Pin hole drill bits - when do you pitch'em / replace'em?

Racer88

Racer88

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I don't think I've ever seen this discussed.

At some point, any cutting tool will get dull and not work as well. It's pretty easy to tell when your pocket knife needs sharpening. Not so easy to tell when your drill bits are getting dull.

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I would imagine a dull drill bit is still going to go through a plastic P80 frame. BUT... I also suspect that rather than only cutting, it may also be doing some melting / deforming of the plastic. This could result in less precise pin holes. And as we all know, First Time Quality pretty much begins and ends with perfect pin holes.

So.... those of you who have built many frames... Did you replace your bits at some point? If so, at what point? What was your determining factor? How may frames before you switch to new bits?

Go! (and thanks!)
 
So I've drilled holes in 14. All aren't completed yet thought most are. The first 2 or 3 I used the P80 bits with a hand power drill and then somewhere in the mix started using a Dremel Press with the Dremel brand brad point bits. As I recall I used the same P80 bits on the first few as they worked and I didn't want to switch out a known quantity. Haven't swapped out the Dremel bits either.

I respect your point though drilling through polymer, I can't imagine how much use would be needed for the metal bit to truly dull - I don't drill with the rails installed ;) Haven't even put a thought out there on bit replacement. Guessing I'll be on my third or fourth safe full of stuff before I get to that stage ?!
 
Michele said:
Frankly I think you’d get bored, tired of making or just have way too many p80’s before the bit got dull on that plastic.
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I don't know. Knives get dull cutting on paper / cardboard. Ask me how I know (since that's about all I cut with my pocket knives).

BTW... How many is "too many" P80s??? :unsure: Asking for a friend, of course. ;)
 
If you are worried about dulling the bits just order a few sets off amazon. Stub drill bits should be stupid cheap.

I worry more about bits not being sharpened equal. A bit that can appear sharp can be sharpened wrong and make oversized and or oval holes. Not really much of a worry in plastic with smaller bits but larger bits in a harder material like al can be a big deal. Will also create extra side wear on the jgbs from the created bit wobble from being offset sharpened.
 
axkiker said:
If you are worried about dulling the bits just order a few sets off amazon. Stub drill bits should be stupid cheap.
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I wouldn't say I'm "worried." It's just something that occurred to my analytical brain. :)

Cutting tools DO get dull. The question is... how much use does it take in this case? I don't know. I haven't had any problems after drilling 4 frames, so far. But just a question that occurred to me.

Yes... they are relatively inexpensive to replace.

axkiker said:
I worry more about bits not being sharpened equal. A bit that can appear sharp can be sharpened wrong and make oversized and or oval holes.
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Or being out of true from the factory. Or not centered in the collet when it's tightened.

Before I drill, I run the bit in the Dremel at speed (turning on and off) to observe if it appears to be running true. It will appear to get "wider" when run at speed, if it's not running true. And I HAVE had to loosen the collet, re-seat the bit, and re-tighten to get it to run true.
 
Bits dull down, even when cutting plastic. Personally, I think the plastic used by P80 has some form of filler in the mix, like silica. I don't know that as fact, this is just on observation of what the shavings look like compared to other plastics.

Now, I've never had a reason to re-use the bits, since they came with the kits. Once used on the kit, the bits went into the drawer of drill bits and get used on other things until they obviously are dull. The point where you stop seeing ribbons of material coming up the flutes of the bit is the warning the bit is dull. You can also feel the bit start to chatter. It is easier to tell when drilling steel because instead of ribbons of material, you start getting a slurry of cutting fluid and metal dust. If you see smoke and hear it squeal, you are past the point where you should have changed the bits.

So, well, I would just go with the general idea to start each frame with new bits. They are relatively cheap. If you have to re-use bits for some reason, practice sharpening them and test your work out on scrap bits. Otherwise, just chuck-em in a drawer when you are done and use them for other work...pilot holes for nails, etc.
 
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clm2112 said:
Bit dull down, even when cutting plastic. Personally, I think the plastic used by P80 has some form of filler in the mix, like silica. I don't know that as fact, this is just on observation of what the shavings look like compared to other plastics.

Now, I've never had a reason to re-use the bits, since they came with the kits. Once used on the kit, the bits went into the drawer of drill bits and get used on other things until they obviously are dull. The point where you stop seeing ribbons of material coming up the flutes of the bit is the warning the bit is dull. You can also feel the bit start to chatter. It is easier to tell when drilling steel because instead of ribbons of material, you start getting a slurry of cutting fluid and metal dust. If you see smoke and hear it squeal, you are past the point where you should have changed the bits.
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Good post. I have never used the bits that came in the kits. I use the SAE sized bits (as per @MarineGunBuilder's advice): 5/32 and 7/64, both in brad points. The 5/32 is from the Dremel brad point kit (since it has a reduced 1/8 shank). As much as I can tell, Dremel does not sell these bits individually. Gotta get the whole kit.
Amazon product ASIN B000H7D3QE
View: https://www.amazon.com/gp/product/B000H7D3QE/
The 7/64 bit is one I got on Amazon from a company called "WL Fuller" (since Dremel doesn't make one)
Amazon product ASIN B001HL8QTS
View: https://www.amazon.com/gp/product/B001HL8QTS/
They work really well... and leave my pin holes on the "tight side." I usually have to hand ream the 7/64 holes with the 3-mm bit that comes in the kit in a "pin vise." I do it just enough to get the pin to go in with a fair bit of tightness.
Amazon product ASIN B082823TZ9
View: https://www.amazon.com/gp/product/B082823TZ9/
^^^ I've inserted Amazon links. But if you have an ad blocker activated, Amazon links don't show up.
 
