Over heating during sharpening

[tundratrekers@mtaonline.n]

I have seen many posts saying that you do damage to HSS gravers if you see colors running during sharpening.Thats just FALSE info! The tempering of high speed steel is in the range of the hardening temps. for carbon steels.You can get HSS into the red range when viewing in the dark without ruining the temper. What will ruin it is to get it hot during sharpening,and then cool it with water.That will lead to the graver becoming brittle.If you get it hot,let it cool in still air.You can use water,but only to keep it from getting hot,not after it becomes hot.Temper brittleness happens approx. between 400-700 deg.fehr.,if quenched in this range. God Bless,mike

 

[tundratrekers@mtaonline.n]

The temper range for most HSS is in the 900-1100 deg range ,i believe.And that temper brittleness holds for carbon tool steel also.You never want to stop a temper heat with a quench.That sets up internal stresses that then need to be tempered also.I learned my forging and heat treat from a fourth generation german smith in his 50's or 60's.Also you can get good specs. from Crucible Tool Steel.Now there are always exceptions to the rule.Technique needs to suite the application.

If you are losing hardness in HSS from sharpening,either it wasnt tempered to begin with,only hardened.Or,wasnt fully hardened when made. Carbon steel is in the red/orange range at critical temp..Temper is done between 300-700 deg,straw-blue ,respectively.HSS is in the orange/yellow range at critical.Temper average,900-1100.This is beyond the blue color of 700 deg.If you are getting a dull red glow in the dark,which is approaching tempering heat,then that is to much time /pressure on the tool.Diamond laps work on grit size,not pressure.Get a bigger grit for cooler grinding.

Tempering is meant to relax the stresses set up in the steel by the hardening quench.Everytime you do a quench,you set up new stresses.Use a water coolant from beginning sharpening,flooding the cutter like a lathe,never allowing the bit to get hot.They dont have an intermittent flooding of coolant,only applied when wanted,as that action will ruin the tool.Always air cool from tempering/getting hot.I believe the same applies to carbides. Now, i was taught that a double temper at 400 deg.,with cooling at room temp between,is good for HSS,in some cutlery forging/heat treating . If you have basic knowledge of heat treat and metallurgy,you can modify these standards to suite your needs. mike
mike

 

[tundratrekers@mtaonline.n]

I started this thread,in response to inquiries as to gravers that always chip.Just wanted to help some eliminate a possible unknown variable,to better understand what may be causing chipping when proper technique in cutting has been eliminated as a variable. If i get much disagreement , i will get out some reference material. The info is general.Some steels will fall outside the info i have given.mike

 

[tim halloran]

The Secret Is To Not Get The Graver That Hot While Grinding It. I Use A Wet Paper Towel In My Left Hand And Grind With My Right Hand, Grind A Little Then Cool It Down And Grind Some More. You Never Let The Tool Get That Hot. I Use Diamond Wheels To Sharpen All My Tools And Have Been Known To Use Window Cleaner Or Water On My Wheels. Its The People Who HOG Gravers On Their Bench Grinders That Get Them To Hot, But They're The Ones That Sharpen Their Knife Blades On Them Too. The Wheels On A Bench Grinder Travel A Lot Faster Than A Power Hone.

 

[Tim Wells]

Tundra,
Not to be argumentative but take a HSS graver blank and grind the face on a fast hone and change the color straw, blue, purple or whatever and don't quench it. Now put the angles on it you want and try to cut with it on gun steel and let us know what happened.

You probably already know this but there are air, water, and oil hardening tool steels and HSS is a tool steel. Each responds differently to heat but if you change the color you have taken the temper out.

 

[Gargoyle]

For carving stone, I use both tempered high carbon steel and carbide tipped chisels. I've seen other carvers break a lot of carbide chisels within minutes after sharpening them- they either overheated the carbide, making it brittle, or weakened the solder bond that holds the carbide tip to the shank.

With tempered steel tools, I've seen some problems, but not as many. It seems rare that a carver grinds it so hard that it heats into the tempering/color range.

 

[Andrew Biggs]

I have to agree with Tim.

When I shape up the gravers I like to hog them to shape as quickly as possible. Then finish up at a much slower pace. If there is any colour change because I get a bit over enthusiastic with the grinding........... then I grind the tip back so all traces of colour are gone and then some. Most gravers are very long and give you plenty of room to play with

A section of the graver with color on it will not last for long when cutting.

I mean no disrespect to Mike and I don't pretend to understand any of the science behind any of this......................... But my experience is that theory and practice are two different things.

Cheers
Andrew

 

[tundratrekers@mtaonline.n]

Here is the Crucible site.

http://www.crucibleservice.com/eselector/general/generaltitle.html
You wont soften the steel til you exceed the tepering temp of over 1000 deg. You can find all the steel specs on the site link.

 

[tundratrekers@mtaonline.n]

....................... But my experience is that theory and practice are two different things.

Andrew ,how true.Have you checked to see if your graver glows red in the dark? With enough pressure and fine grit,it would be easy to reach that temp. on a small graver. mike
Also,HSS is standard drill bit steel.Think of how hot a drill will get at the cutting edge. HSS is made to work at high tool temps and still hold its hardness.Temper colors are not really very accurate in high alloys with refractory elements.There is time lag between temp and color.Didnt want to start a big metallurgical debate.Just make known a potential variable,to what some say is a bad graver,beacause they have addressed all known variables.Yes ,quenching after heating can get you hard,but brittle at the same time.Tool steels are capable of machining the same steel as the hardened tool,in an annealed state. Mike

 

[Andrew Biggs]

Hi Mike

No, never tried that. I always shape my gravers with as much light around me as possible..........I need all the help I can get

I pretty much do now what Tim Halloran does with a wet towel/tissue or just dip it in water every couple of seconds........that's for the rough part.

