Carbide reamer finish / Rainbow

[Jonnyofalltrades]

I've never used a carbide chamber reamer before, but I have noticed that effect often when using carbide drill bits. Just last night in the shop I was drilling through the case on induction hardened shafts and the rainbow effect was very apparent, and mesmerizing.
I have always assumed that it was caused by the different edge geometry of carbide tooling, and the burnishing done to the work surface as a result of that geometry.

 

[Wild Bill IV]

Just an interesting tidbit. Got my first carbide reamer (Alpha Legacy 308) - Did some test cuts and a full chamber today. Really interesting that the finish always has a rainbow in it, it's not just in the photo. I cleaned this one with acetone to remove any oil and the rainbow remained.



View attachment 1339533

Isn't tungsten/carbide tooling wonderful!!! If the turning speed (or spindle speed) and feed are right, and you pull the tool as fast as you can when hitting the mark (eliminating chatter) you gets these results!! Even in cast iron!! I worked with tons of carbide tools as a toolmaker (and resharpening) using diamond wheels and cups!!! But be aware, carbide will grow with time (in a few years) unlike HSS tooling!!!

 

[LVLAaron]

carbide will grow with time

explain

 

[Wild Bill IV]

I've never used a carbide chamber reamer before, but I have noticed that effect often when using carbide drill bits. Just last night in the shop I was drilling through the case on induction hardened shafts and the rainbow effect was very apparent, and mesmerizing.
I have always assumed that it was caused by the different edge geometry of carbide tooling, and the burnishing done to the work surface as a result of that geometry.

You're talking about the narrow cutting angle and the much wider secondary relief angles!!! Yeah, I made those on the 4 flutes and the primary cutting head of gun reamers with a 4 inch long tungsten/carbide head and 12 in HSS shaft!!! Used diamond cups for sharpening!!! This was the late 70s and the cup cutters were over $400 each!!! Had one cup blow up!!! The pieces we found were shipped back to the manufacture!!! There was an air bubble in the epoxy cup and ruptured turning 3600 rpm while in contact with carbide!!! There is a lot of heat generated when cutting or sharpening carbide!!!

 

[Wild Bill IV]

explain

The length and diameter will grow!! But to see maybe 0.001" in diameter would be around 10-15 years!!!! Carbide is is so dense and compressed that it will expand over time!!! Kinda like really, really old window panes will show a wave of flow due to gravity!!!

 

[Wild Bill IV]

explain

Aaron:
I have worked with mill cutter inserts, lathe tooling inserts, form tools (SAE and NPT thread), thread chasers, rod grinder guides, pre-reamers, gun reamers, O-ringer cutters, step drills, and drills that were all tungsten carbide!!! I have seen that tooling explode where HSS tooling just breaks!! You can hit a piece of carbide and it shatters worse than glass! DONT DROP THIS TOOLING OR YOU WILL SEE CHIPPED AND/OR CRACKED CARBIDE!! But, in the long run, you will see a lot better quality over HSS if you are gentle, but firm, with those carbide tools!! And they last a lot longer than HSS!! You are going to really enjoy using them. And, the carbide tooling can be resharpened by removing a little of the cutting relief edges or flute faces, or can be reshaped!!! And if a section breaks, send it back and the broken carbide can be removed, a new section of carbide is silver soldiered on, and recut!!

Now, we found some really old SAE form tools during inventory!! I was assigned to see if the tooling was inspec!! Using scrap castings, the tooling had grown 2 thou!! I took 2 thou of the four flutes faces! Back in spec on the light side!! What I want you to be aware of is setting that reamers aside for a long time (10-25years) and pulling it out!! It will grow, but it may still meet your specs!! If not, send it back and with very little carbide removal on the cutting relief or the flute faces, it will be back in spec!! You just have to cut a little slower with cutting relief being wider!!! Avoid chatter at all cost!! It can break carbide and looks like shit!! But a fast, light but firm, touch with the reamers will clear the shatter and give you that mirror finish!! Yeah, the SAE face surfaces cut on castings will be shiny and gives of that rainbow reflection!!! Aluminum milled parts are by far the brightest and most colorful!!! Blinding with bright light!!

