# Calibrating Incra LS System



## Jerry Bowen (Jun 25, 2011)

O.K. here I am again with a nit picking thread that wll drive some of you nuts and probably tell me so, but....., it might interestest a small number of those of you that read thIis thread.

In an earlier post a member asked about precision setting of the TS fence, and a post to that thread brought up the Incra LS System and I posted to it and in my post I talked about the error that just happens when cutting wood because of the nature of the material, blade flutter etc.

The obvious question that anybody like myself would ask is, then how do you calibrate the system since you can't cut a perfect cut to the a thousandth of an inch. I do not actually have the answer but will explain what I do. 

I get the scale as close as I can in the normal manner, then I make ten cuts and using the dial caliper I measure all ten of the parts which will vary by several thousandth, add them up and take the average and then use the micro adjust to set the scale at the setting revaled by the average of the ten cuts. Now, I will be the first to admit that a dial calipber is not a high end measuring tool, and that after making ten cuts, if you let them set for a while they will all measure differently and that I am chasing shadows when even thinking about such things but I can't help myself, maybe a small number of members will understand my thinking problem and I hope that the rest of you will just indulge my weird and strange thinking. I am not really wanting to make excuses, just wanting to talk about something that others may have thought of and wondering if anybody else has ever wondered about the matter.
Let's see what posts come from you that read this thread.

Jerry Bowen


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## jw2170 (Jan 24, 2008)

Jerry, if I can get down to 1/64th, that is good enough.

Wood will change by 0.001" if you breath on it.

IMO, I would not worry about 0.001".


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## Dmeadows (Jun 28, 2011)

Jerry, I fully agree with James.. 1/64th is close enough for most any application in wood. That is 16 thousandths in round numbers! Or 0.015625 if you really want to nit-pick. But unless you really need the ten boards you cut, that's a fairly expensive method without any real gain. Once you have "calibrated" the fence.. the parts you cut will *still* vary by a few thousandths!


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## cagenuts (May 8, 2010)

The way I see it is this;

If you can get your cuts as accurate as possible without spending 7 hours micro adjusting the fence and then ploughing through a cube of prized wood making a zillion test cuts then why not?

If everything is 'close enough' then don't b1tch when your inset door clearance is not perfect.

Errors are compounded.


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## 4042 (Sep 30, 2004)

Here is how I do it. I bought a set of feeler gauges, bring the fence as close as the eye can see then using feeler gauge 0015 I adjust the fence with the micro gauge to just touch the a tooth on the blade. Then I set the magnetic laser ruler to zero. My cuts are within less than a 1000th of an inch. If I can' work with that tolerance I should go play golf.


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## Dmeadows (Jun 28, 2011)

CaptainBart said:


> Here is how I do it. I bought a set of feeler gauges, bring the fence as close as the eye can see then using feeler gauge 0015 I adjust the fence with the micro gauge to just touch the a tooth on the blade. Then I set the magnetic laser ruler to zero. My cuts are within less than a 1000th of an inch. If I can' work with that tolerance I should go play golf.


Are you assuming they are within .001"? Or have you actually measured them?


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## Dmeadows (Jun 28, 2011)

cagenuts said:


> The way I see it is this;
> 
> If you can get your cuts as accurate as possible without spending 7 hours micro adjusting the fence and then ploughing through a cube of prized wood making a zillion test cuts then why not?
> 
> ...


Hmm.. probably why one should size inset doors to the already constructed opening rather than a measurement off a plan?? Sure we should be as accurate as possible, but that doesn't eliminate the need for some craftsmanship?

Also there is a difference between precision and accuracy. Just because the size of something is stated to 6 decimal places, does not make it accurate! If you measure an opening with a tape measure accurate to 1/16th of an inch, does it really help to cut parts accurate to .001". I think not.


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## Jerry Bowen (Jun 25, 2011)

Dmeadows said:


> Hmm.. probably why one should size inset doors to the already constructed opening rather than a measurement off a plan?? Sure we should be as accurate as possible, but that does eliminate the need for some craftsmanship?
> 
> Also there is a difference between precision and accuracy. Just because the size of something is stated to 6 decimal places, does not make it accurate! If you measure an opening with a tape measure accurate to 1/16th of an inch, does it really help to cut parts accurate to .001". I think not.[/QUOTE
> 
> ...


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## Willway (Aug 16, 2012)

Hi Jerry, I agree with you on accuracy, but you can cut a piece of wood, measure it, leave it lay for a half hour, measure again and it will have changed. I like the multiple cut and average idea. Saw you lurking out there. Hope you have your desktop up running.


