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Evan
12-06-2007, 08:24 PM
I was in the local job shop yesterday and the lead machinist was turning something that caught my eye. He was almost finished the cut so I only managed to snap a quick picture and a few seconds of video. I looped it a few times so there is something to see.

http://vts.bc.ca/pics3/hotchips.jpg

Video here, about 6 seconds, 850kb:

http://vts.bc.ca/misc/hotchips.wmv

I asked Jason what the heck the material is and he told me "no idea but it's harder than the hobs of hell". I asked him what it's off of and he said "no idea". They get jobs like that all the time where somebody brings in a piece and asks to have it cleaned up or whatever. Then you find out that it will eat your tooling just to earn a few bucks.

Fasttrack
12-06-2007, 08:31 PM
Evan -

You really shouldn't post videos like this. It will give newbies the wrong idea about machining and put them in potentially dangerous situations. You should be encouraging proper machine tool use and ettiqute.

:D :D

I really should have left the hatchet burried - i'm sorry

Neat video, i had some flaming chips last spring when i was working on my mini-bike transmission. The sprocket i was using had a goldish tint and it was hard as all get out. Had to use carbide with high feed and speed to get it to cut but the result was lots of heat and sparks. Left a good finish though.

tattoomike68
12-06-2007, 08:38 PM
That looks just like well drillers guide bushing and yes they are hard as hell ( I will bet im right on what the part it, any bets?). iv done a few dozen and the as cast skin is the worst, you will index the chips the few times.

For things that are harder than that I have used ceramic chips and run the lathe wide open, it looks like the 4th of july, white hot chips flying everywhere.

Ceramic chips are costly and dont like an interupted cuts but when the part is super hard it will eat it right of at .025" a pass. It leaves a mirror finnish on hard metal.

When I worked ay a foundry the jerks who worked on the pouring deck would throw pop can in the ladel wich ate up the carbon and the castings would turn super hard to the point of being un machinable.

The carbide tool holders would rub till they got hot and the casting would fly out of the lathe in peices. They were not little parts they were 350 LBS +

It was not funny at all!

jimmstruk
12-06-2007, 08:39 PM
Did you ask what sort of tool would live to finish that cut???

lane
12-06-2007, 08:47 PM
Just another day in a machine shop

tattoomike68
12-06-2007, 08:48 PM
Did you ask what sort of tool would live to finish that cut???

a good kennemetal chip will eat it but will need indexed every pass or every other pass.

If a guy with a well drilling company brings in a bushing and needs it machined its not going to be a part you will ever forget. after the second one you will be saying "not another one of those hard %#@#%#"

Carld
12-06-2007, 08:49 PM
I'm guessing he's using ceramic inserts. I worked part time at a shop that makes rollers for asphalt machines and sometimes we had to use ceramic to cut with and it looked just like that. Regular carbide won't last under those conditions. I burned regular carbide inserts up and Don handed me the ceramic and it cut like crazy.

tattoomike68
12-06-2007, 08:52 PM
The last time I bought ceramic chips they were $50 each. thats a high cost for 3 corners.

what else is funny is they dont weigh anything, they are as light as plastic. you would never mistake one for carbide.

Evan
12-06-2007, 09:01 PM
I didn't ask what he was using but I doubt it was carbide. As far as I know it doesn't do that, not for long anyway.

Fasttrack
12-06-2007, 09:15 PM
I didn't ask what he was using but I doubt it was carbide. As far as I know it doesn't do that, not for long anyway.


Oh it does it :D

That sprocket used up 1 and half carbide inserts to get done and the amount of material i took off was not significant, so no it doesnt last for long like that. But then these were $5 a pop inserts from china...

wierdscience
12-06-2007, 09:30 PM
That's a fairly common sight at work,I use Kennametal KC850 DNMG inserts to turn hard stuff all the time.They will rip the splines off a truck axle fairly easy.
I have found though that parts like he is turning there respond better at lower than recomended speeds provided the lathe is rigid as hell.Still .030" is a heavy cut above 50-52rc.

50-52rc in steel is childs play though compared to cast ni-hard,that crap is pure evil.Hard,tough and covered in sand inclusions,ohh joy:mad:

Davyboy
12-06-2007, 11:24 PM
I used to finish turn hardened A2 bushings, with ceramic inserts. .002 DOC. The chips would come off literally burning, as in the photo above. You could pick them up in your fingers and they would crumble like dry leaves. I figure the heat and large surface area just oxidized the carbon and iron quickly. Really hard stuff, we used PCD inserts poly-crystal***-diamond, at a premium cost of course.