I hope this PRO/CON reply will ease your mind!!! Personally, if I was a Smith today, I would have nothing but carbide reamers, cherries, and other tooling!!!

aim small
HIT BIG!!!!
BILL

 

[gunsandgunsmithing]

Aaron:
I have worked with mill cutter inserts, lathe tooling inserts, form tools (SAE and NPT thread), thread chasers, rod grinder guides, pre-reamers, gun reamers, O-ringer cutters, step drills, and drills that were all tungsten carbide!!! I have seen that tooling explode where HSS tooling just breaks!! You can hit a piece of carbide and it shatters worse than glass! DONT DROP THIS TOOLING OR YOU WILL SEE CHIPPED AND/OR CRACKED CARBIDE!! But, in the long run, you will see a lot better quality over HSS if you are gentle, but firm, with those carbide tools!! And they last a lot longer than HSS!! You are going to really enjoy using them. And, the carbide tooling can be resharpened by removing a little of the cutting relief edges or flute faces, or can be reshaped!!! And if a section breaks, send it back and the broken carbide can be removed, a new section of carbide is silver soldiered on, and recut!!

Now, we found some really old SAE form tools during inventory!! I was assigned to see if the tooling was inspec!! Using scrap castings, the tooling had grown 2 thou!! I took 2 thou of the four flutes faces! Back in spec on the light side!! What I want you to be aware of is setting that reamers aside for a long time (10-25years) and pulling it out!! It will grow, but it may still meet your specs!! If not, send it back and with very little carbide removal on the cutting relief or the flute faces, it will be back in spec!! You just have to cut a little slower with cutting relief being wider!!! Avoid chatter at all cost!! It can break carbide and looks like shit!! But a fast, light but firm, touch with the reamers will clear the shatter and give you that mirror finish!! Yeah, the SAE face surfaces cut on castings will be shiny and gives of that rainbow reflection!!! Aluminum milled parts are by far the brightest and most colorful!!! Blinding with bright light!!

I hope this PRO/CON reply will ease your mind!!! Personally, if I was a Smith today, I would have nothing but carbide reamers, cherries, and other tooling!!!

aim small
HIT BIG!!!!
BILL

Have to wonder how stress relieving or cryo might affect what you've seen.

 

[Wild Bill IV]

Have to wonder how stress relieving or cryo might affect what you've seen.

When putting together the carbide tooling, you silver soldier the carbide on the metal tool body!! Let it AIR cool, and shape the tool using diamond wheels and cups! The tooling gets warm just cutting a couple thou and at the cutting contact area, there is a very small, reddish/slightly orange glow from the carbide and there are no sparks like in grinding or cutting some metals!!! And, you can touch the freshly cut carbide after a few seconds and won't get burnt!!! From thermodynamics, POOR ABSORBERS ARE POOR EMITTERS!! I don't think stress relieving will do any good since carbide is mainly CARBON, a non metal element!!! Add in the metal tool body, the carbide might break from heating and quenching since there are 2 dissimilar materials. And cryo might break or crush the carbide since it is a tight large matrix. Both processes would put stresses on the two dissimilar materials like the bimetal coils in thermostats which coil up tighter when cooled and coil unwinding when warmed due two different thermal expansion coefficients!! The growth is due to the chemical bonding which is very tight with light weight low density molecules!! After years of setting around, those bonds loss energy and the carbon matrix grows!! Think weak gravitational and electrical forces!! Also think about carbon dating and using CARBON-14 half life decay in the calculations!!!
In my opinion, after studies in 105 hours of pure science, stress relieving and cryo might cause problems in finished tools!! I my be wrong!! Would like to research the facts someday!!!

 

[GenePoole]

When putting together the carbide tooling, you silver soldier the carbide on the metal tool body!! Let it AIR cool, and shape the tool using diamond wheels and cups! The tooling gets warm just cutting a couple thou and at the cutting contact area, there is a very small, reddish/slightly orange glow from the carbide and there are no sparks like in grinding or cutting some metals!!! And, you can touch the freshly cut carbide after a few seconds and won't get burnt!!! From thermodynamics, POOR ABSORBERS ARE POOR EMITTERS!! I don't think stress relieving will do any good since carbide is mainly CARBON, a non metal element!!! Add in the metal tool body, the carbide might break from heating and quenching since there are 2 dissimilar materials. And cryo might break or crush the carbide since it is a tight large matrix. Both processes would put stresses on the two dissimilar materials like the bimetal coils in thermostats which coil up tighter when cooled and coil unwinding when warmed due two different thermal expansion coefficients!! The growth is due to the chemical bonding which is very tight with light weight low density molecules!! After years of setting around, those bonds loss energy and the carbon matrix grows!! Think about carbon dating and using CARBON-14 half life decay in the calculations!!!
In my opinion, after studies in 105 hours of pure science, stress relieving and cryo might cause problems in finished tool!! I my be wrong!! Would like to research the facts someday!!!

I really don't like to dis on posts here, but this just rubs my sensibilities the wrong way to see science abused this way. I mean no disrespect, but just a bit of corrective criticism.

