angle between the sole and the plate of the blade. You need to take care to avoid the teeth as that will throw the set up right out, and you also need to make sure the mitre template is perpendicular to the saw blade for a true reading. Really take some care with this and you'll get very close indeed. Any slight variation can then be improved further with an ultra light skimming cut from a block plane either on the inside or outside of the mitre joint as required to get the joint closer.

But be aware, 45 degrees on the cut is only half the equation, you also need to get the length of the two sides perfectly identical, and the lengths of the top and bottom perfectly identical. This is actually every bit as difficult as getting the 45 degrees accurate!

Then the final issue is the glue bond. PVA has zero gap filling properties, so the joint does need to be very, very good if PVA glue is all you're using. A spline would really help re-inforce a mitre joint.

Good luck!

 

[Graham Orm]

Lock-mitre http://www.woodworkerz.com/lock-miters/

 

[Mr T]

If the parts aren't too long you could cut shy of the line then use a 45 degree jig on a shooting board to trim to the line.
If you have a router you could make a jig to do a trimming cut on the ends with a router.
Alternatively you could use a lap joint instead which would look almost as good as a mitre.

 

[RogerP]

Make the mitre board shown by "novocaine". I made one years ago since when accurate mitres have always been quick and easy.

 

[Stocksy27]

festool s55 and guide rail would cut them if you dont have access to a table saw

 

[blackrodd]

As has been said, it's difficult to get the sheets square and same sized even before the mitre.
You must improve you're tool skills for the accuracy needed, This all comes with time and confidence.
Don't lose heart, you'll get there!
Regards Rodders

 

[rafezetter]

To answer the question on a "fix" for the existing mitres, there is a trick used for when window trimming is applied (probably known but frowned upon by the majority here) and that is to run a thin kerf saw down the centre of a mismatched joint starting at the open end, it will cut away the excess thus closing the gap a bit, you will however have to make certain both sections are well clamped and cannot move. It's possible to use 90deg blocks to clamp a little way down from the top edge and bottom, start the cut, then move the blocks as required up and carry on the cut below.

It's best to use a thin kerf blade and take nibbles instead of all at once, and it will also rely on a very steady hand for a long joint like that, but with care it would reduce that gap to the point of acceptability, however getting it "factory perfect" this way is not possible, and will require a whole recut.

Another possibility in this instance may be to close up as above then modify the design adding a very small faceframe to the item, which will actually make your life easier regarding if any doors need to be hung, and is the normal practise for most cabinet faces.

 

[Benchwayze]

('Ediot' A cross between edit and idiot) Because I think I am talking rubbish here! What was I thinking about!!!
So, I edited out this post, because I realised I was thinking completely at cross-purposes on the problem the OP was having. My apologies!

Of course, I was never any great shakes with a Table-saw! :mrgreen: (hammer)

 

[J4m3sg]

Thanks for the suggestions everyone - I'll think I'll give that shooting board a try

 

[Wizard9999]

cut them then shoot them to 45 with a decent plane and a guide jig (top and bottom batten that lets the plane rest at 45 degrees is easy enough to make)

mitreing a long edge like that isn't likely to come off perfect from the cut. impossible to set your fence to the required tolerances.

Another beginner happy to raise a hand to say that getting tight mitres has been elusive - not such a disaster so far as I have used workshop furniture to practice.

That shooting board looks a beauty and I think I will also have a go at one. But am I the only beginner who can't but reflect on the irony that in order to get accurate mitres I need to produce incredibly precise 45 degree angled pieces for the necessary jig :lol: .

Terry.

 

[RogerP]

... but once you've got it right it stays that way and mitres, long or short, become so easy!

 

[novocaine]

as said, you've only got to do it once, so do it a few times and one is bound to be right. lol
because it doesn't matter if the pieces aren't exact thickness (you've removed the need for 3 dimensional accuracy by taking out the need for 2 planes to be exact), you can plane it down to 45 degrees if it isn't right you keep going till it is, as long as the top rail isn't floppy when you are done and the bottom piece is still long enough to support your work piece it and the sides have enough to screw them down it doesn't matter.

I hope that makes sense, it does in my head but it doesn't want to come out very clear.