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## greenacres2 (Dec 23, 2011)

The beauty of the Incra TS-LS, is that once it's set, it's pretty much set. I needed some strips 1/4" wide on Sunday. Walked out to the shop, moved the positioner to the 1/4" mark, plugged in the saw and flipped the switch. Five strips measuring 0.250 in under 5 minutes from the time i walked out of my kitchen. If i wanted to do it again tonight--same result. The wood won't stay true, but it can start that way. 

When i change blades, i slide the positioner to kiss the blade, reset the magnetic tape (if needed), and go to it. I don't use Jerry's method of making 10 cuts, so i might be off by maybe 3 to 5 thousandths (shoot, i may not be off that much)--but that's without using any measuring devices to do the set-up. Slick system, mounts to the vast majority of saws with no modification, plenty of t-track mounting possibilities, and easy to work with. I looked at several different aftermarket TS fences--quite happy with my decision.

earl


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## Willway (Aug 16, 2012)

Hi Earl, I think Jerry is talking about the miter gauge. They can be very tricky on small parts, but so can the wood. Maybe I'm wrong, if he is talking about the fence, it would be really hard to get the exact same cuts if you moved the fence each time.


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## Dmeadows (Jun 28, 2011)

greenacres2 said:


> ...When i change blades, i slide the positioner to kiss the blade, reset the magnetic tape (if needed), and go to it. I don't use Jerry's method of making 10 cuts, so i might be off by maybe 3 to 5 thousandths (shoot, i may not be off that much)--but that's without using any measuring devices to do the set-up.
> 
> earl


Exactly Earl, and that is what I do as well, Jerry. As you said, the strips may very a few thousandths + or -, A featherboard will help some with that. But the bottom line is regardless of how you calibrate the fence. the strips will still vary a bit. If they consistently run over or under, then I can see going to the micro-adjust. All you are doing though, is centering the error, not eliminating it. If that is important to you, go for it. Maybe important when cutting a runner to slide in a miter slot for example(even then if cut that tight, it won't slide if it swells or warps at all!), but for general purposes, that degree of accuracy isn't usually needed.

I fully get _what_ you are driving at, it's_ why_ that I have a little trouble understanding. As Earl said, change the blade and you would need to go thru the whole procedure again. It is a valid enough procedure.. just don't see the need myself. 

Even if you can obtain that kind of accuracy, remember all joints need space for glue, and you don't want to have to drive things together with a hammer! Some small amount of "error" if you will, is needed!


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## al m (Dec 13, 2012)

Jerry
I am a red seal certified machinist, out of the trade 5 yrs, 25 yrs experience before that.I will say a dial caliper is a precision instrument, plenty accurate enough for wood working.Next step would bee a micrometer,own plenty of them and never felt the need to use them to measure a stip of wood. Consider that in machining metal.+/- .oo5 is a common tolerance. Why are you worried about tighter tolerances in wood working?The inca ls system is as good as ever need in this trade,in my opinion.


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## greenacres2 (Dec 23, 2011)

Willway said:


> Hi Earl, I think Jerry is talking about the miter gauge. They can be very tricky on small parts, but so can the wood. Maybe I'm wrong, if he is talking about the fence, it would be really hard to get the exact same cuts if you moved the fence each time.


It's the fence Dick. As long as the carriage or scale isn't moved, with the LS system the positioner can be returned to the same spot, positioning the fence in the same spot. Incra provides stops so the if one did remove the carriage from the rails and returned it, i doubt you'd have a measurable difference. On the other hand, my Incra Pro is not permanently mounted, so its carriage may move or at times i need to move it--so not as repeatable in that sense. But if i don't unclamp it, it'll repeat cuts as well. 

Last weekend i ripped some 3 1/4" boards, a few days ago i ripped some 1/4" widths. If i walked out right now and moved the gauge to 3 1/4" (and did not measure it) the cut would match what i did last weekend within the few thousandths that moving wood has. Jerry tries to dial that out--and the system is capable of doing that so he's perfectly sane (at least in this respect!!  ) in his pursuit. I'm okay with the natural tolerances so i spend my time otherwise. Both approaches are correct.

earl


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## krablins (Sep 23, 2011)

Jerry, too bad we don't live closet to each other. I bet you could sure dial me in on this new pistol I bought. You must be one heck of a shooter with that kind of mindset.


