Shopsmith Forums

At the risk of nauseating charlese, I'll tell you about my experience this morning setting the fence of my new-to-me Incra Miter 5000 sled (thanks again, Jack Wilson!).

I initially set the fence to the blade using a low tech method: a small 6 inch engineer's square with the base of the square against the Miter 5000 fence and the blade of the square resting against the plate of my Shopsmith thin-kerf combo blade. I'm sure charlese would approve.

But then I decided I had to know just how accurate the setting was. So I decided to check using the five cut method using some large ply scraps from my canoe cradle build. The part of this that may nauseate charlese is you need a micrometer to do the five cut test (I used my Harbor Freight digital caliper).

On the fifth cut off of my test piece, I measured a .005 difference between the width of the front end of the cut off vs the rear end of the cut off. That cut off, however, was 21" long! If my geometry is right, that means using nothing more complicated than an engineers square, I achieved fence to blade alignment better than 89.98 degrees(inverse cosine of .005/21 = 89.986 degrees). I did toy with the idea of seeing if I could get it closer but realized it would be nothing but pure luck if I got closer than that!

Incidentally, the Incra Miter 5000 is a heavy beast but it easily cross cut a panel that started life 23 inches wide. I am very impressed with it!

algale wrote:At the risk of nauseating charlese, I'll tell you about my experience this morning setting the fence of my new-to-me Incra Miter 5000 sled (thanks again, Jack Wilson!).

I initially set the fence to the blade using a low tech method: a small 6 inch engineer's square with the base of the square against the Miter 5000 fence and the blade of the square resting against the plate of my Shopsmith thin-kerf combo blade. I'm sure charlese would approve.

But then I decided I had to know just how accurate the setting was. So I decided to check using the five cut method using some large ply scraps from my canoe cradle build. The part of this that may nauseate charlese is you need a micrometer to do the five cut test (I used my Harbor Freight digital caliper).

On the fifth cut off of my test piece, I measured a .005 difference between the width of the front end of the cut off vs the rear end of the cut off. That cut off, however, was 21" long! If my geometry is right, that means using nothing more complicated than an engineers square, I achieved fence to blade alignment better than 89.98 degrees(inverse cosine of .005/21 = 89.986 degrees). I did toy with the idea of seeing if I could get it closer but realized it would be nothing but pure luck if I got closer than that!

Incidentally, the Incra Miter 5000 is a heavy beast but it easily cross cut a panel that started life 23 inches wide. I am very impressed with it!

algale, you did even better than you thought. That angular error accumulated over five cuts, so the contribution from the final 21" cut is only 1/5 of the total. So on a single 21" cut, the error was only 0.001". DON'T TOUCH ANYTHING !!!

But before you get too cocky, I must point out that a micrometer is a different beast than a caliper. A very good caliper is accurate to about 0.001". A micrometer is accurate to about 0.0001".

BuckeyeDennis wrote: algale, you did even better than you thought. That angular error accumulated over five cuts, so the contribution from the final 21" cut is only 1/5 of the total. So on a single 21" cut, the error was only 0.001". DON'T TOUCH ANYTHING !!!

But before you get too cocky, I must point out that a micrometer is a different beast than a caliper. A very good caliper is accurate to about 0.001". A micrometer is accurate to about 0.0001".

Thanks for the corrections. It was indeed a digital caliper not a micrometer.

So if the error on a single cut is .001/21, I think the means the fence to blade angle was 89.997 degrees (and some change). Wow.

Although you made 5 cuts, there are only 4 angles resultant. So .005/4 = .00125/21 which is 89.99658958 degrees.

Such a fantastic result must be due to your use of an 'engineers' square!


It also means the blade is not warped, nor did you cause any deflection of the blade while using said 'engineers' square.





BTW what size calipers did you use to measure within .005" over 21"?

I got similar results on my smaller miter express with a 1000SE using the Ng 5 cut. .0005 per foot (yup 1/2 a thousandth!!) however I used feeler gauges to adjust the gap and extended the fence to get the greatest distance.

http://www.shopsmith.com/ss_forum/viewt ... ut#p173093


of course that accuracy is not needed, but there was something satisfying about attaining it.

Be well,
Ben

algale wrote:At the risk of nauseating charlese, I'll tell you about my experience this morning setting the fence of my new-to-me Incra Miter 5000 sled (thanks again, Jack Wilson!).

I initially set the fence to the blade using a low tech method: a small 6 inch engineer's square with the base of the square against the Miter 5000 fence and the blade of the square resting against the plate of my Shopsmith thin-kerf combo blade. I'm sure charlese would approve.

But then I decided I had to know just how accurate the setting was. So I decided to check using the five cut method using some large ply scraps from my canoe cradle build. The part of this that may nauseate charlese is you need a micrometer to do the five cut test (I used my Harbor Freight digital caliper).

