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Thread: Router circle cutting jig
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20th July 2006, 01:03 AM #1
Router circle cutting jig
Gday all
Mucking about with my WIP wood rack, I (mistakenly as it turned out ) had a need to cut some smallish (42mm) circles.
Remembered this design shown a while back by Template Tom, couldn't find it again on the forum so had a crack at it from memory.
Dug out an offcut of some 190x35 F17, routed a 3/4" trench most of the way across it, drilled an 1/8" hole & inserted a nail, screwed it to the side fence on my hitachi router, chucked a long 1/2" straight router bit in the router & away we went
Worked like a beauty on some 1/2" chipboard scrap. Drilled a centre pivot hole on the workpiece, lowered the pivot pin into the hole, fired up & plunged the router & rotated it around the pivot. Voila - one accurate circle !
Pics are self explanatory I hope. Found it could rout circles from 35mm-240mm dia (per photo). I didn't rout right through (or centre piece would come loose :eek: ), shot would be to stick workpiece down to some scrap & rout through.
Pros: Easy & quick to make, accurate results, easily microadjustable. Dead easy to use, extremely stable and predicatble.
Cons: Thick timber for side fence to clear workpiece means reduced depth of cut. I needed a long router bit to extend below the timber. Different jig (eg: trammel jig) would be needed for larger circles.
Cheers....................Sean
The beatings will continue until morale improves.
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20th July 2006, 11:16 AM #2.
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Sean,
Nice simple solution - well done.
Your jig has ignited an idea of making a circle cutting jig that attaches to a router fence with the rotational pin poking down. Before I reinvent the wheel here has anyone seen something similar to this approach?
Cheers
Bob
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20th July 2006, 11:25 AM #3
Bob, there was a discussion on just this solution (essentially a pin router) many moons ago on another forum. It worked well, however, you need to have at least two anchor points or the bit can grab and move the piece, causing damage where you least want it.
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20th July 2006, 11:44 AM #4.
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Originally Posted by Groggy
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20th July 2006, 11:51 AM #5Originally Posted by BobL
cheers.
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20th July 2006, 01:32 PM #6.
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I understand now, Sorry I should have posted a plan view.
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20th July 2006, 02:35 PM #7
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20th July 2006, 03:33 PM #8.
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Originally Posted by Groggy
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21st July 2006, 10:37 PM #9Originally Posted by BobL
The only potential drawback is the capacity. It looks as though you'd be limited to a circle with a radius about equal to the distance your router bit is from the edge of the table. I would think it would get too tippy if you had the center off the edge of the table.
Again, great idea!
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22nd July 2006, 01:55 AM #10.
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Originally Posted by BuffaloJohn
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24th July 2006, 01:10 AM #11.
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And here it is?
Well I needed a couple of MDF circles today so I whipped up a prototype jig, sort of as per the plans I showed earlier on this thread. This one can be used to cut circles diameters of up to 580 mm and amazingly it works every bit as well as I thought it would.
Photo 1 shows the whole jig. The pin around which the circle is turned is a 3 x 1/4" bolt with the head cut off.
Photos 2/3 show a close up of the pin and router bit.
It was dead easy to operate. It's pretty firmly attached to the router fence and there was no need to use a bush to hold down the wood. I used push sticks to turn the 90mm diameter circle shown in the photos. I made a 210 mm circle buy turning it just by hand. You just need to be careful when the circle is close to finishing and slow down so you can control the breakthrough point.
This jig seems like it is capable of a number of things
- used as pin guide for the router.
- the hole for the pin locator does not need to penetrate all the way through the material. I want to try making a wood or metal clamp that straddles across the middle of the wood you want to make a circle from and then use a hole in the clamp so the object being cut does not need a central hole at all and the pin itself then pushes the wood down onto the table. The clamp will also give you something to hang onto while turning the circle
- Once you have cut an outer template it can be clamped to the bench around the router bit and you can then easily rout out insets from pieces of wood that fit inside the template and are lightly held down by the jig with or without the pin. I made a template consisting of a 120mm diameter hole in a piece of 12 mm MDF and used it as a template to rout out a 15 mm deep x 60 mm diameter inset into the end of a 70 mm diameter wooden cylinder. Sure you can do this on a lathe but this will work for other shapes as well.
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25th July 2006, 04:40 AM #12
Very nice Bobl !!!!!!!!!!!!!!!!
I like it. I also like you idea about not needing a center hole. I'm brainstorming that concept now.
If I can only think of a use for all these circles I want make...
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25th July 2006, 11:28 AM #13SENIOR MEMBER
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Bob, good job.
how about doing away with the slot on the jig. As you move closer to the fence the circle would have to be smaller, eventually disappearing under the jig. If you made the pin end of the jig a little pointed it would give you a bit more room to manoeuvre. maybe marking a slightly oversize circle and cutting the waste off on a bandsaw, to save loading up the router.
Did you consider putting the jig and pin under the workpiece and having a slot for the router bit to work in similar to what Sean had. maybe only a short pin and a simple hold down arm with a central pressure point.
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25th July 2006, 12:55 PM #14.
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Originally Posted by bpj1968
The reason I inserted a slot is because this jig is a prototype and I had no idea what kind of up/down flexing I would get until I actually made it. By building in a slot from the start I could experiment with the degree of vertical play in the system and I could then shorten the pin/fence distance. In the end it is not necessary
Originally Posted by bpj1968
Originally Posted by bpj1968
Cheers
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27th July 2006, 12:18 AM #15.
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Hey, it actually it works!
Today during a meeting I came up with a simple jig to cut a circle using a router without the need for a central hole. I decided to mock up a prototype using MDF. Now I have an idea how well it works I will replace the MDF with maybe Aluminium and maybe use a 3/8" threaded rod instead of 1/4"..
It involves the pin holder from the above posts ,and jig as shown in Picture 1. It's just a length of threaded brass rod and 3 bits of MDF held in position using wing nuts
The jig is placed over the piece of wood as shown in Picture 2. As MDF has a problem gripping MDF, I use a couple of bits of sandpaper between them. To locate the router bit a starting hole on the circle is needed in the wood (not shown)
The wood and jig are then located/connected by a simple press fit to the pin holder . See pics 3&4
Then rotate jig around the pin, taking several passes to perform the cut.
Whala - no central hole needed!!!!
The prototype flexes a bit as MDF is not idea for this sort of thing. Using Al should reduce this.
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