Need help squaring up cross cut sled.

Your back 'fence' must be curved.

That is what I thought, but It's hard maple and it looks straight, when I lay it flat there is no wobble or movement.

Put a high quality straightedge against the fence and look for gaps. That should end any debate about the fence being the culprit. Hardwood is not the best choice for jigs and fences. I prefer finish grade plywood with 9 or more layers for the best chance of keeping things straight and square. Wiping a shellac finish on both sides helps to keep jigs flat as well.

Good luck with it.

Yep, it's the fence. Its a tad bit curved, I see it now.

There is a bit of light through the middle area but the square touches on the right side and the left side.

I'll look into that finished grade ply.

If your fence is straight, then your square…is not square.

Even if you see a curve on a fence, you need a better square. Those kind are for construction type work and are notorious for not being perfectly square.

What square do you recommend?

I have some from Woodpecker, Incra and iGaging.
Starrett has a great reputation for adjustable squares but they're not cheap

In the end, it's worth the money because if you take care of them, you'll be using them for a long time and will greatly improve your cuts and your assembly.

Put one leg of your square against a STRAIGHT fence and draw a line against the edge that goes out at the 90. Now flip the square over and look to see if that leg aligns with the mark you just made. If it does your square is fine. We can't all afford expensive machinist's equipment.

I dunno…the majority of the cut is to the right side of the blade and that seems to be fine…I really never pay much attention to what happens on the left side but that's just me.

Is the fence a lamination?

I glued mine with a piece of 8/4 as a caul to keep it flat.

no, its pure hard maple.

I glued the new one in, so far its measuring up a whole lot truer

I'm letting it glue overnight and then I'll test it in the morning.

It certainly could be that the square is not square. But rather than use a square, try the 5-cut method for squaring the fence. You can get it square to a 0.05 deg or better doing this.

Just google "crosscut sled 5 cut" and you'll get lots of examples of this.

Obviously in all cases you need your fence to be straight.

Alternatively you can use your square like dhazelton described to check it for square. But aside from checking, you can see how far it is off and use that to compensate.

I happen to have two framing squares. One is close to perfect, the other is off about 1/16 th inch over about 18" (0.2 deg).

In regards to the square, 2 points:

You can adjust that type of square if it isn't actually square. Use a punch and a hammer on the face of the tool in the corner where the 2 legs meet. Punch the inside of the corner to make the legs separate, and punch the outside of the corner to close them.

Buying a nice square doesn't have to be expensive and it doesn't have to be a starrett.

http://www.harryepstein.com/index.php/tool-brand/products-engineering.html

US made, factory blemish squares. Only cosmetic issues, and they are 100% square. Shipping is typically pricey from them, but if you order a few things at once it's not bad. I've got 2 squares from them.

If you haven't already, spend 20 minutes and watch William Ng's crosscut sled video with his 5-cut method. You won't need to use a square for that - only a tape measure and a pair of calipers.

I hope your fence goes further to the right than it appears…....

Future reference, sometimes its best to make a fence from plywood in an "L" shape with perfect 90 degree gussets.
This keeps the fence true and square to bed.

As you've discovered, no matter what kind of wood, it could be straight to day and bowed next week. ;-)

Thank you! For the William Ng's video.

My word was that ever helpful!

Agree with Parabola, watch William Ng's video

Just a heads up - I hate to poop on the party, but I got a small square from Harry J Epstein and it wasn't square it was out by probably .003 or .004 over 4". Either that or my starrett is out, and I'm guessing it isn't the starrett. Just know there is a risk when buying. Some are probably good, other probably aren't.