heat treatment question

[Paddytray]

Thanks gents .
Dave I posted in here as I thought i'd pestered you enough lol .

I've brought a Digital IR High Temperature meter for the Furnace/forge that i'm building (slowly).
Thought i'd give it a good run and monitor the heat to see if I can Learn ways of controlling it.
I've also aquired a cast iron scone griddle that fits perfectly as a lid for the Furnace/forge thing i'm working on.
so that should help me keep in some of that heat .

 

[Dave Budd]

IR thermometers are a very rough guide to temperature, I would get a proper thermocouple probe and digital reader. My HT furnaces are gas and I currently have to twiddle the burner to adjust the temperature, but both hold their temperature to within a few degrees and are pretty simple to set up. I've one that has a big burner to do the high temp work, it will hold stable from 300-1200C and the other uses a blowtorch and holds from 120-300+C both have internal volume about the same as a dustbin.

 

[Paddytray]

I would most definitely go for gas if I ever set up properly. But what started as a little project/hobby is starting to become very luring and intersting . I would have rushed in and bodged a blade of sorts in the hope that it gets my boys minds going & teach them something worth knowing. And now I'm studying most nights between bottle feeds and nappies lol. I want to learn more before I touch the steel !
Have you posted any photos of your setup ?. I'd love to see it all .
Paddytray . ;

 

[Dave Budd]

there are some pictures of my set up as was a few years ago on my website (workshop tour on the courses page), but I have been trying to get it updated for a while. Hopefully the weather is on the turn and I may be able to get some tidying done and sort some more pictures out soon

 

[Albus Culter]

Can is ask - Dave mentioned taking it out, testing the hardness, and repeating if needed.

How do you test for hardness at home. Is that possible to do you need specialist kit?

 

[Dave Budd]

well, I do have a hardness testing machine, but that's not really a hobby purchase

Hardness testing files are getting pretty cheap these days. They give you a bracketed range for teh hardness rather than a definate value, but they are very handy and I use them a lot.

If you don't get them, then you can also check to some extent how hard the blade is with a sharp new file (you compare how it bites/skates compared to a blade of a known hardness) or there is the 'brass rod test'. You press the rod against the cutting edge (sharpened) and look at how it is deflected; if it chips then it is too hard. That's also very subjective since the same hardness on a 12 degree angle may chip but will flex on a 20 degree edge, for example (also some blades you will want harder than others according to use)

 

[Albus Culter]

well, I do have a hardness testing machine, but that's not really a hobby purchase

Hardness testing files are getting pretty cheap these days. They give you a bracketed range for teh hardness rather than a definate value, but they are very handy and I use them a lot.

If you don't get them, then you can also check to some extent how hard the blade is with a sharp new file (you compare how it bites/skates compared to a blade of a known hardness) or there is the 'brass rod test'. You press the rod against the cutting edge (sharpened) and look at how it is deflected; if it chips then it is too hard. That's also very subjective since the same hardness on a 12 degree angle may chip but will flex on a 20 degree edge, for example (also some blades you will want harder than others according to use)

Files seem the easiest home option for a hobby project.

Oops bought a set

Thanks Dave

 

[Dave Budd]

yeah, they are nice and cheap now. When I bought a set almost a decade ago they were nearly fifty quid! They take a little getting used to and are still very subjective, but they are much better than nothing

 

[Paddytray]

Dave your Outside Workshop & courses look like a lot fun.
Thanks for the link to the hardness testing files I brought myself some :why:
Gives the missus a reason to moan when I get more parcels than she does from ebay etc lol

 

[Paddytray]

Sorry another quick question gents Butane or Propane when using gas ?
is there any side effects/advantages of using one over the other etc ?

 

[mrcharly]

Butane doesn't burn well at cold temperatures.

 

[georann]

Don't know if theres anything particular for heat treatment, but Butane is generally more efficient, cleaner burning, and burns hotter.

 

[ged]

Given correctly adjusted burners there is no significant difference between butane and propane as far as cleanliness of burning, efficiency and flame temperatures are concerned.

http://www.engineeringtoolbox.com/flame-temperatures-gases-d_422.html

As has been noted, butane is much less reliable outdoors in cold weather because its boiling point is not far from zero degrees Celsius. When you use it at high rates, because it self cools as you use it, you can find that it won't come out of the container even in fairly mild weather.

Propane may be cheaper than butane depending on how it's supplied. You may be able to find packages (usually 'bottles') more suited to your application in one gas or the other. Supplies may be more readily available of one gas or the other.

Almost all the flame cutting of steel that I've ever seen (and all that I've ever done) has been done with propane+oxygen.

 

[thebushcrafter99]

okay this might end up kind of long but here goes
this is how i do it

to harden
this is just a rough guide and isnt specific for any particular metal
heat metal up to non magnetic (test with literally any magnet ive tested with the magnet on the end of a scraper thingy)

quench vertically in preferably used oil you can use new oil but its a waste and it doesnt work as well, you can use water but it cools too quickly and your beloved blade can warp and/or crack so dont use water

it is know very hard and brittle (as mentioned before in this thread)


tempering
tempering is taking some hardness out so it isnt so brittle and so it will hold an edge

put blade in kitchen oven preheated to 150 degrees c for 1 hour
raise temperature to 250 degrees c give it another hour at that
raise temperature for final time to 30 degrees c and give it a last hour and that
after the third hour in the oven turn oven off and leave blade in oven to cool with oven

i hope this makes sense

oh and its recommended that you wait till the missus is out until you temper the blade ;D

 

[Paddytray]

sorry to thread jack again . I've seen a gas forge on fleabay and was wondering if it was too good to be true .http://www.ebay.co.uk/itm/121058926441?ssPageName=STRK:MEWAX:IT&_trksid=p3984.m1423.l2649

 

[Dave Budd]

that's a new design for them.I've seen their forges and burners on ebay for a couple of years but I've no idea if they are any good or not. The design and parts are nice and simple so I see no reason that it wouldn't be good(may be thirsty on gas, but extra insulation would help that).

 

[Colin.W]

Is this the words of experience?

 

[Paddytray]

CHEERS DAVE !
refractory cement should fix that .
Maybe line the walls then add the wool .
Add a back door that can be closed for the shorter stuff also .
It's very tempting as it saves me waiting for the time to build one.


Oh I was caught out by the missus when a Thermometer came in the post "what the fornication is that for"
she so sweetly asked me
So I went on to explain Heat treating knives in the oven but only after i'd tested it's temperature She was not so keen on the idea .
I think i'll use the cover of darkness for that job

 

[Paddytray]

I brought it .


But betsy will still get to have a proper run first

 

[Dave Budd]

it'll be interesting to see how they both do With lining the gas forge, don't bother with castable refractory fo the liner. Use the fibre (1" thick blanket) and a couple of coats of rigidiser to hold the loose fibres in. The wool is much much more economical with fuel,ligher, easier to fit and repair. As long as you don'tdo too much welding in it then it lasts for years and years (borax will eat it quickly, but you can put a cast/brick floor in to catch it). Generally a gas forge works well with 2" thick lining, but I've got 4" in one simply because the wool to bulk it out was cheaper than the gas I was burning in the huge space!