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Using Router Bits To Create Cavities Vs Hogging It Out With A Forstner


bluesy
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Just a quick question... Not being very experienced with router bits, I was wondering why some people use, say, a forstner bit to remove the bulk of the material in a cavity, then clean up with a router? Do the router bits wear out too fast if you use them to mill out the whole cavity?

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Its just faster to remove the bulk with a forstner then clean up with the router. Its also quieter :D

It will put less strain on the router bits too. because they spin so fast, its also not a good idea to use a router to hog out wood... for safety reasons.

OK, thanks for that. ...going out to get a Forstner bit today :D

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So, with the diameter of the end of the bit making depth stops impossible to use, what's the best way to stop at a pre-determined depth with forstners?

Drill press?

Please elaborate.

Your question doesn't seem to make sense... Drill presses have depth stops. The diameter of the forstner bit has nothing to do with the drill press depth stop. I don't understand what your problem is?...

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Why only? I use smaller diameter bits in handheld drills fairly frequently, for example to drill holes for jack sockets. Don't have (correction, until very recently didn't have) a drill press that could accomodate a full body, so doing it by hand was the only option. Certainly a smoother ride than spade bits.

For hogging, though, it's gotta be a drill press.

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I'm not surprised there's confusion. I have access to three drill presses, and they're all different as far as depth stops go.

The one I chose to use for hogging out my cavities was, not coincidentally, the one I thought had the easiest to use depth stop.

That one had some big bolts / washers on a threaded cylinder. I put some wood as deep as I was drilling (I was leaving 1/4" behind, so I used 1/4" plywood) under the bit, then set the washers to that position. They would hit a stop when I lowered the press, so the press could absolutely go no lower.

I realize that sounds confusing. I looked through my photos to see if I took a picture, and unfortunately it looks like I didn't.

Another one had a depth stop on the side that could be set with a set screw. Unfortunately, if you pulled hard enough, you could go deeper than you set it. When I Google Image Search "drill press depth stop", the first few that come up look like this one.

That drill press had an table with an adjustable height, and if I was forced to use it, I probably would have needed to set the table height to get the depth set. Obviously not ideal, or as accurate (when you would tighten the table down, the height would change slightly), and since you'd have to lower the drill as far as it possibly could go, it would even take longer.

The third one was a really small one. It had a threaded cylinder with a small bolt, kind of like a depth stop that some routers have. I suppose it's similar in principle to the first one, but it looks quite different.

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I think my new press has a decent depth stop mechanism, which will be useful. As you suggested about setting the table to use as a depth stop, this would actually work and is what I always did with my old press. If you have a benchtop style press, I would place some support beneth the table, so you'll have little variance in cutting depths. With the flex of those tables, you could end up with some uneven holes. I usually have some scrap wood lying around and this is how I judge the depths, some scrap and calipers.

FWIW I try to leave the forstner bits shy of the final depth by a bit so I can come through with the router and have nice clean pockets and cavities. Obviously, this is completely neurotic and pointless, but I prefer it this way, though some wicked "Tone Divots" sound cool, unless Mattia decides to patent that one :D

J

Edited by jmrentis
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Why only? I use smaller diameter bits in handheld drills fairly frequently, for example to drill holes for jack sockets. Don't have (correction, until very recently didn't have) a drill press that could accomodate a full body, so doing it by hand was the only option. Certainly a smoother ride than spade bits.

For hogging, though, it's gotta be a drill press.

I do stuff like that from time to time as well.

Yes, it can be done, but it can be pretty dicey. Forstner bits, especially larger ones, can jump off track very easily and it's usually not pretty when they do.

I was being conservative in my comment.

:D

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Here's a related question/situation:

I have a bench-top drill press. The table will not rotate so that I can clamp the body to the table and make a clean hole for the jack on the side of the body. Bummer. When I did the jack, I was forces to use a hand drill. I made a pilot hole, then followed it with either a forstner or a spade - I don't remember. I'm pretty sure it was a spade, but I can't be 100% sure. Anyway, it skipped just a little when it first got going, but was then fine.

Unless I can come up with a better solution, I'll be using top-mounts in everything, which isn't always desirable. Is there a better way of doing this with what I have available?

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... I made a pilot hole, then followed it with either a forstner or a spade - I don't remember. I'm pretty sure it was a spade, but I can't be 100% sure. Anyway, it skipped just a little when it first got going, but was then fine ...

I'm not a fan of drilling a pilot hole first, if too big, it can cause the bit to wobble / chatter as you start the hole.

Your best bet is to mark the center with a punch and use a sharp quality forstner bit at a slow speed.

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Agreed – punching a central mark and having good lighting shining on the drilling area is a must (I have an additional clip-on light).

For side-jack holes, I mark the path through the body as a line and make sure the drilling path lines up with the bit all the way down to the base of the pillar drill. Total overkill. I swivel the table to 90° (vertical) and clamp the workpiece to the table. Cork mat is extremely handy when doing this.

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Mark jack position in the scrap you got when you cut out the body shape.

Cut a flat surface where you need to drill the hole (because starting a hole neatly, on a curved surface, with a Forstner bit is HARD!)

Drill hole in scrap using the Forstner bit.

Clamp scrap wood bit guide to guitar with some padding.

Drill hole very carefully.

Pays to save your scrapwood!

:D

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  • 1 month later...

i used my router to make my control cavities, and they came out pretty well. I did one cavity freehand, and i did the other with a stencle. This is the example, not the rule; but my freehand one came out neater and cleaner lol.

Either way, what i did was i found the zero by lowering my router bit till it was just touching the wood surface. Then i set that at zero. Then i went down 1/8 of an inch, and locked it. Then i pulled up, and angle plunged a bunch of holes until i had something that i could go in the correct direction to in relation to the cutting direction, and the bit's spin direction. After i had that all roughly cleared out, i moved down another 8th of an inch. I continued doing this till i was 5/8" down, as my pickup is 6/8" or 3/4" thick. After i had a rough depth routed out, i smoothed out the edges at one depth with a heat treated double fluted 1/4" bit. I recommend using a stencle and practicing on a scrap piece of the same type of wood though.

If you need clarification, let me know and i'll make a slideshow :D

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Avengers63:

When making side mount jack holes in the past, I've used normal 1/8" bits to make a pilot hole, and then followed them up with a Unibit/varibit (I've also heard them called a "step drill" sometimes) - they're usually used for drilling holes in metal or plastic panels, (I use them when making stomboxes)

They look like cones, with "steps" going up a small increment in size at a time. The one I used last starts at 1/8" and tapers out in 1/8" increments to 1" or something like that, but they come in a variety of starting and ending sizes, and with different numbers of "steps" in varying increments.

I happened to have one thats largest diameter was the same as the hole I needed for my jack. It worked well. They handle quite well in a hand held drill, as the shape of the drill bit sort of guides it. If you drill a pilot hole the same size as the tip of the unibit, it shouldn't skip at all.

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