Fences and Tape Measures

[Mini Me]

To avoid taking the current safety thread totally off topic I will quote Chuck S here.....

There is a very good reason why not using the scale on the saw, but a tape measure is the right thing to do.

If you measure, for example, an opening and need to cut a piece to the exact width of the opening, you must set the fence with the tape measure (unless the tape measure used is the same as the scale on the saw, which is usually not the case).

This is the exact reason why I had a standard aluminium calibration "stick" made that is used to ensure all five of the fences on my machines cut to the same length and the measuring tools I use match the fences. It might not be to metrology standards but for woodwork I always get what I measure.

 

[ChuckM]

Yours sounds like a very efficient set-up.

Among the half a dozen tape measures I frequently use in my shop, only two of them giving the identical results. The situation becomes even worse if the steel rules and combo squares join the mix. I don't think the scale on my SawStop matches the scale on any of the measuring tapes or rules.

Two days ago, I was setting my fence at 132mm for a rip cut, but when I checked the distance between the fence and the blade (tooth), one rule said it was a hair under 132mm, while another rule said it was a hair under 132mm plus:

[attachimg=1]

The fence has been calibrated zero to the scale on the table saw.

 

[jonnyrocket]

Among the half a dozen tape measures I frequently use in my shop, only two of them giving the identical results.

I appreciated this video Sedge made. Important to calibrate the various rulers in your shop to a single standard.

 

[kevinculle]

Or equip your table saw or router table with an Incra fence system...I have the TS-III on my Delta table saw with cast iron router extension table.  The system uses toothed racks that interlock available in either 1/32" or 1mm increments.  These provide repeatability in setting the fence of +/- a few thousandths of an inch or about 0.05mm.  There is a vernier adjustment that is settable to 0.001" or 0.025mm increments.  Mine has about 0.002" of lash in the vernier.  So long as you know the width of your saw kerf you will never need a tape measure at the table saw again.  There is a downside...the fence system mechanism protrudes out the right end of the saw so it's a bit of a space hog but well worth it.

[attachimg=1]

 

[Mini Me]

Among the half a dozen tape measures I frequently use in my shop, only two of them giving the identical results.

I appreciated this video Sedge made. Important to calibrate the various rulers in your shop to a single standard.

It is pointless doing the tapes if your fences don't cut to the same measurements that only gets you back to the same problem of needing to measure each cut because the fence does not match the fence measurement.

 

[Packard]

Yours sounds like a very efficient set-up.

Among the half a dozen tape measures I frequently use in my shop, only two of them giving the identical results. The situation becomes even worse if the steel rules and combo squares join the mix. I don't think the scale on my SawStop matches the scale on any of the measuring tapes or rules.

Two days ago, I was setting my fence at 132mm for a rip cut, but when I checked the distance between the fence and the blade (tooth), one rule said it was a hair under 132mm, while another rule said it was a hair under 132mm plus:

[attachimg=1]

The fence has been calibrated zero to the scale on the table saw.

I usually stand directly in front of the blade on my table saw.  I have to shift to the right to read the scale on the fence.

There is a fairly significant gap between the hairline plastic and the scale.  That allows for a fairly significant amount of parallax in the readings.  I have to stand directly in front of the hairline in order to avoid parallax errors. 

I assume that gap between the clear plastic with the hairline and the scale is intentional to make it easier to blow out sawdust that migrates between the surfaces. I do have to clean that out fairly often as the saw dust make it difficult to read the scale. 

The biggest thing I did for accuracy was to order the 51” fence.  A smaller fence would mean doing math and I hate math. 

I prefer to transfer dimensions to reading a ruler and I will use the actual part to set the fence if possible. Or a story stick or (most frequently) a 36” or 48” aluminum ruler with stair stops to mark the length.

 

[ChuckM]

In addition to Mini Me's point, there're two more issues with calibrating tapes based on bending the hooks:

1) It only works when measurements (e.g. of the outside of a surface) are taken using the inner face of the tape hooks. The measurements of the inside of a surface may still be off among the so-called calibrated tape as in the case of measuring the distance between the fence and the blade. I also wonder that calibrations based on bending hooks might not work for thinner stock as the bend may not the same among tapes.

2) In use, many people let the tape slam into the case (I never do that for accuracy and safety reasons), and that means unless they calibrate all their tapes all the time, the one-time calibration is worse than none.

