Thin-Strip Cutting Jig With Micro Adjustment

Intro: Thin-Strip Cutting Jig With Micro Adjustment

How can you consistently rip-cut thin strips on a table saw to a precise thickness? How do you adjust the table saw fence to cut a groove with a precise width? Build this simple and inexpensive jig from easily available parts and you can get accurate cuts down to about 0.008 inches (1/128”) - at least in theory. That is more than you need for any woodworking project! I’ll show you how to build the jig.

STEP 1: Make the Jig

A drawing of the jig is shown above and attached as thin-strip-jig.pdf.

Make a short piece (5 inches) of miter bar from hardwood, typically 3/4" by 3/8" cross section. I had a left-over piece from an aluminum t-track/miter bar which I used for this jig. Be sure the miter bar fits snugly into the table saw miter slot with no play. Attach the miter bar to the plywood board with recessed screws, about 4.75" from the short edge.

Cut a couple of hardwood blocks 2.25" by 1.5" by 7/8". Drill a 3/8” hole 5/8” deep into the wood blocks in the location shown in the drawing. In the same location drill a 1/4” hole all the way through. Screw the threaded inserts into the 3/8” holes. Then insert the threaded rod so that the two blocks are about 2.5 inches apart. Glue the two blocks to the plywood board while the threaded rod is in place. This insures proper spacing between the two threaded inserts.

3D print the dial wheel and a couple of thumb wheels, stl files attached. The thumb wheel lets you fix the dial wheel in a preferred position during use; for example where the main tick and handle is on top. The dial wheel has 8 tick marks. Each tick mark represents a 0.00625" adjustment of the threaded rod in or out. Accurate enough for wood working projects! Insert a short 3/16" dowel into the dial wheel for a crank.

An acorn nut fixed at the end of the threaded rod makes the contact with the table saw fence; and prevents scratching the fence.

STEP 2: Calibrate the Jig for Your Blade Kerf

First make sure that your table saw is properly tuned and adjusted; i.e. blade parallel to miter slot, fence parallel to blade and miter slot.

To use the jig you should first determine the actual kerf size of the blade. You need to do this only once for each blade you are using. Cut a 1/4 inch deep groove the width of your blade into a test board. Then set the fence and make a rip cut to trim one side of a second test board. Without moving the fence, set the jig into the miter slot and adjust the threaded rod/acorn nut so it just touches the fence. Then back off the threaded rod by a number of turns, e.g. 5 full turns of the dial. 5 turns will move the rod by (5 turns) ÷ (20 turns per inch) = 0.25 inches. Now move the fence against the rod/acorn nut and lock it. Remove the jig. Make another rip cut on the second test board. You should get a thin strip. Test the strip in the groove of the first test board. Repeat this procedure until the cut-off strip fits perfectly into the groove in your first test board. Write down the number K = one-half the number of turns for this cut; this corresponds to the kerf size of your blade. Keep this blade kerf parameter K for future reference.

To illustrate with an example, let's say you make 4 full turns of the dial to get a strip that fits perfectly into the groove, so your number K = 2. This corresponds to the actual blade kerf of (2 turns) ÷ (20 turns per inch) = 0.1 inch, which is a thin-kerf blade. The spec of my blade says 0.098" for the kerf! Pretty close!

You may round your blade kerf parameter K up/down to the nearest eighth to make the adjustments mentally easier. Experiment to get the value that works best for you!

As a rule of thumb, a full-kerf blade is about 1/8" (0.125") thick for a K = 2.5; a thin-kerf blade is about 3/32" (0.94") thick for a K of about 2. This is a good starting point for your calibration.

STEP 3: Cut Thin Strips

Now you can cut thin strips to any desired thickness. I use thin strips for splines in cutting boards and boxes. Thin strips are also used when you make curved or bend laminations. I have included a table for common widths, be sure to add your blade kerf parameter K to the value taken from the table.

