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Questions about edge profiling with a router - jihhwood - 03-04-2016
I need a little guidance about a project I'm about to undertake. Here are the facts:
Task: to rout a Roman ogee profile on a table top. Table is a rectangle with rounded corners. It is small (27 x 18)
Bit: Bearing-guided Freud quadra-cut (1 3/8" diameter); half-inch shank
Router: Porter-Cable 690 LR (NOT variable speed). The rpm's on this machine are 27,500
Method: Router will be hand-held -- I do not own a router table.
Concern: Given the high rpm's and the size of the router, I am concerned primarily about safety and secondarily about avoiding damage and burning to the workpiece
Solutions I'm entertaining: (1) Buying an after-market variable speed control for the router. However, I don't know whether such a device can be used with this router without risking damage to the motor. (I called Porter-Cable and they could offer no help whatever.) (2) After ensuring that the workpiece is secure, I am thinking that if I make several shallow passes, I may be able to achieve the results I want.
Note that I use the router fairly routinely for many typical tasks (mortises, rabbets, etc.), and have used small (1 " and less) bearing-guided bits without trouble. My concerns arise from the large size of the bit and the high rpm's.
Your knowledge, thoughts, and recommendations would be very much appreciated.
Re: Questions about edge profiling with a router - Bill Schneider - 03-04-2016
This information came packaged with a router bit years ago, and I made a spreadsheet to preserve the info.
Re: Questions about edge profiling with a router - jasfrank - 03-04-2016
On a bearing guided bit, its not possible to make shallow passes unless you use an edge guide. or if you were to run 2 or 3 layers of masking tape around the table top where the bearing rides for the first pass. Then remove the tape for your last pass. That would be the equivalent of making a shallow cut. Or if you had other bits with slightly larger diameter bearings that you could substitute onto your quadracut for the first pass.
That said, If the grain was not real wild, I'd just run it and keep my feed rate slow. You will be fine.
Re: Questions about edge profiling with a router - jteneyck - 03-04-2016
I've spun bits that large in my PC-690 but don't recommend it as it's higher than the safe limit. I tried one of those router rheostats about 10 or 15 years ago and found it worthless, but maybe they have improved since then. I was fortunate to get a large Variac from our lab and that worked pretty well although with no electronic feedback the router would easily bog down so you had to be really in tune with the sound to keep the rpm's fairly steady. But it worked and I ran some pretty large bits with that set up until I finally bought a variable speed router.
You are going to have to spend money one way or the other to spin that bit safely. I recently bought a Sears fixed base, variable speed router, with 1/4" and 1/2" collets, and dust collection, for $79. It seems pretty well made and runs fine. It's certainly not as nice as the Bosch 1617 EVS I bought about a year ago, but that cost $200+ with both the the fixed and plunge base. Still, if I only wanted to buy one router and have it do everything well, it would be the Bosch.
I've done several table tops with bits just like you described. I find hand holding is much better than trying run the top across a router table. Using it hand held allows me to safely use a climb cut (R to L) which pretty much eliminates tear out. I take several shallow passes around the top until the bearing is riding on the edge, then make one pass back around L to R to finish up. The key to avoid burning is to keep the router moving.
John
Re: Questions about edge profiling with a router - JGrout - 03-04-2016
unless there was a change in the speed ratings a 690 rates at 23K; no matter really it is still too fast
I too would pass on the speed controller, it is not a viable solution the router will not act as you would hope. You have one other issue and that is the base plate hole is too small for a bit that large.
my thought: see about renting or borrowing a VS router or look for a VS on line new or used
Bosch makes a good one that I have seen in the past for about 100-140 bucks.
If when you find a proper set up the way to make smaller cuts is to climb cut (clockwise) with the top held firmly to a bench with clamps and some sort of piece under the top to raise it enough so the bearing will clear the bench . You have to hold on to the router firmly and short cutting lengths are the order of business . This is a bit of a learning curve to get it right but you can practice on scrap first to get a feel for the actions.
The other way is to lower the bit in increments to the work piece and cut the correct way(counterclockwise) so no edge guide needed. you have to be much more careful on the rounded corners to prevent tearing out the end grain
Joe
Re: Questions about edge profiling with a router - jihhwood - 03-04-2016
Very informative chart, Bill. Thank you. It confirms that my wariness is appropriate.
Re: Questions about edge profiling with a router - jihhwood - 03-04-2016
Thanks, John. Yes, it does appear I should get ready to open my wallet. Not surprising that this "little table" project has turned into more than I'd bargained for. Nonetheless, I enjoy learning . . . and I'm doing that. So thank you for your suggestions and for telling me about your own experiences.
Re: Questions about edge profiling with a router - jihhwood - 03-04-2016
Thanks for your response, Joe. I always appreciate hearing from you. It's pretty clear that I'd be unwise to try using an after market speed control to turn my router to a variable speed model. And -- yes -- I won't take the chance of using it "as is" -- much too fast. I have to consider my options. One I did't mention in my original post is to use a smaller bearing-guided ogee bit (one inch diameter). I have one and have practiced with it successfully, so far. The only drawback is that it has a 1/4" shank. Incidentally, my set-up for the cut is as you've described -- solid support that raises the workpiece off the workbench top to the bearing is clear. However, I was planning to use double-sided tape, rather than clamps, to affix the workpiece to the support. (Support will be screwed into the workbench top.) Do you have any reservations about that? Thanks.
Re: Questions about edge profiling with a router - jihhwood - 03-04-2016
Thanks, JASFrank. My desire to move forward on the project is being tempered by cautions -- yours and the other members' who have been kind enough to respond.
Re: Questions about edge profiling with a router - jteneyck - 03-04-2016
Actually, it is possible to make shallow passes when you use a climb cut (clockwise) because the bit wants to run up over the wood and not dig in like it does going CCW. The cut isn't uniform, but doesn't matter; you can still take light passes around the top and when the bearing gets down to the edge it will all be nice and smooth. Then go back around CCW and you're done.
John