whats a good speed for drilling metal?
- Thread starter dj
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I don;t think there is a good speed with a standard bit in a grade 5. It may need be all that hard, but it's probably harder then the drill bit. I use a grinding bit (silica carbide or some such) for stuff that hard.
dun
dun
SSS Angus
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Keep the bit drenched in oil and drill then let off and give the bit a chance to cool down the repeat till you get thru.
denoginnizer
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Make sure your metal is secured. I had a piece "walk" up my drill bit and shot off through the air like a helicopter blade.
DiamondSCattleCo
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Sorry if this sounds ignorant, but I know of no other way to put it: Buy some better bits. I regularly drill Grade 5 bolts with a press running faster, and never have trouble. Grade 5 bolts aren't all that hard. Grade 8's a little tougher.
Rod
Rod
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dj
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The bit is carbide(not cheap). Maybe burning up was the wrong term but it does start heating up even with an oil drench. Have been doing a little and letting it set for awhile and going back to it. But I can't get a good spiral of cut material like the old blacksmith who was gracious enough to let hang out in his shop 30 years ago. He started drilling something and it cut just just a long curled piece. Kinda like peeling an apple with the peel in one piece. Looked at Grizzley's site they have some that go down to 190 rpm.
Bama
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Speed & feed - thats two terms used in most metal shops. That ain't really two fast for a SHARP 5/16 bit. If the bit is sitting on a chip it ain't cutting and is heating up, use cutting fluid as mentioned before and you can even go much faster. The slower rpm's you are talking about are for much larger bits. A 5/16 don't really have to produce the nice little curls to cut well, just keep the chips cleared. The curls indicate that the speed and feed rate is about right. Smaller bits need faster speed, larger (3/4" and up) bits need slower speeds. Another problem is drilling into something that cant dissapate the heat. In this case you can set up a air nozzle to blow on the part to get rid of the heat. BTW I ain't a machinest, I just work with some really good ones.
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dj
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Thanks Bama I'll rig up an air line to blow on it. Chips in the bottom in between stabs may be the problem. Let's see an oil can in one hand an air line in the other and the press arm under my chin.....do you all want ER pics? :lol:
just use a carbide bit and take it in small passes....the oil should cool it off....just lock your vise to the table so it goes in the same place each time, then clean the hole after each pass....q tip or air work well but use goggles with the air....(i speak from experience on that one 
)
)eric
Well-known member
If this is a problem you have frequently, then you might want to invest in a (less than $100) Kool-Mist system. It has a magnetic air nozzle and mixes oil and water together and sprays directly on your drill bit. If you use the drill press often enough, it will pay for itself. Not to mention it is alot cleaner than oil all over the place. It actually uses a water soluable coolant mixture. We just run the same coolant mixture we use in our lathes in the tank, and it is alot cleaner and the drill bits seem to last forever.
By the way, 620 rpm for a 5/16" bit isn't too fast. Grade 5 bolts are fairly soft, so I would look into making sure your bit is sharp and ground correctly. Good luck!
By the way, 620 rpm for a 5/16" bit isn't too fast. Grade 5 bolts are fairly soft, so I would look into making sure your bit is sharp and ground correctly. Good luck!
Saltydawg
Well-known member
I'll just throw my 2 cents in backing up what others have already said.
Grade 5 bolts are pretty strong but they aren't as hard as most drill bit metal is.
Sounds like your bits are ground/cut wrong or just plain dull and chipped. They should cut into a grade5 bolt without much trouble.
If you're actually cutting, which your bit should be, there shouldn't be a lot of excessive heat at those rpm's.
Grade 5 bolts are pretty strong but they aren't as hard as most drill bit metal is.
Sounds like your bits are ground/cut wrong or just plain dull and chipped. They should cut into a grade5 bolt without much trouble.
If you're actually cutting, which your bit should be, there shouldn't be a lot of excessive heat at those rpm's.
bgm
Well-known member
The speed you are running is about appropriate. I would guess you could get by with somewhere around 80 SFM (surface feet per minute) on a high speed bit in grade 5 bolt. That would make the correct RPM 977 (SFM/DIA/.262=RPM). You can get by with a feed rate of .005 IPR (inches per revolution) or since your running 977 RPM you will be feeding at 4.8 IPM (inches per minute).
I would recommend in a home shop environment a black cutting oil, in an industrial environment we'd use a coolant (water mixed with soluble oils). If you ever go to the Kool Mist setup, never use regular cutting oils in it, and be careful of the coolant you use. Remember you are blowing mist and you'll be breathing the stuff. Check the MSDS sheets carefully.
One common mistake drilling is lack of feed. If the drill is babied too much in high or sometimes even medium carbon steels, you can build up too much heat and work harden the piece making drilling almost impossible. The condition is aggravated by dull or improper ground tools.
It could be like was suggested a build up of chips in the bottom of the hole, spinning and keeping the bit from getting a bite on the material. I've had that happen on drill presses lots of times. Proper feed and chip control are the key to eliminating the problem. Air blasts can get the chips out, but like you said wear proper eye protection.
I would never recommend a carbide drill bit for a hand fed drill press in general. While the bit is much harder, it's way to easy to over feed it at hole exits and shatter the tool. Just my opinion. By the way if it's a good carbide bit you could run 2100 RPM and 10.5 IPM. If it's a masonary style carbide bit, the geometry is all wrong for metal and that's the whole problem.
Good luck with your project.
I would recommend in a home shop environment a black cutting oil, in an industrial environment we'd use a coolant (water mixed with soluble oils). If you ever go to the Kool Mist setup, never use regular cutting oils in it, and be careful of the coolant you use. Remember you are blowing mist and you'll be breathing the stuff. Check the MSDS sheets carefully.
One common mistake drilling is lack of feed. If the drill is babied too much in high or sometimes even medium carbon steels, you can build up too much heat and work harden the piece making drilling almost impossible. The condition is aggravated by dull or improper ground tools.
It could be like was suggested a build up of chips in the bottom of the hole, spinning and keeping the bit from getting a bite on the material. I've had that happen on drill presses lots of times. Proper feed and chip control are the key to eliminating the problem. Air blasts can get the chips out, but like you said wear proper eye protection.
I would never recommend a carbide drill bit for a hand fed drill press in general. While the bit is much harder, it's way to easy to over feed it at hole exits and shatter the tool. Just my opinion. By the way if it's a good carbide bit you could run 2100 RPM and 10.5 IPM. If it's a masonary style carbide bit, the geometry is all wrong for metal and that's the whole problem.
Good luck with your project.
