lathe ???

kinda o/t but it pertains to machining so I thought it might be ok??
the kids in my shop cl*** are restoring an old montgomery ward mini-bike. we took the rear friction band drum brake apart and I noticed that the drum was quite out or round. I thought this would be a great exercise on the lathe for the kids. Got it all chucked up and when I put the tool to it (it was obviously WAY to fast) it through some red-orange sparks?? After I got the speed right it cut fine, but what kind of material would spark like that???

 

magnesium but more likely it was burning rust.

 

low carbon drawing quality steel

 

I've seen cast iron when machined too fast throw a dull red/orange spark. Of course since I can't see/feel your drum I don't know if I should even be throwing out a FERROUS suggestion around. If it is ferrous and cast iron the "chips" really won't be chips at all, but instead a power of sorts. If it were steel it would be able to be removed as an actual "chip". BTW CI plays hell on your cutters - result of inclusions mostly.

 

it is definately steel of some sort, not mag or aluminum - I'm anxious to turn the kids loose on it next hour. Most kids are scared of the lathe but the slow speed that we need to turn this I think will be a good intro for them...

 

My buddy ran a lathe for 40 or 50 years - 6 months short of retirement he lost his finger while polishing some 1/2" shaft. Those kids are smart to be cautious and even a little scared!!!

So what'd the chips look like?????

 

yeah we definately keep safety a top priority! we're gonna do it this next cl*** period so I can give some more info afterwards. It doesn't "powder" when cut, it definately "chips" or more accuratley "shaves", the bit I am using is kinda dull so the swarf (??) has been kinda hard to get a read on.

 

first safety lesson...use a sharp cutting tool

 

good point, I always try to make it clear to the kids that stressing a tool is a good way to have an accident...sharpening the lathe bits is definately something I need to get more proficient at.

 

cool...went great! the kids thought that was pretty neat! A handful of them took turns and we got it cleaned up, made some pretty deep cuts of .005 and then finished with a couple at .002, on some of the deeper cuts it did howl alittle and I've got the lathe down as slow as it will go, dull bit I am ***uming?? The long strands of shavings that came off looked like any other mild steel. Every kid in cl*** wanted a turn but we ran out of work, thats cool though, now I can come up with some other jobs for them!

 

Magnesium throws a bright white spark. ***anium throws a silvery spark. Iron and steel throws a red spark, color & brightness depends on alloys. Aluminum doesn't spark at all, of course.

 

Almost anything running way too fast will throw sparks,
and ruin the cutter real quick.

 

Just a thought another way to spark on the lathe is not have the correct clearance on your cutting tool, if it rubs it may have caused the issue.

 

thanks for the responses guys, all good ideas, I am pretty new to the lathe so I am learning along with the kids

 

to keep it from humming, on a brake lathe, We use a rubber strap with lead weights. You need to hav a good hold on the drum or rotor, or you end up facing it crooked. Brake lathes have an "axle stub" sticking out and use rounded cones that center in the race, good hold and better for turning drums than a regular lathe.

 

If you're all just learning you could consider some carbide tip cutters. They cost more, but you can flip them around a few times to a clean edge. We use them at work, but I only like to rough things down with them. You can get a good finnish, but you can't take really small cuts with them unless you sharpen them up on a diamond wheel, or siliconcarbide wheel.

 

Yeah, skim cuts don't work because most of those inserts have a very small radius on the edge.

Here's 4340, at full tilt boogie with a few thousanths deep cut... just for fun.