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## Jerry Bowen (Jun 25, 2011)

al m said:


> Jerry
> I am a red seal certified machinist, out of the trade 5 yrs, 25 yrs experience before that.I will say a dial caliper is a precision instrument, plenty accurate enough for wood working.Next step would bee a micrometer,own plenty of them and never felt the need to use them to measure a stip of wood. Consider that in machining metal.+/- .oo5 is a common tolerance. Why are you worried about tighter tolerances in wood working?The inca ls system is as good as ever need in this trade,in my opinion.


Al,
I certainly do not want to offend you or anybody else, but like the rest of the folks posting to this thread, you still don't get what I driving at, or at least it doesn't appear that you do. Let me try again. What I am attemping to do is to get the fence and the scale as close to being perfectly calibrated as I can them them. I know that if I could get this accomplished to perfection that it would make absolutely no difference in the performand and/or the accuracy of the LS system due to all that has been said earlier, it is just issue that is important due to the fact that I think this way, and wheather or not it is a hinderence to me or not, it is just the way I think and I am coming more and more to realize how differenct my mind works than does the average person. I the future I will give more thought to starting a thread that is so non relative to the majority if not all of the other members of the forum. I must say that I am a little embarrassed about some of the things that I have been taling about now and in the past that come out of my unusual thinking, but I am catching on and from now on I will try to talk about issues that have more substance to the avage member of the forum, hope you all can forgive me for not being more considerate of you.

This formum has been of great value to me and I thank those of of your that have been so helpful to me in the past.

Jerry


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## Jerry Bowen (Jun 25, 2011)

krablins said:


> Jerry, too bad we don't live closet to each other. I bet you could sure dial me in on this new I bought. You must be one heck of a shooter with that kind of mindset.


Hi Steve,
What pistol did you just buy? I must tell you that I am not a handgun enthusiast other than for defense and hunting. I own only two handguns a S&W Model 29, and a .45 ACP Colt Cammaner.

My interest in shooting was, in the past, precision benchrest shooting and some of the thinking that was needed in that endeavoer has probably carried over to my new found interest in woodworking and maybe this post will afford an opportunity to explain a littld bit of what makes me think as I do. I'll use one example, bench rest shooter do not use commercially made ammunition and certainly not commercially made bullets. The bullets used are all had swaged on special dies that when used proberly minimize the toleranes. Case in point, a bullet in flight spins a very high rate and if it is not perfectly balanced it will wobble. In order to balance a bullet the issue that causes a bullet to wobble is due to the difference in weight of the material that jacket of the bullet is made of and lead core inside of the jacket. I tried swaging some bullets on some jackets that I acquired from the Sierra Bullet Company. These jackets varied in wall thickness by as much as .0005" and bullets made from these jackets were far from being good enough for competition shooting. The jackets that were being used by most shooters at the time I was shooting were made by a company by the name J-4 and these jackets varied by no more than .0002" (two ten thousands) and were, of course of the quality that required to shoot well enough to be competitive. Keep in mind that by precision shooting I talking about a rifle capable of keeping all its shot inside less than .:moil:200" at 100 yards all day long, not many shooters are capable of the same accuracy as are the rifles that are being used by the way. Maybe this will shed some light on why I think the way I do and enjoy think in such terms even it has very little to due with wood working. Thanks Steve for giving my the chance to explain a point about the subject. Still anxious to hear about that new pistol of yours.

Jerry


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## Dmeadows (Jun 28, 2011)

greenacres2 said:


> It's the fence Dick. As long as the carriage or scale isn't moved, with the LS system the positioner can be returned to the same spot, positioning the fence in the same spot. Incra provides stops so the if one did remove the carriage from the rails and returned it, i doubt you'd have a measurable difference. On the other hand, my Incra Pro is not permanently mounted, so its carriage may move or at times i need to move it--so not as repeatable in that sense. But if i don't unclamp it, it'll repeat cuts as well.
> 
> Last weekend i ripped some 3 1/4" boards, a few days ago i ripped some 1/4" widths. If i walked out right now and moved the gauge to 3 1/4" (and did not measure it) the cut would match what i did last weekend within the few thousandths that moving wood has. Jerry tries to dial that out--and the system is capable of doing that so he's perfectly sane (at least in this respect!!  ) in his pursuit. I'm okay with the natural tolerances so i spend my time otherwise. Both approaches are correct.
> 
> earl


I agree, Earl. That is the beauty of the Incra system. Actually you can move the carriage.. I move mine occasionally from one tool to another. Just zero the fence to the bit/blade, reset the scale and you are good to go!

