Squaring up a mitre saw accurately

[Waka]

RD

Thanks for sharing your method of checking for accuracy, very informative. I to have the kapex and have to admit that I haven't done any checks apart from checking the result.

And all you guys that are talking about PT setup, how about sharing with the not so knowledgeable?

 

[wizer]

I use a dial gauge. It's explained in the videos on this site:

http://wiki.owwm.com/Jointer%20And%20Pl ... ideos.ashx

Tho, MarkW showed me how to do it, I found these after.

 

[joiner_sim]

so what do you do to correct the 45 mitre?

Adjust the saw until the cut on the head and cill are correct to my framing square.

 

[Jeremys]

Thank you for posting this RinkyDinky, its an interesting technique.

For my money I would put the inaccuracy down to your square. You are measuring .1 out at 33 to 50% of the square length. (guessing from the pics). assuming the square is perfectly straight it would only have to be out by .2 to .3 mm over the whole length, and I dont think you would detect this by flipping it over and scribing a reference line. And at that tolerance assuming an inexpensive square is straight (as opposed to square) is risky. If you want to work to these tolerances I would invest in a decent starrett or incra square, and treat it like its made of glass!

 

[FatFreddysCat]

What a complex way to achieve a simple result. Squares should always be checked for accurracy against a straight piece of material especially if they've been dropped. Once you have a square which is accurate making a test cross cut in an offcut will allow you to check for verticality first and to adjust accordingly. Once you are cutting vertically the squareness of cut can be checked by making another test cut and checking that with a square then adjusting until it's bob on. Lastly make two 45° mitre cuts and offer up the pieces to each other then check with the square. If you see any light then the cut isn't square. Mitre Mate helps do this check.

Every sliding compound mitre saw I've ever used has showed signs of the frame or arm flexing and the larger the blade the more likely it is to flex. Also a cross cut will flex the blade less than a dust or trim cut where only one side of the blade is in contact with the work.

We bought a Kapex at work a couple of months back and it's better than many (less flex) but it still goes out of alignment just the same as the Makitas, DWs, Hitachis and Elektra-Beckums especially if you throw it in the back of a van and take it out on site anywhere.

As for twenty thou accuracy in a 12 inch cut all I can say is that wood can swell or shrink more than that in a cold van or a warm shop so in my trade we tend to rely on a sharp block plane or sanding block to quickly touch up a joint to make a good fit. It's more important for it to look right tha be right IMHO