What did I do wrong drilling these holes?

[5030]

... I might add the TIN coated drill bits are a gimmick. TIN (Titanium Nitride) coated bits, the TIN coating does nothing except promote easier chip flow from the cutting lip. Nothing more and it wears away quickly too.

 

[LD1]

... I might add the TIN coated drill bits are a gimmick. TIN (Titanium Nitride) coated bits, the TIN coating does nothing except promote easier chip flow from the cutting lip. Nothing more and it wears away quickly too.

I dont like the TIN bits either.

Once sharpened....there is no coating on the edge that is cutting....and I have found that the underlying steel just doesnt seem to be as hard as good plain HSS bits.
One good thing I DO like the TIN for is certain alloys of aluminum that tend to want to get "gummy" and pack the flues of the bit and almost gald themselves to it. The TIN seems to be more of a anti-stick coating

 

[sailonner]

As others have said, lower the RPM to SLOW. I concur with others about the type of bits to use. The titanium coated, or cobalt bits tend to hold up longest. When I've manufactured steel or stainless steel parts, I use auto radiator coolant for the lubricant. It evaporates quickly, helps to cool better, and washes off with water. Which is great if you're going to paint the parts.

 

[mapper]

The only TIN bits I have are Brad points for wood, they seem to be ok for that.
My father who was a very smart man and an engineer once told me after I had destroyed a drill bit in metal,( one of his of course) always use the lowest speed available on the drill press.
Good advice, I've broken some small bits on occasion but I don't think I've smoked one in the last 60 years.
My drill doctor has been an invaluable purchase, my hand sharpening was always kind of hit and miss.

 

[Root Cause]

Good info here.
Blue chips are bad unless using carbide cutting tools.

I have a few years working in a machine shop where we drilled water lines in tool steel with HSS bits. Speed and keeping a hole straight were critical.

I use a cheap paintbrush and load it with coolant. (keep a small pan of coolant close by)
Apply light pressure for about 5 seconds then wipe the bit with the brush with my off hand while pulling it out. You don't want to ever see long, stringy chips. This clears the chip, cools the bit, and allows some coolant into the hole. You will get a rhythm to it soon enough and it is the fastest method and increases the life of the bit.

good luck.

 

[LD1]

Good info here.
Blue chips are bad unless using carbide cutting tools.

I have a few years working in a machine shop where we drilled water lines in tool steel with HSS bits. Speed and keeping a hole straight were critical.

I use a cheap paintbrush and load it with coolant. (keep a small pan of coolant close by)
Apply light pressure for about 5 seconds then wipe the bit with the brush with my off hand while pulling it out. You don't want to ever see long, stringy chips. This clears the chip, cools the bit, and allows some coolant into the hole. You will get a rhythm to it soon enough and it is the fastest method and increases the life of the bit.

good luck.

I disagree about never wanting a long stringy chip.....

A long chip is a pretty good indicator that you have good and consistent feed pressure.

Long and stringy chip on a late is not good....but nothing wrong on a drill

 

[ranchito]

Help a novice here. I thought the long stringy chip on a lathe was probably a good thing. What should I look for?

 

[ruffdog]

Long stringy chips can be dangerous and are a pain to clean up. Maintaining chip control means using a chip breaker and correct feed rate to break the chips into small pieces.

 

[oldtimer 66]

I have an old ENCO drill press. I run it at the slowest speed all of the time. I don't use any coolant. I also hand sharpen all of my drill bits. No problems. I have mentioned this before to the machinist on hand, Rule of Thumb, spindle speed = 4 X SFM / Dia. is a starting point for spindle speed for drilling/ milling and or lathe work. HS tooling = 100 SFM, Carbide tooling = 300 SFM. These are just starting points then adjust up and or down for the material. But for my work I run as slow as possible.

 

[ptsg]

Help a novice here. I thought the long stringy chip on a lathe was probably a good thing. What should I look for?

On a lathe, you'll want small chips, preferably with blue colour. That means the heat is coming out in the chip and not staying in the part or the cutter.

Something along these lines:

Of course, this is not always possible due to a lot of different factors like, speeds and feeds, material, cutters, etc.