Still I wonder how well they would sell if the setup suggested cutting 10 samples and averaging the error? That's kinda the point. In real world woodworking that is what Incra systems should eliminate! I was able to do very accurate joinery and machining long before I even owned a dial caliper(which I do use a couple of these days, but that is another story)!


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## Jerry Bowen (Jun 25, 2011)

Dmeadows said:


> I agree, Earl. That is the beauty of the Incra system. Actually you can move the carriage.. I move mine occasionally from one tool to another. Just zero the fence to the bit/blade, reset the scale and you are good to go!
> 
> Still I wonder how well they would sell if the setup suggested cutting 10 samples and averaging the error? That's kinda the point. In real world woodworking that is what Incra systems should eliminate! I was able to do very accurate joinery and machining long before I even owned a dial caliper(which I do use a couple of these days, but that is another story)![/QUOTE
> 
> ...


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## Dmeadows (Jun 28, 2011)

Jerry Bowen said:


> Duane, you still are not listening to what I am saying are you. Don't know how I can make it plainer.
> 
> Jerry


Jerry, I have read, reread, and re-reread your post several times. As i understand it, you asked how we calibrate our incra fences. You explained that you cut 10 test pieces, measure them with a dial caliper, average the measurements, and then use the microadjust on the LS to match the average measurement.

As I understand it, cutting 10 pieces at 1 setting of the fence gives some very small difference in actual size of the 10 pieces.

If you mean anything other than that, yes I don't understand what you are saying!


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## TwoSkies57 (Feb 23, 2009)

Jerry, 

on one end of the jig you need to take into consideration: 
Arbor runout
Blade wobble
Tooth offset
Applied pressure to the fence
While the amount of arbor runout should be pretty consistant, the others may vary greatly. At least to your way of thinking. Changing the blade changes everything, as does pushing the stock along the fence, past the blade. The most obvious blade issue would be thin kerf vs. standard kerf blades. Then there is tooth configuration and offset variations between mfgs. 
A little change in pressure as you run your stock through can translate into several thousandths' variance. Featherboards can/would assist, but i can't see how they would take this variable comletely out of the equation. 
The jig itself is fairly predictable and I've never had an issue with it not getting back to where I wanted it. The mechanics of the jig are IMHO absolutely sound and reliable. The only real issue I have with the jig in terms of setup is the alignment of the cursor and rulers. Running your fence up to the the blade and then trying to zero out the cursor to within a couple thousandths is darn near impossible. Tilt your head one way or the other after an initial setup and you're going to be way off. Stand too far away and same thing. I've toyed with the idea of modifying a Dixey digital readout gauge from their tablesaw setup to the LS setup. But honestly, I've not felt the need to take it that far. Coming off the tablesaw, for me anyways, anything withing .010-.015 is easily within "live with it" tolerances. 

I do hope this addressed your original question.. 

Bill


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## Jerry Bowen (Jun 25, 2011)

TwoSkies57 said:


> Jerry,
> 
> on one end of the jig you need to take into consideration:
> Arbor runout
> ...


Bill, Bill, Bill, you don't get it either and it has to be my fault, not yours. Let me try to explain my point in nother way. Due to all he issues that youhave mention in your post along with the nature of wood not being stable, it is impossible to cut several cuts that are the same width. Consequently you never know for certain if the fence is set exactly as the cursor indicates and as I have agreed with everybody that this has nothing to do with the real working of wood. What I have been attempting to do, just for fun, is to see how close I can get the actual position of fence to match that of the cursor and the scale. If this could be accomplished, the theory is that if wood were stable, which it isn't, and none of the other issues that you listed existed, then you could make cut after cut that was not only consistant to .001" and would match the setting of the cursor on the scale. This is of no value to anybody but it's just a quirk of something that I am thinking about. I almost wish I had never brought it up, I'm under suspect already on this forum.

Jerry


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## billg71 (Mar 25, 2011)

Jerry,

No one has asked the question: Does it work? Do you get measurably more consistent results after your process than simply setting it in a simpler manner?

If it works go for it, don't read any further. Just say so and I'll go throw my crow on the grill... :blink:

But the methodology seems suspect to me: introducing a deliberate error in a precise setup just to account for random inconsistency in how that setup is used. As TwoSkies pointed out, there a lot of variables that effect the output from a table saw and while you can compensate for the ones in the machine(arbor runout, blade wobble, tooth geometry, etc.) I fail to see how applying a correction for the operator-induced variables is possible. If they were always on the fat or skinny side you could probably do something with that but all you said was "which will vary by several thousandth".

