22.5 degrees?

[Osric]

Anyone know of a good way to verify a 22.5 degree angle?  I'm trying to make a octigonal poker table and I cut my pieces to 22.5 degrees (according to my miter box), put them all together and turns out I have like a 1/2" gap when I put them together.  Very frustrating getting all the prelim work done, gluing the boards together and then finding out that the angle is off.

[LeeB]

If you have a good try square, butt two cuts together and measure for 45*. Make a few test cuts before comitting to the actual peices and dry fit to check everything before even thinking about glue.

[Radar67]

Make sure the length of the wood is exactly the same from long point to long point as well.

[Osric]

Make sure the length of the wood is exactly the same from long point to long point as well.

This is the one thing that I am 99.9% sure of.  I have a fence on my box that lets me adust the length to be cut.  I used the same setting for all cuts.

[LeeB]

Another way to check would be to take a scrap 2 or 3 ft long na cut it in the middle. Take the off cut and flip it so you are cutting the first cut off at the opposite angle then butt the two ends together and use a straight edge to check for alignment. That was probably clear as mud. Maybe someone else can explain it better.

[low_48]

LeeB,
I had that thought at first, but it will only work on 90 degree cuts. If you put the two angle cuts together like that, they will only go point to point.
I would suggest that you measure at a longer distance away from the point. Take a 12"long board and cut the end at a 22.5 degree. Put the angle on a flat surface, and the same surface as the point, will be 4.59" off the table. If you like fractions, (4 out of 3 people don't understand fractions  ;)), use a 15 11/16" long board. It will be 6" off the table on the far end.

[TexasTimbers]

Not trying to sound wiseguyish but how come you don't buy a more accurate tool? If you want to use miter boxes they do make affordable but high precision boxes. You should not be having such a significant gap. I suspect your box is worn pretty badly?

You can even make a miter box fairly simply, but you don't want to throw it together. For it to be accurate you must take your time cutting the parts, on a precision table saw (I suspect you don't have a power miter saw?) and be careful gluing and screwing it together so that all 90s are 90s and not 90.2 or those .2 errors end up giving you a 1/2" gap in the end. ;)

[Osric]

Not trying to sound wiseguyish but how come you don't buy a more accurate tool? If you want to use miter boxes they do make affordable but high precision boxes. You should not be having such a significant gap. I suspect your box is worn pretty badly?

Not to sound smart-assish, but as I tell my kids, because I'm not made out of money.  Most of my tools are bought from auctions or from schools that have used them well.  I can live with tools that aren't 100% perfect.  When they do something like this that don't let me make a cut once in a blue moon, I look for ways I can improve the accuracy rather than buying a new tool.

(I suspect you don't have a power miter saw?)

you would suspect incorrectly.  I have a Hitachi 8.5" sliding compound miter.  Picked up at auction for $40.

Thanks to all those who have given me ideas on this.  I'll certainly try them and see how far off I am. 

[Furby]

Ah........ so is your little pointer that tells you what angle you are cutting, set correctly?
Set your saw to 90° and then check against the fence with a square.
Once everything is squared up, then reset your little pointer.

[flip]

I got a guy at the sheet metal shop to stamp me out a pattern that is something like 22.8.  Why heavy you ask.  When I lay up a circular table veneer each piece will be a bit heavy.  When you assemble the two halves they will look, for lack of a better word, like a packman.  If you lay the two halves on top of each other you can use a straight edge and just nip the extra off with the router and you will have two perfect halves to glue together.  No one will notice the minute difference in the center 4 pie slices.  Any way that's how a lot of guys that do veneer do their layups (unless you have a laser cutter).

[SwampDonkey]

Wood shrinkage possibly?

[treecyclers]

I personally did the trick with the 2 pieces at 22.5 equal 45, as in make a test cut and flip one piece over and checking for 45 degrees against a known square that's true.
I also bevel the cuts slightly to accomodate slight variations in the final assembly.
Superdave