On a drill press, if the chip is coming out long, I'll just release the pressure momentarily to stop the chip from forming and then apply pressure again. I typically leave my chips getting like 1.5" to 2" long.

 

[rScotty]

Feed rate is just as important as speed.

Since this was a press....and not a hand drill you should have been able to feed at a pretty good rate.

But for starters....mistake #1 was drilling a pilot hole for such a small final size anyway. That puts all the load and cutting action on less than half the bit...

You only need to pilot larger bits that aren't split point. Then you only need a pilot the size of the chisel point/web thickness of the bit.

Second mistake was light oil instead of cutting fluid.

Others mentioned quality bits. Have no idea what you were using...so that could be a factor.

Third thing.....learn to read the chips.....feed it too light for the speed....the chips coming off turn blue......that's too hot. You either need to slow down the speed or increase feed rate......don't let the chips turn colors more than a light straw color on HSS tooling.

100o rpm on a good press with roughly 5/16" holes....going through 7/8" total....should take no more than about 10 seconds per hole. And that would be at a rather light .005 feed rate had you set automatic feed.

I doubt work hardening was an issue with mild steel. Stainless is notorious for work hardening.....as are some high carbon hardenable steels. But not mild steel.

LD1, what do yo use for cutting fluid? What is the difference between light oil and cutting fluid?
Agree... I also wonder what metal the OP was trying to drill. Sounds like he was drilling stainless.

 

[5030]

Sounds to me like there was enough carbon the steel that it work hardened from the dull drill that was being forced into it and ended that fiasco.

 

[rScotty]

Sounds to me like there was enough carbon the steel that it work hardened from the dull drill that was being forced into it and ended that fiasco.

I agree. There just isn't any way to work harden mild steel... so it probably wasn't really mild steel.
Or maybe not a consistent steel.

Someday I hope to find the perfect cutting and lubricating oil for use on my machine tools, but I guess it's confession time: I use whatever is handy as a drill lube.... Light oil, heavy oil, spit, antifreeze, water, candle wax, or even snow... & my drills seems to work just fine and last a long time.

Most of my old drill bit collection are Chicago-Latrobe HSS. They cut fine & sharpen well. Aluminum does tend to stick to the flutes... but for steel they are fine. For stainless steel caution is needed. But for SS, nothing beats very low speed, lots of pressure, a continuous chip, a waxy lube, and hopefully all with a brand new factory drill bit.

TIN coating is a good anti-stick for chips in the flutes....but I've not noticed it making any particular difference in drilling a hole.

A Drill Doctor is a marvelous tool and takes up a prominent place in my shop along with several well-sorted narrow boxes of drills awaiting attention. A kitchen tableware tray makes the perfect place to put drills waiting for attention. And wait they do; in fact in my shop they've been sitting there by the Drill Doctor waiting for years now.... Being lazy, I tend to just hand-sharpen a bit when I need it.

I will say this about the Drill Doctor..... if you are good enough to use one to advantage you are probably pretty good at sharpening generally. The DD does take some practice. Once figured out, it is better than hand-sharpening.

Lately it seems like more and more of my drills are ruined by poor chucking than by not being sharpened right. Or is it my less tight chucking - getting old now - or are chucks just not as good today?

Drill slowly with enough pressure to keep a chip forming. The lip should be cutting, not skidding.

rScotty

 

[5030]

I have the Darex Professional drill sharpener myself. It's a bit beyond the reach of consumers as it was 2 grand years ago. I rarely use it because I offhand sharpen most times. I do use it on small diameter drills because at 72, it's hard for me to see the ends of the drills and sharpen them correctly and the one I have will sharpen parabolic twist drills as well.

The Chinese drills are junk btw. None here. I tend to use Tap-Magic as drill lubricant. I drill and machine a lot of 300 series stainless and it works quite well.

 

[NoTrespassing]

Tapfree Comparison Chart

 

[5030]

Never consulted that chart. I machine a lot of exotic metals and it just works for me. I use Trico Mist coolant as well on the mills and Flood coolant on the lathes and surface grinders.

 

[Smokeydog]

Technique and cutting fluid always a trick.

