How to Bend HSS?

[MrAudio815]

Hey Everyone,


I have a small or mini Wood turning set that I have not used at all really, used didn't like...since I have my oland tools that work great.

Anyway I have a small may 1/8 round or less mini tool and wanted to know if I can bend the HSS with a vise and a blow torch or something? I want to curve the tip a little for cutting anyway rings. I have been turning bowls and small cup and use the inner wood to make rings or mini goblets and it would be so much easier if I could bend that HSS tool that is collecting dust.

Thanks again,


Matthew

 

[Gotcha6]

If you want to practice bending some, get some dull drill bits you no longer use that are HSS & practice on them. I've never personally tried it, but I've had many a drill bit dulled and blunted after it turned cherry red in the DP. The trick will be re tempering the bit. Most HSS is oil hardened, meaning it is heated to a dull red & then quenched in an oil bath to prevent cooling too rapidly & avoid steam pockets associated with water quenching. It's a complicated and time consuming process involving altering the grain structure of the iron & carbon. Why not make what you want from a piece of drill rod & then temper it up?

 

[CrealBilly]

that's easy - just don't set the router bit in the collet all the way and take a bit bite out of a hunk of wood with it - it'll bend and had me running for the shop door too :confused_. Dang routers can be dangerous

 

[scsmith42]

As Dennis stated, you will need to heat it and re-temper it.

Generally speaking, HSS is tempered to the point where it's yield and tensile strengths are too close for cold bending. I would use a higher temperature torch with a more focused tip (such as acytelene), but propane may work.

I seem to recall a great post in the archives about quenching and retempering metal.

Scott

Here is some info cut and pasted from a different forum. Note that "O1" refers to a type of tool steel:

"I only treat the cutting end--using a propane torch till a magnet doesn't stick, keep hot for five minutes for 1/4" stock, then swirl it around in some canola oil from Costco (we didn't like the taste/smell for cooking, but it quenches O-1 pretty good.) To temper it, sand it shiny and heat it with a paint stripper (or VERRRY carefully with a torch) until the shiny part just starts to turn yellow.)

Later, if I get it too hot on the grinder, I can quickly re-harden it. Sand it shiny after, and heat it with a paint stripper gun until it just starts to turn yellow. Too hard to file after this."

 

[Elmojo]

That cut/paste info from the post above mine is the most accurate.
You'll need to anneal the metal first, which means un-hardening it.
Heat it with a torch until it's medium cherry, then bury it in DRY sand or dirt (not potting soil!) and let it cool very slowly. It needs to take about an hour or more before you can touch it barehanded.
After it's totally cool, try a file on it. If it cuts, it's annealed and ready to bend. If the file skips off, it's still hard and you'll have to do it again and insulate it better so it cools slower.
After you have it bent to your liking, heat it back up with the torch (MAPP works well, propane may not get it hot enough in an open environment) until a magnet does not stick, then IMMEDIATELY quench in a light oil. Any cooking oil with a high smoke point will work, or old motor oil. Be sure to go this outside, since it will mostly likely ignite. Keep it in the oil until the flames go out, or if no flames, until the oil stops looking "swirly" around the metal.
As mentioned above, you only need to harden the last inch or so.
After it's quenched, do the file test again. If it skips, you're good. If not, you can try to harden again, but the second quench will often shatter the steel, so listen carefully for "pings" and look closely for spiderwebbing or other cracks. If you see any of that, toss it, it's not safe to use.
If it's hardened well, polish it up a bit to make it shiny and either use the suggested heat gun or if you can remove the handle, put it in your oven on 350 for about an hour. You want a light yellow to "straw" color. This is the temper. Be sure not to heat it too long. If it does into dark brown or blueish, you've removed too much hardness and will have to start over. The oven is safer, since it's never gets too hot.
I learned all this making knives in my forge, so feel free to ask any additional questions.
Be safe!

 

[froglips]

I've been studying this topic (tool making) and HSS is not going to be easy to bend or reshape.

At least as the books talk. As others said, the problem you will face is just how high a heat you'll need. HSS for turning tools is "formulated" to withstand high temps and not lose temper.