Then I just use the power hone for finishing up and putting the face on.

If I'm feeling in a really pedantic mood I refine the shape a bit further with my E-Max and a small flat diamond wheel under the microscope. That works really well.

When I first started engraving I really butchered a few gravers with overheating.......and done it once or twice since by not paying attention

Cheers
Andrew

 

[Tim Wells]

That is true, a standard jobber drill bit is made of high speed steel however, they are useable in a narrow temperature range and if they change color they are ruined and won't cut hot butter.

I have drilled literally millions of holes in Boeing aircraft as well as others in my day job as an aircraft mechanic over the past 25 years and even with coolant/lubricant such as Boelube, tap magic, or oil the bit will last longer if you keep it cool but you don't have to by any means get it hot enough to glow red to ruin the temper, thus softening the steel and stopping its cutting action. Once you change the color at all you are just burnishing your way through the metal, or at least trying to

If I have to drill out an aluminum rivet or a thousand of them on a piece of skin on a 777, then I don't care what the bit is made of because I'll never overheat it. On the other hand, if I drill out a galled titanium fastener I use a cobalt bit because it will put up with the heat a lot better but will also burn if you spin it too fast. Slow speed and high pressure works best but they are not indestructable. Carbide drill bits are hard to come by in most tool rooms and are worthless in a hand drill, you'll break them every time if they're small diameter.

So, with that said, I have made those HSS gravers on Tom White's fast hone as well as bench grinders and got them too hot and put them down to cool after turning them blue. I tried to sharpen that blue tip just to see what it would do and it dulled and curled as soon as I tried to cut a piece of steel. This was all the proof I needed as to exactly what would happen.

I also have made dot punches and background matting punches and got some of them too hot and blue but never red. This was with 1/8" O-1 tool steel or as some call it, drill rod. I formed the tip, and used it only to mushroom it after only a whack or two with a chasing hammer.

There is a reason everyone who has instructed me in making these things has told me that if I change the color I'll have to start over. People like Alain Lovenberg who was the first one to guide me, then Jim Small, Paul Hamler, John Barroclough and a host of others. They all share this same view because it is from personal experience just like the ones I just described and it is real.

While there is some fine and technical information on the web to pick up on the theory of things, and I thank you for posting those links which I'll check out soon; but first hand experience is hard to dismiss. Not trying to be a snoot or anything, just relaying the facts as I've seen and experienced them; not read about them in a chart somewhere and that's not to imply that is what you did, just speaking for myself sir.

I play around with things a lot because I have always been a curious sort and that is how I learned what to do and not to do and the resultant outcome of both, trial and error, a lot of error.

Steve Lindsay had some carbide mixed with cobalt in an effort to come up with a graver material that would cut really hard steels but not be as brittle as solid carbide is so it has a hard and tough characteristic. He called it Carbalt and you can grind the crap outta that stuff and get it hot and as long as you don't quench it, the temper, molecular allignment, grain structure will not be harmed. The same holds true for carbide I believe but don't quote me on that as I've not tried it.

I ground almost a hundred of those things into that universal point he supplies with each airgraver he sells and never messed one up and they all got too hot to hold in my hand. I ended up putting a leather glove on to hog the mass off on a 80 grit diamond lap then finished them fast on a 1200 and not one had a bad tip. If I did that on a bunch of HSS blanks, I'd of had a pile of junk gravers. That's why in an earlier post I mentioned that every alloy reacts differently to heat in varying degrees. I tend to make tools out of material that I know what I'm doing with these days as I know what outcome to expect when I finish. Sorry for the long winded post...

 

[BES]

Hi Alaska!

Hi Alaska!
I am surprised that in Your climate, something can is strong overheats!
(It is a joke)!

That wouldn't overheat descend under this reference!

http://igraver.com/forum/showthread.php?t=9040

http://igraver.com/forum/showthread.php?t=9010

All so have got used to automated manufacture,
That have absolutely forgotten that they have hands!

The electric sharpened, the pneumatic engraver, the printer, the scanner!

But thus, all name the work — Hand Engraver!

Such gentle tool is better to sharpen hands!
And then небудет an overheat!

 

[James Roettger]

I use a water cooled lapidary to hog the tool shape down so rarely burn a tool. However if I overheat a graver and burn blue 3 mm on the end it does curl and dull quickly. So much so that I've learned to just grind that area away. I've always treated HSS and high carbon steel the same when hardening and tempering and it has always produced a workable tool. Any variation from the red quench and light straw temper produces a tool that either dulls quickly or breaks.

 

[KCSteve]

And I just hog out my gravers with my finger on top so I won't overheat them.

 

[dlilazteca]

Thanks all

Carlos De La O III

 

[Haraga.com]

Here is what works for me. When I am removing a lot of material off of my tools, they spend more time in the water than they do on the grinder.

 

[airamp]

I always use a drip system on the lap so it is always wet when grinding for two reasons.
1. I do not breath the metal dust.
2. The tool will not get hot.
Cut a plastic one gallon container in half and a hole in the bottom to fit your spindle so you don't take a bath when grinding. (home made water shield and make a drip system (like a IV system used in a hospital) Drip it on to the lap and there you have it.

I personally use a faceting machine. All this is built into a good machine.
AirAmp