Thread: The Arcane art of mitre cutting

Aaahh Yes the old dodgey mitre trick, well all will be revealed. All you have to do is search for "shooting boards" and a post by Derek Cohen around august this year (I think). Behold yourself of a good (or even not so good) low angle plane and thou shalt be a master of the "no more gaps" mitre.


However, you may end up like me and still not be able to get all the skirting boards sweet as a shooting board is not practical in this regard. Thats another whole bundle of posts altogether.

Cheers

Yes well I must be careful because I don't want to find a bomb in my jocks, but ...

There are two basic choices to make. You either puchase some machine or jig to cut mitres or you cut them by hand. To do that you need either a compound mitre saw (makita will do) or a good tennon saw. You will also need a good set of marking tools and a bench. But you cannot put a bench in the middle of the back yard so of course you will need a shed. But unless the timber is straight and square to begin with there is little chance that your miter will join properly. So then you need a jointer or a good No 7 jointer plane first , probably both. But then a jointer will not give uniform thickness so you will need a thicknesser as well . But all the dust is bad for you so you will need a dust extractor for healths sake. You will also need some pipe clamps and a band clamp to hold the joints together while drying. But since mitre joints are mostly end grain to end grain joints they will need to be reinforced so you will need a biscuit joiner as well. So before you start make sure that you have you basic equipment at hand:
A well ventilated and lit shed, a SCMS and tennon saw, square and marking qauge, steel ruler, thicknesser and jointer, dust extractor, biscuit joiner a bench and an assortment of clamps . You will also need a linisher or disk sander to touch up the surface of the joints before you apply glue.

Then live a good clean life for at least two week and pray every morning, with fasting before you begin. If all goes well with a tube of filler or two you should have gap free mitres.

Best of luck.

Peter, as one who happily hand cuts dovetails and most other things, I sympathise. I've never been able to hand cut mitres - at least not without a great deal of successive approximations- and have has some limited success cutting them on the table saw. The way that I was shown, that seems to work best, is to do them using a sanding disc.
The disc needs to have a table that's exactly perpendicular to the disc, and a fence that's exactly perpendicular to the table. Set the fence at as near as possible 45o to the disc, and cut two test pieces at about 45o. Sit the (short) inside of the test pieces on top of each other against the fence, and trim them on the sanding disc. Remove them and sit their long sides against each other. The two 45s should now make exactly 90o. If they don't, adjust the fence and try again.

When you have it right, mark the outside of the work pieces to length with a marking knife (not too deep), and cut slightly over length. When you do them on the sander, you'll see a small sliver of wood come away as you get to the mark.

This works really well for me BUT....(there's always a but, isn't there) if the timber you're working with is too thick, the difference in expansion between long & cross grain means that it will open up sooner or later. Splines or slipfeathers are recommended.

Cheers & good luck.

Originally Posted by Corunetes

In the perfect world of mathematics, a ninety degree angle that is halved will leave you with two forty five degree angles right?….. ergo, (great word that eh?) four pieces of wood with the ends cut at 45o when joined will make a box shape Y/N?

Whilst that is true, a 44 degree angle and a 46 degree angle also make 90 degrees. This also works with a 43 and 47 etc.

So if you cut one angle a bit crooked cut the other crooked as well with a corresponding error and ergo a 90 degree angle.

As you have a Triton use the mitre gauge to cut one angle from one side and the other angle from the other side of the mitre gauge and you will have perfect joints.


Peter.

I was going to tell you a really simple way to cut perfect mitre joints every time, but then I thought "No, bugger it. He'll probably send me a bomb anyway so I won't take the chance."

Have I missed something here, or have the above luminaries failed to illumenate those who have eagerly read thus far to the fact that not all mitres are indeed intended to be equal?

Nor do they have to be 45°, which of course will only produce a right angled result (if the pieces are of the same dimension)

If two pieces (or more) of a differing thickness are intended to be joined, the required mitre will be a bastard!

The bastard mitre may also result in angles of other than 90° but I don't know if that would give something other than a right bastard?


:confused: :confused: :confused:
P

Peter,

I dunno if you saw my recent post on a mitre sled in the jigs forum. It works for me

Rocker

Peter,
I would agree with Alex, but using a belt rather than a disk sander. I bought a WASP a couple of WWW shows ago and it has proved to be very useful. I takes only a few seconds to fit to the drill press with its table and has the advantage that all parts of the sanding surface are travelling at the same speed, while a disk varies its lineal speed with the distance from the centre.
Graeme

I have read the replies that this post has received up to now and quite frankly I believe that the replies prove my case. Mitre cutting is not rocket science or brain surgery, .....It is much more difficult than either or both.

Special message to Bob Wilson:... "Very good non move sir!. I congratulate you on your circumspection!"

Peter

A bomb in my undies, eh? I'll take the risk.

While you may of read of my previous recommendation for a shooting board, while fairly straightforward, this is not for everyone.

What I mostly do is send my mitres to Rocker for cutting on his sled. This is quite pricey, but they return perfectly sliced. Kidding aside, a tablesaw sled is a great tool. I don't use one only because I have a sliding table for my saw towhich I can attach a mitre fence. Actually, I prefer the Triton set up, and made one like this for my tablesaw several years ago. This is sort-of "designed inaccuracy on purpose". You'll know what I mean if you look at the Triton system.

If I want a mitre, such as a frame, then I first turn to a mitre saw. No, not a powered version. Just a hand mitresaw, a cheapie I bought at Carba-tec a few years ago. Must have cost about $50 and does not allow for compound cuts. Amazingly, it is very accurate (as long as you clamp down the timber to prevent any movement as you cut). This produces a cut that is good enough for most work (you can fit a multitooth blade). If I want a superclean cut, that is when I go to the shooting board.

I go to the shooting board first when I need to mitre wide boards. Well, I rough cut on the table saw, or with a handsaw, then go to the shooting board.

My next addition will be a "donkey's ear" shooting board, which mitre planes the length of a board (rather than just the cross grain).

Peter, my recommendation would be to buy a hand mitre saw (or send your timber to Rocker).

Time to clean out my shorts.

Regards from Perth

Derek

I took up the challenge and knocked up this in 15 mins,
which included consoling my 5 yr old who had somehow jammed his finger in a clamp.
Tool of choice Nobex Champion mitre saw.
The joints aren't glued just held together with 1 V nail.

Darren

Originally Posted by Rocker

Peter,

I dunno if you saw my recent post on a mitre sled in the jigs forum. It works for me

Hello Mr Rocker...... I have just had a look at your mitre sled and let me say that I think that it looks to be a simple, elegant and efficient way of cutting mitres........... I shall build one tommorrow.........
If it doesn't work, Check your undies for pyrotechnics!

I just use my Incra mitre gauge on the table saw. perfect picture frames every time

Ok here goes. Now I amd going to get a good flaming from one and all.

Answer is simple the Mitre is perhaps the most pointless joint known to wood work! They wont stay closed. They dont look good. They are a pretense attempting to hide something that cannot be hidden compromising the appearance and construction.
In fact they are banned from my workshop!!!!
I believe this is not a case of how but rather Why?
Sorry I usually shut up when I cant say something nice but the Mitre is a pet hate.

Ross