Jump to content
Chris Christenberry

Vermiculite..........where and what to buy?

Recommended Posts

Slowly trying to get set up to make knives.  One thing on my list is vermiculite.  I don't know where to buy it..............or if there are different types/styles/grades, etc., etc., etc..

Share this post


Link to post
Share on other sites

Check the gardening section, it's an ingredient for some potting soil mixes. I've also seen it used in the outer part of the double box used when shipping hazardous liquids like bottles of acid. It absorbs liquid in both uses and is fairly inert too.

Share this post


Link to post
Share on other sites

If you are wanting vermiculite for annealing your blades I would say forget about it.  Most of your steel comes already annealed and if you try doing a critical anneal you could grow the size of the carbides in your blade and make it harder to machine and sharpen.  My recommendation is that you stick with normalizing your blades.

 

Doug

Share this post


Link to post
Share on other sites

You can get a large bag (2 cubic ft, $20) at Home Depot.  I start all my heat treatments from an annealed state.

Edited by Gerald Boggs

Share this post


Link to post
Share on other sites

Depending on the steel you're using,  a slow cool in vermiculite may or may not be a good thing.  For most steels beyond low-manganese 10XX series like 1095 and 1075 it's a bad thing.  It doesn't affect future heat treatment (if you do your part), but it can make for difficult drilling and grinding.  5160 and O-1 in particular form sheets of carbides that will eat drill bits in seconds.  What steels are you wanting to use?

Share this post


Link to post
Share on other sites

Right now I'm using 01 and some recycled Delta wood planer blades, Alan.

Edited by Chris Christenberry

Share this post


Link to post
Share on other sites

Ooh, those are the worst things to put in vermiculite.  The planer blades are usually D2, a very high carbon, high chromium (almost stainless) air-hardening alloy that needs a furnace to anneal properly, and normalization is not recommended.  O-1 (if you don't have a furnace) works best if you normalize, then overtemper (heat to not quite hot enough to show color in the dark).  A proper anneal for O-1 requires holding at 1350 for a good while, like half an hour, then cooling to 1100 or so at a rate not exceeding 20 degrees per hour.  I don't know about D2 (or if the planer blades are in fact D2, that's just the usual).  

 

That anneal for O-1 is what's called a spheroidized anneal, which means the carbides form little balls that are easily machined through because they pop out when hit with a drill, file, or whatever.  Heating to non-magnetic and cooling in vermiculite forms a lamellar anneal, where the carbides form sheets.  The ferrite is soft as can be, but the carbides can't pop out of the way.  Normalizing leaves evenly distributed carbides.  Overtempering softens the whole thing just enough to drill without wrecking the bit too fast.

 

Some people try to anneal high-alloy steels by putting them in a gas forge, heating to orange, then shutting down and blocking the doors overnight to get a slow cool.  This may or may not work, depending on how slow it cools off.

Share this post


Link to post
Share on other sites

There are other media you can also use to slow cool steels that are easy to get. 

 

simple wood ash I've used for to soften up my tools before grinding to shape.

Sand, Although I have not used that method yet. 

A simple bag of Lye is from what I understand the old fashioned way and is really effective to a slow cool. 

 

However what Allen's got there is pretty much the best way to go as all our modern steels have set perimeters to achieve maximum qualities. Because I'm normally heat treating a tool, that will eventually wear out, I slow cool it to help with grinding and filing.  If I forge an unknown alloy steel, I thermal cycle it (an attempt to normalize it) before forging just to reduce stresses in it.  Once I'm finished with the tool, I normalize it again and depending on what I'm going to do with it, then HT or leave it alone. 

 

I'm still quite new to tool steel and alloy steels, but so far I have not cracked any of my Heat treated tools.

Share this post


Link to post
Share on other sites
41 minutes ago, Daniel W said:

Lye

 

Make that lime.  You really don't want lye!  :lol:

Share this post


Link to post
Share on other sites
1 hour ago, Daniel W said:

simple wood ash

Wood ash works, but my side by side home test against Vermiculite, cools twice as fast. 

Share this post


Link to post
Share on other sites

From the ASM heat-treater's companion re: D2:

 

forging: Start forging at 2005 F, stop forging at 1695 F, cool slowly.

normalizing: do not normalize.

