Incra question. Didn't fly down under

[Steven Bolton]

Incra jigs work, as I understand, in increments of 1/32 of an inch. It does this by interlocking saw tooth racks. The racks keep things at the 1/32 increment.

I don't understand how the fine tuning feature that allows you to adjust by 1/1000 of an inch works. If you adjust by 1/1000 of an inch, does the entire set of of saw tooth racks (both racks) then move by 1/1000 of an inch, or when you put the locking lever down, does it then jump to the first closest saw tooth it can find. It seem like if it jumps to the first closest saw tooth rack it can find, you have defeated your efforts of adjusting by 1/1000 of an inch.

If one rack on teeth are moved, I can't understand how the microadjustment works, as it seems like it would simply interlock with the next mating tooth on the other rack of teeth.

I have the Incra Ultra Lite which uses the hard plastic racks. I think the LS uses iron teeth racks.

Obtuse question at best.

But thanks for any input.

sb

[Dale Lesak]

when you lock down the saw tooth engage, locking the base in place. the other parts are still movable for fine adjustment then lock it down. :)

[Don Bullock]

Steven,

Go to the Incra video site http://www.incra.com/video_demos.htm and play the first video on the list. It explains how the system works.

[Jim O'Dell]

I think the 1000th inch increments comes in with the fine adjustment knob that is also on a lead screw thread set up. Makes for very fine movement. I still haven't figured out how to track the 1000th increments. May need to hook up a micrometer to the system. :cool: Jim.

[Brandon Shew]

On my TS-III - the plastic saw tooth mechanism locks the fence positioner into place at the 1/32" increment using the teeth. You can then "unlock" the fence positioner adjusting mechanism from the saw tooth guide (saw tooth positioner stays locked in where you set it originally) and adjust with a dial to the .001 within that saw tooth position. Lock the fine adjuster back in and make your cut.

Just make sure that you zero out the fine adjuster again before making another cut at a different saw tooth position or you'll be off.

I really liked my TS-III. I found it well built, easy to use, and (of course) extremely precise. The T-Tracks on the fence face, top, and side made it easy to attach jigs, sacrificial fences, etc. It is just a great design IMO.
Unfortunately due to a shop downsizing, I had to trade it out for a Biesemeyer (which I am expecting any day now). I'm not sure if I'll like the Biese as much or not.

[Scott Rollins]

The incra system will snap into the threaded lead screw in 1/32 increments. If you choose to adjust 0.001 or any amount you have effectively "shimmed" every point on your scale. (think of it as the sacrificial face on the table saw fence) Every point on the scale will be moved by the adjustment. This is handy if you have an undersize bit and need to step over 0.010" to adjust the fit on dovetails or box joints. You can simply repeat the cuts and you will remove material from one side. Or you can take 0.005" off each side of your cut line. Yes it is that accurate (I checked it with an indicator). You must then "remove the shim" by moving the leadscrew back or move your magnetic scale to read zero again.

[Steven Bolton]

That makes sense to me. In other words, if you use the micro adjuster, both tooth racks move by .001 or whatever you move it. Otherwise, if only one tooth rack moved, when you tighten it, you would be back in the next 1/32 of an inch rack.

Thanks

sb

[Gary Muto]

Steve,
I have the Incra Ultra Lite. It has no fine adjustment like the higher end models. My interpretation from the directions and video is that the system has 1/32" resolution with 0.001" repeatability.
It can achieve the same or any 1/32" increment within +/-0.001".
I hope this helps.

[Eric Gustafson]

The Incra LS series has a 1/32 pitch screw that runs the length of the positioner. The adjustment wheel has 32 detents in it. That wheel moves the 1/32 pitch screw. So it further divides 1/32 inch 32 times, yielding a resolution of 1/1024 of an inch per click. Or each click equals .0009765625 inch! In woodworking terms, we round up to .001 inch. :D

[Bill Wyko]

I've been waiting for you to post this Eric:D what he said.

[Cliff Rohrabacher]

I think the 1000th inch increments comes in with the fine adjustment knob that is also on a lead screw thread set up. Makes for very fine movement. I still haven't figured out how to track the 1000th increments. May need to hook up a micrometer to the system.

Every screw thread is mathamatically precise. Simply divide 1 by the thread pitch and that is how many thousandths of an inch one rotation will move the nut.

Similarly for metric 1 divided by the pitch = ho many millimeters it'll move on one rotation.

[Steven Bolton]

I have the Incra Ultra Lite and it has a micro positioner. I observed that the both racks move when you use the micro positioner. It could be different on the LS.

sb

[Gary Muto]

I checked last night. I have an Incra Universal, not an Ultra Lite and that model does not have micro adjust. I'm sorry about the mis-information.