What did I do wrong drilling these holes?

[etpm]

we use them for lathe work live center support since they are 60 degrees like the center.

That's why they are called center drills. They are drills for centers, which are typically 60 degrees.
Eric

 

[oldtimer 66]

Just to muddy up the waters. Centers as in dead centers that are use on lathes and grinders are generally ground to 60 deg 15 min. The part center that is machined is machined at 60 degs. You don't want to point load the center because that will cause TIR and machining problems.

 

[Williy]

I like to keep some hydraulic oil in an old can so I can
put the bit in every now and then to help keep it cool

willy

 

[LD1]

Center drills with the pilot point make it so the point/tip of the center (rather live or dead) isn't actually contacting the work.

But yes, if you are using a dead center oil is a must

 

[oldtimer 66]

LD this is a pun but you missed the point.

 

[big bubba]

did you drill a center punched pilot hole 1st? i've used Tap Magic as cutting fluid for tapping & drilling as machinist w/good results many yrs, + all about rpm but you know that, regards

 

[tshep]

Too fast on the rpm
NEVER use petroleum lubricating oil. It acts as a coolant at best on steel. Canola oil, or any vegetable oil is 100 times better, but Messy. WD-40 is Worthless for steel, but great for ALU.
Use water to keep thing cool. (100 times better than lubricating oils.) (soda water keeps things from rusting up)

Also, did you mention the size of the pilot hole?, It should be about the size of the web of the final drill.

When drilling steel, MAINTAIN THE CHIP! that is, keep the cutting lips cutting, don't RUB.

As others have mentioned, once the hole gets hot and blues, it's going to take a good High Speed Steel (HSS) or better to penetrate the hard parts. Or a few trips to the grinder to re-point the drill. If the drill bit gets burned, it's a thankless job to re-point. You are best off just to cut off the business end and grind a new point. An acquired art. DON'T Burn the lips when sharpening!

It's all so hard, but as your post testifies, we git it done! I've got hundreds of twist drills with spoiled cutting lips or broken corners*, I'll get to them "someday" (*from my aviation days)

ruffdog and cal - you have changed my life. I came up through a couple of trades where you just drilled holes, were supposed to have been born knowing it. I just did a project where I concentrated on 'chip load', got it done, and put a good bit back in the rack. (Found pressure much more productive than speed.) I gonna' guess it was stuff I should have known, or did know, just hadn't' put it together as 'chip load'.
While you guys are teaching, how to stay perpendicular with a hand drill, and the same with starting and completing a 'large' tap?
THX

 

[CalG]

ruffdog and cal - you have changed my life. I came up through a couple of trades where you just drilled holes, were supposed to have been born knowing it. I just did a project where I concentrated on 'chip load', got it done, and put a good bit back in the rack. (Found pressure much more productive than speed.) I gonna' guess it was stuff I should have known, or did know, just hadn't' put it together as 'chip load'.
While you guys are teaching, how to stay perpendicular with a hand drill, and the same with starting and completing a 'large' tap?
THX

When drilling, I like to set "something square" near the hole location to give my eye a reference in two planes. A square cut piece of wood does just fine.

For starting the tap, I use the tap holder/alignment tool OR drill a hole in a piece of wood using the press drill.

Tap Aligner - - Tap Aligner

www.msdiscounttool.com

 

[bcp]

Long ago had an electric drill that has several bubble levels mounted into the case. That made it really easy to keep it vertical or horizontal. Haven't seen one since, but haven't looked for one.

Bruce

 

[gsganzer]

Another trick when drilling holes in a piece lying flat horizontally is to lay a large flat washer on top of where you're drilling and fill it with cutting fluid. It acts as a reservoir to keep the cutting fluid contained to where you're drilling.

As other have pointed out, work hardening can happen if your RPM is too fast, bit is dull or not enough pressure. It's especially bad with stainless.

 

[oldtimer 66]

From my apprentice days when using a dead center in a lathe we would use red lead to lubricate the center. I don't know if they make that any more. There was also a yellow lead that we would use for gear messing. It was easier to see in that application. When wheel pressing we used the AAR wheel mount compound. The old wheel mount compound was a mixture of twice boiled linseed oil and white carbonic lead/ 12 lbs. to one gallon of the boiled linseed oil. The wheel mount compound has been replaced with a non lead compound. The new wheel compound is linseed oil based but with out the lead compound. This is all from memory so some of these details may not be accurate.

 

[Torvy]

Threads like this leave me in awe. The more I know, the more I realize I don't know. I am torn between jumping in and learning more or accepting my limits and leaving such work to experts. Thank y'all for the education.

 

[rScotty]

Threads like this leave me in awe. The more I know, the more I realize I don't know. I am torn between jumping in and learning more or accepting my limits and leaving such work to experts. Thank y'all for the education.

