Cutting Mitres

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thecoder

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No matter how I try to get the mitres correct with my mitre saw (handsaw in a frame type) I just dont seem to be able to get them bang on. How do you guys out there that make boxes etc get your mitres perfect ?
 
Cut your mitres best you can with your frame handsaw then use a shooting board to get them dead accurate.

Here is a design for a board which I've used for years. The advantage over other designs is that it it cuts the mitre with the board flat therefore there is no reasonable limit to the width of board - ideal for box making.

The addition of a toggle clamp makes it even better.

It's very worthwhile taking the time to make this before embarking on much box-making. It will save heaps of time and frustration in the long run :)
 
One tip I picked up is to mark your cut line with a scribe, fairly deeply, cut it roughly to size and then sand it to length on a disk sander.
As you get close to the line the wood starts to break off and you can see when you've reached the line.

It's not easy to explain but you would see what I mean when you tried it.
 
Have a look here http://www.youtube.com/watch?v=H0-m1TzWsFY at about 2min 30secs.
I have a table saw and have made a crosscut sled with the kerf cut at 45deg, the trick is to make the front fence EXACTLY 90 deg to the blade, when I tilt the blade to 45deg. I use a digital angle meter, bit of a roundabout way but I can finally achieve perfect mitres.
Andy
 
Mitres are the most difficult joint to cut correctly, and the easiest to machine, if you have the equipment.
If you have a router table with a track built in then use a 45 degree cutter.
If you have a TS make a mitre sled, either that or you'll go bald with the head scratching.

Roy.
 
Accuracy, Yetty, is a misnomer when it comes to mitres, people sweat blood attempting to obtain two perfect 45s. And they are not necessary!
What we need is a perfect 90 degree when brought together, thus on a table saw provided you cut to the left of the blade and then to the right of the blade, 45 degrees, more or less, totals 90.
Every time a coconut!

Roy.
 
Roy, I've definitely sweated blood trying!

Point taken about the sum needing only be 90 degrees, thanks. With the equipment available to me, the router table with 45 degree cutter worked best by far.

I must be having a grey moment. I can't understand how you can achieve a 90 degree mitre joint, using table saw (I assume we are talking about tilting the blade here), unless the blade angle is at 45 degrees. Surely cutting the work left or right of the blade makes no difference - the resulting angles on both pieces are same angle. Have I misunderstood your post?

(I appreciate this approach works when butt jointing to make a flat panel, but not 90 degree mitre joint.)
 
Digit":1tm8wqdo said:
Mitres are the most difficult joint to cut correctly, and the easiest to machine, if you have the equipment.
If you have a router table with a track built in then use a 45 degree cutter.
If you have a TS make a mitre sled, either that or you'll go bald with the head scratching.

Roy.


I have a router table with track and have looked at the possibility of buying the locked mitre cutters , are they the same ad the ones you mention ?
 
They aren't very complicated - just get yourself one of these:
images

and cut the opposite sides in pairs so they are exactly the same length. It doesn't matter how accurate you mitres are, if the opposite sides are different lengths then the corners will be out..

Steve
 
Yetty, picture frame type mitres on a TS are cut with the blade vertical, again more or less, 'cos if you cut alternative left then right the joint matches in both planes.
Box type mitres are cut as you understood with the blade canted over.
Let us assume that you cut with the wood on the left of the blade. Now let us assume that the blade is 47 degrees.
The piece that you wish to join to that cut is now cut on the right of the blade.
The first cut was at 47 to the TABLE + 90, thus the right hand cut is 43 to the TABLE.
Total, 90 degrees.
They must be cut in matched pairs.

Roy.
 
Yetty":g5ok8r43 said:
Roy, I've definitely sweated blood trying!

Point taken about the sum needing only be 90 degrees, thanks. With the equipment available to me, the router table with 45 degree cutter worked best by far.

I must be having a grey moment. I can't understand how you can achieve a 90 degree mitre joint, using table saw (I assume we are talking about tilting the blade here), unless the blade angle is at 45 degrees. Surely cutting the work left or right of the blade makes no difference - the resulting angles on both pieces are same angle. Have I misunderstood your post?

(I appreciate this approach works when butt jointing to make a flat panel, but not 90 degree mitre joint.)

Here is a page describing one table saw method.
 
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