Table saw accuracy - Woodworking Talk - Woodworkers Forum
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post #1 of 47 Old 08-06-2020, 06:57 PM Thread Starter
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Table saw accuracy

I'm making sort of an art piece for my father, and really trying to dial in the accuracy of these pieces. Thus far, it's 90% table saw work, and by the time I drew it up (to scale) with 1mm spacing between the keys, width of dado cutouts of numbers like 6.5mm, I realize I may be at the limit of my (current) accuracy levels. I'm making test cuts, moving the fence a hair, measuring the result with a caliper, etc. Once I get it as close as I can, I make all the cuts of that size. It's going ok, but boy if I screw up one of these keys, getting the saw set to the same spot later is going to be a project. And it seems like there may be a better way.

So I was wondering if folks have any tips for this kind of thing. I see there's a product from Wixey that allows you to dial in a measurement and set the fence very accurately... any feedback on those? If I wrote down a measurement, could I come back a week later, just set the fence at 6,5mm and expect it to be "right"? Any other thoughts for cutting to very exacting tolerances?
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post #2 of 47 Old 08-06-2020, 07:09 PM
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Dave,

When I need to make another identical cut, I use one of the good pieces that I need to match. Place it between the fence and blade and adjustment/lock the fence so that when I move the blade by hand (saw unplugged) the carbide tooth just clears the sample. I then do a test cut, check the test piece against the original, and most of the time itís perfect. Otherwise a slight tap with my hand on the fence and re-lock usually does it. You will need to get the ďfeelĒ for how this way of aligning works on your saw, but once you figure it out itís repeatable.

Tom
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post #3 of 47 Old 08-06-2020, 08:32 PM
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That is exactly what I do. Much simpler and more accurate that the measuring tool.


George
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post #4 of 47 Old 08-06-2020, 08:39 PM Thread Starter
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But how do you set up the first one, when the size dictates 6.5mm wide, by 8mm tall or so. Trial and error and calipers, or some other way?
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post #5 of 47 Old 08-06-2020, 08:47 PM
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Whenever accuracy and repeatability are paramount I make fixtures to use. I try not to ever move the fence, usually using some sort of sled that will run in the miter slot. Sometimes it may take you longer to design and make the fixture than to do the cuts, but think it through. It will come to you. I find I can never have complete accuracy or repeatability if I am moving parts, such as a fence. Another option, where appropriate, is to make templates and use a pattern bit on a router table.
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post #6 of 47 Old 08-06-2020, 11:22 PM
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A Incra LS Positioning fence would allow you do what you want. The American version locks down every 1/32 in, the metric 1mm, but if you want to do a cut between you can dial that into hundredths. It is repeatable and you can go back at any time in the future and dial in the exact measurement as previously.
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post #7 of 47 Old 08-06-2020, 11:25 PM
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This cheap incra jig attaches to your own fence. To give 1/32nd accuracy on your fence, problem is once you set up you only have 8" of working room. Good for drawers though.
https://www.ebay.com/itm/Incra-Jig-U...wAAOSwYYBfI2Hk

Edit: I realized after the fact your measurements listed were in mm. Not much good for a 1/32nd jig.

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post #8 of 47 Old 09-05-2020, 12:16 AM
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That Incra LS positioning fence seems to be for a router table. I don't understand how that could be used on a table saw.

Am I missing something?

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post #9 of 47 Old 09-05-2020, 12:27 AM
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A simple jig for re-positioning the fence might be a stick of hardwood cut to fit the miter slot. Drill a countersunk hole on the under side and run a machine screw through it. Then all you need is a piece of hardwood or baltic birch with a slot to fit over the screw, and a washer and wing nut.

Now, once your fence is set properly for your original cuts, position the jig with the slotted piece pressed against the back side of the fence and tighten the wing nut (or if you want to be fancy, a threaded knob). Label your jig and set aside for next time.

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post #10 of 47 Old 09-05-2020, 03:48 AM
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Ive got the Wixey gauge on my saw, had it for a few years now. Gotta say, its really a game-changer for accuracy, i highly recommend it. You do have to calibrate it every so often, but it gives bang-on results. The biggest advantage is exactly what youre trying to fix; if you move the fence, you can get it back to the exact same spot with no fuss

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post #11 of 47 Old 09-05-2020, 08:41 AM
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This is the old trick from the rule die trade when you need to match the width of a ripping exactly: take the piece, place it against the fence, set the fence a bit wide, rip a scrap piece using the edge of the original ripping as a guide, then set the ripped scrap against the fence and make your new ripping using the edge of the scrap as a guide. It works to match the length of an existing piece on a radial arm saw as well. With small pieces, you may have to think a bit about push sticks and hold downs to do this safely.
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post #12 of 47 Old 09-05-2020, 08:42 AM
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Table saw accuracy

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Originally Posted by brucet999 View Post
That Incra LS positioning fence seems to be for a router table. I don't understand how that could be used on a table saw.

Am I missing something?

Yes you are, they make one for tablesaw as well.


https://incra.com/table_saw_fences-tsls_fences.html
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post #13 of 47 Old 09-05-2020, 09:57 AM
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Good tip ?

Quote:
Originally Posted by JohnGi View Post
This is the old trick from the rule die trade when you need to match the width of a ripping exactly: take the piece, place it against the fence, set the fence a bit wide, rip a scrap piece using the edge of the original ripping as a guide, then set the ripped scrap against the fence and make your new ripping using the edge of the scrap as a guide. It works to match the length of an existing piece on a radial arm saw as well. With small pieces, you may have to think a bit about push sticks and hold downs to do this safely.

