Thread: Cutting accurate 45° Mitres

Depends on what you want to do I suppose but Bunnings have some mitre saws on special for $49 at the moment. Not great quality or large size at that price but what have you got to lose? It cuts up to 120mm wide boards I think.
I wanted to cut some for new skirtings and architraves in our rumpus room and trying to cut 5m of mdf skirting on a Triton table saw is just not my idea of fun. I just bought a cheap GMC compound mitre saw which will do the job a lot easier. Cost me $92

Hi dan,

Not sure what you are after with your question. It implies that you can't/don't want to buy anything otherwise the answer to "How do I mark and cut accurate 45° mitres and compound cuts without a compound saw, a 45° square etc" would be to buy a mitre saw or a square.

Assuming you just want to mark out something using your existing gear, then try these websites with explanations of how to mark out with a straightline and compasses:

http://home.wanadoo.nl/zefdamen/Cons...uctions_en.htm
http://whistleralley.com/construction/reference.htm
http://mathforum.org/library/drmath/view/55019.html

For info, you can find these sites and other maths sites on http://mathforum.org/

Simon

One way is to make a square and join opposite corners. So if you're making a frame for example and you want a 45 deg. mitre at the end of piece of timber: Scribe a line across the end that is the same distance from the end as the thickness of the timber, forming a square. Then join opposing corners giving you 45 deg.

Another way is with a compass. You need two lines at 90 deg to each other. Scribe an arc that bisects the two lines. Draw a line that joins the two points where the arc intersects the lines and you have 45 deg.

For a compound cut, you need to perform the same process on both the face and the edge, then join the dots.

Are you cutting with a handsaw?

Thanks for the replies,

I would buy the right tools but I mauled the woodwork budget at the WWW show. The purse strings are now drawn tightly shut. That leaves me with the option of a handsaw. What I am using it for is the jewellery box I'm making MrsP for her birthday. It is on the top so i want it to be square and accurate, with nice tight joints. Also what is the best way to join these corners. I don't have a biscuit joiner (see budget comment above).

Dan

Also what is the best way to join these corners.

Mitred joint with spline. Use a contrasting wood and it'll look flash.

Dan

Without power tools (and even these are definitely no guarrentee of accuracey!), then you must use hand tools. In particular, you will need a backsaw with a mitre box, or better still a mitre saw, and finish with a plane and shooting board. This can produce the most accurate of results.

A hand mitre saw (includes saw and guides) from Bunnings or, better still, Carba-tec, will cost about $45. Or if you already have a backsaw, then just build a mitre box.

The shooting board just requires a few scrap pieces to make it (see the "Best of .." section for details. You can use any hand plane here. Some are better at this task than others, but basically you can use any to do the job.

Method: mark off the mitres so that you have a few mm extra after cutting. Plane this off on the shooting board.

This combination is so good at the job that you may never use another!

Regards from Perth

Derek

The problem with that method is getting the fence on the shooting board exactly square or 45 degrees.

I suspect mine is a bit out but it's screwed and glued down Maybe I should have made it adjustable (i.e pivotable)...........

Adam

When I made my Quick-and-Dirty shooting boards (see http://www.woodworkforums.ubeaut.com...ad.php?t=10855), I first glued and clamped the fence with the aid of an accurate square, and only screwed it down once the glue had dried. I didn't want to risk anything moving. It is very accurate.

Regards

Derek

Thanks all.

I have lashed out and purchased a 45° bevel from Carbatec. With it I will make a shooting board as Darth Cohen suggests (he's using the force ). Just a question on shooting boards, If I make a ramped shooting board for 45° mitres, will the ramp have any effect on the 45°? I wouldn't have thought so but maths was never my strong point.

Dan

No, as i have found out, the ramp does not have any affect on the resulting 45°.

G