Joining wood at 135°

[nigelmercier]

I'm going to build a [45°] slope fronted box to flush mount my CP180 and ... [Matsutec HP-33A AIS Transponder] ...

Woodwork has never been my best skill, so looking for tips. The box will be made of strips of solid 15mm thick Sapele, butt-joined on the sloping face to give a 170mm width.

My original plan was to make the 135° corners by cutting a mitre that bisected the angle, but now I think that it will be easier and neater to cut the edges at 135° so the joins are about 20mm from the front face. Picture below: red lines are the constraints, the black lines are the outline of the proposed box.

I've got a wood router, and access to a router table if I need it. I had hoped to use a 45° dovetail cutter, but none of them seem to cut to 15mm depth.

Using a circular saw will leave the edge too raw, and I am incapable of doing this with a wood plane.

Any suggestions on how to best cut these angles, or any other tips?

 

[Robert Wilson]

Keep drinking plenty of water - was my first thought for working in that heat......................... doh!

 

[Deleted member 36384]

Use dowels to locate the two halves of the butt joint if you do not want screw holes visible on the outside.

 

[prv]

Not sure I've entirely understood the question, but part of the solution might be a router jig knocked up out of scrap wood that allows the router to cut the required angle. Basically just a couple of rails at the correct (different) heights to tilt it over the right amount.

Another cheat I've used when joining at a random angle is to round-over one edge, and cut a matching concave groove in the other. Now there's a tight wood-to-wood joint at any angle (within a certain range). Not quite as strong, perhaps, as a joint cut specifically for the correct angle, but often strong enough for what's required.

Pete

 

[Giblets]

Where' Captain Coochie when he is needed?

 

[ghostlymoron]

The secret of successful planing is to have the blade razor sharp blade - I only discovered this recently. I can now slice through the toughest end grain with ease! If you can't use a plane, you won't produce neat work. Sharp blade and practice. I'd just do a butt joint with dowels for a 45° join.

 

[lw395]

Last time I did something similar, I clamped the belt sander to the bench and used a 45deg guide.
I'm sure isn't not purist, but it worked OK.
Alternatively, mitre saw?
Razor saw in mitre block?

What could look nicer than a good fillet of WEST?

 

[nigelmercier]

Picture added to OP, mockup below: [Oops! Too big, replaced]

The added space around the CP180 is deliberate, I may get a CP300 one day.

I may make it a bit shorter on the RHS, but this size will just allow my printer to fit alongside and covers the holes left by the old plotter mount.

This is where it is going, the red constraint in the drawing is the upright on the left:

 

[sarabande]

have you come across Kreg pocket screws ?

https://www.kregtool.com/store/c20/kreg-jigreg-screws/

 

[Lakesailor]

My original plan was to make the 135° corners by cutting a mitre that bisected the angle, but now I think that it will be easier and neater to cut the edges at 135° so the joins are about 20mm from the front face.

However there will be end-grain visible which may colour differently when varnished. Go back to bisecting the angle. You only need the mating edges to be spot on. Join using filled epoxy. Wood flour from the same wood will be invisible.

 

[rogerthebodger]

Join using filled epoxy. Wood flour from the same wood will be invisible.

Last time I suggested that I was accused buy another prolific poster of being a bodger. But I have used that technique for years with good result. In fact I was learned it from my woodwork teacher at school over half a century ago .

 

[nigelmercier]

However there will be end-grain visible which may colour differently when varnished...

Grain runs along the length, see the mockup. At first I thought this would be odd, then remembered that the original table had a hinged flap with longitudinal grain.

 

[prv]

Using a circular saw will leave the edge too raw

Surely you're going to be sanding the whole thing before finishing anyway?

If you've got a saw that can accurately cut the required angle, that's probably the right answer.

Pete

 

[PuffTheMagicDragon]

I would suggest that it would be aesthetically better to have the top overlapping the front, perhaps extending it by 3mm, cut at 90 degrees but with the edges slightly rounded. This would also hide the "raw" finish that you mention as being a result of the circular saw and will provide a sort of neat 'frame' to the face upon which the instruments are fitted.

