Thread: Making my first box

I’ve used a lot of different mitre saws and I’ve never seen one that can cut a truly accurate LONG MITRE. Basically, they’re a ‘site tool’, useful for things like trim carpentry but not for fine woodworking.

With mitres, there’s short mitres like on a picture frame, and long mitres like up the side of a box. Short mitres are relatively easy, but I think accurate long mitres are one of the most difficult things to do in woodworking. I believe it’s actually easier to learn to do handcut dovetail joints then it is to do good long mitres. Setting up to do long mitres involves a lot of trying and failing, and purchase and bedding in of accurate equipment.

I agree with Double.D. The best way to do ‘one cut mitres’ is with a specialised tablesaw sled on a good tablesaw.

The best way to do ‘multi cut mitres’ is with a shooting board.

I used to have two homemade tablesaw sleds - one for long mitres and one for short. Over time I added a lot of refinements such as swing up stops which made cutting the opposite sides to identical lengths easy, nonslip surfaces, clamps and holdfasts, and eye and finger protection for the user.

Tablesaw technique, tuning and very sharp blade are important too.

The short mitre sled was a real beauty. You can make these so that the actual cut angle is non-critical - in other words if your blade has drifted out of alignment it will cut one side of the mitre at say 44.9 degrees and the other will be cut at 45.1 automatically. Just as good.

Also, another thing to worry you about. Don’t use the band clamp to crush illfitting mitres into shape, or a box with illfitting mitres into square. It only introduces tension into the glueup and may very well fail sometime into the future.


By contrast, handcut dovetails require a saw, a chisel or two, and some practice.


Cheers
Arron

I dont think it's too much to ask from a mitre saw to do a mitre cut. I spent some time finetuning mine when I bought it but now I trust it blindly and it never failed me. I've done 7 or 8 boxes with it and they all fit perfectly, even squeeze out, no gaps anywhere, perfectly square corners.

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I think filling the corners will result in a poor visual outcome, depending on the level of chipping and size of any gap you've got in the mitres. You could consider doing a round-over on the edge which could help to disguise the problem.

I've found a couple of photos of a box I made years ago with a rounded effect.

rounded corner 1.jpg rounded corner 2.jpg

if you put a backing piece against the fence that makes the gap less and when you cut the breakout is manageable. I use only SCMS and don't have an issue.

I made sure the SCMS was 45. I didn't think to make sure it was perfectly vertical before I cut. I did do that when it was new but I haven't checked it since.

I was going to use a backing board but I ran into a problem with securing the backing board when doing a long cut. I still haven't figured out how to resolve that without drilling through the cast fence.

So yes the LONG mitre was 1 or 2mm out across the width of the piece. So then I made up a shooting board which improved it. But the shooting board needs some improvements to keep the plane at 45. I think I mostly fixed one issue but introduced other imperfections.

The main issue are these gaps from blow out in the outer corners. I have been thinking of rounding over the top edges to reduce the issue but I'm not sure.

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The problem with long mitres is that, even if they're accurate when they are cut, they won't stay that way for long. As soon as the wood expands or contracts across the grain due to humidity change, the angles will no longer be 45. The only way around this is to use a bridled mitre.

Originally Posted by AlexS

The problem with long mitres is that, even if they're accurate when they are cut, they won't stay that way for long. As soon as the wood expands or contracts across the grain due to humidity change, the angles will no longer be 45. The only way around this is to use a bridled mitre.

What is a bridled mitre on a long mitre for a box?
Plenty of people seem to make small boxes with either mitres or box joints. I am trying to keep it simple and learn the basics. Are you saying my efforts are doomed to fail anyway?

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Your efforts aren't doomed to fail but if you get the same results a second time then a technique change is required. Try getting hold of some pallet material and practice while making adjustments to the set up.

Originally Posted by DaveVman

What is a bridled mitre on a long mitre for a box?
Plenty of people seem to make small boxes with either mitres or box joints. I am trying to keep it simple and learn the basics. Are you saying my efforts are doomed to fail anyway?

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Sorry Dave, my misunderstanding. I was thinking of mitres that were wide across the board, like a picture frame or door. Blame the early start and thinking about my current project. Of course, they are not meant for box corners.

I don't know if you have a disc sander, but if you do you can use it to make accurate mitres. First, set up a fence against which to hold the workpiece, at 45 to the fence. Use two test pieces to get the angle exact - when you put them together they should make exactly 90. The sander table must be at right angles to the disc, and the fence at right angles to the table.
Mark the mitres on your workpiece with a marking knife (not too deep), and cut the pieces close to the marks. Sand the rest of the waste away. When you get to the mark you will see a thin feather of wood peel away. At that point, you have the mitre at the correct angle and length.

Originally Posted by AlexS

Sorry Dave, my misunderstanding. I was thinking of mitres that were wide across the board, like a picture frame or door. Blame the early start and thinking about my current project. Of course, they are not meant for box corners.

I don't know if you have a disc sander, but if you do you can use it to make accurate mitres. First, set up a fence against which to hold the workpiece, at 45 to the fence. Use two test pieces to get the angle exact - when you put them together they should make exactly 90. The sander table must be at right angles to the disc, and the fence at right angles to the table.
Mark the mitres on your workpiece with a marking knife (not too deep), and cut the pieces close to the marks. Sand the rest of the waste away. When you get to the mark you will see a thin feather of wood peel away. At that point, you have the mitre at the correct angle and length.

That is a brilliant suggestion!
I just bought a small sanding machine from ALDI the other week. It's still in the box.
If I can devise some jig to hold pieces at precisely 45 then this would be a great way to go. I must give that a go next time.
What grit is best for that purpose?

Incidentally I am doing this project to develop a few skills before making a large mirror frame in pine. However for that I was planning to do standard mitres with splines. I'll do some YouTube research on bridled mitres first.

Are you painting the mirror frame ?

Dave, here is a pic of the accuracy of using a 45deg sled. Not mine, but one I have access to.

IMG_3689.jpg
And again using the blocks/spacers that Arron described. And the second picture these were off cuts from the first picture.

IMG_3802.jpg

If I can devise some jig to hold pieces at precisely 45 then this would be a great way to go. I must give that a go next time.
What grit is best for that purpose?[/QUOTE]
I just clamp a block (cut at 45) onto the table and adjust the angle by successive approximations (aka trial & error). I'm not sure what grit is on mine but it's pretty coarse - probably 120.
Disc sander.jpg

Originally Posted by Arron

Are you painting the mirror frame ?

Yes.