I had exotic platinum/iridium alloy needing micro deep holes. Killing parts and breaking carbide drills. Luckily the shop had over 100 years experience of retired ORNL machinists. Supplied them with 200 proof ethanol to lube/cool the drilling solved the issue.
Monarch 10” lathe with 0.00005” runout incredible.

 

[LD1]

Help a novice here. I thought the long stringy chip on a lathe was probably a good thing. What should I look for?

What ruffdog said below.
Lathe tooling usually has chip breakers. IF your speed and feed is set correctly....should see a bunch of little 6's coming off.
The long stringy stuff can wrap around the spindle and fling stuff everywhere, or worse, wrap around the part and break tooling.

Long stringy chips can be dangerous and are a pain to clean up. Maintaining chip control means using a chip breaker and correct feed rate to break the chips into small pieces.

LD1, what do yo use for cutting fluid? What is the difference between light oil and cutting fluid?
Agree... I also wonder what metal the OP was trying to drill. Sounds like he was drilling stainless.

I honestly dont know the difference other than the stuff I use is super sticky and will cling to parts and tooling rather than just run away.
Bout like asking me what the difference between hydraulic oil and engine oil is? I dont know the technical details other than I dont run hydro oil in my engine and dont use engine oil in my HST. Beyond that....i dont know the technical "engineering" difference.

As far as what I use....I like tap magic for aluminum. Its thinner....dont really need tacky/clingy properties for aluminum. For everything else I use either ultra SP which is really good Ultra SP Super Premium High Viscosity Cutting Tool Lubricant Display Unit 4oz Bottles, or CRC Crc 14050 $9.42 Cutting Oil, 12 oz, Aerosol | Zoro.com

I find myself using the ultra-sp for smaller projects or shorter holes. And the CRC for bigger/longer working times simply because the aerosol is easier to apply without stopping.

 

[rScotty]

What ruffdog said below.
Lathe tooling usually has chip breakers. IF your speed and feed is set correctly....should see a bunch of little 6's coming off.
The long stringy stuff can wrap around the spindle and fling stuff everywhere, or worse, wrap around the part and break tooling.



I honestly dont know the difference other than the stuff I use is super sticky and will cling to parts and tooling rather than just run away.
Bout like asking me what the difference between hydraulic oil and engine oil is? I dont know the technical details other than I dont run hydro oil in my engine and dont use engine oil in my HST. Beyond that....i dont know the technical "engineering" difference.

As far as what I use....I like tap magic for aluminum. Its thinner....dont really need tacky/clingy properties for aluminum. For everything else I use either ultra SP which is really good Ultra SP Super Premium High Viscosity Cutting Tool Lubricant Display Unit 4oz Bottles, or CRC Crc 14050 $9.42 Cutting Oil, 12 oz, Aerosol | Zoro.com

I find myself using the ultra-sp for smaller projects or shorter holes. And the CRC for bigger/longer working times simply because the aerosol is easier to apply without stopping.

The reason I asked about the composition of cutting oil is that a few years ago - around 2006 - I got into some projects in my day job that involved chemistry of fluids. And found to my surprise that a lot of what was being sold in the specialty chemical market was nothing more than bottling and advertising of commonly known solutions used for many years - often with an emphasis on using less expensive ingrediants.

And then I remembered an old machinist who used rendered lard for his cutting lube. I have no idea what else he mixed into it, but he was one of the standouts in a trade that has many..., so that got me wondering.

rScotty

 

[Smokeydog]

The reason I asked about the composition of cutting oil is that a few years ago - around 2006 - I got into some projects in my day job that involved chemistry of fluids. And found to my surprise that a lot of what was being sold in the specialty chemical market was nothing more than bottling and advertising of commonly known solutions used for many years - often with an emphasis on using less expensive ingrediants.

And then I remembered an old machinist who used rendered lard for his cutting lube. I have no idea what else he mixed into it, but he was one of the standouts in a trade that has many..., so that got me wondering.

rScotty

Stearic acid is chemically made lard. Dissolved in acetone and applied for coating punches and dies is a preferred high pressure lubricant to prevent galling for our applications. Machinist made some wicked brews for cutting and penetration.