HSS bit 'coatings'... differences?

[techenthusiast]

enco's HSS jobber length Triumph bits range in price

the black oxide and bright ones are roughly 95-120 and the 'bronze oxide' one is like 170.. it's labeled heavy duty while the other ones are labeled general purpose use...

what is the difference in coatings and why the big price difference?

isnt this just the outer layer which is gonna be taken out anyway? and isnt bronze a soft metal? i dont get how this makes it heavy duty, please help

 

[neophyte]

To make sure we can give you the proper information, you need to post links to the actual drill bit sets, or list the item number, otherwise it's mostly speculation.

First, to answer your question about "Bronze Oxide" finished drill bits. The Bronze Oxide finish on drill bits has nothing to do with bronze, except for the color. The finish is used on some drill bits including regular High Speed Steel/ HSS types as well as more specialized drill bits such as ones manufactured out of Cobalt steel. Supposedly Bronze Oxide helps with "Lubricity" although how much probably depends on the material you'r drilling, and the lubricant you'r using if any.

Black Oxide is the finish found on most general purpose drill bits. The Black Oxide provides protection against corrosion, and I believe it also helps hold drilling lubricant. It's generally good for drilling steel and some iron alloys. I believe Black Oxide isn't recommended for drilling aluminum because it can cause problems with galling. If you have to use the drill bits for drilling wood occasionally I would also recommend against Black Oxide finished bits. I'm not sure exactly why, but the bits don't seem to clear wood chips as well.

Bright Finish drill bits, are bits that have been ground but not given a surface finish. Usually bright finish bits are recommended for drilling aluminum, and possibly some brass, bronze, or copper alloys. I can't remember exactly of the top of my head. Titanium Nitrate coated bits, are usually preferred over the Bright Finish bits for drilling aluminum, but good Titanium finish industrial quality bits are very expensive, as opposed to the cheap ones that are found all over the place. Bright finish bits are also probably best for general purpose drilling in materials like plastics and wood.

Some Triumph drill bits, such as their regular Thunderbit brand ones, are finished with Black Oxide in the flutes, and Bronze Oxide on the outer surface. The Bronze Oxide provides Lubricity to the outside of the drill bit, and the Black Oxide hods lubricant for better chip clearing, and cutting performance. This is the finish found on the Standard Thunderbit sets Snap-On sells.

 

[Mohawk Dave]

Good write up Neophyte.

So, if someone were to buy one set for the garage, and mainly drill steel, but some wood and plastic and aluminum as well, what set/design would you recommend? Just a pretty damn good jack of all trades kinda bit.... Thanks.

 

[Outlawmws]

Std unfinished HSS is hard to beat and usually less expensive. Some production environments may benefit from the trick finishes, but for the general garage hack (including me), save the $$ for something useful.

Besides, sharpen it once and its gone anyway...

 

[dankicksass]

I've always heard it was all about making the drill slippery.
Titanium Nitride>Gold Oxide>Black Oxide>Nickel

 

[Outlawmws]

"Slippery" Hmmm it's a cutting tool...

 

[neophyte]

Good write up Neophyte.

So, if someone were to buy one set for the garage, and mainly drill steel, but some wood and plastic and aluminum as well, what set/design would you recommend? Just a pretty damn good jack of all trades kinda bit.... Thanks.

I would probably take Outlawmws's recommendation and go with bright finish. The galling issues with Black Oxide bits and aluminum, as well as some plastics, would make the Black Oxide bits problematic unless you only had to drill those materials once in a blue moon. Ideally industrial quality Titanium Nitrate bits might be best for general use, with a few exception for a few specific materials. Unfortunately industrial quality Titanium Nitrate bits from a major industrial manufacturers like Precision Twist Drill/PTD, Norseman, Triumph, etc. tend to be significantly more expensive. Some power tool companies offer more affordable options, but the difference in cost compared to the industrial bits makes me think the coatings must be significantly thinner.

If you're still interested in Black Oxide bits, you might try checking Ebay. You have to be careful about brands and the descriptions, but I've seen new USA made 29 piece sets listed for about $50 some major tool stores also used to sell USA made sets for about the same. Some stores such as Lowes also used to have 29 piece USA made black oxide sets for about the same. I don't know whether those deals will turn up again though since most affordable sets I've seen are now imports. This is a set of Ace branded USA made bits that Cripe currently has listed. You'd need to purchase an index for convenient storage though.

http://www.ebay.com/itm/Ace-29pc-Fr...850?pt=LH_DefaultDomain_0&hash=item5aed068bda

http://www.amazon.com/dp/B00018A1YQ/?tag=atomicindus08-20

 

[neophyte]

I've always heard it was all about making the drill slippery.
Titanium Nitride>Gold Oxide>Black Oxide>Nickel

Part of the importance of the coating is making the drill "slippery", and I believe the technical term some manufacturers use for this is "Lubricity". There are other issues as well, one of the major ones is "galling". Some cutter finishes work great for some materials, but are problematic for others. A Black Oxide finish is usually not recommended for aluminum due to the issue of galling. If I recall correctly, one or more of the high end Titanium finishes, such as Titanium Nitrate, or Titanium Aluminum Nitrate, was specifically not supposed to be used for some alloy types, maybe titanium ones, because the surface coating actually caused problems with cutting performance. I think Zirconium Nitrate may have been recommended instead and it also had to due with galling.

