How long should a drill bit last?

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How long should a drill bit last?

Post by kmx321 »

I know the answer varies depending on how deep you drill and how many repairs you do.
I do about 10 repairs a day on average and use 1 drill bit every other day.

After a while, they get burnt or remains of the glass stick to the bit which makes them dull.
I feel like I'm wasting drill bits because I can't get that residue off.

So how long should they last on average and how do I take off that residue in order to make them last longer?
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Re: How long should a drill bit last?

Post by screenman »

I would say 20 repairs is quite good, I seldom drill and cannot remember the last time I changed a bit, certainly not for a few months, but that is the joy of using Delta injectors, they just do the job so well.
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Brent Deines
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Re: How long should a drill bit last?

Post by Brent Deines »

Depends on the bur but the burs I use most frequently last about 10 repairs. Actually they will last longer than that, perhaps as many as 20 as screenman suggested, but I don't like to waste time or take the chance of a bur getting hot and snapping during the drilling process. At 10 holes each it is pennies per hole so not a big deal in the grand scheme of things if I change them a little earlier than necessary. I don't like running bald tires on my car either.

As a general rule tapered burs last longer than round burs but even with tapered burs the shape, size, style, and overall quality of the bur are all factors that affect performance. I always use a quality bur and I use a specific taper shape and size for terminating long cracks. Other than terminating long cracks I rarely ever drill, but if I just need to clean out a pit or drill into a break with no surface damage I use a very small round bur. I also use different methods of drilling depending on the bur I use. It's a very simple process and I don't mean to over complicate it but there are subtle differences in techniques that will greatly improve the efficiency of the glass drilling process.

To answer your second question, after every hole I drill I use a butane lighter to burn off the glass residue that basically melts onto the bur rendering them pretty much useless after only a hole or two. Just turn the drill on and hold the flame directly under the bur for about 30 seconds as it is spinning and then wipe the bur off with a clean towel. If you are not doing that now you will see a huge increase in the life of your burs and the speed in which you can drill a hole. It will also minimize the chances of the bur breaking.

If you find it necessary to drill anything other than long cracks on a regular basis there are likely some other technique and/or equipment concerns to address.
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Re: How long should a drill bit last?

Post by Nomad »

If you look at the end of the bit, the tapered one not the ball end, when it is dull it will be shiny. Two things you can do. Use a good small pair of needle nose pliers to snap a little piece off the end of the bit. This will almost always give a cutting tip that is at least as good as new. It can be renewed this way three or four times if you don't break off too much. The use of a tool that has a tight pivot is essential, it is too precise of an operation to have poor fitting pliers.

Second: you can use a diamond drum sander on a Dremel or maybe a disk if you can't find a drum. Leave the bit in your drill and hold the bit against the drum or disk to grind a 45 degree angle or so on the end of the bit. It only takes a second on each side. Turn the drill 180 degrees to grind the other side. Inspect with a magnifying glass to see if you have it close. A sharper angle will drill faster but wear more quickly. Run the drum at slow speed. This takes less time than changing the bit, but I have a Dremel dedicated for that purpose. You'll need another drill to do this but I always carry an extra (or two or three) just in case. I keep two drills with two different bits, one larger and one very small, the larger one to terminate cracks. I have another with a polishing buff on it to polish the pit. It impresses the clients more than anything.

I also use a drill to clean out the pit, it's much faster than using a scribe.
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