Let’s say you want to cut 1/16” thin strips. 1/16” requires 1/16" x (20 turns per inch) = 1.25 turns of the dial. So take a board and make a rip cut along the left edge. Don't move the fence yet. Set the jig into the miter slot and adjust against the fence, just touching. Then back out by K plus 1.25 turns. In our example from step 2 you turn the dial 2 + 1.25 = 3.25 times. Now move the fence over against the acorn nut, lock it, and remove the jig. Make the rip cut and you have your thin strip at 1/16”. For each additional strip turn the dial again 3.25 times, move the fence over, and cut.

STEP 4: Cut a Precise Groove or Dado With a Regular Saw Blade

Another way to use the jig is for cutting grooves or dados to a precise width with a regular saw blade, no dado blade required. First, set the fence and cut the left edge of the groove. Set the jig into the miter slot and adjust it against the fence. The number of turns for the groove width is calculated like so: W = (groove width in inches) x (20 turns per inch). Then turn the dial by (W - K), and move the fence against the acorn nut. This will cut the right edge of the groove. After this remove the wood between the left and right edge doing multiple cuts. For K = 2 as in step 2 above, a groove that is 1/2 inch wide will take 8 turns between the left and right edge setting. Do some test cuts first on scrap pieces to fine tune the settings.

Groovy!

Comments

[RickM69]

Sorry to rain on your parade but the problem with this method is that you have to move the fence for every cut. I've tried this before and even with a jig you always run the chance of having a slight error when you move the fence. I've been doing some pinstripe inlays with 1/16" strips and there is no room for error. I use a jig that is just a 4" wide piece of wood with a tab to push the strip at the end of the cut. Once I'm dialed in I can cut as many 1/16" strips as I need without moving the fence and they all come out exactly 1/16" Here's a video where he uses a slightly different method but the same concept.

https://www.youtube.com/watch?v=fvMrDNPSoRM

[rschoenm]

Another great idea! So you can use my jig to dial in the correct settings for a chosen width, then cut the thin strips on the right side of the blade using a push board as you described. As you pointed out you’ll never have to move the fence so you won’t introduce that potential error. Thanks for the suggestion!

[schreib]

Great little jig and idea.

Alternate idea, hopefully I will describe without adding confusion: The idea is to simply use a caliper's already excellent accuracy combined with the slot's own accuracy to offset the fence a tiny amount for similar thin strip rips.

-- Cut a thin kerf in any board, measure the kerf width directly with a digital caliper, "K", usually about 1/8".

-- Rip a board to 1.5" width. Later, this highly accurate 1.5" board will be used to make the first, thin 1/16" strip. This will work with a 4" caliper, 6" calipers(more common) can accommodate wider boards.

-- using a digital 4" or 6" caliper place the Right side of nearest jaw against the saw's guide slot: it's right internal face and extend the jaws until the extended internal nose projects against the Fence(now set accurately to cut 1.5" boards).

-- Zero the caliper, then, retract the jaws: the blade's kerf width, K, + 0.062" or ~0.187"; LOCK the caliper at this setting - 0.1875"

-- Loosen Fence, move it LEFT towards the caliper probe; when it just touches the caliper, tighten Fence. Verify the "feel" and, again, tune it a bit until it REALLY just barely touches the caliper. Now it is set to cut a 1/16" strip-- including kerf width.

-- Rip a 1/16" strip from the 1.5" board.

Pros: uses the equipment you have already. (If you don't have a caliper already, buy one; the expensive table saw is nothing if you cannot measure what you make.)

Cons: May require a "feel" for setting the caliper against the Fence not required so much with YOUR jig; May require an additional block of wood, accurately cut to place as a spacer against the Fence for wider input boards than the caliper can reach.

[rschoenm]

Great idea, I'll try it sometime soon. I'm still using an old fashioned 'analog' caliper, really need to upgrade. Thank you for sharing!

[ihart]

Hi. Looks like a great project. Can you post a youtube video of it in action? Either for thin strips or dado cuts?

[rschoenm]

Thanks. Happy to do it. Will take a little while!