As for the C14 thing. C14 is less than one in a trillion in natural carbon. with a half-life of 5730 years, you are going to see less than a 1 in 500 trillion reduction of carbon in tungsten carbide in your lifetime. Totally irrelevant to the topic.

As for the bimetallic argument, this is for two dissimilar metals layered one on top the other. Tungsten carbide is a crystal lattice, ideally with equal numbers of carbon and tungsten atoms arranged in a hexagonal arrangement.

 

[Wild Bill IV]

I really don't like to dis on posts here, but this just rubs my sensibilities the wrong way to see science abused this way. I mean no disrespect, but just a bit of corrective criticism.

As for the C14 thing. C14 is less than one in a trillion in natural carbon. with a half-life of 5730 years, you are going to see less than a 1 in 500 trillion reduction of carbon in tungsten carbide in your lifetime. Totally irrelevant to the topic.

As for the bimetallic argument, this is for two dissimilar metals layered one on top the other. Tungsten carbide is a crystal lattice, ideally with equal numbers of carbon and tungsten atoms arranged in a hexagonal arrangement.

But, the form tool body is dissimilar to the carbide, therefore they have different thermal coefficient of expansions!! And, the carbide is layered to the body and bonded by the very thin layer of silver!!! Carbide is very brittle, and the thermal expansion of the body is greater than the carbide!! Something has to give in the cryo stress relieving processes. Maybe the silver binder itself may give!!! The soldier itself may melt, or turn plastic in the heat stressing relieving process!!!

 

[GenePoole]

But, the form tool body is dissimilar to the carbide, therefore they have different thermal coefficient of expansions!! And, the carbide is layered to the body and bonded by the silver!!! Carbide is very brittle, and the thermal expansion of the body is greater than the carbide!! Something has to give in the cryo stress relieving processes. Maybe the silver binder itself may give!!! The soldier itself may melt, or turn plastic in the heat stressing relieving process!!!

I'll give you that. I misread that part.

 

[Wild Bill IV]

I'll give you that. I misread that part.

I'm going to do further research in why the carbide grows!! Both the carbon and tungsten have been used in light bulb!! There is something about the lattice itself and the elemental bonds and or the geometry!!! I might even look at the alloy of carbon steel too! There is something mysterious about carbon/metal alloys and maybe my SCOOBY SENSES will help!!! I never had a study in metallurgy!! Maybe I need to do future studies!!!

 

[gunsandgunsmithing]

I thought this was related to solid carbide tooling, ie a chamber reamer. fwiw
It'd be easy enough to test if anyone sent in to be cryo'd

 

[WSnyder]

I thought this was related to solid carbide tooling, ie a chamber reamer. fwiw
It'd be easy enough to test if anyone sent in to be cryo'd

Yeah it seems the other guy is referring to brazed carbide tooling. Not the same thing in this case

Although I've never looked at it much I've seen a lot of info on cryo treating solid carbide tooling. Nothing ever jumped out that it had any bad consequences over doing it.

 

[Wild Bill IV]

I thought this was related to solid carbide tooling, ie a chamber reamer. fwiw
It'd be easy enough to test if anyone sent in to be cryo'd

Really!!! A uni body tool, not a composition!!! Yeah, cryo could work then!!

 

[Wild Bill IV]

Yeah it seems the other guy is referring to brazed carbide tooling. Not the same thing in this case

Although I've never looked at it much I've seen a lot of info on cryo treating solid carbide tooling. Nothing ever jumped out that it had any bad consequences over doing it.

Not brazed, silver soldiered!!! Big dif!!!

 

[Wild Bill IV]

I'll give you that. I misread that part.

I FOUND OUT WHAT MAKES CARBIDE GROW!!
Tungsten oxidizes very easily at higher temperatures!! Time can do the same thing!!! The growth is oxidation!!!
SCOOBY DOOBY DOO!!!
Knowing this, using heat to stress relief could accelerate oxidation!! Cryo COULD be used! The question I have to ask, could liquid nitrogen have a chemical affect on the easily oxides property of tungsten in the carbide?????

 

[LVLAaron]

Off topic, but it'll really blow you mind when you find out that the weight of certain metals changes depending on their altitude.

 

[Wild Bill IV]

It is just not certain metals, it is all bodies with mass!!! Yes, the pull of earth's gravitational force changes with respect to distance from the center of the earth!! Altimeters work on this principle!!! They are extremely sensitive scales!! The further you move away from the earth, the less that body weighs, but the mass will stay the same!!! Only the force of gravity is decreasing!!.W=mg

 

[GenePoole]

Off topic, but it'll really blow you mind when you find out that the weight of certain metals changes depending on their altitude.

The weight of anything changes with altitude.