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How to cut a clean 10" hole in 3/4" plywood?

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Forum topic by b2rtch posted 07-18-2012 09:59 AM 4299 views 0 times favorited 23 replies Add to Favorites Watch
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b2rtch

4349 posts in 1744 days


07-18-2012 09:59 AM

Topic tags/keywords: question

I have to make 48×14”x14”x 3/4” plates out of plywood and to cut a 10’ hole in the center to install speakers.
What it the best way to cut clean holes in the center?
Thank you for your help.
Bert

-- Bert


23 replies so far

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Jamie Speirs

4146 posts in 1552 days


#1 posted 07-18-2012 10:01 AM

Bert I use the router.

-- Who is the happiest of men? He who values the merits of others, and in their pleasure takes joy, even as though 'twere his own. --Johann Wolfgang von Goethe

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b2rtch

4349 posts in 1744 days


#2 posted 07-18-2012 10:05 AM

Ok and router and what?
A downward spiral cut bit and what do I use to keep the radius,? A home made jig?
Can I do that on my router table?

-- Bert

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crashn

518 posts in 1161 days


#3 posted 07-18-2012 11:29 AM

router with trammel. easiest way to explain is pictures. here is a link to the thien baffle page, where a person goes through building the thien separator. http://www.cgallery.com/smf/index.php?topic=429.0 in that page, he shows a trammel.

-- Crashn - the only thing I make more of than sawdust is mistakes

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Alexandre

1417 posts in 886 days


#4 posted 07-18-2012 11:41 AM

LOL, this is hard to believe, but there is a 10” hole saw I have.
You want a 10 Foot hole?

-- My terrible signature...

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b2rtch

4349 posts in 1744 days


#5 posted 07-18-2012 12:00 PM

no, I do not want a 10 foot hole, sorry for the typo.
I figured it out this morning.
I made a jig already, thank you all.

-- Bert

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Alexandre

1417 posts in 886 days


#6 posted 07-18-2012 12:04 PM

LOL
Imagine a 10 foot hole
LOL

-- My terrible signature...

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b2rtch

4349 posts in 1744 days


#7 posted 07-18-2012 12:37 PM

especially in a 14”x14” plate!

-- Bert

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Bluepine38

2919 posts in 1780 days


#8 posted 07-18-2012 01:54 PM

And I was just going to say that a circle cutting jig on a big bandsaw would work, I missed the typo, and then
I realized that it would have to be a scroll saw cut. Time for another cup of tea.

-- As ever, Gus-the 75 yr young apprentice carpenter

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PurpLev

8476 posts in 2344 days


#9 posted 07-18-2012 02:03 PM

I cut some really clean circles (external and hole) here:
http://lumberjocks.com/PurpLev/blog/7085

-- ㊍ When in doubt - There is no doubt - Go the safer route.

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b2rtch

4349 posts in 1744 days


#10 posted 07-18-2012 02:25 PM

Thank you Sharon, I have a similar guide for my Bosh router but is it mounted in my router table. I want to try to use my rigid trim router (not plunge) as it is easier to handle.
I have a pretty good idea how to make a jig, my concern is that the Rigid router it not plunge, I do not know how this is going to work.

-- Bert

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BinghamtonEd

1451 posts in 1065 days


#11 posted 07-18-2012 02:30 PM

If you need to work around the plunge issue, You could drill a pilot hole larger than your router bit that just touches your circle’s radius. Mount your circle jig such that the router bit starts in that hole. You can make multiple passes from this pilot hole by adjusting your bit depth. Put your piece on a sacrificial board, clamp it down, and make sure your circle jig is fastened through the workpiece into the sacrificial piece. This will help prevent tearout underneath and make sure your jig stays put on that last pass when the circle becomes separated.

-- - The mightiest oak in the forest is just a little nut that held its ground.

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b2rtch

4349 posts in 1744 days


#12 posted 07-18-2012 02:31 PM

BinghamtonEd, good idea , thanks

-- Bert

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woodworm

14129 posts in 2286 days


#13 posted 07-18-2012 02:58 PM

Watch the vid presented by MLCS, you will have the idea to make your own Circle jig on Router Table. I made one for cutting full and part of the circle using the same jig. Good luck.
http://www.mlcswoodworking.com/shopsite_sc/store/html/smarthtml/graphics4/router_circle_jig104.jpg
http://www.youtube.com/watch?v=_loCptLUKoc&feature=player_embedded

-- masrol, kuala lumpur, MY.

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b2rtch

4349 posts in 1744 days


#14 posted 07-18-2012 03:17 PM

woodworm, I really like the video, it gives me all kind of ideas.
Thank you very much.

-- Bert

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BinghamtonEd

1451 posts in 1065 days


#15 posted 07-18-2012 03:36 PM

Do you have another piece with a similar 10” hole? If so, you could just use a pattern bit to duplicate the hole. Back in my college days I used to build subwoofer boxes for cars and had several patterns for 8, 10, 12, and 15 inch speakers. Sold them for beer money :)

-- - The mightiest oak in the forest is just a little nut that held its ground.

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