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Discussion Starter · #1 ·
Guys... I'm running into a problem here. I have 2 drill through 2 layers of 12ga steel and a layer of 5/8th drywall. I predrill then I use my self cutting screw.


Self cutting by itself doesn't work because once it hits the 2nd layer of steel it threAds onto the first pushes out and cut.


I'm running through bits like crazy here. I only have to install 45 sheets of steel and I use close to 30 bits Already!!! We dip the bit in oil before every use.

Can bits bits be sharpened? What brand/type will last long? What kind of drill and technique are you guy using? I'm predrilling Like 24 holes per sheet.


ThAnks
 

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Thom
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use cobalt coated bits.

They last much much longer. Oftentimes you need to look at a tool supply store to find them.
 

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Mickey
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The new Drill Doctor works really well, takes a little bit to get the hang of it, but does an excellent job once you do. Although I have seen some old timers sharpen bits on a grindstone that were better than new. Never could do that myself though.
 

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KemoSabe
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I have the drill doctor also. It works great, but you have to watch the pitch angle. The bit needs to have a slight angle back from the cutting edge. Too much and the edge won't last long, not enough and it won't cut at all. We went through a bunch of bits on this job, but by sharpening them, you get at least 20 times the bit life, more if you don't snap them. The back-cut feature is nice for metalwork also.:thumbsup:
 

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I drill a lot of 316 SS & have had good luck with cobalt bits, & they resharpen well. Like mentioned the drill dr works great once you get the hang of it. I see your'e in NYC, call Randy at Colonial 800-345-8665 ext 112 & tell him what you need, he'll hook you up plus it ups's the next day free.
 

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2 sheets of 12 gauge is less then a 1/4 inch correct?

Can you not use a screw intended for thicker metal?

Like this:



I'd go bananas drilling all thoes holes.

I never had good luck re-sharpening. I spend alot on good bit sets but I've found that buying bulk packs of Triton black-oxide bits are the fastest. I really want to try some Japanese bits for I have heard good things.
 

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Discussion Starter · #13 ·
2 sheets of 12 gauge is less then a 1/4 inch correct?

Can you not use a screw intended for thicker metal?

Like this:



I'd go bananas drilling all thoes holes.

I never had good luck re-sharpening. I spend alot on good bit sets but I've found that buying bulk packs of Triton black-oxide bits are the fastest. I really want to try some Japanese bits for I have heard good things.
hrm... whats the name of that screw, or where could i get it. It might work. Im almost done with the steel.. but im facing another issue is attaching the drywall. The self cutting drywall screws i have works well when we drywalled over 1 layer of steel, but now that theres 2, the head cuts on the 2nd layer of steel.
 

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Roof deck screw, that pic is a hilti.

http://www.hilti.ca/holca/page/module/product/prca_rangedetail.jsf?lang=en&nodeId=-68228

Never used em but I have used these for plywood to metal:

http://www.hilti.ca/holca/page/module/product/prca_rangedetail.jsf?lang=en&nodeId=-68236

Normally I don't need the countersunk head so I use Hex-Teks. I've screwed plenty through 1/4 inch rolled steel and they go in pretty easy.

Screwing on drywall with roof deck fasteners could be a slow and messy. I would look into an adhesive and just use a few.

Your local fastening store should be able to help you out in a pinch.
 

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I like the TiN Bullet drills for hand work. The key is speeds and feeds. "Keep the heat in the chip" was one of our mantras in the machine shop.

Most people consider high speed equilivent to efficiency, not so in metal drilling. What you want is a nice, curling chip. Try backing off on the speed, hard to do with a small drill. A 1/2" drill motor usually max's at around 580 RPM. I'd start at about half of that.

In 12ga. you should have chips about 2-1/2 to 3" long when you break through. I've done a lot with 11ga. SS.
 

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A trick I learned watching a construction worker drilling into heavy steel beams is to Vary the speed-up & down alternately with your trigger, instead of just one speed. The drill bit will bite & grab on the way down & back up in speed- instead of a constant speed where it just sits there turning & doesn't grab & so it heats up ruining bits...............
 

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that's right, your speed should be slow enough to create a spiral of metal coming up. How is it that you're killing the bits? is the heat melting the tips?
 

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Capra Aegagrus
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Although I have seen some old timers sharpen bits on a grindstone that were better than new. Never could do that myself though.
I spent a few years in a machine shop back in my 20's. Guess I'd be one of those guys. :thumbup:

As Lone says, it's all in the angle, or backrake. You grind that differently depending on what kind of material you're going to be drilling. That's what makes the difference from the "as manufactured" drill bit. It's been too long for me to remember actual angle degree numbers, but I still do a pretty fair job of it freehand.

The comments on drill speed above are right on.

Plaza, if I remember right, aren't you actually drilling a steel/drywall/steel sandwich? Though a bit of a PITA, it might work better to first drill a body hole through the first layer (using a stop), then follow with either your self-cutting screw, or a smaller drill and then the screw.

If the two layers of steel are in contact with each other, the only real way to avoid their getting pushed apart by the screw even a little bit would be to pre-drill those body holes before mounting the second sheet.
 
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