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By contrast, I've never used the plunging dremel method of drilling the pin holes. I've always done them on either a drill press or in a chuck loaded in the milling machine. By the same token, I'm spinning the bit at much slower speeds.

I'm not debating the merits of MGB's way of doing the holes, I just do it the way I was trained. We both seem to end up at the same place.
 
clm2112 said:
By contrast, I've never used the plunging dremel method of drilling the pin holes. I've always done them on either a drill press or in a chuck loaded in the milling machine. By the same token, I'm spinning the bit at much slower speeds.

I'm not debating the merits of MGB's way of doing the holes, I just do it the way I was trained. We both seem to end up at the same place.
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Well, I have neither a drill press nor a milling machine. :)

I've modifed MGB's method just a little bit by setting up the starting point of the Dremel press quite close to the top of the jig.... so the plunge stroke distance is reduced as much as possible (to minimize any possible deviation off center during the plunge stroke.

I also added a foot pedal so that I don't have to use the switch on the Dremel, which could also jostle the drill off center before the plunge.

I made a video! (For those who haven't seen it.)

For my next build, I was thinking of trying to start the plunge with the brad point lightly engaging the frame BEFORE turning the drill on (with the foot pedal) and then hit the gas and finish the plunge. What do you think?
 
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Racer88 said:
For my next build, I was thinking of trying to start the plunge with the brad point lightly engaging the frame BEFORE turning the drill on (with the foot pedal) and then hit the gas and finish the plunge. What do you think?
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I don't think it will make much difference. The brad point of the bit is going to create a pilot hole when it touches the plastic regardless of what speed it is rotating at. Touching the point at zero rpm will have the same effect as making contact at a few thousand rpm. It is geared more for drilling wood to help center the bit before the flutes start chopping though the wood fibers. Plastic is more homogeneous a material, and even a common 118 degree twist drill point can center itself.
 
clm2112 said:
I don't think it will make much difference. The brad point of the bit is going to create a pilot hole when it touches the plastic regardless of what speed it is rotating at. Touching the point at zero rpm will have the same effect as making contact at a few thousand rpm. It is geared more for drilling wood to help center the bit before the flutes start chopping though the wood fibers. Plastic is more homogeneous a material, and even a common 118 degree twist drill point can center itself.
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Agreed. But my point was more about ensuring that the bit doesn't stray off course during the plunge. Basically, taking my 1/4-inch clearance (reduced compared to MGB's demonstration) before the plunge and reducing it to ZERO inches before activating the drill and the plunge. This is enabled by having the foot pedal and not having to operate the switch with one of my hands. I need both hands elsewhere.

Without the foot pedal, and only two hands, you have to use one of them to turn the Dremel on. This would negate the ability to bring the drill bit to "point zero" before turning it on. And manipulating the drill switch increases the probability of the bit moving slightly off the intended axis.

See what I mean, Jean?

I think I'm going to have to make a new video!
 
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I used the drill bits that came with the kit. When done, I put them in a little baggie along with the chunks that get cut off the frame. The baggie is put in the P80 box along with the jig. So the answer is they get used once per side. I suppose being a "packrat" has helped as I have a number of "used once" jigs in inventory... ;)

Since I have the luxury of a few DPs at my disposal when I drill, I use those. No Dremel press here. I tape the jig tightly together with packing tape not overlapping the sides. Then the bit is installed in the DP, I adjust the height so the bit is just over the jig about 1/4". I get the jig lined up with the bit by bringing the press down (DP is off) and bit is in the jig hole, raise the DP making sure the jig doesn't move, put a drop of mineral oil in the jig hole, start the DP, lower it into the hole (low speed) then raise. If all goes well, no red shavings will come out, only the color of the frame. I do one hole at a time. The oil is to protect the jig, IMO.
 
After doing 14 frames, most using the Dremel press an Brad point bits, I can detect no difference in cutting performance.
I believe the polymer is reinforced with something, as. clm2112 suggests that may eventually dull the bits, but I'm guessing it will be North of 25-30 frames.
I use a power strip, because I already had it. Lightly touch the Brad point to the frame, and then turn on with my foot.
Been working well. Baby oil for lube.
 
Once the project is complete, I cut the jig in half and put the bits back in the box and recycle it. I always use the bits that come with the kit.

For drilling I use a small vertical drill press that is very much like the Dremel rig.
 
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