Out of square 45’s

[Aaron Rosenthal]

I’m making a base for some small cabinets, and mindful of the general advice of the furniture makers here, I decided to use my table saw to cut the 45 deg. mitres and not my sliding mire saw.
Setup: Incra 1000SE mitre gauge, set to “0” against the saw blade. To set the 45, I used a tilt meter after zeroing on the saw table, and got within .05 indicated degrees.
Every one of my cuts was off square (Starret and checked by a Veritas engineer square). By playing with the micro degree setting on the Incra gauge, I could make it almost passable, but the finikyness finally drove me back to the mitre saw, which made a more acceptable cut.
I accept that the idea “do what works” is first in getting the project finished, I’m still confused about the lack of accuracy of the table saw cut.
It’s a higher end Ridgid granite top table saw (at the time) and tuned.
The saw blade is square to the mitre slots, and with the Incra setup, it should be dead square, so I’m lost.

[Grant Wilkinson]

I'm confused when you say that you used a tilt meter. Are you mitring or bevelling?

If mitring, have you followed the instructions that came with the incra to get it dialed in? If not, that will very likely help. I had to play with mine for while when I first got it, but now it's spot on. FWIW, for me, the big thing was taking out all the play in the mitre slot.

[Brian Tymchak]

Do you get a square cut with the blade @ 90*?

I had a lot of difficulties getting my 1000SE to cut square. Tightening the screws when adjusting to square vs blade would always pull the fence a tiny but off square. It was the primary reason I moved to an Osborne gauge.

[Doug Garson]

Is your saw blade parallel to the fence when it is tilted at 45 degrees? Check out this article to adjust your saw so it cuts 45's accurately. https://www.popularwoodworking.com/t...your-tablesaw/
Here's a quote from John Jordan on this forum back in March 2019 , this is the one I used to adjust my saw worked for me. I have a PDF of this file somewhere if you can't find it.

"There is also an article by Tom Burroughs in American Woodworker, Feb '95, on "Supertune Your Tablesaw". Excellent article and great diagrams. On the following page is a review by Ellis Walentine on a couple of tools that could help. Hmmm, also 4 pages..."

JKJ

[Mel Fulks]

Remember the saw is cutting with grain on one side ,against grain on the other side . I get better result with coarser
blade.

[Aaron Rosenthal]

Grant, my thinking is; if I tilt the blade of my table saw 45 deg off perpendicular, place my wood flat on the table against the miter fence set at 0 deg, you can cal it a bevel or a miter but I need it to meet the corresponding piece to make a 90 deg. corner, and it should be perpendicular off the bottom.
And yes, I followed the Incra manual to the letter when I was setting it up.

[Aaron Rosenthal]

Thanks Doug; I've not seen the article before, so I'll get into the saw and check it out. After the project is over, though, since I'm under time pressure to get it finished.

[Alex Zeller]

Like others have said make sure your saw is set up correctly. I haven't bought a digital tilt meter yet but my plan is use my machinist 45 square to zero the tilt meter. By placing the 45 square on the table and then holding the tilt meter on the square this should set it up exactly at 45 (although if you zero it it'll read 0). Then measure it a few times by rotating the tilt meter and then putting it back on the 45 square. It could read exact every time or it might be off slightly due to the limited accuracy of the tilt meter. Once you do it a few times you should be able to get an average. Now set your blade with it. That's about the best way I could think of to get an accurate cut.

Since I don't have one what I do now is set my dial indicator on the saw blade. If my 45 cuts are off slightly I make an adjustment. The dial indicator lets me know that I'm adjusting the tilt. With the blade full extended I'll adjust the tilt by about .010" measured on a blade tooth. The number doesn't mean much but it gives me an idea of how big of an adjustment I might need to make. For example if I went too far and it's about the same amount off, just in the other way, I'll do it again but only move .005". If I went the wrong direction (it happens) I know that I need to go back .010" just to get to where I was. I'm sure people with more experience proficient or have a better way but for now that's what I do.

[Steve Demuth]

Grant, my thinking is; if I tilt the blade of my table saw 45 deg off perpendicular, place my wood flat on the table against the miter fence set at 0 deg, you can cal it a bevel or a miter but I need it to meet the corresponding piece to make a 90 deg. corner, and it should be perpendicular off the bottom.
And yes, I followed the Incra manual to the letter when I was setting it up.

There are three adjustments you have to have right for this to work:

1. Your miter slot and blade have to be parallel. Lots of threads, articles and videos on how to get there, but it's the first thing.

2. Your miter gage has to be dead nuts square to the blade when set at 0deg. Again, lots of material on how to get there. But verify it with the blade set vertical first, and get it dialed in.

3. Your blade tilt has to dead on 45deg to the table. You're probably getting that with your digital tilt meter, but it's not a certainty. If you have a very accurate square, then you can check this independently of the other issues by cutting a miter on close grained hardwood, ripping two 1/8" (or even thinner) strips from the result, assembling them with the two faces of the first rip cut up, and checking the resulting angle with the square. Ripping that way will eliminate most influence of the other two factors and give you a clear read on the blade tilt alone.

[Brian Tymchak]

...Check out this article to adjust your saw so it cuts 45's accurately. https://www.popularwoodworking.com/t...your-tablesaw/

Thanks for that link Doug. Excellent article.

[Bob Jones 5443]

Mark carefully, cut with a machine close to the line, and finish to the line with a shooting board.

[Steve Rozmiarek]

SCMS are specifically made for cutting miters, any mitre jig on a conventional tablesaw is an afterthought. You have a lot more variables with a mitre jig than you do with a mitre saw. Why is the mitre saw the wrong tool?

[Doug Garson]

I believe the issue, which is addressed by the article I posted, is if your trunnions aren't shimmed properly, your blade doesn't remain parallel to the miter slots when you tilt it. Before I "supertuned" my saw I had to set the blade slightly off 45 to get tight miters. When I went thru the process described in the article and measured the distance between the blade and miter slot front and back of the blade it was within 2 thou at 90 but out 8 to 10 thou at 45. It's not about getting it exactly at 45 its that when you are at 45 the blade is no longer parallel to the miter slot.

[glenn bradley]

My knee-jerk reaction to your CMS being more accurate than your tablesaw is that your tablesaw needs some serious TLC. The number of folks using saws that have been roughly aligned with the blade at 90 degrees and nothing more is pretty high. I find this forgivable with contractor saws because the ability to align this format of machine and have it keep that alignment at 90 degrees and various bevel angles is extremely challenging if not impossible on most contractor saws out there. Mine certainly behaved this way.

If you checked out some articles on full tablesaw alignment you have got the gist of the geometry that allows a saw to cut perfectly at 90 degrees but, fail as the blade is tilted. Cabinet mounted trunnions make this process a walk in the park. If your trunnions are table mounted I would lean toward using your tablesaw as a 90 degree cutting machine and do something else for bevel cuts. This precludes easily making pieces that involve longer miter joints but, short miters can be accomplished with a CMS or a hand plane.

I am not belittling your saw. I am just making the observation that the number of contractor saws out there that can be aligned and remain aligned on multiple planes probably come down to 2 or 3 models. I think the older Powermatic 64's were one. I haven't really read of anyone bragging on their current contractor as being able to do this reliably over time. Don't think less of your machine for being what it is. Amplify its value by using it within its capabilities. I did this for many years with good success until I moved to a more robust machine.

[johnny means]

Try double cutting. Make the first cut a 16th or so long, then cut to the line. It sounds to me like your work piece is moving.