On the fifth cut off of my test piece, I measured a .005 difference between the width of the front end of the cut off vs the rear end of the cut off. That cut off, however, was 21" long! If my geometry is right, that means using nothing more complicated than an engineers square, I achieved fence to blade alignment better than 89.98 degrees(inverse cosine of .005/21 = 89.986 degrees). I did toy with the idea of seeing if I could get it closer but realized it would be nothing but pure luck if I got closer than that!

Incidentally, the Incra Miter 5000 is a heavy beast but it easily cross cut a panel that started life 23 inches wide. I am very impressed with it!

Trying to clear up things a bit in my head....
If all 5 cuts were on a board that started at about 24" by 24" (what I presume since the last length was about 21") then your error is .005 in roughly 89" or less than .00068 per foot. SLACKER!! I mean what happened to precise?!?!
Seriously VERY VERY NICE!!

Be well,
Ben

algale wrote:At the risk of nauseating charlese, I'll tell you about my experience this morning setting the fence of my new-to-me Incra Miter 5000 sled (thanks again, Jack Wilson!). ...

This is funny, Al Didn't get a bit sick. Enjoyed your post!

I'm happy that your sled is working to the degree (Pun) you like .

The "mis-alignment" of your blade must be on the waste side of the cut.- - - Always a good practice.

benush26 wrote:

algale wrote:At the risk of nauseating charlese, I'll tell you about my experience this morning setting the fence of my new-to-me Incra Miter 5000 sled (thanks again, Jack Wilson!).

I initially set the fence to the blade using a low tech method: a small 6 inch engineer's square with the base of the square against the Miter 5000 fence and the blade of the square resting against the plate of my Shopsmith thin-kerf combo blade. I'm sure charlese would approve.

But then I decided I had to know just how accurate the setting was. So I decided to check using the five cut method using some large ply scraps from my canoe cradle build. The part of this that may nauseate charlese is you need a micrometer to do the five cut test (I used my Harbor Freight digital caliper).

On the fifth cut off of my test piece, I measured a .005 difference between the width of the front end of the cut off vs the rear end of the cut off. That cut off, however, was 21" long! If my geometry is right, that means using nothing more complicated than an engineers square, I achieved fence to blade alignment better than 89.98 degrees(inverse cosine of .005/21 = 89.986 degrees). I did toy with the idea of seeing if I could get it closer but realized it would be nothing but pure luck if I got closer than that!

Incidentally, the Incra Miter 5000 is a heavy beast but it easily cross cut a panel that started life 23 inches wide. I am very impressed with it!

Trying to clear up things a bit in my head....
If all 5 cuts were on a board that started at about 24" by 24" (what I presume since the last length was about 21") then your error is .005 in roughly 89" or less than .00068 per foot. SLACKER!! I mean what happened to precise?!?!
Seriously VERY VERY NICE!!

Be well,
Ben

Where did 89 come from?

Anyway the total 'circumference' is not relevant anyway. We are making repetitive cuts at a near 90 degree angle. The side to side measurements are to determine the angular accuracy only.

BTW which sides are measured does not matter(they should be the same - with the same end to end variance). Each cut contributes 1/4 of the total variance.

I still like the cut a board in two and stack the ends so one can see the deviation from 90 for miter gauge checking/adjusting. Multiplier is 2 and uses only one cut.

Ng 5 cut better for sleds.

[quote="JPG"


Where did 89 come from?

Anyway the total 'circumference' is not relevant anyway. We are making repetitive cuts at a near 90 degree angle. The side to side measurements are to determine the angular accuracy only.

BTW which sides are measured does not matter(they should be the same - with the same end to end variance). Each cut contributes 1/4 of the total variance.

I still like the cut a board in two and stack the ends so one can see the deviation from 90 for miter gauge checking/adjusting. Multiplier is 2 and uses only one cut.

Ng 5 cut better for sleds.[/quote]

Actually the 89 or perimeter (I guess we could go with a four sided circle if you want circumference - works for me ) is used. Of course you know when you make the 5th cut, you use the sliced off piece that remains, measure the difference of the two ends, divided by the total length of the first four cuts (approximately) to give the variance from precise 90 degrees.

My total dumb ass GUESS of 89 inches was deduced because of the length of the final piece at 21" (with an approximate width of 1" - though different at each end). I presumed (though maybe I should have ASSUMED) that the board was initially 24" square. Whew, trying say that fast three times!! Glad charlese isn't sick cause MY head is spinning!!

I agree that the 5 cut is extraordinary for truing sleds. For my SS miter I always go to the Miter-set. It is certainly close enough for me. However on my 12" miter saw I just use the digital protractor (not trusting the indents and factory). Different devices for different devices (or should that be vices )

Be well,
Ben