Review Cobalt bits from Amazon

I just bought some of the F size in a 12 pack. I used one today and it’s the worst hole I have ever drilled with a new bit. My old wore out bit drills a nicer hole then these new ones.
 
Bob Duguay said:
I just bought some of the F size in a 12 pack. I used one today and it’s the worst hole I have ever drilled with a new bit. My old wore out bit drills a nicer hole then these new ones.
Click to expand...
Are they the same as the ones I got? Those were only available in 10-packs. I got some 1/4" as well, but haven't used them yet.
 
I just replaced a 3/16" drill in a job today. It has drilled 1,600 holes in .205" CPM 3V since I installed it at the start of the job. This is probably a two or three dollar drill bit. Chicago Latrobe 118° standard point black oxide.

it was still working fine, I just noticed it was starting to squeak a little bit and didn't want to push my luck.

4.5 ipm, 1,200 rpm, flood coolant. No peck. Not rocket science.

I mention this because it always baffles me, the trouble people have drilling holes and the interest in special drills. IMO it boils down to using the correct feed.
 
Last edited:
Lubrication/coolant is why industrial folks get a thousand holes a bit.

Most hobby guys burn the bit up in a few seconds and don't know why it stopped cutting. They say, "I gave it a squirt of Molly-D, and it didn't help". They don't realize that the lube was smoked off about three seconds after applying it.

Flood coolant is a far different thing. I am setting up my drill press and metal band saw in the new shop for flood coolant.

Don't get me started about the shots on FIF where they have the drill bit so hot it is red ... and can't get it to drill (or weld it solid in the hole).
 
Last edited:
Stacy E. Apelt - Bladesmith said:
Lubrication is why industrial folks get a thousand holes a bit.

Most hobby guys burn the bit up in a few seconds and don't know why it stopped cutting. They say, "I gave it a squirt of Molly-D, and it didn't help". They don't realize that the lube was smoked off about three seconds after applying it.

Flood coolant is a far different thing. I am setting up my drill press and metal band saw in the new shop for flood coolant.

Don't get me started about the shots on FIF where they have the drill bit so hot it is red ... and can't get it to drill (or weld it solid in the hole).
Click to expand...

I don't know, I'm not sure that lubrication is really the answer there. Coolant helps control temperatures so speeds can run faster and it helps flush chips during a peck when cutting thicker stock but I don't think a lot of coolant is making it down into the cut to provide much lubrication at the point of cut. There is high pressure through the spindle coolant than can be run down through special drills made with coolant holes but I think the actual cutting edge of most drilling operations is largely dry down at the cut in that hole. I haven't done an experiment to prove this, but I expect I could probably get a similar number of holes cut dry if I were to reduce my speeds to eliminate heat issues. I really think the real reason industry gets more holes from a drill is controlled feed. I think that amateurs in their garage tend to underfeed during most of the hole leading to work hardening and abrasive wear and then over feed once the web of the drill passes through the back of the work which wipes out the corners of the tool. I think knifemakers would get better results by optimizing the use of the tool, not by the use of special fancy tools.
 
You are correct. I used the wrong word. It should have said coolant flow. I'll fix it.
 
Nathan the Machinist said:
I haven't done an experiment to prove this, but I expect I could probably get a similar number of holes cut dry if I were to reduce my speeds to eliminate heat issues. I really think the real reason industry gets more holes from a drill is controlled feed. I think that amateurs in their garage tend to underfeed during most of the hole leading to work hardening and abrasive wear and then over feed once the web of the drill passes through the back of the work which wipes out the corners of the tool. I think knifemakers would get better results by optimizing the use of the tool, not by the use of special fancy tools.
Click to expand...
Most new knifemaker have no previous experience in working with steel and there you go .......Hundreds of topic how to drill hole ,which drill bits are best ........etc
 
I am no expert but I think the cheap flimsy chinese table top drill presses also are a problem in the equation. When the force from your arm isn't transmitted only vertically through the drill bit, but all over the place through flex and wobble in the system, you have a good recipe for bit wear and also have a harder time controlling feed rate. The harder the material and the larger hole diameter the worse it gets.
I recently upgraded to a Strands S25 gear head press, and it's just a whole different thing to drill now.
 
xxx from ebay, yyy from Amazon

ebay and amazon are not suppliers, only platforms for sales.

There are good and bad suppliers selling the whole range from good stuff to ccc.
 
I watched a few tutorials. Was able to regrind and reuse a few burned and broken bits. After a few minutes of eyeball grinding they cut like new.

As to the pros with lots of proper equipment,...
I do have a cheapo drill press.

I have drilled with the speed up and speed down.

No feed controll other than my arm. No coolant flush. But I have tried putting fluid on the piece. Does not seem to make much of a difference.

But I have been able to get the 15n20 drilled. Based off of tips on here, and drill bit sharpening tutorials on YouTube.

Willie71 said:
I like the HSS twist drills from Lee Valley.
Click to expand...

I did get a Graham blown Atlas forge. I've fiddled with it a bit. I don't know that I can get it down that cool, let alone hold it.

But I do have vermiculite, so I could pump it in and out, snd then stuf it in their to cool slowly.

Seems like just hitting it with my torch has been enough so far.
 
Last edited:
You must log in or register to reply here.
Back
Top