Replies

1. 
   rob_ss | Jan 30, 2022 01:31am | #1

   A feeler gauge is the best way to measure it, but you don't really need to quantify the gap. What you need is a piece of wood that is the exact length and you can measure that with a tape, or if you are being particular a suitable rule.
   A more reliable way is to cut a piece likely to be a hair longer than needed, see if it fits, and use a marking knife to mark what it needs to be. Sneak up on the fit with a table saw or a good mitre saw.

   For completeness, absent feeler gauges, you can also measure the gap with a thin shim planed to an exact fit, then measure the size of that with a caliper.

2. 
   kudzupatch | Jan 30, 2022 10:38am | #2

   Since you are going to cut the new one using a tape measure of ruler it just make sense to use the same tool with the same accuracy to measure the gap.

   But cutting it long and trimming it to fit is the time honored way.

   You may can measure in 1ooth of an inch but wood working tools are not set up to cut (first time) to a 100th of inch. So there isn't a lot of advantage to measuring to that sort of accuracy.

3. 
   jharveyb | Jan 30, 2022 10:45am | #3

   Assuming your goal is to make the longer piece, use a feeler gauge or shim stock or a cut piece of wood to fill the gap, then do the following:
   Put a stop block on a fence attached to your miter gauge, that would cut a piece a couple inches longer than your desired piece. Put the feeler gauge/shim against the stop block, the too-short piece against the feeler gauge/shim, and a scrap piece (with a square end) against the too-short piece. Cut the scrap piece. Now place the cut scrap piece against the stop block and a new to-be-longer blank against it, and cut the new piece to the proper length. I use this frequently to duplicate parts (without the feeler gauge); takes the worry out of making mistakes sometimes.
   I can also duplicate ripped pieces by putting the original piece against the TS fence, ripping a scrap piece against it, and then putting the ripped scrap piece against the fence to rip the desired duplicate. To give appropriate credit, this came from a long ago article in FWW.

4. 
   gary_vaiskauckas | Jan 30, 2022 04:07pm | #4

   Here is a way to help visualize the good advice from above comments.

   FWW Bob Van Dyke: "Story Stick for Accurate, Repeatable Cuts
   Learn how to use a story stick to accurately repeat cuts and map out joinery for an entire project on one piece of wood. Measure once and cut 100 times!"

   https://www.finewoodworking.com/2009/08/20/story-stick-for-accurate-repeatable-cuts

5. 
   spog_uk | Jan 30, 2022 05:28pm | #5

   Feeler gauges are great for some tasks like this, although 2/32 (or 1/16) is maybe a bit thick to need them. I also keep a deck of old playing cards on hand, for use as random shims and impromptu measuring devices. 1 card ~= 8 thou ~= 1/128" ~= 0.2mm (exact value will obviously vary depending on your cards, and it doesn't matter if used as a basic referential measurement unit in itself, eg "this gap is 2 cards thick"). Can also wedge however many it takes into a gap, then pull them out and measure with calipers, if this proves to be more practical.

6. 
   Kurt_Battles | Jan 30, 2022 09:11pm | #6

   I love FWW forum. This is about the 4th question I have asked here and I always get thoughtful responses. I learn a lot. Off to find a feeler guage just because I want to quantify the gap, it should be cheap fun. I have an 18" Starrett ruler on the way and will compare my results. Thanks for the feedback.

7. 
   Kurt_Battles | Jan 30, 2022 09:26pm | #7

   FYI, I picked up a feeler guage, my gap was 3/64ths. Now to cut a slightly larger new peice and "sneak up" on the final size. Thanks for all the good advice, I am still learning, as are we all, huh?