Drill Bits - Need some help and advice

[oldtimer 66]

SFM is surface feet per minute. That can be the tool and or the material. That is how much of the material and or tool that passes by a theoretical point in one minute in feet. Mild steel about 100 sfm. Inconel maybe 20 sfm. Aluminum say 300 sfm. Example 1.0 dia. drill in mild steel. RPM per the formula 400 rpm. Now the same drill in Inconel 80 rpm. Same drill in aluminum 1200 rpm. This formula is a rule of thumb for a starting point on cutting speed. This should all be on the Internet some where. Machinery's Handbook covers this extensively. Have at it. Later.

 

[LD1]

SFM is surface feet per minute. That can be the tool and or the material. That is how much of the material and or tool that passes by a theoretical point in one minute in feet. Mild steel about 100 sfm. Inconel maybe 20 sfm. Aluminum say 300 sfm. Example 1.0 dia. drill in mild steel. RPM per the formula 400 rpm. Now the same drill in Inconel 80 rpm. Same drill in aluminum 1200 rpm. This formula is a rule of thumb for a starting point on cutting speed. This should all be on the Internet some where. Machinery's Handbook covers this extensively. Have at it. Later.

And a 1" bit will have no trouble @ 400 in mild steel if the press is large enough and has the power. The heat is removed from the bit and part in the form of the chip. If you dont have the power to remove a sizable chip like most small presses, you toast the bit.

Most small benchtop type presses arent good much beyond 1/2" bits.

 

[oldtimer 66]

SFM is surface feet per minute. That can be the tool and or the material. That is how much of the material and or tool that passes by a theoretical point in one minute in feet. Mild steel about 100 sfm. Inconel maybe 20 sfm. Aluminum say 300 sfm. Example 1.0 dia. drill in mild steel. RPM per the formula 400 rpm. Now the same drill in Inconel 80 rpm. Same drill in aluminum 1200 rpm. This formula is a rule of thumb for a starting point on cutting speed. This should all be on the Internet some where. Machinery's Handbook covers this extensively. Have at it. Later.

 

[Shield Arc]

If the web of the drill gets to wide for my liking. I grind it to a point using the edge of the grinding wheel between the flutes.

 

[oldtimer 66]

Since we got into H.P. rule of thumb, one HP per c.i. metal removal per minute for steel. Roughly .5 HP per c.i. metal removal per minute for cast iron. Question: does it take more or less HP to machine aluminum and why? As compared to steel.

 

[KennyG]

I'm always surprised at people who don't like Drill Doctor. I'm not great at hand sharpening. I get variable results. The Drill Doctor is a breeze, takes only a minute or so and gets consistent results. I probably resharpen more often than I need to because it's so easy. I guess everyone is different.

 

[Big Barn]

I'm always surprised at people who don't like Drill Doctor. I'm not great at hand sharpening. I get variable results. The Drill Doctor is a breeze, takes only a minute or so and gets consistent results. I probably resharpen more often than I need to because it's so easy. I guess everyone is different.

Perhaps the entry level models aren't as good? Sometimes there's a reason for higher prices.

Terry

 

[Shield Arc]

I was given a Drill Doctor years ago. I thought it did an OK job. It just took to long to set up. I can sharpen a bit by hand before I could get the bit in the Drill Doctor clamp. So I gave it to my brother-n-law. He loves it.

 

[bigdeano]

I was surprised he didn't make much of a fuss about overheating the cutting edge. I always thought that once you turn color on a cutting edge you just ruined the heat-treat on the steel, at the worst location. Now you have to grind all the colored metal off plus more (also slower and still keeping it cool). Otherwise your bit won't keep it's sharp edge. When he's all done you can still see the discolored steel at the cutting edge and he proclaims it ready to go.

Have I been worrying about this for 40 years for nothing?

You're not likely to soften HSS by grinding. You can silver solder it to a boring bar (red hot) and it will still be hard when it cools. Carbon steel is a different story.

 

[LD1]

More HP for aluminum overall cause you are running faster and removing material quicker.

But I imagine the HP per ci is similar for alum as it is for cast iron.