Thread: How do I get precise 45 degree corners?

Hi Alan,

For repetitive cuts without setting up the table saw I built myself a table saw sled with a 45 degree fence. Works a treat for me however keep in mind if you want super prescise then then your table saw will need to be finely tuned. The only limitation is the blade height which is further reduced by the thickness of the sled.

Cheers

Personally I have never have much luck hitting the perfect 45 degree's straight from a saw.

I get as close as possible then fine tune it with a handplane and shooting board.



joez

I do my mitres on the disc sander.
First, mark the mitres on your work with a marking knife. Don't cut too deep, especially on the outside.
Set up the disc sander. First, get the table square with the disc. Then, make a fence that you can clamp to the table. It needs on 45 deg (approx) end. The top & bottom of the fence need to be square to the face. Clamp the fence to the table. It must be square to the table and close to 45 deg to the disc.
Cut a piece of scrap with parallel sides in half at about 45 deg. Using the fence, sand the two 45 deg ends against the disc. Flip one of the pieces over and place the two ends together. The angle between the two pieces of scrap should be 90 deg. If it isn't, adjust the angle of the fence and repeat until it is.
Now, with the inside of the joint against the fence, sand the mitre. As you reach the line you marked, you will see a small feather of wood start to peel off. You have now reached your cut line, and should have perfect mitres.

I use a docking saw preset with an 80 tooth fine blade which gives a great result.

I also have a picture framers guillotine but found that the saw gives just as accurate cut and quicker for mass runs.

Other than that cut as close as you can with a backsaw and as suggested earlier shoot with a plane.

One other option that I use and it is quite good is a framed saw and miter box set up.

Don't know about the really cheap ones but I have picked up a couple of Stanley ones from ebay. Anywhere from 10 - 40 bucks plus postage.

I use them at trade shows when i'm doing box making demos.


Cheers


Steve

G'day y'all
If you want precise results on miter cuts for a picture frame then try a cross cut sled set up with a guide bar. For miter edges on a box use a donkey's ear set on guide pins Take a look at my sled on http://www.woodenclockparts.com
I build the sleds on a CNC machine so they are slap on.
Regrds
Joe

I have found using the Wixi digital angle gauge gives me a perfect 45deg. I stet it on the top of the table saw and zero it then I set it on the side of the saw blade (the magnetic base is good) to check the blade is at 90deg to the base then I roll the blade over till it reads 45deg make two cuts in two different pieces of wood then line the cuts up flat on the saw table if I can't see any light through the cut I know that the angles are dead on 45deg. This method has never failed me I usually only have to make one test cut, the digital angle meter gets it right every time so far.

Hi AllanS,

The best method for cutting precise mitres for this sort of work or for picture framing is to cut 1mm or thereabouts outside the designated length and then do a finishing cut or two with a gilluotine. You can do the same job with a picture framing drop saw if you can afford the $12 to 15 k needed to acquire one.

When cabinet shops used solid timber in the old days everyone had a precision gilluotine that was originally foot operated or latterly converted to air actuation. Used mostly for fine fitting of door mouldings or panel mouldings on furniture.

You can buy a bench top hand lever operated one from Carbatec for a very reasonable price around $200 I think. I've got a colleague who has one of these and its a super machine for the job.If he didn't have one then I'd have to have one!! Just don't use it for cutting to length from the solid...it's not meant for that sort of heavy duty application.

Happy paring. Old Pete

Originally Posted by AlanS

From time to time I make small wooden boxes...all with mitered corners. My 'chop box' has too much slop to allow for consistant/ percise cuts...If I set up my TS, then I have to remember to do all my preliminary cuts first...then the miters. Last nite, after having re-set the TS to 90 degrees, I wanted to make the box smaller...back to trial/ error in setting the blade to 45.
Any ideas? I always wanted a small, table top TS that is SET to a precise 45...and I mean PRECISE. I do not want gaps.
PS...tried the 45 router bit idea...didn't have much luck.

I have tried many methods in my time having made many picture frames and boxes. I had a hand operated guilotine and found it useful but didn't use it very much. If you set your TS up accurately, (I use the digital angle guage) and a good cross cut sled, your angles will be perfect every time. You can also set up the saw blade with one of those plastic 45deg angles that you get from office works. You don't need the digital angle finder if you don't want the expense of buying one. The shooting board is another cheap and easy way to do the job.

The secret is cutting the sides and front of the box exactly the same length as each other.. Any slight difference in the lengths on any of the pieces will result in a bad mitre and throw the whole thing out of whack.

Originally Posted by munruben

The secret is cutting the sides and front of the box exactly the same length as each other.. Any slight difference in the lengths on any of the pieces will result in a bad mitre and throw the whole thing out of whack.

Ain't that the truth!

Something to remember when doing mitred frames for frame & panel lids is that even if your mitres are spot on, if the frame stock is too wide, the mitres will open up. This is because the frame pieces will expand & contract across their width with humidity changes, so the angle will no longer be 45*. In this case, you are better off using a mitred bridle joint.

I finish up mitres on the disc sander. There's probably loads of fancy kit out there that does amazing angles, but this is the best I can manage with what I've got.

I calibrate the shelf angle to the disc before each sand. The only other thing is to make sure that along with your perfect angles you have perfect side lengths, otherwise it gets wrecked anyhow.

-Matt

I made this to cut mitres on my table saw. The adjustable fence allows me to cut each piece and mitre it to exactly the same size. To get a perfect mitre I cut and mitre to about 2 mm longer than required and then adjust to take 1 mm off each end.

I got myself one of these and it has taken all the pain out of checking angles.

Heavy Duty Digital Angle Finder : CARBA-TEC

regards

wixey digital angle guage and an incra 1000se mitre guage with shopstop. spot on for angle and length first time every time. no test cuts, no shooting boards, no sanders, no second cuts to sneak up on it a mm at a time. just set it, cut it and move on with the next phase. and if something happens to a piece the setup is totally repeatable so you can easily duplicate the original piece if you need to. Its almost like cheating.

Doug

I take the board I am going to use for my box and use a 90 degree V bit on my router table with the size of the bit being dependent on the board thickness. I cut just deep enough that it doesn't cut all the way through so that when I fold the board at the perfect 45 degree cuts the grain is intact all the way around the box. It will sometimes break when you fold it together, but the grain is still continuous. I of course cut the slot for the box bottom before I cut my miter joints as well as any other cuts that would be a little tricky once the carcase is glued and dry. I then use, depending on the wood thickness either a 1/16" slotting bit or a 3-3/8" carbide tipped saw blade in my router table to separate the lid from the box bottom.