Otherwise you'd not be able to turn with them. Oh sweet irony.

In one book, the guy thought it'd be fun to turn old planer knives (HSS M2) into turning tools. His tale of all the work that went into it was quite amazing. He ended saying he'd never do that again.

What you might consider is using those tools as they are but convert the to oland style/replaceable cutter tools. I've seen ENCO sells HSS cutter bits. You could shape those on a grinder, drill/tap into the original tool.

I'm crazy for doing things the hard way, and reworking HSS is not something I wanna try. Its been a bitter pill for me to swallow

Jim

 

[erasmussen]

I have been reading about tempering HSS, not something to do at home like you can carbon steel.

" Austenitising temperatures are critical with HSS and strict adherence to the steelmaker's recommendations must be observed. Whilst high austenitising temperatures are necessary to ensure that the maximum amount of carbide is taken into solution the recommended temperatures are not far below the point of incipient fusion. For this reason accurate temperature control of the heat treatment process is essential.
Heat Treatment

Double step preheating of HSS prior to full austenitisation is recommended to minimise thermal shock. These treatments are usually carried out in the ranges of 600 – 650°C and 840 - 880°C, depending on the grade of HSS. After preheating, the tool should be raised to the recommended austenitising temperature and held for two to five minutes only before quenching.
Lower Temperature Hardening

There is a variation in opinion between various authorities on lower temperature hardening of HSS. With lower temperature austenitisation less alloy content is dissolved in the austenite (‘underhardening’).
Some authorities claim that low temperature austenitisation helps to achieve a higher toughness for tools with hardness levels of 54 - 56 HRC required for hot punching applications. Others claim that best results are obtained by adhering to recommended austenitising temperatures and tempering to achieve the desired hardness which results in superior toughness. This is a situation where a particular heat treatment procedure suits a particular operation and needs to be proven in practice.


Source: Abstracted from “IMMA Handbook of Engineering Materials”, 5th Edition"

 

[Gotcha6]

Another source on tempering at home is a series of 3 softbacks called 'The Machinist's Bedside Reader' by Guy Lautard. Anyone involved in metal working should enjoy his short stories with a technical insight as well as some of his small tools & jigs plans. It's been some time since I've opened mine, but IIRC he has a segment in one about case hardening & blueing of steel. It also covers the metallurgical transformations in the processes. The mention of heating until a magnet no longer stuck to it is what reminded me of it.

 

[toolman]

This is very interesting, but Earl said it best.. But to add to Earl's post you must soak your tool steel a hour per inch. If it is less than a inch soak one hour. As for as trying to bend HSS good luck. If you know the steel (O-1, O-6, D-2, A-2) just to name a little, you can get it soft if you heat it up to the temp for that tool steel and soak it a inch per hour. then let it cool slow like 4 to 5 hour min.. you will be able to bend it but you must now the type of tool steel to heat treat it O = oil, D and A = air. If you air quench oil it will be soft.. All I can say is have fun..

 

[DaveD]

It may be easiest to buy a HSS lathe blank and just grind away what you don't want. All kinds of blanks on ebay. Or buy a small boring bar (ebay again) that will hold a small piece of HSS that you can custom grind.

Or make a boring bar. Take a piece of steel (just about anything should work) and drill an appropriate hole (sideways) in it, grind off the cutting shaft of the one you currently have, drill/tap another hole in the steel to clamp on the HSS in the newly drilled hole. Figure out how to put a handle on it.

 

[MrAudio815]

After reading and trying to bend even the smallest mini fluted tool steel, I couldn't. Don't have all those torches.

So I turned a piece of oak into a handle and drilled a small hole in the top and pounded a nail into it and bent the nail, sharpened it on the grinder and went to town. It sure doesn't cut like HSS, but it worked and I got the ring out of the middle of the cup I am making. Just trying to consrve wood and make more items out of the throw away middle part.

Thanks for the help~!

 

[NCTurner]

http://www.woodcentral.com/cgi-bin/readarticle.pl?dir=turning&file=articles_624.shtml