The ones I have had would display 90 correctly when it was measured against a known square.  the problem was it would also display 90 if it wasnt a true 90.  I havent seen one yet that didnt have some slop in it.

I’ll have to try getting it where it just turns 90 and then see if I can see light up against my squares.  If you can, how do you calibrate something like the TS55 which can only cut so thick?  I suspect the naked eye can’t see as accurately as even a sloppy digital protractor?  I know you can use feeler gauges on metal but on an inch and a half thick wood I’m not sure how accurate the sliver of light test can be?

I would first check the blade to the base for square with a small machinist type square.  Then find some flat scrap and make a test cut. The thicker the better but 18mm will work fine.  If you wanted you could glue 2 pieces together so you would have almost 1.5 inch thick piece. MDF works well here flat and cheap and easy to cut. The track could possibly introduce some error into the equation so make a cut with the track. Check the test cut with the square holding it up to a bright light.  Mark the face that you put the track on so if there is any further adjustment needed you know which way to adjust the saw. The light test is actually very accurate.  Accurate enough for any type of wood working project. However I guess that also depends on the person and their eye. Its easy to spot if one side of the cut has no light and if there is a sliver of light at the other end.  I dont have hard numbers but a good eye could probably spot anything over a few thousands off.     

Quote from: Bugsysiegals on November 16, 2020, 06:30 PM

I was going to use my drawer lock router bit but my zero clearance fence isn't working as well as I'd like so I've decided to use Domino's instead.  I thought it would go smooth until the machine started feeling funny at the end of the plunge.  I wasn't sure what was going on until I removed the Domino ... the bottom of the bit flares out and the bit was elongating the hole as well as burning the wood! 

It seems I need to stop as soon as I feel this different feeling and then just cut off the excess Domino?  I'm unable to move on to the middle Domino until these are cut flush but wonder whether there's any particular type of hand saw I should buy which will cut the excess Domino while minimizing the scaring of the wood itself?

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Hi @Bugsysiegals

I see in a couple of the pictures that you have posted that you have the Trend digital angle finder. Trend also do a rather nice folding pull saw. It has no set and so can cut flat on the surface of your drawers without marking them. The trick is to press the smooth surface of the blade against the drawer front as you saw (remember it cuts on the pull so do not push hard).

Peter

Thanks Peter, I'll have a look!

Now I'm curious whether it's thousands or hundredths of an inch that the human eye can detect with a machinist square and light ...

Thousandths...as in around .001-.002. More than that is easily verifiable using a feeler gauge.

I also concur with afish and would use a Woodpeckers square or a Starrett combination square, something where the blade cannot be moved from 90º.  The digital square is good for getting approximate angles.

An easy way to check that digital square is to set it at 90º, place it along an edge of a board and mark the blade length with a pencil, flip the square over and mark the blade length again.

Quote from: Bugsysiegals on November 17, 2020, 09:28 AM

Now I'm curious whether it's thousands or hundredths of an inch that the human eye can detect with a machinist square and light ...

Thousandths...as in around .001-.002. More than that is easily verifiable using a feeler gauge.

I also concur with afish and would use a Woodpeckers square or a Starrett combination square, something where the blade cannot be moved from 90º.  The digital square is good for getting approximate angles.

An easy way to check that digital square is to set it at 90º, place it along an edge of a board and mark the blade length with a pencil, flip the square over and mark the blade length again.

Interestingly enough when I zero my digital calipers and begin opening them up against sunlight I can see light as soon as it says 0.0005" but my caliper is only accurate to +/- 0.001" ... even still, I checked it against my feeler gauges and it accurately measures the first 3 which are 0.0015, 0.0020, and 0.0025 so if the eye can see light at 5 ten thousandths of an inch that's pretty impressive and accurate!

Yea, as I mentioned it's pretty darn accurate way to check quickly. I never tried to measure it but If there's a woodworking project that requires an edge to be more square then I can detect using a good fixed square and bright light I won't be anywhere near it and Im pretty finicky.  Its virtually splitting hairs at that point. Those digital protractors are good for running trim and such not for checking square when it counts.

For my Table Saw, I use the Wixey digital angle gauge which is accurate to within ±0.2°.  While only slightly less than the protractor, the max cutting depth on the TS is only 3 1/8" so the max error is 0.001".  Now I'll have to check that against a square and the light to get it down to 0.0005" accuracy!! 

Good luck with the drawers. Im sure if you stick with it and work out the bugs you will love doing the domino drawers.  One of these days Im going to try and do a drawer with the ddf40 and exposed dowels.  The ddf40 goes deeper so thats good but the domino will still look better I think.  For people who arnt in the know it looks really unique and looks difficult to do, so most love the look. At this point its really the only reason I havent sold my 500