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Discussion Starter · #1 · (Edited)
So i just found the circle cutting jig on http://www.jpthien.com/cj.htm
which i found after admiring his design for a cyclone dust collection contraption & saw that'd be not only a neat way to finish perfect circles w/ a router, but inherently a great way to get the circular boards needed to build the cyclone attachment.

My question is this, in order to cut the slot in the board for the circle cutting jig, would i need a plunge base router? I was just watching some New Yankee Workshop episode where Norm was routing a groove between two mortises and just dropped it in place mid-way through the board onto the router bit on his router table.. I'm no Norm, but could i do something similar w/ my fixed base router in the table, or would i be asking for trip to the ER? I'm still very new here & after learning about kick back on my TS, just want to do everything safely as well as effectively.

Thank you for any input!
 

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no doubt a plunge would be easier and safer

You could pre-drill a hole the same size as your cutter to avoid any tendency for it to wander. That's what I would do, lacking a plunge base.
 

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You don't need a plunge base to drop onto a bit in a router table, or to drop down with a handheld. Those procedures were common to do long before plunge bases were available. If you drop down on a router table or do it by handheld, it's a matter of just tipping in, in the direction of movement. You can do that ahead of the stopping point, and then carefully back up. Rout forward, and back up, and tip out, or shut off the router while holding in place.






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Discussion Starter · #5 ·
Thank you guys again for sharing your experience w me. I'm comfortable doing it once I know there's guys who've done it safely, especially with techniques shared, thanks woodnthings & Cabinetman! :)
 

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I did it for breadboard ends I made once I know others have done it and it's a common practice but I just didn't feel right about it.
 

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here's the issue

Because the router has a rotating cutter, one side will self feed in the direction of rotation, a climb cut. The other side will cut against the rotation, a normal cut. The bit is now "trapped" on both sides, so you need absolute control over the work piece, no lateral movement allowed! :no:

A router table would be best on that narrow thin piece, BUT I would attach it to a larger block to gain more positive control, especially for your initiation on the procedure. Save your fingers, that doesn't mean fish them out of the DC afterward either. :laughing:
OR you could simply make the slot in a larger piece to start with and cut it down afterward. :blink:
 

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Discussion Starter · #10 ·
If you do it on a table, Norm has a great idea to mark the outside dimension of the router bit on the table and mark the wood so you'll know exactly were to stop
Yep, that's what i saw him doing.. think he was building a bookcase in this instance :) & yes, I will be using the fence on my table for sure, thanks Cabinetman.

Woodnthings, I've got a piece of scrap poplar from my 1st project that I'm planning to trim down for the jig. Doing the slot after jointing the edge to ride the router table fence & before trimming the excess sounds like a good order in which to tackle the project, though i'm not sure it even needs to be quite as thin as the picture shows.
 

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don't confuse safer with complex

It's not complex at all, but it does need to be done safely, and the explanation of the operation and the physics involved will always be useful to a novice. It's always about the physics and the forces involved which way things want to move. turn, rotate, climb and why.
Larger pieces are safer to work with than smaller, narrow pieces when spinning cutters are involved and fingers may be close by. Push blocks and feather boards will help secure the work and keep your fingers out of the cutter path. :yes:

Safety first above all else and as mdntrd said "If you don't feel comfortable,.....Don't do it" :no:
 
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Use a platen like this piece of cast off 2 X 10. Anything for handles and dbl-sided tape will hold your work. Leave the work poking outside on the fence side so that only the work contacts the fence.
I've never had consitent results with drilling holes on each end...just drop it over the spinning bit. I use marks on blue tape for start/stop.



 

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Discussion Starter · #14 ·
Lots of ideas here, thank you all. At least one way or the other it looks like i can safely get the jig made w/o needing to buy a plunge base right now. Which means i can get started on the next project out of scrap from the last, despite december being a slow month. I've got plenty of left overs to try both using the two drilled start/stop holes & the platen idea. :smile:
 

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I've never had consitent results with drilling holes on each end...just drop it over the spinning bit.
+1. :yes: Drilling holes and getting the slot to line up IMO, is not the way to do it. Once the bit is down just running it to stop points makes for a cleaner cut. It does take backing up to a start point, which when done carefully works out just fine. With holes, it's possible to forge past once the bit breaks out of the material, and rout past the drilled hole. There's also the being slightly off on the alignment of the bit and the placement of the holes.

It's easier to control the router when the entire pass has the same resistance.






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i prefer stop blocks to start and finish groove. i will only back up against a stop block (had board ripped out of my hands backing up without a stop block). plung cuts require smooth pressure down. make sure the bit can "bottom cut" for a plunge cut. it will have cutting profiles on the end of the bit. some are only side cutters.
 

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drilling a start hole

If you accurately drill the start hole, it can be any place in the slot BTW, you simply raise the bit through the hole until it's exposed, slide the fence over to meet the edge of the workpiece and rout, fore and aft to either marks or stops. It's not rocket science, very simple indeed, no plunging required.
That's the way I do it, others may not, but that's the beauty of this forum, so many different answers/solutions to the same issue. :yes:
 

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That's the way I do it, others may not, but that's the beauty of this forum, so many different answers/solutions to the same issue. :yes:
You're absolutely right. Some of us have tried drilling holes and found we don't like that method. That's the beauty of this forum, that there could be different answers/solutions to the same issue.:yes:






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Discussion Starter · #19 · (Edited)
Well, it's done! I tried just marking start & stop points then dropping it over the bit & leaving the board wide enough to keep a good hold with my fingers well away from the bit & that turned out pretty well so I didn't even try again w the drilled hole method. All day it cost me one scrap piece, about $6.00 in nuts, washers, & a bolt with a crank on it. Now I'm ready to use some scrap mdf & start building a cyclone top hat. :) thanks for all the advice along the way. Ran into no real problems & it looks like it'll work perfect for what I need.
 

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Well, it's done! I tried just dropping it over the bit & leaving the board wide enough to keep a good hold with my fingers well away from the bit & that turned out pretty well so I didn't even try again w the drilled hole method.
Congratulations. It's just a matter of getting a feel for it.




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