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One beer
Post  Post subject: Speed of drill when drilling metal?  |  Posted: Tue Jul 11, 2017 1:14 pm
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Hi, I recently changed the car brake discs and pads for a friend, but the disc retaining screws, (made of steel with a female TORX head), had been rounded off by somebody, so I had to drill them out.

Question:
How fast should one turn a metal drill bit? I used a handheld battery drill on a very slow speed setting,(and some penetrating oil as cutting fluid), and long helical pieces of swarf were produced.

This was OK, but it took ages, and as I changed up to larger and larger diameter drillbits, they started digging in and jamming. If I turned the drill much faster, the jamming did not occur, but neither did I get the long pieces of swarf.

What is the best speed to use? The drill bits are called HSS, high speed steel - does this mean they should be spun very fast?

OB


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gbalkam
Post  Post subject: Re: Speed of drill when drilling metal?  |  Posted: Fri Jul 14, 2017 7:21 pm
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So, this isn't really the "sciencey" answer, but since i had the same issue on a smaller scale...
You are using the wrong tool. You want a screw/bolt extractor. Basically... it drills in one direction, revers the drill and it bites into the metal so you can remove the bolt of screw.
https://youtu.be/y8RCsu3BzUM
https://www.thegrabitstore.com/pages/how-to-use

I know there are similar tools, I have a smaller version 3mm coming for use on tiny screws that are stripped.

Not intending any advertisement value from links, just as a product solution to OP.


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One beer
Post  Post subject: Re: Speed of drill when drilling metal?  |  Posted: Tue Jul 18, 2017 12:57 pm
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No, I was drilling a hole through the bolt, a) to weaken it, and b) so I could then use a stud extractor to remove the bolt.

This worked perfectly, but my actual question was about drilling speeds into steel.

Does anybody know the answer to this?

OB


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Chrispen Evan
Post  Post subject: Re: Speed of drill when drilling metal?  |  Posted: Thu Jul 27, 2017 11:04 pm
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There is no standard answer. Depends on the hardness of the steel being drilled. Here is a guide.

http://www.vikingdrill.com/viking-Drill ... dSpeed.php


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One beer
Post  Post subject: Re: Speed of drill when drilling metal?  |  Posted: Tue Aug 08, 2017 11:57 am
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Thank you.

OB


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Pong
Post  Post subject: Re: Speed of drill when drilling metal?  |  Posted: Tue Aug 15, 2017 6:42 am
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Feed rate in practice means the pressure you're applying. The main challenge with a hand drill (as opposed to drill press) is exerting a good portion of your body weight straight through the spinning bit without deflecting and breaking it. I normally lean on it with my chest and (wimp) ease off to gasp for breath.

If friction overheats the bit it loses temper and becomes softer than the metal you're drilling. Ejecting large chips is, for the bit's sake, ejecting heat.


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DrKrettin
Post  Post subject: Re: Speed of drill when drilling metal?  |  Posted: Tue Aug 15, 2017 12:28 pm
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Pong wrote:
Feed rate in practice means the pressure you're applying. The main challenge with a hand drill (as opposed to drill press) is exerting a good portion of your body weight straight through the spinning bit without deflecting and breaking it. I normally lean on it with my chest and (wimp) ease off to gasp for breath.

If friction overheats the bit it loses temper and becomes softer than the metal you're drilling. Ejecting large chips is, for the bit's sake, ejecting heat.


I'm only quoting that post because I can't even work out how to make a post without a quote.

But by coincidence, this week I have had the task of drilling several large holes in a strip of metal of thickness 10 mm. Until now, I have always wondered how one manages this without a bench drill, because I have always failed to make any hole in metal with my hand-held Bosch drill, even when using drill bits specifically for metal. They just failed to make an impression. So I asked at the local hardware store, and they revealed the secret that there are (at least) two qualities of drill bit for metal. The default option is always the cheap one, which is useless. You have to ask specifically for the better quality one. So instead of buying a 5mm bit for € 1.50 I invested € 2.70. Using this bit, I used the drill at extremely low speed, squirting WD40 now and again to keep the hole moist and cool. And behold - I actually drilled a hole in metal for the first time in my life. It seems that the slower the drill, the more effective it was, maybe around 2 revs per second was optimum.

I actually need 10mm holes, so I have invested in an 8mm and a 10mm drill bit to work on the holes already 5mm wide. Why do they market 10mm drill bits for metal at € 2 which are absolutely useless, when for € 6 you can get a bit which actually works?


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