Author Topic: Proper application of cutting force!!  (Read 5957 times)

Offline SPiN Racing

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Proper application of cutting force!!
« on: January 30, 2012, 09:06:41 AM »
Morning all,

So.

I have been working on spacers for the front wheels for my race car.

I will start a snip/thread on them elsewhere goinginto more detail. BUT.. Picture if you will a chunk of steel carved via torch from the side of a Cold Asphalt milling machine that was scrapped. That is 1.5 inches thick.

I bored a hole in the center of it, that had a shoulder.
Then made a arbor for it, and then deftly mounted the slab that weighs prolly 40 pounds on the arbor.. and then chucked the beast into my handy dandy rotary table with motor drive!

Here it is in the chuck of the lathe...(serious hard axle steel was 2.5" diameter. Drilled a hole and a bolt pressed through it)


Then started it spinning slowlyyyyyyyy.. and fired up my .75 single sided indexed carbide end mill to clean up the high spots of the torch work around the perimeter.
(Here is a pic of it mounted Vertically.)


SO as its going around I realised this was toooo Slow.

SO I stopped.. and turned the rotary table vertical. (no pics sorry)

Then fed the end mill into the work at the TOP of the disk... so that it was cutting away from me.. and the work piece was turning towards me....

Now think of this...
The cutter enters the work about 1/4 inch into it.. and takes a small cut, and then turns AWAY from the rotary table.. (the table was to the left)
SO as it chatters away with little smoking chunks of hot metal and slad from the torch work, its chomping with a bit of vibration as that cutter will give.. but i am taking a TINY cut.

I set it to rotate slowwwwly.. and after about 2 HOURS of slowly rotating and cutting the high areas down so its now only high in about 25 percent of it... I kick off a cut.. flood cooling is running.. and I turn my back, step 3 feet away to get a drink.. and hear a HUGE KABANGGGGGG

Leaping nearly 60 feet in the air I spin around to figure what happened.. as the sound of cutting had stopped and the mill was free running, as was the rotary table....
I realise that the force of the mill slowly thudding away at it.. had caused the arbor to slowly wiggle itself and pop OUT of the jaws of the rotary table chuck!!!

After taking a hour or 2 break I went and changed the direction of rotation and side I was cutting from.. so that it was cutting against the disk, but the force was pushing the disk INTO the face of the rotary table..

Huge improvement.. but still spooky.

So I decided I was chicken and did this instead...


As you can see it was pretty nasty stuff...



Moral of the thread....

Dont just think about conventional milling.. or climb milling... Thing of the forces of the cutter against the work! Is it going to loosen the work because of the direction its biting into it??
I do now!
SPiN Racing

Offline velocette

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Re: Proper application of cutting force!!
« Reply #1 on: January 30, 2012, 12:53:04 PM »
Wow you have set your self a task here. Any cutting with an Oxy-Acetyline  torch will produce a thin layer of Carbon Enriched Steel
read that as "Case Hardened".

This is best removed by grinding off with a disk grinder or bench grinder until all the black scale - slag is removed.

Not knowing the composistion of the steel can lead to problems. Coming from machine that has to resist abrasion and corrosion it could well be work hardening.

NOT ideal for machining

I find it hard to understand that you would use "Steel" for wheel spacers on a "Race Car" why all that extra 'Unsprung Weight"


Eric   

 

Offline SPiN Racing

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Re: Proper application of cutting force!!
« Reply #2 on: January 30, 2012, 03:11:41 PM »
He he he
Well yes.. matter of fact.. the machine it came from was a monster. And yes the steel was ultra hard to begin with.. carbide only would touch it. And I could only do a 2 thou cut.. 5 thou once through into the softer material past the surface.

My rationale was this....
Wheel spacers used by the masses are most often made of aluminum.
These are drilled with 10 holes.. and are bolted to the hub.. with studs out of the other 5 holes.. that were pressed into the spacer.
As aluminum work hardens.. I have found that a lot of people have had them fail, and break in half at one of the holes.

So being "smart" I decided to make ones made from steel.. so that the material would have a bit of give to it without work hardening as fast as aluminum.. and not be so brittle.

However after spending a couple weeks of free time screwing with it.. I went and bought some 6061-T6 and zipped out 2 spacers in about 2.5 hours.
SPiN Racing

Offline Jonny

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Re: Proper application of cutting force!!
« Reply #3 on: January 30, 2012, 04:47:15 PM »
Heres me thinking you crashed the M300 cross slide with the job :clap:
I usually run out of travel on mine to centre line, one thing the L5 and 140 had plenty of.

Decent carbide cutters bull nosed or similar would eventually take them rough edges down, i have a few left of the Kenametal Top Notch that take intermittant cuts in hand.

Maybe i should start my own thread, i have recently had the D1-4 small chuck come adrift 4 times, its a common problem.

Offline loply

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Re: Proper application of cutting force!!
« Reply #4 on: January 30, 2012, 04:56:15 PM »
Do you mind me asking why you didn't you just grind it a bit to interrupt the hardening, then pop it on the lathe to turn true?

Offline SPiN Racing

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Re: Proper application of cutting force!!
« Reply #5 on: February 06, 2012, 01:52:50 PM »
Had the carbide cutter in there.. and it was very easily chewing away at it..

It was in the rotary table on the mill where things fell off.

It was the lathe that was really nice for cleanup once I got the nasty stuff chewed off it in the rotary table.

I shoulda used a angle grinder to clean it up.. but I didnt think it would be that bad... cough WRONG. :Doh:
SPiN Racing

Offline Jonny

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Re: Proper application of cutting force!!
« Reply #6 on: February 06, 2012, 05:55:08 PM »
Similar tips to these but bull nose was what i was thinking about. They take intermittant cutting, turned many tool holders down.
http://www.ebay.co.uk/itm/Kennametal-NR-3031R-K68-Carbide-inserts-lathe-grooving-CNC-/160719704016?pt=UK_Home_Garden_PowerTools_SM&hash=item256ba40fd0