Jasper 400 Jig Confusion

[Double_J]

I have a quick question about using the Jasper 400 jig. On the back of the package it states that it is designed for use with a 1/4" bit. After that it states that when using a 1/4" bit you need to add 1/2" to the measurement. I just want to clarify that is in fact true. The way I read that is if I want to make a 3" circle with a 1/4" bit, I need to put the pin in the 3 1/2" hole. Is this true, or is it a misprint on the package?

Thanks in advance for the help.
JJ

[dcgold2000]

I think if you want a 3" hole you set the pin in the 3" setting. If you want a 3" wheel (the cutout from a 3.5" hole) then you use the 3.5" setting.

[E Biddy]

Measure it from the middle of the pin to the outside of the bit. That way you know for sure.

[jeff_free69]

I always use the hole with the exact marking.
... and do a quick test cut (doesnt have to go all the way around or though)

besides, if you always had to add 1/2" , wouldn't they just change the markings?

[generic]

It's been awhile since I've had to break mine out, but I'm pretty sure the extra 1/2" is if you want to cut out a circle. You add the extra 1/2" to get the outer diameter.

For cutouts, a 1/4" bit and the measurement guide will get you what you want.

[50 watt head]

Measure it from the middle of the pin to the outside of the bit. That way you know for sure.

+1

As well as: grab a scrap of 1x12 pine and cut a practice circle to get the hang of it before you get near your baffles

[ToddO]

3" will get you a 3" hole with a 2.5" disc
3.5" will get you a 3.5" hole with 3" disc

If you are using a 1/4" bit.

[johnastockman]

Using a 1/4" bit, the pin in the 3" Jasper hole gives you a 3" diameter recess/mortise or a 3" diameter through-hole. The advice about cutting some practice mortises is a great tip. On my Ryobi 160, there's only two mounting screw holes for the Jasper, so it has a tendency to be off just enough that the recess diameter can be off about 1/32". I make a practice "scribe" on some scrap where I lower the bit just enough and rotate the router around so the bit scratches the arc into the surface; I measure the diameter of the driver flange with some in/out calipers and see if it matches up with the mark I just scribed. Since I started doing the practice "scribe", I haven't had any problems with the recess diameter fitting the driver's flange.


John A.

[arlis_1957@yahoo.com]

i test cut every hole for proper fit everytime. i never trust the numbers.

[Paul K.]

Don't know whether I'm stupid, a dare devil, or just plain lucky, but I never cut a test hole for my Jasper Jig attached to my DeWalt 621. When laying out the panel to be cut for driver holes, I do draw with a pencil and compass the circles I want to cut, and before starting the cut with the router and circle jig placed on the pivot pin, I lower the bit to see if it looks like its outer part matches the circle's diameter I drew on the piece. Of course, I do measure the drivers' outer diameter rather than relying on manufacturers' specified dimensions. So far, so good on lots of speakers, and I hope my luck doesn't run out.
Paul

i test cut every hole for proper fit everytime. i never trust the numbers.

[Double_J]

Thanks for all the replies. I do plan to test cut before I actually put it on a baffle, just wanted to clarify what I read. On a positive note, it mounted to my new Craftsman plunge router no problem, and I was able to get it very well aligned with the pin and alignment disc that it came with. Now to test it out and make sure everything is good to go.