When I need to use a tape measure in a project, I stick to the same measuring tape till the end. The same applies to steel rules, and I have more than half a dozen of them, too.

 

[ChuckM]

Snip.
I assume that gap between the clear plastic with the hairline and the scale is intentional to make it easier to blow out sawdust that migrates between the surfaces. I do have to clean that out fairly often as the saw dust make it difficult to read the scale.Snip.

Without the gap, the marking on the scale would be rubbed off quickly. Even with the gap, I still have to use a black marker to highlight some of the fainting numbers once in a while.

 

[Packard]

Snip.
I assume that gap between the clear plastic with the hairline and the scale is intentional to make it easier to blow out sawdust that migrates between the surfaces. I do have to clean that out fairly often as the saw dust make it difficult to read the scale.Snip.

Without the gap, the marking on the scale would be rubbed off quickly. Even with the gap, I still have to use a black marker to highlight some of the fainting numbers once in a while.

Regardless of the reason for the gap, parallax is significant and must be addressed. You could end up with a dimension error of 1/16th of an inch due to parallax alone.

Note: The only table saw I have ever used is a Contractors’ II from Delta with the optional 48” fence.  I am basing that discrepancy possibility above on my experience with my saw.  I am assuming that other saws have potentially similar parallax discrepancies.

 

[alltracman78]

This is why I personally don't like tape measures for finish or precise measurements. No matter how accurate they are, because of how they're shaped and how they work they're inherently more prone to error than an inflexible tool.

Also why it's better to use a story stick or similar instead of using numbers when you can; no counting and guessing between lines.

Or equip your table saw or router table with an Incra fence system...I have the TS-III on my Delta table saw with cast iron router extension table.  The system uses toothed racks that interlock available in either 1/32" or 1mm increments.  These provide repeatability in setting the fence of +/- a few thousandths of an inch or about 0.05mm.  There is a vernier adjustment that is settable to 0.001" or 0.025mm increments.  Mine has about 0.002" of lash in the vernier.  So long as you know the width of your saw kerf you will never need a tape measure at the table saw again.  There is a downside...the fence system mechanism protrudes out the right end of the saw so it's a bit of a space hog but well worth it.

The problem isn't how accurate (or innacurate) his table saw fence is, the problem is the table saw and the tape measure don't agree on the same measurement.

Obviously you want your measuring tools to be as accurate as possible, but it's more important that they all agree (This is the difference between precision and accuracy). If all your measuring tools are off by 1/4 inch, as long as they're all off by that same amount you will get the same distance no matter what measuring tool you use.

 

[alltracman78]

Among the half a dozen tape measures I frequently use in my shop, only two of them giving the identical results.

I appreciated this video Sedge made. Important to calibrate the various rulers in your shop to a single standard.

Bending the hook isn't the right solution, I would return it and find one that is accurate.
This trick is better for finding what tools need to be replaced/retired than for adjusting.
He should have put a mark for the start point as well. Or used the edge of the board instead of using the middle.
To illustrate: if you measure from the edge directly across to that line you get 300mm, if you measure from the top left corner to that line you'll get a different number.
Obviously you're not going to measure that far off; but IMO tool calibration should be to a higher tolerance than the work being performed.

*The other problem with this is you can have 2 measuring tools that agree at 300m and be off at the 200mm mark, or the 400mm mark. I've ran into this problem.
The more points you compare at the more precise your measuring will be.

I know this is kind of nitpicking, but I figure most of us on here are more concerned with precision than the average joe or jane.*

 

[twistsol1]

I know this is kind of nitpicking, but I figure most of us on here are more concerned with precision than the average joe or jane.*

I actually don't care at all about precision. Consistency/Repeatability are more important to me. My shop is metric, except for an ancient ShopSmith, and I use one and only one Starrett folding rule to calibrate the scale on all of my machines that have scales. I don't care if my 500mm measurement is 498 or 503mm in reality as long as 500mm on the table saw comes out the same length as 500mm at the miter station and the panel saw.

I often use story sticks ripped from 1/2 or 1/4 plywood waste for measurements in the field and throw them away when I'm done with the project. It has saved me from poor penmanship errors countless times.

 

[alltracman78]

I know this is kind of nitpicking, but I figure most of us on here are more concerned with precision than the average joe or jane.*

I actually don't care at all about precision. Consistency/Repeatability are more important to me. My shop is metric, except for an ancient ShopSmith, and I use one and only one Starrett folding rule to calibrate the scale on all of my machines that have scales. I don't care if my 500mm measurement is 498 or 503mm in reality as long as 500mm on the table saw comes out the same length as 500mm at the miter station and the panel saw.