BTW, unless the "raw" finish is really bad (in which case you probably have a blunt blade) sanding after assembly (using a sanding block) will quickly remove any signs and will give a good finish. This can also be done with a router by using what will be the vertical face as a support and setting the end cutter just the thickness of a paper above the router base.

 

[rob2]

Another cheat I've used when joining at a random angle is to round-over one edge, and cut a matching concave groove in the other. Now there's a tight wood-to-wood joint at any angle (within a certain range). Not quite as strong, perhaps, as a joint cut specifically for the correct angle, but often strong enough for what's required.

Pete

This is the way that wood strip hulls are built, allowing each strip to twist and turn relative to its predecessor without leaving a gap. In this instance a biscuit joint would be much better suited as the OP wishes to create a flat surface. I agree that it would look neater with the horizontal and vertical elements shaped to the angle, so that they frame the panel. Incidentally how are you going to open it for access - even as an instrument panel you have to get at the mounts and wires from time to time...?

Electric planes are very cheap and effective if you have no skill with handtools.

Rob.

 

[nigelmercier]

I would suggest that it would be aesthetically better to have the top overlapping the front, perhaps extending it by 3mm, cut at 90 degrees but with the edges slightly rounded...

... I agree that it would look neater with the horizontal and vertical elements shaped to the angle, so that they frame the panel...

Not quite sure what you guys mean. The 135° edges are going to be rounded at the same radius as the upright on the left, I haven't added this to the drawing yet as I'm still tinkering.

To fix it I plan to slide the whole thing right to left into a hidden flush mount (see below) with a single screw on the right hand face to hold it in place.

 

[PuffTheMagicDragon]

Perhaps this sketch will be easier to understand. What I have in mind is a top that is unbroken so that any movement in the wood does not give rise to problems as when there are two pieces that are joined at different angles.

The rounded front edge of the top will mimic the rounded side piece of your chart table, seen on the left of your photo.

 

[LadyInBed]

I would cut both edges at 67.5° so that they butt up with no end grain showing.
Or you could even leave the horizontal and vertical sections at 90° and cut the angled face back at 45° top and bottom, any joint overlap would be on the inside and not seen.

 

[usernamenotvalid]

Join using filled epoxy. Wood flour from the same wood will be invisible

That's not the case. Even if you use the lightest coloured pine when mixed with epoxy it will turn a darker shade of brown and will get darker with subsequent varnishing. Go back to the rough sketch above and reverse the lower angle to hide the endgrain. If you use epoxy, and you don't really need to for this, very carefully mask off any area where you don't want to have to sand the resulting stain. Personally I would use a PVA adhesive and lightly sand the edge to match the curve on the upper flat piece.
Cheers John.

 

[Amulet]

You need this cutter to do the mitres:
http://www.trenddirectuk.com/11-17x1-4tc.html
or one of the many 45 degree bevel cutters available from the same source if you want to do it that way.

Modern glues are good enough to make a butt joint strong enough. Doweling is a problem because it will be hard to get the position accurate so some planing up will be necessary.

You say you can rough cut angles on a saw. You could make a fillet to screw in from the inside to hold it together. You could even remove the fillet after the glue has set if you cover it in shiny packing packing tape to stop the glue sticking to it.

Here's a silly idea:

I assume the geometry stops you from taking the simple approach of sticking in a plank at 40 degrees and doing away with the horizontal or vertical bits. If you this were possible you would have a simpler job on your hands and would be free to choose an angle other than 45 degrees if it suited. (You could make a fairly bodged of the edges as they'd be completely invisible.)

From general expertise exhibited on the forums, I'm sure a man of your stature can learn to use a plane. Buy a good stone and a honing guide. Make it sharp, set the capping iron really close to the cutting edge (less than 1 mm). Set the plane fine. Wax the bottom if it is sticky. And cut the wood in the direction it wants to be cut.