Thread: Simple box with beveled corners. What am I doing wrong?

Four corner miter joints = the hardest joint in woodworking by a country mile!

The problem is that your angle is greater than 45°. You need to tilt the blade a little further. Treat the digital angle gauge as a good start and then refine from there from the actual cuts instead of the readout on the gauge.

When you "zero " your angle gauge, do you do it on the surface of your sled, not the table saw?
I found that can make that fraction of a degree difference.
I still prefer to refine my mitres on a shooting board though!

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Some potential issues that I can anticipate;

Have you checked the flatness of the table saw top?
Is it pressed metal or cast?
A pressed metal top will rarely be flat or consistent across its surface, so the point on the top where you zero the digital angle gauge becomes way more critical for setting the blade angle accurately, similarly, a poorly machined cast top may be almost as bad.

Are the mitre gauge slots identical depth?
Are the runners on the sled slightly shallower than the slots in the table?
If the table top is flat, the sled should be allowed to slide across the top of the table, and just use the runners as guides. If the runners are contacting the bottom of the slot, they may be skewing the top surface of the sled slightly out of parallel with the table top if there is any discrepancy in slot depth. My experience of mitre slots on lower price bracket table saws has been that manufacturers often struggle to get two slots parallel, and of equal width and depth, unfortunately an attitude of 'if it looks like a table saw at 1m distance it can be sold as one' seems to prevail.

Is the plywood used for the sled base truly flat, void free and of consistent thickness. Any of these errors will complicate setting up for the cuts you are making, particularly as the parts you are making are quite short relative to the thickness of the material. I would definitely advise following Brian's suggestion of establishing your angle gauge zero from the top of the sled and basically as close as you can get to the blade without touching it.

Don't be discouraged. You'll get there, it will just take a bit of trouble shooting. And the next time you come across this issue, you'll know what to do.

Using thick stock is tricky as it amplifies any errors in your setup. The good news though is that once you nail thick stock, thinner stock will be a doddle.

From your photo it looks as though the gap is consistent along the length of each joint. Can you confirm this? If that is the case, the issue is with the angle not being 45 deg, and others have given you good suggestions to try.

If the gap differs from one end to the other, the issue it's most likely with the angle between the blade and sled fence. One thing to check is for sawdust against the fence, which will stop your stock being able to register perfectly against it. A trick when building sleds is to provide some relief at the base where sawdust can "hide".



Also, if you use masking tape to "roll up" the box (common technique for small boxes), it is pretty clear if the box isn't rolling up square, again pointing to the fence/ blade not being a perfect 90 deg.

Now having said that, no matter how hard I try, mine never line up without at least a tiny step on the top and bottom, but that's simple to plane flat after the glue up.

Again, don't despair, you'll get there.

Kind regards,
Lance

take it from me, so far your not doing anything wrong, what you are doing is something just isnt right, that you shouldnt do again, we learn from others about out so called mistakes. learn from this dont be hard on yourself or discouraged mate, some of the guys here have made monumental stuffups, only difference is they have been too ashamed to admit it.
You asked for advice, learn and teach yourself again.

Biggest thing to remember ....timber is replaceable, digits aren't

Hi Everybody

Thank you all so much for the responses so far and the encouragement. It really helped to put me back in the right frame of mind for this project!

I decided to take the simplest advise and re-check the bevel angle of the blade in reference to the sled base, not the table base. In hindsight this is a really obvious oversight. It turns out that the angle in relation to the sled was 45.20 degrees. This morning I made the adjustment, and have achieved some much better results. A photo below for proof.

20190819_133329.jpg


The cuts aren't absolutely perfect, however I'm pretty sure with some fine tuning using a shooting board (my next project, perhaps) the alignment would be almost spot on. the edges as they are now still look pretty good and with some light clamping and a little planing, I'd expect the joins to look quite good on a finished piece. What do you guys think?

Woo hoo!

Great job.

so whose a happy chappy? good to see

Thanks guys! I am pretty happy to have gotten this one sorted

The way that I have always done the cuts is with a dual side of the blade mentality.

First - The height of the blade doesn't matter much, as long as it cuts all the way through the timber.
Second - Set the blade to 45° or as close as possible.
Third - Cut the front and back bevels with the fence to the right of the blade. Cut all 4 bevels w/o moving the fence during the second cut.
Fourth - Cut the left and right sides with the fence to the left side of the blade. Cut all 4 bevels w/o moving the fence during the second cut.

Effectively what you are doing is making the front / back pieces the same size and the bevels all with the same angle. With the fence moved to the other side of the blade, the left / right pieces are the same size AND the at the complementary angle to the front / back angles.