suggestions for a drill bit to use - Woodworking Talk - Woodworkers Forum
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post #1 of 5 Old 03-16-2009, 02:11 PM Thread Starter
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suggestions for a drill bit to use

I'm currently drilling 1&5/8" holes into maple/walnut laminated blocks. depth of the hole is anywhere from 2.75 inches up to 3.5 inches and i'm drilling through the blocks all the way.

I'm using a 1&5/8" forstner bit and i'm noticing a CONSIDERABLE amount of tearout. each block has 5 holes drilled into it and the thickness between holes is about 3/16". naturally i'm getting alot of tearout because this is a very large bit, and it's very violent when it punches through the other side. I'm going at 450rpm on the bit, and when i get close to the end of the block, I go very slow on the pressure to minimize the tearout but I feel i'm wasting way more than what I want to.

The bits themselves are tool shop brand (off brand from menards) and though they're cheap, they've served their purpose well. they do not have smooth rim's on them, instead they're jagged and I think this might be the cause of my tearout.

I tried to purchase a bit from rockler which has only 2 teeth instead of a rim on the bit, and the teeth just keep snapping off during mid boring.

Would switching to a flat rimmed forstner bit alleviate tearout, or does the leading edge of the rim always cause this?

I'm really thinking that a different kind of bit is the way to go. I've found a 1&5/8" box cove router bit with 1/2" shank and i'm considering purchasing an extension that would allow me to mount it into my drill press and use that as my primary boring mechanism.

I was wondering if they make twist bits with 5/8" shanks that go up to 1&5/8" diameter, and if so, where would you find one. I've emailed grizzly customer support asking if they've got them, but i'm thinking that I'll need to go into the industrial supply to find something like this.

The last idea I had was to find a hole saw. THough not ideal, the smaller teeth might help fix the tearout. do they even make 4 inch deep hole saws?

any help is appreciated. Thanks.
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post #2 of 5 Old 03-16-2009, 02:26 PM
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First I assume your tearout is at the bottom. If so, are you using a backup block and letting it drill into it? It's the only way I can drill with forstner and not get tearout. I think that you need to do that regardless of what type bit. And forstner would be my choice.
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post #3 of 5 Old 03-16-2009, 02:51 PM Thread Starter
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definitely using a block below. in fact the drill press table I built uses an insert, so I change it out whenever it's ground down too far.

I've drawn up a diagram that shows the location of where my tearout is occuring. sorry for the crude nature but mspaint can only do so much for me on short notice.

I guess if I used a flat rimmed forstner bit, would that help to alleviate some of my tearout? seems logical that it would. could anyone recommend one at a good price. I need to drill maybe 1000+ holes into these blocks over the next few months, so i'd like something that will last that long.

I forgot to also mention that the bits i'm currently using tend to get clogged up quite a bit and i'm forced to back them out, shut down the press, clean it up and then finally start again.
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post #4 of 5 Old 03-16-2009, 07:50 PM
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When using forstner bits, you should be backing them out about every 1/2" of depth drilled to clear the hole. Air nozzle with a dust collector hose nearby works well. If you are using a back up block and still getting tearout, I would try drilling almost all the way through using the depth stop on the drill press. I would stop just as the point of the bit just makes it's presence known. Then flip the block over and use the teeny hole as a pilot and line the block back up and gently finish the hole. What are you making that you have to drill a thousand holes?
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post #5 of 5 Old 03-17-2009, 11:43 AM Thread Starter
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Hey guys, thanks for all of the responses. I'll try backing the bit out every half inch or so and sucking the chips out with the shop vac. I'm also ordering a new bit as I really think this is my culprit. 3/16" teeth on the bottom of the bit might just be tearing too much out instead of severing the stock before the cutters get to it.

I'm also going to use a full stock piece of board below the holes when I drill them out instead of the insert. the insert is just 3/4" ply that I cut 4x4 square, so maybe a full piece of hardwood would make it a little easier to manage.

I'm making poker chip trays, so that's why there's a huge number of holes to bore. each set of 2 trays is 5 holes 2.75" deep, or 4 holes at 3.375" deep. I prefer to make the 5 slot trays as 20 chips is more common than 25's in a casino.

Thanks for all the advice, and i'll make sure and post some results when I'm done.

Oh the reason that I prefer not to flip the block over and drill from the other side is that the holes themselves might not line up and sometimes will create an offset hole which could be detrimental to the final product's detail. I've tried flipping it over, and just couldnt get the hole close enough so that sanding doesnt remove too much material. if I remove too much material, the poker chips will slosh back and fourth and wont look very nice.

Last edited by divi2323; 03-17-2009 at 11:47 AM. Reason: additional information
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