I often use story sticks ripped from 1/2 or 1/4 plywood waste for measurements in the field and throw them away when I'm done with the project. It has saved me from poor penmanship errors countless times.

That's exactly what precision is. Consistency and repeatability. You can be completely wrong and be precise. You just won't be accurate.
Accuracy is getting the correct answer (or measurement).

 

[Mini Me]

As a general work practise I don't use a tape with a hook due to the problems most tapes of that type have. The BMI Quicky tapes I use are without hooks and i highly recommend them. Besides being a measuring tape they do an excellent job as a straight edge as they can be placed and used to draw lines if needed. They used to be available in a combined metric/imperial configuration but I don't know if that is still the case.

Quicky Tape

 

[Mini Me]

I know this is kind of nitpicking, but I figure most of us on here are more concerned with precision than the average joe or jane.*

I actually don't care at all about precision. Consistency/Repeatability are more important to me. My shop is metric, except for an ancient ShopSmith, and I use one and only one Starrett folding rule to calibrate the scale on all of my machines that have scales. I don't care if my 500mm measurement is 498 or 503mm in reality as long as 500mm on the table saw comes out the same length as 500mm at the miter station and the panel saw.

I often use story sticks ripped from 1/2 or 1/4 plywood waste for measurements in the field and throw them away when I'm done with the project. It has saved me from poor penmanship errors countless times.

This man gets it. Everyone recommends using the same tape totally ignoring what the tape on the machine reads compared to the measuring tape. With the cheap and accurate DRO's now available that now have programmable resolution to a very fine degree tapes on machines are somewhat old hat so to speak. No guessing or parallax error with those.

 

[ChuckM]

Story sticks are good but not always as good as a measuring tape like this one:https://www.leevalley.com/en-ca/sho...apes/71705-auto-lock-write-on-measuring-tapes

Where can you find or make a story stick that you can put in your pocket? A story stick that can be reused (erased) over and over again without worrying about confusing leftover marks. I have only one Fastcap tape, but it is my go-to story stick instead of a wooden strip when it is the best tool for the job.

 

[mwolczko]

Or equip your table saw or router table with an Incra fence system

I have a TS-III on a SawStop PCS. Beyond the right wing I added a router table and attached a WonderFence to the other end of the Incra positioner.  If I had a bigger shop I would keep the table saw and router table separate but in the limited space I’ve got this combination works very well. 

 

[Crazyraceguy]

This all has to come from the comment I made on another thread.
My point was basically alltrackman78 said, your tape measured reading from the piece you just cut should match the number on the scale of the machine. There is absolutely no reason not to do this. The machine is adjustable, the tape measure effectively is not. (assuming undamaged)
I work in a fairly large cabinet shop with 3 SawStops, a sliding saw, a vertical panel saw, and of course the computerized beam saw. Keeping all of this as equal as possible is a bit of a challenge at times, coming to the point that only two of us are allowed to adjust any of them. We can't have just anyone adjusting something, that we all use, to match their own (possibly off) tape. You just have to know and be aware of the difference.
This is way out of the realm of the average guy in his home shop. The saw should match the tape, so you always know what you are going to get. Is it 100% accurate? not necessarily, but it is relative and repeatable, which is all you need.
The tape to the fence method is fraught with problems. The tape has to be square to the fence, the blade has to have zero wobble, etc. The only time I ever do it is with a dado stack. The width of the blade throws the scale off. Test cuts are always there to maintain accuracy.
It is pure theatrics for video, no way they do that on a regular basis.

 

[festal]

Or equip your table saw or router table with an Incra fence system

I have a TS-III on a SawStop PCS. Beyond the right wing I added a router table and attached a WonderFence to the other end of the Incra positioner.  If I had a bigger shop I would keep the table saw and router table separate but in the limited space I’ve got this combination works very well.

do you have any pictures of your setup?

 

[Packard]

I found that the repeatability of my cuts on the table saw improved once I got my Magswitch magnetic feather board.  It is so quick and easy to use that I use it on the majority of my cuts.

I find that my cuts and my fence’s scale match up extremely well.  It is as accurate as the line thickness of my trusted ruler.

When I changed blades, I had to re-calibrate the fence.

My Magswitch featherboard: