Form tools on the lathe

[Mayhem]

After melting several of my wife's fridge magnets, I decided to give up on that route. The temp crayons look interesting.

[dallen]

(01-29-2015, 06:31 AM)Mayhem Wrote: After melting several of my wife's fridge magnets, I decided to give up on that route.  The temp crayons look interesting.

reason I have a ceramic one stuck to the side of my gas forge, pull the part out touch it if it sticks its back into the heat for a minute or two longer. 

DA

[vtsteam]

Another reason color varies is how much ambient light there is. I've heated a part and let it cool to dark gray, turned out the shop light for a moment, and in the dark, it's glowing red. Blacksmith shops were traditionally darkened, in order to better read metal temps, and keep judgement consistent. There, welding and working do benefit greatly from distinguishing the different reds and oranges. Cameras also, will often show photos as much hotter red than the eye sees. So photos often fail to show the actual color a person would see at a specific temp.

Having said all that, I generally heat to what I think of as cherry (bright) red in daylight before plunging, wthout a magnet test, or any other. At least in my experience, as long as it's hot enough, and not to the point where you've melted or burned the part, it will harden properly. Having poured iron, to me, going too far happens more towards the orange/yellow range in daylight. But heated to what I think of as cherry red, I always get hardened steel after plunging. If you're new to it, testing with an old file after plunging will tell if you made it to full hardness, or copped out too soon. If you did the latter, just re-heat to a brighter red.

Out of the plunge, it's basically too hard (glass hard), except for some special purposes. To me the tempering is the critical color and temperature part, and that's where an educated eye (or crayons, or thermostatic oven or thermometer -- pick 'yer poison) makes a real difference. But that's much easier to judge because the color range is so wide for different tempers -- and it leaves a record on the steel itself, so you can see how well you did. Photos also are much more accurate for this range of colors, since they aren't photographing a hot object. It's easy to compare and learn the proper colors from photos in this case.

[Baron]

Hi All,

Just a quick tip, I often use cheap carbide router cutters as form tools on both the lathe and the mill.  I use the 1/4" shaft ones.  Here is a couple of pictures of a job I did recently.

       

[Shawn]

Thanks Baron, I happen to have a full set of router bits, will have to give this a try.

Cheers
Shawn