Annealing: heat slowly to 1600 F, hold 1.5 hours for thin sections up to 6 hours for heavy sections.  Cool to 1000 F at a rate not to exceed 40 degrees F per hour, then cool in still air.

 

So, the vermiculite will help with slow cooling after forging to prevent full hardening!

 

O1

do not forge below 1550F.

normalize at 1600 for 15 minutes, cool in still air.

anneal by heating to 1400 F and hold for one hour, then cool to 1000 F at a rate not to exceed 40 F per hour.

 

I don't think vermiculite is going to help that.  ;)

 

Get some 1075, 1080, 1084, 1095, or W1/W2.  It's cheap and it'll do what you want with minimal equipment.  5160 is almost as easy, but don't try to anneal it.

 

Or, invest in a heat treat setup that can hold at temperature like the one John N posted in the pinned tools and toolmaking section.  If you can find the right sort of torch head, that's a pretty cheap way to go provided you have the thermocouple to verify you're at heat.  

Share this post


Link to post
Share on other sites

Well Alan, it's obvious I'm a newbie and have lots to learn here.  I heated the blades in my oven to a point of being non-magnetic.   I let them air cool for a couple of hours and hit'em with a file and it cut, so I should be able to saw out the blade shapes on my little bandsaw.  Okay, so no vermiculite.

Share this post


Link to post
Share on other sites

Non-magnetic for all steels is 1418 degrees F, and if you left them in there to cool a bit you pretty much normalized them (assuming the O-1), which is what it's all about!  As long as you can file and drill, you're good.  Just remember when it comes time to harden that O-1 needs to be at 1525-1550 degrees for a few minutes to get full hardness, a bit more than 100 degrees past nonmagnetic.

If the planer blades are in fact D2, nonmagnetic is just a very soft temper.  B) Either way, if it's workable, it's workable!

Share this post


Link to post
Share on other sites
On 11/4/2019 at 7:39 AM, Alan Longmire said:

5160 and O-1 in particular form sheets of carbides that will eat drill bits in seconds.

I did not know that, but then I don't make many blades.  I did a rough test of this, yesterday I took O-1 and 5160, drilled holes and then heated to yellow (yes, I know too high for proper annealing)  Then overnight in the vermiculite.  O-1 drilled just fine, 5160 ate the drill bit with that nasty sound you get when drilling something hard.

Share this post


Link to post
Share on other sites

I'm glad you tested it out!  I am a bit surprised with the O-1 not doing the same thing, maybe it was because of the yellow heat giving you enough time in the vermiculite to do a true anneal?  Or maybe your O-1 is just friendlier than mine... :lol:  the composition can vary a bit from mill to mill.  

Share this post


Link to post
Share on other sites

Thanks for the affirmation, Alan.  Hope to get time in the shop this week to make 6 or 8 blades for these carving knives.  I keep meeting myself coming around the corner and often feel like a one-armed paper hanger, so there's lots going on in my life right now.  Trying to get a whole bunch of stuff done in the shope because I've got a serious eye surgery coming up and I want to get a bunch of things out of the way before!

Share this post


Link to post
Share on other sites
2 hours ago, Alan Longmire said:

maybe it was because of the yellow heat giving you enough time in the vermiculite to do a true anneal?

I pre-heated the vermiculite. it's been cold these last few nights, so I figured no good would come from putting the steel into 30 degree vermiculite and anyway, I always pre-heat to warm it up and help remove any moisture

Share this post


Link to post
Share on other sites

Good idea.  When I used to anneal 10XX steels I usually preheated the vermiculite, and then put the blade in there with a larger hot bar at the same time.  Sandwich a file between two bars of 3/8 x 1 mild, heat to bright orange, then jam it in the preheated vermiculite.  Buttery soft the next day!  Probably had terrible grain growth, though.  Now I just normalize and, if needed, overtemper.  

 

Good luck with the surgery, Chris!  

Share this post


Link to post
Share on other sites

That is an interesting idea, Gerald..............also a good'n from you Alan.

 

Surgery should go okay.  Doc says I'm going blind in that eye and she's tryin' to alleviate that problem.  This will be the second surgery on it in 8 months.  First one didn't do so well!

Share this post


Link to post
Share on other sites

Create an account or sign in to comment

You need to be a member in order to leave a comment

Create an account

Sign up for a new account in our community. It's easy!

Register a new account

Sign in

Already have an account? Sign in here.

Sign In Now

×
×
  • Create New...