Dumb question about Incra jigs

[sbolton]

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 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 efforst of adjusting by 1/1000 of an inch.

Obtuse question at best.

But thanks for any input.

sb

[Chris Parks]

I have never used one, but will take a stab at this. The rack locks and the fine tuning is a thread that moves the head while the rack is still locked but the head can move vis the thread until it in turn is locked. So the head has two locks, one locks the rack and one locks the fine adjuster.

[Big Shed]

:whs:

.....................but the fine adjustment only works with the locking lever in the middle position. Down it is unlocked, middle you can fine adjust, up locks it. Hope that helps.

[Caliban]

I have the cheap plastic (original) incra system and from what I understand it is the racks that lock to that tolerance.But when you move to the next tooth it is still 1/32" away not 1/1000" away. But your 1/32" move will be accurately 1/32" distance from the last, right down to 1/1000" accuracy. That is 1/32 exactly not 1/32 plus or minus anything. Exactly on the money, to that 1/1000 tolerance. It's a bit of a seppo wa^k if you ask me. If you get a bit of gum on your router cutter there goes that 1/1000 accuracy. But hey it souds good in the promo.
I'm unsure if the fancy gold ones are any different, the racks are the same principle, the pretty knobs might let you have more fine adjustment.

[Big Shed]

Caliban, I take it that the Original Incra does not have the micro adjustment?

My LS17 does, and I have used it on several occasions, it is not a w*nk, seppo or otherwise.

If you have a look here (http://www.woodshopdemos.com/sstat-22.htm), you can see it being used to widen a dovetail groove by a set amount.

I have used it to do the same thing for my template storing racks, and it works very nicely (and precisely).:2tsup:

On the Incra LS17, it is the leadscrew that gives the 1/32" increments, not the plastic racks, they do not come in to play for moving the fence backwards and forwards, unlike on the Original.

[junkboy999]

Hey Sbolton.

Sorry for the late replay. I read a lot of forums and usually get in the conversations a bit late.

Big Shed is dead on about the newer Incra router table jigs and the lead screw with the 1/32" increments.

For the older Incra jigs there are the plastic Racks with the 1/32" interlocking saw tooth racks. Bare with me, this might be a bit to describe. In side the center of the carriage is what I’m going to call the LOCK piece because I’m not sure if it has a name. This Lock has a Rack installed on it just like the ones all along the sliding positioner that is connected to the fence. When you pull up the large level it pushes the rack on the lock in to the racks on the positioner and pushes the positioner against the carriage a with a good deal of friction. This give you your, lets say 5 - 1/32" setting for a cut. If you would like to use the micro adjust you push the smaller level down. This in turn does two things. It pushed the larger level half way down and release a bit of the friction on the lock piece ( but still keeps the two Racks touching at your 5 - 1/32" setting ) and it pushes the top of the lock to engaged a threaded rod. This threaded rod is attacked to the micro knob. With the threaded rod engaged you can dial in your 1/100. Now you have your 5 - 1/23" + a 100th or so to the left or right, for your fine adjust. The lock plate it self move a bit to the left and right along with the positioner. Finely you pull back up the larger, pushing the small lever out of the way and applying all the friction back to holding the positioner in place with your new setting for your cut. There is a bit more to it with some more groves and friction sliding plates, but that is the best way I can describe it.

I hope this helps.

[simso]

An easier way of understanding it is think of two slides, one slide moves the unit 1/1000 of an inch at a time and the other slide moves it 1/32 seconds measurements,

Steve