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View Full Version : Couple of Q s ... for the engineering types - spark testing steel?



rsser
28th July 2007, 12:59 PM
I read somewhere that you can tell the difference between carbon and HSS by the colour of the sparks ... can anyone confirm? What are the colours?

Plus I've just mounted a new grindwheel - 5/8 bore on a 5/8 shaft, only there's a bit of slop. I laid a narrow strip of alum flashing along the shaft while slipping the wheel on. Trued the wheel and it seems to work .... but is it likely to last?

Advice appreciated :2tsup:
.

Gil Jones
28th July 2007, 01:05 PM
Yup, Ern, the HSS gives off redish-orange, ball-type sparks; and carbon steel gives off much brighter and whiter exploding sparks. I am looking for the data, and will post it when i find it.
edit 1: (check your email)
To test the suitability of steel on the spot try punching, filing or hacksawing it, you'll soon know if it is hard enough because the file will skate off it without cutting it. Back in your workshop you can use a spark test to get an idea of the composition of the steel. Touch a piece of mild steel on your bench grinder so you get a stream of sparks out into space. Take a good look at the sparks and compare them to the sparks you get from the tip of a file or an allen key (both are high carbon steel). Notice how carbon steel produces a lot more sparks than mild steel and they are much finer and whiter and they explode much more in flight. The more little explosions, the more carbon in the steel.
Basically, any steel you want to use for tool making must make sparks exactly like those made by the allen key. Just for fun check out the sparks from the back end of a drill bit or from your best gouge (high speed steel). HSS produces very few sparks, they are deep red in colour, they don't explode at all and they fly in curving paths.

rsser
28th July 2007, 01:13 PM
Many thanks Gil :)

... have just been asked by an old-chisel dealer for whom CS is stock in trade but has come by a set of Record turning tools.

OGYT
28th July 2007, 01:55 PM
I've heard Gil's description once before, somewhere, and I've tried to look at the sparks, and can't even tell one from the other... to me, it either sparks or it doesn't... sparks is sparks, to me. :D Far as I know, I've never seen one explode.
I'm not disputin' the facts; I'm just indicating that I guess I'm too ignernt to read the sparks. :)
As far as the wheel's concerned, the time to worry would be if it ever slipped on the shaft. A thinner piece wrapped around the shaft might be more conducive to longevity. I'd be interested to know if a strip of paper of the necessary length, CA'd as it's wrapped, might enlarge the shaft enough to take out the slop. Might not be enough slop in it to make a complete wrap of the shaft... I dunno. Just jabberin'...

DJ’s Timber
28th July 2007, 03:10 PM
Here you go Ern, Spark test (http://www.aussieweld.com/arcwelding/page15/chart2.gif) and a Magnetic test (http://www.aussieweld.com/arcwelding/page14/chart1.gif).

As for the shim in the grinding wheel, it should be okay as most of the wheels tension is taken by the washers and nut. That's why they have the paper on the wheels, which is for mounting purposes not for identification

rsser
28th July 2007, 03:31 PM
Well we just played around on the grinder with the CS and HSS and the spark colour was a good indicator. Also the rate of removal. Thanks all.

And thanks for the grindwheel diagnostics. The main reason for replacing the pink wheel was that I could never get it to stay true. A 1" wheel it was with 3/4" nylon shims with half another set butted alongside. That may have been the problem, or it may have been flexing in the cheap Chinese tool platform. I tried various methods to deal with the flex but no luck. Got sick of the wheel in any case as the bond was hard and it glazed over quickly.

One thing of interest in Lee's book on sharpening (from memory) is to set your pointed diamond truing tool aiming slightly downwards to reduce the chance of shattering it against the oncoming wheel surface.

Al 'jabbering' is AKA as thinking out loud or speculating verbally ;-}

hughie
28th July 2007, 04:27 PM
And thanks for the grindwheel diagnostics. The main reason for replacing the pink wheel was that I could never get it to stay true. A 1" wheel it was with 3/4" nylon shims with half another set butted alongside. That may have been the problem, or it may have been flexing in the cheap Chinese tool platform. I tried various methods to deal with the flex but no luck. Got sick of the wheel in any case as the bond was hard and it glazed over quickly.
Could be that the wheel is from Taiwan, such being the case your shaft is most likely metric and wheel bore imperial... and some slop will be the case....:U




One thing of interest in Lee's book on sharpening (from memory) is to set your pointed diamond truing tool aiming slightly downwards to reduce the chance of shattering it against the oncoming wheel surface.

Also it will stop the diamond from digging in, causing you to lose a great chunk out of your wheel especially after truing it up and heart failure..:U

rsser
28th July 2007, 06:19 PM
Nothing wrong with a good heart workout Hughie ... whether in or over the bed ;-}

.... moving right along now ... no, it was a Norton pink wheel. Got it as a Carbatec special way back when, when folk talked of advances etc etc. This wasn't one of those as it happened.