method for checking the accuracy of a 45 degree angle tool?

[goldspanner]

Anyone know of a straightforward method for checking a 45 degree angle tool (on a combination square for example) for accuracy?
Of course there's a very easy way to check a 90 degree square, but I can't think of anything simple for other angles?

Maybe such a method doesn't exist?

 

[tomasg]

Hello Goldspanner
Ive seen this guy on youtube a good while ago, but recently had another look at his page.
Maybe i overlooked it at first ..
here's a method
https://www.youtube.com/watch?v=3lRQyIBjDJ4

Mitch Peacock
His videos contains some of answers to questions like this..
I was looking for advice on how to check the accuracy for a straight edges using 3 against each other
flipping each other alternately to eventually make real precision ones
and could not find with a google search
thankfully found that guy has a video for checking this aswell.
T

 

[marcros]

Could you do it the same as a 90 but 4 times instead of 2. It would multiply the error but should work. Or put a digital angle finder on it.

 

[Tom K]

Draw lines on a table as per checking square then check intersection for square using known true angle?

 

[nanscombe]

If you draw a straight line and flip a square to test it for 90 degree, why not use a tested square to draw two lines at 90 degrees then flip your 45 degree tool, against the two lines you've just drawn, to see if they line up.


Alernatively How to construct a 45 degree angle with a compass and a straightedge

 

[Derek Cohen (Perth Oz)]

Check the 45 against a plastic version from your local newsagent. These cheap squares, triangles, etc are extremely accurate.

Regards from Perth

Derek

 

[Mr T]

How about getting a piece you know has absolutely parallel sides, perhaps run through a planer if you have one, then mark 45 degrees form one side then try lining up from the other side. The wider the piece, within the limits of the square, the better.

Chris

 

[Fat ferret]

Corner of a sheet of ply should be pretty square.

Or just cut some mitre joints and check them with 90 degree square.

 

[Billy Flitch]

This is a method I was taught a long time ago as a first year apprentice and it stayed with me ever since and it has served me well over the years. When I was taught it it was called splitting the angle but I have heard it called dividing the angle no big deal really.
I thought it would be better to use pics to explain and for ease of vision I used a carpenters pencil but you could do it just as good with a knife.

Ok pic No 1, mark a square of the shoulder of a piece of wood, for ease of explanation the shoulder I will call the base line and the line marked with the square the Vertical line .

Pic No 2, flip the square over to check the square for true, we all know this right.

Pic No 3 and 4, place a parallel piece of wood against the base line and mark.

Pic No 5, do the same on the vertical line.

 

[Billy Flitch]

Ok Pic No 6 shows the intersecting lines

Pic No 7, place the shoulder of the miter square against the base line and connect the two points check for True.

 

[RobinBHM]

It is easy enough to mark out a board with both 90 and 45 degree marks, you need 1 straight edge to a board.

90 degrees use 3 4 5 to mark out (eg 600mm, 800mm, 1000mm)

45 degrees use 1 1 sq rt 2 (eg 600mm, 600mm, 848.52mm)

 

[goldspanner]

Ok Pic No 6 shows the intersecting lines



Pic No 7, place the shoulder of the miter square against the base line and connect the two points check for True.

Billy this looks like a great way of doing it! Thanks for sharing!

 

[Billy Flitch]

No problem your welcome sir, this is a method used by Carpenters going back in the reaches of time.I hope you wont mind if I explain how this is used to pick up angles all over the place. Again I think it would be better if I explain this with pics.
If this was skirting board you would be looking at it in plan view if it was a chair rail winding its way around a stair well you would be looking at it face on, when used with moulded timbers the mouldings pass 100% to each other.

Pic No1, a sliding bevel is used to pick up the angle where the wood joins together.

Pic N0 2, the angle is transferred to a piece of wood.

Pic No 3, parallel lines marked out.

Pic No 4, Set sliding bevel to intersecting angle

Pic No 5 you can see the angle split and the sliding bevel can be used to transfer the angle to a chop saw or layed out and cut by hand.