 

[djjsr]

In the future, if you would like to get some better bits just for wood, I recommend checking into brad point and forstner bits. They make a much cleaner hole than a twist drill and the forstner bits are available in much larger diameters.

 

[Big Pete]

"Slippery" Hmmm it's a cutting tool...

It helps with chip clearance, and reduces the heat generated during the process, which can make a significant difference if you are drilling stainless. I lean towards cobalt alloy drills for sizes that I may end up using in a hand drill (which has less controll over pressure and speed) as they cope better with heat. I get TiN ed ones if I can (they turn up as surplus stock fairly often) but I'm not obsessive about it.

For industry use in machining centres TiN drills are worth the money, for home use, not so much, especially if you are running them in a lathe, mill or decent drill press.

 

[PT Doc]

For the home shop, one could easily recommend cobalt bits. A bit pricier but you will not need to resharpen as soon. Do you know how to sharpen bits on a belt grinder or bench grinder?

 

[Outlawmws]

In the future, if you would like to get some better bits just for wood, I recommend checking into brad point and forstner bits. They make a much cleaner hole than a twist drill and the forstner bits are available in much larger diameters.

Second this!

 

[Outlawmws]

Part of the importance of the coating is making the drill "slippery", and I believe the technical term some manufacturers use for this is "Lubricity". There are other issues as well, one of the major ones is "galling". Some cutter finishes work great for some materials, but are problematic for others. A Black Oxide finish is usually not recommended for aluminum due to the issue of galling. If I recall correctly, one or more of the high end Titanium finishes, such as Titanium Nitrate, or Titanium Aluminum Nitrate, was specifically not supposed to be used for some alloy types, maybe titanium ones, because the surface coating actually caused problems with cutting performance. I think Zirconium Nitrate may have been recommended instead and it also had to due with galling.

So this makes much more sense, a table for the coating vs. materials to use with and to NOT use with is needed before choosing. have to look for something like that...

I think I have some black oxide drills that were not happy in aluminum, I simply attributed it to the Grade/temper of aluminum, as some are excellent for machining, an some machine like bubble gum...

 

[larry_g]

http://www.guhring.com/Catalog/Drills/

Spend a few hours wandering the above site, reading the technical sections of the catalogs. They also have some good training pages. At the very least find and print out their drill/tap size chart, one of the better ones on the net.

lg
no neat sig line

 

[techenthusiast]

Neophyte your responses are exactly what I was looking for. Thank you. I noticed you mentioned so thunderbits. I can get the set brand new and shipped for only 150 and I'm gonna go that route. I like dealing with snapon industrial, they ship to me for free and I don't gotta do anything. it's worth it because I have that extra pocket money at the moment. What is the warranty like on the bits Anyway I want these babies to last a lifetime. I know how to sharpen them manually and I have cobalt for extracting purposes already

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[uart]

It's generally good for drilling steel and some iron alloys. I believe Black Oxide isn't recommended for drilling aluminum because it can cause problems with galling. If you have to use the drill bits for drilling wood occasionally I would also recommend against Black Oxide finished bits. I'm not sure exactly why, but the bits don't seem to clear wood chips as well.

Great info neophyte.

Interestingly I noticed exactly this problem with black oxide when I was drilling timber just a few weeks ago. I can't remember exactly what type of wood it was, but the flutes on my black oxide bits where just jamming up like crazy with very tightly packed chips. I was literally drilling for 5 seconds and then spending the next 50 seconds trying to clean the flutes. I swapped out to using uncoated (shiny) HSS bits and the problem went away.

At first I wasn't sure if it was the coating or if it was because my uncoated HSS bits are much nicer quality (polish and finish) than the cheap black oxide ones. So I also tested a few holes with some cheap nasty Ti-N (gold color) coated bits that I got off ebay. These ones are as rough as guts (see http://www.garagejournal.com/forum/showpost.php?p=3690980&postcount=2). Worse quality finish than the black oxide ones, but they still performed well in the wood and didn't suffer from the blocked up flute problem. So yeah, there definitely seems to be something going on with black oxide and wood.

 

[Steinmetz]

"...I believe Black Oxide isn't recommended for drilling aluminum because it can cause problems with galling…"

Yes. In fact, you can often find quite a bit of aluminum deposited on the black oxide finish of the bit when used to drill aluminum.

 

[woody 73]

Good write-up information from above What I have found is the black oxide coating is a very good protection from keeping rust at bay on the drill bits. Granted for the most part if left in a humid environment most tools will start to rust and that coating sure helps slow that process down.

 

[sasquatch12]

Interesting question, but i still consider them a kind of modern day gimmick. I will stick with my HSS american made drills with the required coolant.

 

[techenthusiast]

Well I took the plunge and went with the snapon HSS thunderbits and 18v lithium hammer drill paid $314 for both brand new


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[buening]

My understanding is the coatings increase lubricity, which reduces heat from friction on the sides of the drill bit when drilling through thicker material. The coating does not eliminate the need for drilling fluid, however. I too think it is too small a difference production-wise for a home shop, and stick with the black oxide and natural finishes.