MFT3 table newbie

[woodferret]

Don't forget digital calipers are kinda crappy.  I know it says xxx accuracy, but most of the time, they meant precision - not accuracy.  It also matters on how you hold it.  As for the linked 5-cut PDF, also keep in mind that when you trim off that 24mm piece, it's not fence supported, so it may wobble a bit before falling off.  I've had the dreaded toe-in/out at the end of those offcuts before.*

* note that cut under the rail is still fine, just the offcut moves into/out of the blade.

 

[Birdhunter]

I’ve seen a very similar problem making drawer fronts and I was using a very accurate big heavy table saw that was perfectly dialed in.

After way too much head scratching and some impolite words, I found the long sides of one of the 6 drawer fronts were not parallel. Not sure how this happened. When I cut the short sides, the angle was off.

 

[tsmi243]

OK so you're missing the last part of the 5-cut test.  The error and the length are two sides of a triangle.  Dividing them out gives you the cosine of that angle (0.0000296) 

Arccos of 0.0000296 = 89.998304 degrees.  That's extremely good, my dude.  You're chasing two thou of a degree. 

 

[Out of Square]

OK so you're missing the last part of the 5-cut test.  The error and the length are two sides of a triangle.  Dividing them out gives you the cosine of that angle (0.0000296) 

Arccos of 0.0000296 = 89.998304 degrees.  That's extremely good, my dude.  You're chasing two thou of a degree.

Thank you, I was not sure how all the formula worked but I knew if I put the numbers up then someone would be able to help me out. What is the number I am missing? So I can post it.

 

[jeffinsgf]

The reason I originally started this thread is when I made some drawer (false fronts) and used my known to be extremely accurate woodpeckers square they were way off and it was very upsetting to me. 3 sides were dead on but the fourth corner was off about 1/16 to 1/8th of an inch.

If you're saying the assembled box was not square, that has more to do with dimensional accuracy than squareness.

 

[Out of Square]

Thanks , good information to remember.

 

[tsmi243]

Arccos of 0.0000296 = 89.998304 degrees

What is the number I am missing? So I can post it.

It's this whole line that's missing.  The number you get when you divide isn't the answer you're looking for.  It's the cosine of the answer.  So doing an arccos function turns it back into the angle- which in your case, is about as dead-nuts 90 as you can get with sintered wood. 

 

[Out of Square]

Arccos of 0.0000296 = 89.998304 degrees

What is the number I am missing? So I can post it.

It's this whole line that's missing.  The number you get when you divide isn't the answer you're looking for.  It's the cosine of the answer.  So doing an arccos function turns it back into the angle- which in your case, is about as dead-nuts 90 as you can get with sintered wood.

okay, learning alot.
How do you do arcos function? is that on the calculator?
looked it up and see it is trigonometry, so i don't expect you to explain it to me, but if you have simple equation?

 

[raylaray]

okay, learning alot.
How do you do arcos function? is that on the calculator?
looked it up and see it is trigonometry, so i don't expect you to explain it to me, but if you have simple equation?

here's a link to a calculator and explanation:https://www.rapidtables.com/calc/math/Arccos_Calculator.html

example from their page explaining the relationship between cosine and inverse of a cosine (arccos) of an angle:
"For example, If the cosine of 60° is 0.5:
cos(60°) = 0.5
Then the arccos of 0.5 is 60°:
arccos(0.5) = cos-1(0.5) = 60°"

 

[Out of Square]

okay, learning alot.
How do you do arcos function? is that on the calculator?
looked it up and see it is trigonometry, so i don't expect you to explain it to me, but if you have simple equation?

here's a link to a calculator and explanation:https://www.rapidtables.com/calc/math/Arccos_Calculator.html

example from their page explaining the relationship between cosine and inverse of a cosine (arccos) of an angle:
"For example, If the cosine of 60° is 0.5:
cos(60°) = 0.5
Then the arccos of 0.5 is 60°:
arccos(0.5) = cos-1(0.5) = 60°"

Thank you, I have book marked this page for future use.

 

[Michael Kellough]

“about as dead-nuts 90 as you can get”

Now that you’re there, keep that piece to use it to reset 90* in the future.

I would also carefully add some stock on top of the rail side to increase the height so the new square can be used for thicker stock.

If you keep this piece you won’t need to go this process again.

Even if you choose to do the 5 cut method again you don’t need to do the trig. You just need to move the fence 1/4 of the difference between the beginning and end cut of the cutoff piece. If the difference is 1mm you just need to move the fence 1/4mm. First clamp a stop against the fence then move the fence away from the stop and put a .25mm shim between the fence and the stop then tighten the fence against the shim/stop and then remove that stuff and you’re corrected.

 

[Out of Square]

“about as dead-nuts 90 as you can get”

Now that you’re there, keep that piece to use it to reset 90* in the future.

I would also carefully add some stock on top of the rail side to increase the height so the new square can be used for thicker stock.

If you keep this piece you won’t need to go this process again.

Even if you choose to do the 5 cut method again you don’t need to do the trig. You just need to move the fence 1/4 of the difference between the beginning and end cut of the cutoff piece. If the difference is 1mm you just need to move the fence 1/4mm. First clamp a stop against the fence then move the fence away from the stop and put a .25mm shim between the fence and the stop then tighten the fence against the shim/stop and then remove that stuff and you’re corrected.

So you are basically saying use the saved piece of baltic burch left over from the 5 cut test and use it essentially as a square for the fence and guide rail?

 

[Michael Kellough]

“about as dead-nuts 90 as you can get”

Now that you’re there, keep that piece to use it to reset 90* in the future.

I would also carefully add some stock on top of the rail side to increase the height so the new square can be used for thicker stock.

If you keep this piece you won’t need to go this process again.

Even if you choose to do the 5 cut method again you don’t need to do the trig. You just need to move the fence 1/4 of the difference between the beginning and end cut of the cutoff piece. If the difference is 1mm you just need to move the fence 1/4mm. First clamp a stop against the fence then move the fence away from the stop and put a .25mm shim between the fence and the stop then tighten the fence against the shim/stop and then remove that stuff and you’re corrected.

So you are basically saying use the saved piece of baltic burch left over from the 5 cut test and use it essentially as a square for the fence and guide rail?

Yes As long as you still know which corner was the last cut. It’s bigger and probably more square than the Woodpecker square. Build up the rail side so it will work for thicker stock.

 

[Out of Square]

Yes As long as you still know which corner was the last cut. It’s bigger and probably more square than the Woodpecker square. Build up the rail side so it will work for thicker stock.

Thanks , that's what I thought you meant. One more question, the piece I have is raw and unfinished, would you put a finish on it? say linseed oil or sanding sealer to help preserve it?

 

[Michael Kellough]

Sure, just be sure to knock down any fuzz that gets stiffened by the finish. Doesn't take much more than an extra thick hair to throw you off, a little.

 

[mkasdin]

Woodpecker makes a thick  black phenolic 90 degree triangle for square up the rail. It works exceedingly well. I bought mine years ago it was a fair price. Not sure what the current price is or if they still are in production