Answer to template size problem

[ceetee]

Since I was a quality engineer when I was working, I place a large importance on numbers, and being correct. While checking through a lot of woodworking notes, I came up with the solution to my problem - and it works. So here's my answer to making a male circle jig to use on my 12" finished wood boards so that I leave a 1/4" wide lip around the entire circumference of the top surface. If anyone has a easier way to accomplish the same thing - I'm all ears/eyes!

This answer is based on an imaginary beginning male jig of 12". Subtract the outer diameter of the guide portion of the bushing twice. Then subtract the lip width twice. Then add the difference between the bushing diameter and your cutter diameter - again twice.

12.000 diameter of lazy susan board
- 1.250 .625 (5/8) bushing diameter times 2
- 0.500 .250 (1/4) desired lip width times 2
+ 0.250 .125 difference between bushing & bit diameter times 2
_____
10.500 = male template diameter

This type of approach will work when constructing male templates, especially circles. Female templates will require a reversal in additions and substraction. I've used this concept before when making both male and female jigs - though it has been some some now. It will apply to both linear and radial dimensions.

I should have solved and confirmed my solution the way I ended up doing it - which was drawing everything to scale and checking my numbers more than once - before posting my question on this site. The answer was in my old notes but I was hoping someone would offer me this logic.

Thank you all!

[bobj3]

HI ceetee

Thanks for numbers,,The numbers are great but keep it simple, the Jasper jig will do all the math for you just pop in a pin and get the job done quick and easy..


http://www.soundlabsgroup.com.au/c/J...rcle+Jigs.html

http://www.amazon.com/Jasper-200J-Ci...0651896&sr=1-1


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Originally Posted by ceetee

Since I was a quality engineer when I was working, I place a large importance on numbers, and being correct. While checking through a lot of woodworking notes, I came up with the solution to my problem - and it works. So here's my answer to making a male circle jig to use on my 12" finished wood boards so that I leave a 1/4" wide lip around the entire circumference of the top surface. If anyone has a easier way to accomplish the same thing - I'm all ears/eyes!

This answer is based on an imaginary beginning male jig of 12". Subtract the outer diameter of the guide portion of the bushing twice. Then subtract the lip width twice. Then add the difference between the bushing diameter and your cutter diameter - again twice.

12.000 diameter of lazy susan board
- 1.250 .625 (5/8) bushing diameter times 2
- 0.500 .250 (1/4) desired lip width times 2
+ 0.250 .125 difference between bushing & bit diameter times 2
_____
10.500 = male template diameter

This type of approach will work when constructing male templates, especially circles. Female templates will require a reversal in additions and substraction. I've used this concept before when making both male and female jigs - though it has been some some now. It will apply to both linear and radial dimensions.

I should have solved and confirmed my solution the way I ended up doing it - which was drawing everything to scale and checking my numbers more than once - before posting my question on this site. The answer was in my old notes but I was hoping someone would offer me this logic.

Thank you all!

[ceetee]

Thank you Mr. bobj3! I found out I already own a Jasper 300 circle jig by looking around my 2 1/2 car workshop. The funny part? It has never been used. I'll definitely give it a try. I hope I'm as successful as the people/places that have written great reviews on it. I have several routers in my arsenal and am sure I'll find one to hook up to it quite easily. It would have saved me a lot of grief and math work! All I would have had to do is figure out the final diameter. Thanks again!!

[bobj3]

Hi ceetee

You'er welcome,, the Jasper as a built in error that you can fix easy,

The mounting screws holes are drilled to deep and they do like to snap out the plastic BUT if you drill out the center hole to take on a 3/4" or 1" hole to take on a brass guide the jig will stand up very well and it's makes it easy to use by just dropping the brass guide in the router then just drop the router in the jig hole,, no screws to hold the jig to the router is needed plus it helps keep the cord out of the way because the router can spin in the jig... plus you can use a bigger bit when needed like a 1/2" one...unlike the one called for by the jig ... ( 1/4" bit size )

final diameter,, is a easy setup ,just drill your 1/8" hole, set the Jasper in place with a brass guide in place that will take on a standard round pencil ,spin the jig with the pencil in place then lift the jig off and get your ruler out and see what you got b/4 you do the route job...your pencil mark will be right in the center of the router bit path...then just do a bit of math for the bit you are going to use and your set...then move the jig to the right hole and check it one more time, wright that number down then plunge and cut out the lazy susan

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[ceetee]

Hey Mr. Bobj3: I am relieved - but embarrassed - to say that the simplistic solution was within 10 feet of my main workbench - a Jasper 300 circle jig. If it had been a snake - well, we all know the answer to that! I do not know the specific reason I bought it - maybe it was on sale wherever I got it. I checked at our local Woodcraft store and it's much more $$$ today. I've never used it to date but surely will in the near future. One question: Do you Mr. Bobj3, or anyone else, have a good method of what to use to put in the hole that dictates the diameter? A small screw? A special fastener of some sort? What do others, who use a Jasper circle jig, use to spin the jig around? Thanks for the great info! I sure wish I had seen my Jasper much sooner!

Measure twice, talk about it a lot, cut once!

[bobj3]

Hi ceetee

I use a 1/8" dowell pin and/or 1/8" welding wire to set the diam. of cir..

The easy way to get the bigger hole right on dead center is to use your drill press..you may need to make a insert ring for the Jasper 300, I'm not sure what size of hole is now in the jig, but a plastic insert ring is easy to make with some hole saws...and some 1/4" thick plastic///// >>>

Chuck up a 1/4" drill backwards in the chuck,put some scrap wood under the Jasper jig on the drill press , push the drill bit in the 1/4" hole in the Jasper then clamp the Jasper and the scrap wood down to the table top, then check it one more time to make sure the drill bit goes right inside the 1/4" HOLE TRUE AND FREE,,, Once it's set chuck a 3/4" Forstner Bit and drill the 3/4" hole out...


http://www.amazon.com/Jasper-300J-Ro...sim_hi_title_3
This jig is calibrated for a 1/2-inch router bit.

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http://www.amazon.com/review/product...owViewpoints=1

One of the reviews below
" 2 of 3 people found the following review helpful:

2.0 out of 5 stars Great idea but poor router mount design

I tried to mount my router on this jig for the first time and the plastic cracked. The places where the screws are attached only have 1/3 of the thickness. This is too weak! If I loosen the screws a bit, the router would not stay at a fixed position. This jig would work well if the material is metal or the mouting area is made stronger. I've wasted $35 for this piece..."

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Originally Posted by ceetee

Hey Mr. Bobj3: I am relieved - but embarrassed - to say that the simplistic solution was within 10 feet of my main workbench - a Jasper 300 circle jig. If it had been a snake - well, we all know the answer to that! I do not know the specific reason I bought it - maybe it was on sale wherever I got it. I checked at our local Woodcraft store and it's much more $$$ today. I've never used it to date but surely will in the near future. One question: Do you Mr. Bobj3, or anyone else, have a good method of what to use to put in the hole that dictates the diameter? A small screw? A special fastener of some sort? What do others, who use a Jasper circle jig, use to spin the jig around? Thanks for the great info! I sure wish I had seen my Jasper much sooner!

Measure twice, talk about it a lot, cut once!