Statistically speaking, if you ran 100 pieces through and plotted the results you'd most likely get a bell curve with the majority of errors closely surrounding the center point which should be the actual setting of the fence. All you're doing is shifting the center point of the curve which does nothing to eliminate the errors. And I'd say your sample set of 10 is way too small. 

And what are you using for test cuts? If it's anything other than a good grade of MDF there's a whole 'nother bunch of random variables you've thrown into the equation. 

Just MHO.

Best,
Bill


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## TwoSkies57 (Feb 23, 2009)

Jerry...

So, all things being equal or in this case, consistant/fixed/predictable we come down to setting the cursor/ruler at exactly zero. I see what your saying about this not being a wood working issue, but one of simply setup. Honestly, I don't know how one might go about "zeroing" out the cursor/ruler without incurring considerable expense in doing so. One can relatively easily set the fence to zero, but the design of the "cursor/ruler alignment' does not lend itself to being repeatedly and accurately set to zero. Some sort of "Micro adjuster" for the ruler itself perhaps? A much thinner high def cursor line? Something of a magnifying device over the cursor? A over/under thin high def cursor perhaps???? As the jig sits, I don't see any means by which to achieve the ends your speaking of (Lord knows, I hope were on the same page now..  ). 

As for being suspect...don't sweat it. I've been suspect for years in here by some, and I've come to find it rather entertaining *L*. Keep posting your thoughts and query's. Alot of folks in here find it all very interesting at the very least, and at times, thought provoking. 

b.


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## Jerry Bowen (Jun 25, 2011)

TwoSkies57 said:


> Jerry...
> 
> So, all things being equal or in this case, consistant/fixed/predictable we come down to setting the cursor/ruler at exactly zero. I see what your saying about this not being a wood working issue, but one of simply setup. Honestly, I don't know how one might go about "zeroing" out the cursor/ruler without incurring considerable expense in doing so. One can relatively easily set the fence to zero, but the design of the "cursor/ruler alignment' does not lend itself to being repeatedly and accurately set to zero. Some sort of "Micro adjuster" for the ruler itself perhaps? A much thinner high def cursor line? Something of a magnifying device over the cursor? A over/under thin high def cursor perhaps???? As the jig sits, I don't see any means by which to achieve the ends your speaking of (Lord knows, I hope were on the same page now..  ).
> 
> ...


Bill, I must say that what you say in your latest post makes a lot of sense and has made me think it through again. By the way, I have modified the curse setup by first cutting a two inch wide hole in the plastic window that the curse had been on replaced it with a piece of very thin thread and then mounted a powerful magnifying glass so that the thread is easier to see and center on one of marks on the scale. This makes it much easier for me to set the cursor more accurately to the marks on the scale. Before doing this, the issue of the cursor being way to large for me and the fact that the plastic window was a fraction of an inch above the scale, parallex was easily introduced if one was not careful. I do like the set up. And.... you probably haved steered me awy of attempting to accomplish what I have been talking about in this thread.

Jerry


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## TwoSkies57 (Feb 23, 2009)

Jerry,, there ya go...I think when it comes down to dollars vs. benefits, you've most likely have already come up with the most practical application. I may just do something very much similar to my LS router table....

btw. I just checked out Wixey's website. and here's the info. on the table saw digital readout. I do believe it could easily be modified to accommodate an LS system. 
Measuring Length: 60 in. (1500 mm)
Resolution: 
Decimal = .005 in.
Fraction = 1/32 in.
Metric = .1 mm
Accuracy: 
Decimal = +/- .002 in. per foot
Fraction = +/- 1/500 in. per foot
Metric = +/- .13 mm
Battery: 6 months life; type CR 2032
Functions: - Constant memory retains calibration even when OFF
- Incremental measuring mode
- Absolute measuring mode
- Millimeter, Inch and Fraction readout
- Auto shut off

you see, even an affordable digital readout has a +/- of .002 per foot. I'm thinking that this would be the closest one might get without getting into machinist level tooling.


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## Dmeadows (Jun 28, 2011)

TwoSkies57 said:


> Jerry,, there ya go...I think when it comes down to dollars vs. benefits, you've most likely have already come up with the most practical application. I may just do something very much similar to my LS router table....
> 
> btw. I just checked out Wixey's website. and here's the info. on the table saw digital readout. I do believe it could easily be modified to accommodate an LS system.
> Measuring Length: 60 in. (1500 mm)
> ...


Hmm, .+/-.002/ft. But it only displays to the nearest .005. Ooookaaay!:haha:


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