Drill Bits - Need some help and advice

[LD1]

Here is what i use to get me in the ballpark. mild steel 80sfm x 4 = 320 rpm for a 1 " drill. So just divide it from their. if 1" =320rpm then 1/2" = 640rpm and 1/4" = 1280rpm and so on. For Stainless steel i cut the speed by 1/2 and aluminum i go about 25% faster This gets me in the ballpark and i dont burn up my drill bits.

Those numbers are right, but as I mentioned a few pages ago, you gotta have a press with enough power. Bench tops dont. You will burn up 1" drill bits ALOT faster on a benchtop 3/4hp press vs a 3 or 5hp press where you can actually remove some chips.

Remember, heat is removed in the form of the chip. IF you aint removing sizable chips, you toast the bits.

 

[Redneck in training]

Here is a sharpening system that would do beside drill bits also knives, scissors and woodworking tools.
Tormek T7

 

[woodlandfarms]

So is it just as bad for a bit to go too slow? Meaning I am working mild metal and putting 1/4" holes at 300RPM. Seems to slow from what you guys are saying.

 

[SweBota]

One other thing. Standard drill points are 118 degrees nothing else. If it 135 degrees or something else it's not standard. Later.

True. Drills specifically made for stainless steel f ex have 135 degrees. Dormer A108 is one.

/Marcus

 

[bcp]

Does drill bit RPM mean anything other than maximum speed for the bit and material?

I've never had any problem switching from a 1/2 inch bit at 500 RPM to a 1/8 inch bit at the same speed. I don't want to (and don't) rearrange belts every time I change bit size.

Bruce

 

[LD1]

Going too slow is not an issue.

The general guides online are theoretical maximums. Slower dont hurt anything but productivity. And you can even drill faster if you have flood cooling.

The whole idea of the speeds are based on temperature. Gotta keep the bit cool. Removing an appropriate size chip removes heat from the bit and part. Thats why an undersized benchtop drill press is gonna burn up larger bits even if running at the recommended 80-100sfm. Because they lack the power to be able to cut a decent size chip. Going slower gives you more torque. So you can remove large chips at a slower rate as opposed to tiny chips really fast.

 

[BukitCase]

For those interested in annular cutter tap sizes (Like Carl), I just came across this the other day -

https://www.evolutionpowertools.com/downloads/booklets/us/steelcatalog.pdf

If you scroll down to annular cutters (page 16), they have a separate page JUST for larger tap drill sizes.

Found out if you enter "evolution + the part# from the above" (without quotes) into Amazon's search box (for example, evolution CC17/32L you can cut through all the crappy search engine's attempts at help and go straight to the 5/8"-11 x 2" depth tap size.

For those NOT familiar with annular cutters, these are NOT recommended unless you have either a mag drill, a milling machine, or a REALLY heavy duty drill press - they tend to break easily with any amount of side play... Steve

 

[downsizingnow48]

I've used the Jancy style annular cutters horizontal in a lathe, also works good.

I've also used these Champion cutters for holes up to 2". Kind of a hybrid between annular cutter and hole saw. They work much better than a hole saw, and can be used in a not-too-rigid drill press and also hand held.

Amazon.com: Champion CT7-1 Tungsten Carbide Tipped 1-Inch Hole Cutter-1-Inch Thick Metal: Home Improvement

 

[muddstopper]

I dont know about the comment that you cant run big bits in a cheap drill press. I have a Crapsman floor model. I think it will go down to 240rpms. I regularly run the cheap Northerntool 1 inch drill bits in it and I havent burnt one up yet. I also run up to 4in hole saws in the same drill and cut thru 1in thick steel, without the bit getting hot. One thing I am convinced of because I have proved it for myself. Using just any kind of oil will burn up a drill bit. WD40, PB blaster, never on a drill bit, or a bandsaw. I use the Lennox brand cutting oil and I can tell a difference as soon as the oil is applied. The bits, or saw will cut faster and stay cooler than any other oil I have tried. The only thing that I think might be better is the LPS1 spray oil I find at Granger. I can have a bit just throwing a few chips and squirt it with the Lennox or LPS1 and it will start throwing curls. I have tried water, transmission fluid, 3M machine oil, motor oil and for me, nothing beats using the Lennox or LPS1 when it comes to cutting and drilling. and it dont take but a drop to get the job done. If you can take a 2 1/2in hole saw and cut thru 1in of steel and as soon as you get thru the metal take your hand and grab hold of the bit and not get burnt, and the only difference is in the oil you choose, then I say stick to that oil.

Now as to why I feel so strongly on this subject is because I was sawing some 2 1/2 in shaft on the bandsaw, while drilling some 2 1/2 in holes in 1 in steel on the drill press. I was spraying PB blaster on the saw and using the cutting oil on the drill. Well while going back and forth between saw and drill, I managed to get the oils mixed up and used the Lennox oil on the band saw and it immediantly started cutting faster thur the steel. I thought huh, and sprayed the hole saw with the pb blaster and it almost immediantly started heating up and stopped cutting. Put the pbblaster down and put a drop of the lennox oil on the hole saw and it went back to cutting and actually cooled off. Thats my story and I'm sticking to it.

I also want to add that I just got thru drilling a 1/4 hole thru 12 inchs of round stock and then followed it up with the cheap Northern tool 1in drill bit, using the same Lennox oil on my lathe, and when I got done I could lay my hand on the round stock. My lathe doesnt have any coolant pumps or fancy coolers.

 

[SweBota]

The best I have found, been using it for over 20 years is Rocol RTD. Especially the compound because it melts slowly and stays in place for a long time. We used lots of it when I worked with building dairy machines all in in stainless steel.

https://www.rocol.com/products/search/type:brand/brand:rtd

/Marcus