I just think the breadth of knowledge here is wonderful. Everytime I read a new post I learn something. A couple of things on my to-do list with my own drilling are a resolution to do more of my own sharpening on everything and to mix my own cutting oil. What in the world is red and yellow lead??

When I was a kid, an uncle had a dog-eared old book like a Machinery Handbook, but it was formulas for making everything from paint to putty.

Just finished putting new bushings and bearings in our old 1930s bandsaw - It took a week of pleasant evenings, but it sure works nice now. About $100 bucks in parts. Mostly Amazon and McMaster-Carr.
I could have bought a new one just as good, but it would cost 5x that amount, or more.

rScotty

 

[ruffdog]

From my apprentice days when using a dead center in a lathe we would use red lead to lubricate the center. I don't know if they make that any more. There was also a yellow lead that we would use for gear messing. It was easier to see in that application. When wheel pressing we used the AAR wheel mount compound. The old wheel mount compound was a mixture of twice boiled linseed oil and white carbonic lead/ 12 lbs. to one gallon of the boiled linseed oil. The wheel mount compound has been replaced with a non lead compound. The new wheel compound is linseed oil based but with out the lead compound. This is all from memory so some of these details may not be accurate.

I have some extreme high pressure grease in a tube made by CMD that we used for dead centers. Get it from amazon:

https://www.amazon.com/Allstar-Perf...t=&hvlocphy=9018912&hvtargid=pla-815813122299

 

[SmallChange]

What in the world is red and yellow lead??

They are lead oxides, along with white lead. Red lead is litharge, PbO, and it's an important industrial substance. I have worked, years ago, on components for litharge processes, though I admit ignorance as to what litharge is used for. Yellow lead is massicot, also PbO, and as far as I know it was important as a pigment though I'm not well informed. What belongs in this list is white lead or lead carbonate, 2PbCO3·Pb(OH)2, which is used to make lead soap for lubricants. It's also the toxic sweet white pigment in lead based paint.

 

[ruffdog]

They are lead oxides, along with white lead. Red lead is litharge, PbO, and it's an important industrial substance. I have worked, years ago, on components for litharge processes, though I admit ignorance as to what litharge is used for. Yellow lead is massicot, also PbO, and as far as I know it was important as a pigment though I'm not well informed. What belongs in this list is white lead or lead carbonate, 2PbCO3·Pb(OH)2, which is used to make lead soap for lubricants. It's also the toxic sweet white pigment in lead based paint.

The places I worked that used lead was to check how gears meshed...checking contact points/areas.

 

[rScotty]

I think the best is to make business regulate itself.

Something like, "If a business sells new oil, they have to dispose of the old".

rScotty

 

[Renze]

When i've burnt a drill bit in a hole, i always flip the workpiece in the vise after sharpening. This way the work hardened hole surface doesnt have to be drilled at once, but with the 118 degree top angle from the other side means the hardened surface is at 124 degree angle to the drill bit point so you dont have to apply as much pressure for it to bite.

Once youre removing material, the chip removes the heat from the drill.

 

[SmallChange]

When i've burnt a drill bit in a hole, i always flip the workpiece in the vise after sharpening.

I did do this. One difficulty is that to do this you need an accurate hole location. Depending on the part geometry this can be pretty challenging for those of us who aren't professional machinists. In my case, because I had drilled a pilot hole, and because my part was flat on both sides with the hole perpendicular to the faces, it was easy. But, then, the pilot hole had caused other problems. Perhaps a very small pilot hole would be the best of both worlds. No bigger than the bit web, and maybe smaller. That might even provide a way to get cutting fluid flowing through the hole and around the cutting edges of the bit the whole time or at least every time we pause the feed pressure.

 

[Mike1955]

Too fast on the rpm
NEVER use petroleum lubricating oil. It acts as a coolant at best on steel. Canola oil, or any vegetable oil is 100 times better, but Messy. WD-40 is Worthless for steel, but great for ALU.
Use water to keep thing cool. (100 times better than lubricating oils.) (soda water keeps things from rusting up)

Also, did you mention the size of the pilot hole?, It should be about the size of the web of the final drill.

When drilling steel, MAINTAIN THE CHIP! that is, keep the cutting lips cutting, don't RUB.

As others have mentioned, once the hole gets hot and blues, it's going to take a good High Speed Steel (HSS) or better to penetrate the hard parts. Or a few trips to the grinder to re-point the drill. If the drill bit gets burned, it's a thankless job to re-point. You are best off just to cut off the business end and grind a new point. An acquired art. DON'T Burn the lips when sharpening!

It's all so hard, but as your post testifies, we git it done! I've got hundreds of twist drills with spoiled cutting lips or broken corners*, I'll get to them "someday" (*from my aviation days)

Very informative Cal.