I am sincerely trying to understand this.
This is the old trick from the rule die trade when you need to match the width of a ripping exactly:

take the (original?) piece, place it against the fence, set the fence a bit wide, rip a scrap piece

using the edge of the original ripping as a guide, .....? (guide?)

then set the ripped scrap (slightly too wide?) against the fence and make your new ripping

using the edge of the scrap as a guide.....? (guide?)


It works to match the length (length? are we now crosscutting rather than ripping?) of an existing piece on a radial arm saw as well. With small pieces, you may have to think a bit about push sticks and hold downs to do this safely.


I'm sorry I just can't grasp this tip.

The answer to your question will only be as detailed and specific as the question is detailed and specific. Good questions also include a sketch or a photo that illustrates your issue. (:< D)
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post #14 of 47 Old 09-05-2020, 10:53 AM
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Quote:
Originally Posted by brucet999 View Post
That Incra LS positioning fence seems to be for a router table. I don't understand how that could be used on a table saw.

Am I missing something?
Incra has units that are just for a router table and they have units that are just for table saws. If you have a router table extension on your table saw you can get their joinery system that has both options.

I put this on a few months ago and after getting it dialed in I cut a 5" board, 4" board, 3" board and a 2" board. When I put the boards together the combined measurement of all 4 pieces was off by just 1.5 thousands of an inch. It is a spendy but incredibly accurate way to make repeatable cuts.

The first picture includes the Incra wonder fence that I use for routing work. The second picture is with just the fence I use when making cuts with my table saw.

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post #15 of 47 Old 09-05-2020, 12:40 PM
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I subscribed to this thread. I hope to learn good techniques for repeatable, resettable rip cuts. I don't have issues with crosscuts on the table saw if I use a sled.

Based on previous experience, I never trusted my table saw rip fence rail scale, preferring "cut to fit" and "adjust fence with blade teeth to match" techniques with test cuts in scrap. That was true for the jobsite saw I had in recent years, and other saws I have used in the past, especially the radial arm saws. Now I use a SawStop cabinet table saw.

I mentioned my reluctance to trust the rip fence ruler to friends who own SawStop cabinet saws. They were surprised, and told me that they relied on their SawStop rip fence rulers for highly accurate, repeatable cuts. They set the width they want and cut without testing on scrap or any other preparation.

After testing with calipers, I learned that my friends are mostly right. Using that approach, I get resettable repeatability between 1/64 and 1/128 inch (around 1/4 mm). That's within the limits of wood and my cutting skills anyway. Accuracy depends on alignment and calibration, and you have to recalibrate any time you change the blade or make an alignment change. (Note: The fence can move as you clamp it. You must check the measurement after you clamp the fence. You can reduce movement somewhat by pulling the fence towards you as you position it before clamping.)

At some point the question becomes moot, because wood itself is unpredictable and there is still room for for me to improve my rip cutting skills.

I am watching this thread with interest.
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post #16 of 47 Old 09-05-2020, 01:35 PM Thread Starter
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I have been doing the same, using just the scale on my SawStop Biesmeyer-style fence, for any normal cut. If I need something 6-5/16" wide, that's fine I just set the fence and cut. That's after a) setting the scale up back when I got the saw and b) making sure I only use blades with 1/8" kerf. The factory supplied combo blade is not 1/8", so I chose to trash it in favor of simplicity.

For these piano keys though, the measurements I was trying to reproduce were to 0.5mm both for rip and crosscuts, and just a bit more granular than I could manage on the crosscuts. I'm sure the Incra fence would do the trick.

What I finally did on this project by the way was the "make a test and adjust from there" method.
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post #17 of 47 Old 09-05-2020, 02:49 PM
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Setting the fence indicator is easy ....

For "no measure cuts" using the hairline indicator and measurement tape on the fence rail, there's an easy way to precisely adjust the hairline indicator.


(1) Set the fence over to any width, say 18" plus or minus. Make a rip cut using the fence. Measure the result as accurately as possible. Then adjust your hairline indicate to that dimension.



(2) Set the fence to a different dimension using the hairline indicator, but less than before and make a second rip cut. Measure the result and see if it's the same as your setting. If not readjust slightly and repeat the process.


This method requires you always use the same kerf blade.
For repeatable cuts, just place a strong magnet on the right side of the fence rail, bumping it to your last fence setting before moving it.
Now you can move the fence to the left in any amount, but not any further to the right than the last rip. For greater rips to the right, just reverse the magnet to the left side.

The answer to your question will only be as detailed and specific as the question is detailed and specific. Good questions also include a sketch or a photo that illustrates your issue. (:< D)

Last edited by woodnthings; 09-05-2020 at 02:59 PM.
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post #18 of 47 Old 09-05-2020, 03:46 PM Thread Starter
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That's a nifty trick with the magnet!
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post #19 of 47 Old 09-05-2020, 06:32 PM
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Quote:
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(1For greater rips to the right, just reverse the magnet to the left side.
Wouldn't that magnet placed to the left of the fence get in the way of the wood you want to rip to a greater measurement to the right?

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post #20 of 47 Old 09-05-2020, 07:06 PM
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You need to choose ...

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Wouldn't that magnet placed to the left of the fence get in the way of the wood you want to rip to a greater measurement to the right?

The magnet I use is attached to the rectangular steel rail (Bisemeyer) the fence rides on. It can be placed as a stop on either side of the fence head, you just need to figure out ahead of time what your work sequence will be. Hopefully, your widest rips will come first, then the narrow ones. It's only a quick and dirty "short cut" and it's always good to measure to be certain.

The answer to your question will only be as detailed and specific as the question is detailed and specific. Good questions also include a sketch or a photo that illustrates your issue. (:< D)
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