What bit would I use to make this cutout - Router Forums
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post #1 of 15 (permalink) Old 12-27-2018, 02:50 PM Thread Starter
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Default What bit would I use to make this cutout

Hello,

I just got my first router (the Bosch 2 1/2 HP Kit) and I need to make a ledger block with a 1/2" hole in it 4 1/8" in diameter. Can anyone here suggest a bit that I could use? I assume I will use my plunge base to make this cutout. Sorry for my lack of knowledge, I have been reading this forum for a while but I finally got my first router. I can hopefully purchase the bit required and start my project.

I was thinking about using a 4" hole saw to create the outline of the circle but I suspect there is a way to do this with a router.

I have included a drawing of what I hope to achieve.

Thanks in advance.
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post #2 of 15 (permalink) Old 12-27-2018, 04:16 PM
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You could use a pattern bit with a pattern with that size hole. Derek Willis came up with the world's simplest circle cutting jig a few years back. It's in this thread, post #2. https://www.routerforums.com/general...-trimming.html You drill a hole in the jig that is the same size as the O.D. of a guide bushing and you just nail it to your template. It might take a few tries to get the diameter right if it's really critical.

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post #3 of 15 (permalink) Old 12-27-2018, 06:05 PM
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still going to need a pattern or a circle jig..
make the pattern w/ a hole saw and then make the cut w/ a top bearing flush trim or mortise bit, both have to cut on the plunge...
Freud Tools - Search Results for top bearing mortise

or that bit and a circle guide...
two very good products to have..
https://www.boschtools.com/us/en/bos...a1054-27229-p/
Products |
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post #4 of 15 (permalink) Old 12-27-2018, 10:17 PM
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I'd cheat. I'd use a hole saw on a piece of 1/2" stock, drill a hole completely thru it, then glue a piece on the bottom.

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post #5 of 15 (permalink) Old 12-27-2018, 10:48 PM
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As others have stated you need a pattern (4") and a pattern bit. If you have a circle cutter then make the cut on a drill press with the pattern clamped down. Then use carpet tape to glue the pattern to your board. Then use the plunge to route out the hole about 1/8" at a pass. You go around the circle with the pattern bit then route out the middle by just moving the router clockwise until all of the layer is cut. Your pattern must be tall enough to have the bearing contact the pattern during the first pass. Your pattern bit needs to be on the top of the router bit. A bottom bearing would not allow you to plunge into the pattern. Just remember if you have a 1/2" bit then never take more than 1/2" deep cut at a pass. If possible make shallower cuts multiple times. There is a lot of material to remove at one time 1/2" so make shallower passes to get a smooth bottom. If you have a larger bit like a 3/4" pattern bit do not make deep plunges because the torque of the router will make it hard to control. The example picture does not have a lot of surface for the router to sit on and your board needs to be secured or you will make a mess.

If you do not have a circle cutter then use a 4" hole cutter. You will get a rough edge. You can still use the pattern bit but you will need to plunge inside the 4" hole with a mortising bit to get a place to get the pattern bit in. Make sure your plunge hole is bigger then your pattern bit.

The suggestion about cutting a 1/2" piece, then cut the hole and glue on a bottom is a good one but the hole still has to be cut.

So if you only want to use the router you need a pattern. The pattern can be made with a hole saw or a circle cutting bit. There are no short cuts. You just keep getting sucked in further and further.

If you do not have a drill press then see if you can go to a neighbor or relative and use theirs. Hand drilling with a large bit and/or hole saw is dangerous. The torque will spin your project around and around. Secure everything to be safe.

If you are wondering how to secure your small work piece then you can cut some plywood strips and put your work piece on top of a piece of scrap plywood then screw the strips around the work piece. This gives you a larger work are for the router to sit on. You could also start with a larger work piece and after you get the hole routed then trim the work piece down to your required dimensions

Always look at a problem from different perspectives. If a carpenter only has a single hammer in his tool bag every problem looks like a nail.
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post #6 of 15 (permalink) Old 12-28-2018, 12:12 AM
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I'm with Theo.
two pieces, cut one with a hole saw, glue them together. All done by the time youve made the template to rout it.
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post #7 of 15 (permalink) Old 12-28-2018, 08:25 AM
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To cut the part with your router, you need a template as has been pointed out. However, I think that it's easier to make the template out of 1/4" hardboard and use a guide bushing rather than a pattern bit which requires a much thicker template. The hole in the template would need to be adjusted to account for the offset between the router bit and the guide bushing - there are several postings on the forum explaining how to do this. You may also need to mount a larger (homemade?) sub-base on the router to provide additional support as you use the router to clean out the center of the circle.

I use a fly cutter in the drill press to cut the hole in the template - probably tales all of 10 minutes to set up and cut the hole - and stick the template to the work with double-sided tape if the work piece isn't large enough to allow clamping while still providing clearance for the router.
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post #8 of 15 (permalink) Old 12-28-2018, 08:45 AM
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One of the methods that I've used is shown in shots 27-32 of this pdf showing the making of a jewellery box. As shown, the simple formula for calculating the size of hole in the template is: template guide dia. minus bit dia. plus size of required rebate.
Assuming that you have a 1" template guide and use a 1/2" straight bit you would add
4 1/8" giving you a hole in the template of 4 5/8"
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post #9 of 15 (permalink) Old 12-28-2018, 09:04 AM
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I've just realised that you probably don't have the means to rout the template hole. Here is one very easy to make circle routing jig.
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post #10 of 15 (permalink) Old 01-02-2019, 05:30 PM
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An easy job on a lathe!
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