Mcgyver
12-06-2007, 11:44 PM
some of this hard machining stuff is neat. guy i know get this wheels case hardened the finish machines them with a dead hard case using ceramics.

now all the guys with there first little lathe 'll be going, where'd my tool bit go? i machined it just like in the vid :D

jimmstruk
12-07-2007, 09:27 AM
Probably a dumb question, but why are these super hard jobs not ground rather than turned?? Just wondered. JIM

mochinist
12-07-2007, 09:42 AM
Probably a dumb question, but why are these super hard jobs not ground rather than turned?? Just wondered. JIMturning is faster

jimmstruk
12-07-2007, 10:07 AM
OK! Now I know thanks. JIM

bobw53
12-07-2007, 10:15 PM
If any of you guys are interested in ceramics, here is an article from Modern Machine Shop (back when they actually had informational content).

http://www.mmsonline.com/articles/049903.html

One of you guys said that ceramics don't like an interrupted cut, but thats just not true. Think about what they are doing, generating a ton of heat, and plasticizing the metal ahead of the cutter, and then pushing away the soft metal. In an interrupted cut, the insert cools when its not in the cut, so you need to simply go FASTER.

As for needing to index every pass, on a manual lathe probably, but 90% of all the wear you will see on a ceramic comes from entering the cut and generating the initial heat, if you could ramp the tool back and forth(CNC), and stay in the cut you cut for a long time.

I just find them fascinating and one of my most fun machining experiences was milling A286 with ceramics (after I figured it out). Ceramics are counter-intuitive, as in anything that you think you should conventionally do with HSS or carbide, do the opposite, and it works, in other words, if there is a problem feed FASTER, and spin it FASTER.

Spin Doctor
12-08-2007, 12:44 AM
I didn't ask what he was using but I doubt it was carbide. As far as I know it doesn't do that, not for long anyway.

IMO the tool in the pic and vid is most likely ceramic. One thing it definetly is not is CBN. Cubic Boron Nitride, not the Canadian Broadcasting Corp.

John Stevenson
12-08-2007, 06:13 AM
Most of my usual lathe tooling is based on the 16mm triangular TPUN inserts as they are readily available in different grades and are the cheapest to buy.

On offer they work out to about 1.00 UKP per tip say $2.00 given exchange rate but you guys can probably buy cheaper.
That works out to 30 odd pence a tip which is good.

I also do a lot of work that been laser cut and even laser cut with interupted cuts, this hammers the tips to hell, One pass, one tip, sometimes not even that on clean up.

When I get these jobs in because I use quick change tooling I set about 3 or 4 identical tools [ I make my own ]

http://homepage.ntlworld.com/stevenson.engineers/lsteve/hidden/Tools.jpg

in holders and use old tips with the edges reground by hand on a diamond wheel.
Nothing fancy just a wheel on the end of a motor.

It might sound jewish and mean but I can usually get 6 regrinds out of a triangular tip before it's totally wasted.

Once I'm under the skin then I can swop to a decent tip and finish.

Some largish plates can take 10 to 15 tool swaps before cleanup and that's a big saving.

Sparks and even the fine shavings actually burning as they are coming off is normal but you do need the horsepower to drive it.
The slightest slowing up and that's the tip gone.

http://homepage.ntlworld.com/stevenson.engineers/lsteve/files/discs.jpg

These are laser cut 10mm thick [ 3/8" ] with the centre bored and two 45 degree chamfers turned on for welding into heavy tubes.

This is done with two tools at the same operation, wind in and it bores then chamfers both edges at the same time.
This whole operation is done on regrounds tips, no new tips were harmed in the machining of these parts.

.

dalee100
12-08-2007, 08:33 AM
Hi,

What, don't you guys always have orange hot chips flying?:D I had to mill .500 off a piece of full hard S7 yesterday. One of my Chittlins' screwed up his off-set on a CNC. Nobody noticed until customer did.

Shoved my favorite 4" face mill into the K&T No.3 horizontal and had at it. .050 per pass @ 6"/min feed. two passes per edge, (TPG-432) and flip. It's purdy:D


dalee

neilw20
12-09-2007, 10:33 AM
The last time I bought ceramic chips they were $50 each. thats a high cost for 3 corners.

what else is funny is they dont weigh anything, they are as light as plastic. you would never mistake one for carbide.

If you use round ceramics you can get lots of good faces before they expire.
The flat ones can be turned over too. Try machining rock crusher cones (at over 1/2 a ton a piece!) That crap is realllllyyyy noisy...... Nice finish but. Real slow speed. Intermiitent cuts are a b!!tch.