Circle cutting jig - Woodworking Talk - Woodworkers Forum
 
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post #1 of 4 Old 05-21-2020, 12:48 PM Thread Starter
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Circle cutting jig

Hi guys,

I've made this steel circle cutting jig for my router and I think it looks gorgeous. I made it from a piece of steal witch already had a slot in it. The jig works, but there is one thing I didn't think true at the start of the project. and that is how I am going to mount the radius adjusting pivot pin (look at the foto's to see what I mean) to the underside of the plate. I now have just a washer and a nut. But this is of course very inconvenient won't allow the base of the plate to sit flush with the wood I'm cutting. Does somebody have any suggestions on how to fix this?

Some details about the jig (sorry for my metric numbers imperial lads):
The slot in the metal plate is 6,5mm wide.
I now use an m6 bolt (bolt with a diameter of 6mm).
the steel plate is 4mm thick.

I'd really appreciate your thoughts on my little problem here.
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post #2 of 4 Old 05-21-2020, 01:33 PM
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is that steel or aluminum ?

if it were aluminum, you would have more latitude of adapting
a pivot pin. steel is very unforgiving when it comes to hand tools only.

if it is steel, I would put on the wall and make a copy of it out of MDF,
plywood, plexiglass or other soft material that will work properly when you want it to.

Edit: if you REALLY want to keep it, if it were me, I would grind a tapered
recess in the slot and grind the appropriate size nut to fit the recess, then the pivot
point on the end of the threaded rod, and use some Thread Locker to hold it in place.
the tightening knob will have to have the hole all the way through for it to work.
and no, it will not always work properly every time. (again, hang it on the wall).

Circle cutting jig-156.png

.

I am a painter: that's what I do, I like to paint things.

Last edited by John Smith_inFL; 05-21-2020 at 03:20 PM.
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post #3 of 4 Old 05-21-2020, 03:16 PM
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My solution:

Materials:
* Flat-headed "T-slot bolt"
* Knob with a matching threaded hole.
* Thin metal rod.
* Thin strip of wood or plastic, the same thickness as the T-slot bolt head, approximately 1.5 cm wide and maybe 5 cm long.

Here are example T-slot bolts and matching knobs. For you, I assume they are available in metric sizes and threads. You get the idea:
https://www.rockler.com/t-slot-bolts...-1-4-20-thread
https://www.rockler.com/rockler-easy...male-threading

Procedure:
* Drill a small hole into the flat end of a t-slot bolt to match the thin metal rod.
* Grind one end of the metal rod to a point.
* Cut the rod short, and glue it in the small hole so that the point protrudes "just enough."
* Use a file to round the ends of the thin strip of wood or plastic, so they can work like the tip of a snow ski.
* Glue the strip to the router end of the jig, to level the jig with the T-slot end. The strip should be tangent to the circle and long enough that the jig won't wobble or rock.
* Wax the bottom of the strip so that it glides smoothly.
* Done.
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post #4 of 4 Old 05-22-2020, 01:30 AM
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I've one similar, this one though is a bit larger is virtually the same concept. If you add another point you can also run ovals. Those are a lot of fun to make.



This one has a square slot underneath and a round slot on top, that way the knob on top can be loosened and moved without having to use a wrench or other apparatus.

-T
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