# Bit for Round Over on Trim for Window



## coxhaus (Jul 18, 2011)

I am new here and new to routers. I just bought my first router, a Porter Cable 7538 on ebay for $102.50. It is missing a base plate. I want to use it to round over the trim boards on a replacement window I am installing. I was thinking of a 3/4" round over with a 1/2" shank. The boards are about 1". I don't think they are a true full 1 inch. Should I be looking for a smaller round over than 3/4"? Also do you think it would be better to router the boards before or after they are put into place. I will have easy acces once they are nailed.
Also should I just get the Porter Cable base plate?


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## jschaben (Jun 21, 2009)

coxhaus said:


> I am new here and new to routers. I just bought my first router, a Porter Cable 7538 on ebay for $102.50. It is missing a base plate. I want to use it to round over the trim boards on a replacement window I am installing. I was thinking of a 3/4" round over with a 1/2" shank. The boards are about 1". I don't think they are a true full 1 inch. Should I be looking for a smaller round over than 3/4"? Also do you think it would be better to router the boards before or after they are put into place. I will have easy acces once they are nailed.
> Also should I just get the Porter Cable base plate?


Hi Lee - welcome to the forum

Last things first - yes, get a base plate. Don't know what a PC plate would cost but here is a good aftermarket that includes a set of guide bushings:
Amazon.com: Milescraft 1211 Base Plate Metal-Nose Bushing Set for Routers: Home Improvement

Roundover bits are spec'd at the RADIUS of the roundover so a 3/4" roundover (fairly large bit by the way) would be more appropriate on 1-1/2" material. To get a nice roundover on standard 1 by stock, actually 3/4" thick, you would want more like a 1/4" to 1/2" radius. 3/4" radius will give you a quarter round molding. 
You would also want to do the routing before it is installed. I needs to be firmly secured along with any addition support needed for router stability. I would suggest doing the routing on the longest stock practicable and cut to length for installation. 
Good Luck


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## Phil P (Jul 25, 2010)

Hi Lee and welcome

Most of the window boards I install are factory profiled with a radius of between 30 and 60mm (1-1/4in to 2-1/2in). With those it is often necessary to radius the visible ends of the returned nosing (the "ears" which protriue beyond either side of the window opening) so for that I use a large diameter bullnose bit (like the T2526-1/2 here) with a plywood or MDF fence plate on the router and sand in to finish. This achieves the edge in a single pass but needs care in setting up the cutter to precisely the right height. Just as John recommends I, too, rout a longer edge than I'm going to use. I also complete all the routing work before installation

With square section (unmachined) stock I prefer to use the same (bull-nose) cutter if I'm profiling the front edges as it's a lot faster and less error prone than making two passes with a quarter round bit IMHO. I'm wary about using a quarter round cutters _with bearings_ because on the second pass the bearing often doesn't have a flat surface to run against, depending on the thickness of the stock and radius of the cutter. And if you run the bearing against a previously radiused surface you'll probably end up with a highly visible step to sand out (not nice). If I have to do this job in the absence of my big bull nose cutter(s) then I ignore the bearing in the cutter completely and just use a plywood plate on the router fence to guide the cutter (because all my round-over bits are the bearing guided variety). 

Regards

Phil


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## coxhaus (Jul 18, 2011)

I like the idea of using a large diameter bull nose bit but I can not figure out which size bit to buy. I want to end up with a full rounded board without much step. What is a good size and bit to buy for my example above?


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## bobj3 (Jan 17, 2006)

1 PC 1/2" SH Double Corner Round Assembly Router Bit | eBay

1-pc 1/2" SH 5/8" Rad. Half Round Bull Nose Router Bit | eBay

1-pc 1/2" SH 3/4" Rad. Half Round Bull Nose Router Bit | eBay

1 pc 1/2" Shank 1-1/4" Radius Convex Edge Router Bit | eBay


1-pc 1/2" SH 1/2" Rad. Half Round Bull Nose Router Bit | eBay

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