I own 5 Incra T-rules (150mm, 300mm, 6in, 12in, 18in) and I got them primarily to measure with rather than to mark saw cuts. While making setup blocks for my MFT table, I found something surprising — they are all precise but they are all offset by 0.25mm.
In essence, since they take a 0.5mm mechanical pencil, these rules mark a cut line rather than a centered line at the desired measurement… that it is, you can get a full width pencil line on the edge of your work piece if you mark at zero. This is a big pain and really destroys the main reason I bought these tools.
I initially discovered this when I was cutting plywood strips to use as setup blocks on my MFT and measuring each block with an Incra to make sure I had cut it precisely. I was losing my mind because the widths were measuring correctly (center of the hole, lined up with the edge marking) but then combined setup blocks were adding up incorrectly.
Using my 150mm Incra, I measured my Veritas metric setup blocks and found all the pieces to be 0.25mm short (center of the hole at 1/4 mm offset, by eye — it could be 0.01 inches or similar) But then, when combining multiple blocks together, the total would also come up 0.25mm short. It therefore must be the Incra that’s off by some constant offset. This is when I checked the zero line as described above. I also double checked the tightness of the metal strip on each T-rule, verified that I could not shorten this offset, and also verified that the 127mm/5in line drawn was the same across all five of my Incra T-rules.
This is really disappointing to have a cut/cutoff line instead of a centered line. When making precision cuts you are rarely sighting the track saw guide rail off of a drawn line, so my main value for these T-rules was to get quick and accurate verification of measurements on cut pieces. Now I have to constantly remember to look through the tiny 1/4mm offset hole below the whole mm, and there is no reference line on the side of the rule either, so it just looks off. Similarly, if you are drawing lines to place fasteners, you would want a centered line so you can drill where the lines cross. With these cut lines, your fastener placement needs to be on one edge of each line, and you have to remember which edge.
Does anyone have any suggested solutions? Do woodpeckers T-rules have centered lines without the offset? Does Incra have a 0.25mm piece I can attach to get rid of it?
Edit: I forgot to mention that the measurements along the bottom edge of the rule do not share the same offset. It really seems like an oversight in the design.
Edit 2: The design oversight comment is based on the fact that there are both pencil slots in the bodies of the T-rules and also measurement markings along the edge. What I’ve discovered is that the pencil slots will draw you an accurate cut off line, but the edge markings are simply inaccurate because they are lined up with the center of the pencil slot. If this had all been intentional, I would expect the measurement markings to line up with the inside edge of the pencil slot to give an accurate measurement.
In essence, since they take a 0.5mm mechanical pencil, these rules mark a cut line rather than a centered line at the desired measurement… that it is, you can get a full width pencil line on the edge of your work piece if you mark at zero. This is a big pain and really destroys the main reason I bought these tools.
I initially discovered this when I was cutting plywood strips to use as setup blocks on my MFT and measuring each block with an Incra to make sure I had cut it precisely. I was losing my mind because the widths were measuring correctly (center of the hole, lined up with the edge marking) but then combined setup blocks were adding up incorrectly.
Using my 150mm Incra, I measured my Veritas metric setup blocks and found all the pieces to be 0.25mm short (center of the hole at 1/4 mm offset, by eye — it could be 0.01 inches or similar) But then, when combining multiple blocks together, the total would also come up 0.25mm short. It therefore must be the Incra that’s off by some constant offset. This is when I checked the zero line as described above. I also double checked the tightness of the metal strip on each T-rule, verified that I could not shorten this offset, and also verified that the 127mm/5in line drawn was the same across all five of my Incra T-rules.
This is really disappointing to have a cut/cutoff line instead of a centered line. When making precision cuts you are rarely sighting the track saw guide rail off of a drawn line, so my main value for these T-rules was to get quick and accurate verification of measurements on cut pieces. Now I have to constantly remember to look through the tiny 1/4mm offset hole below the whole mm, and there is no reference line on the side of the rule either, so it just looks off. Similarly, if you are drawing lines to place fasteners, you would want a centered line so you can drill where the lines cross. With these cut lines, your fastener placement needs to be on one edge of each line, and you have to remember which edge.
Does anyone have any suggested solutions? Do woodpeckers T-rules have centered lines without the offset? Does Incra have a 0.25mm piece I can attach to get rid of it?
Edit: I forgot to mention that the measurements along the bottom edge of the rule do not share the same offset. It really seems like an oversight in the design.
Edit 2: The design oversight comment is based on the fact that there are both pencil slots in the bodies of the T-rules and also measurement markings along the edge. What I’ve discovered is that the pencil slots will draw you an accurate cut off line, but the edge markings are simply inaccurate because they are lined up with the center of the pencil slot. If this had all been intentional, I would expect the measurement markings to line up with the inside edge of the pencil slot to give an accurate measurement.
