Enlarging a porthole window. Ideas needed

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Enlarging a porthole window. Ideas needed

Postby edgeau » Thu Feb 09, 2017 6:30 am

I have run into a small issue and want to throw to the crowd for ideas on how to fix it / the right tool to use.

I have 4 round windows cut and salvaged porthole glass ready to go in. I used a router to put a 5mm rebate around the holes and the glass drops in nicely - except on one, the hole is 1-2mm too small.

What is a good way to reliably shave off that 1mm from the inside of a circle so I can run the rebate bit around again and have the glass fit?

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Re: Enlarging a porthole window. Ideas needed

Postby noseoil » Thu Feb 09, 2017 8:52 am

If you have a "flush-cut" bit, you can swap bearings on the bottom to smaller size, to pilot along the inner circle & use the overbite to chew off what you need. If you have a "reverse flush-cut bit" (one with the pilot bearing above the cutter) you can make a larger circle template out of some cheap material, to fasten (clamp, screw) over the hole & run the cutter down from the top to remove the extra material. This means cutting out a larger circle in the scrap to make it & would take a bit of time, but you can check the fit in the template & then know it will work properly when the cut is made.

That's the easiest way I know to get things right. I'm sure someone else will have a different/better idea.
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Re: Enlarging a porthole window. Ideas needed

Postby H.A. » Thu Feb 09, 2017 4:33 pm

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Last edited by H.A. on Wed Mar 15, 2017 8:39 pm, edited 1 time in total.
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Re: Enlarging a porthole window. Ideas needed

Postby pchast » Thu Feb 09, 2017 8:45 pm

Different approach.

Change router bearings to cut the larger rebate.
Then change bearings to trim the other side to your preferred size.
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Re: Enlarging a porthole window. Ideas needed

Postby edgeau » Fri Feb 10, 2017 5:11 am

Thanks all, esp H.A. I went and picked one of these up after work.
https://www.bunnings.com.au/haron-rotar ... r_p6313841
It worked a treat, only took a few min and a quick go around with the router again then the glass dropped right in.

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