Weee! first time machining Stainless Steel

[ImanCarrot]

And I was scared¬!

It was squealing like a stuck pig- 500 RPM, Manual Lathe, 0.1mm cut (0.2 on diameter) and only WD40/Water sprayed on as coolant hehehe...

Got the diameter to within 10 microns. I love making stuff

How come making things give me so much pleasure? Must be endorphins or summit.

Anyway, gave me an excuse to try out me new DeWalt safety glasses. I look way cool.

[end rant] lol

[Geof]

Originally Posted by ImanCarrot .....How come making things give me so much pleasure?.....

Because you are weird.....like all the rest of us.

Although a secondary reason might be that people buy the things we make which provides enough money to pursue other pleasurable activities...like drinking beer, etc.

[RICHARD ZASTROW]

I'll drink to that!!!!!

Dick Z

[DR-Motion]

What did someone mention beer?

I heard that all the way from over in the Glowball Warmthing forum.

Cheers

[big_mak]

mmm Beer!!!!!!

[BobWarfield]

The squealing is annoying and interferes with a good surface finish. It's a resonance effect. There's lots of things I would've tried to get it to stop:

- I have a variable speed on the lathe, so I'd crank it up a ways on rpms and then back down if that failed. It's real easy to do as you're machining if you've got the ability. BTW, for a 1" diameter, ME Pro (Mike Rainey's software to figure out feeds and speeds) wants about 1500 rpm on stainless.

- Crank up the feed. This was a hard lesson to learn because it feels scary to feed harder when things are in distress. Yet it was the biggest thing that made parting off work better for me. Obviously you've got to stay within reason and know your machine well, but I'll try that next.

- Change up the coolant. When manual machining, I use a set of cheap condiment squeeze bottles to hold various coolants in, together with a chip brush to apply the coolant. Keep a variety of coolants on hand, and experiment. I use heavy sulfurized cutting oil, WD-40, my way oil, and kerosene. All have their place. Aluminum likes thinner coolants such as kerosene or WD-40. Steel tends to like thicker coolants. Given that you were doing stainless, I'd have reached for the heavy sulfurized cutting oil first.

- Of course you have to look at stick out and tool geometry and so forth. You've got a pretty short part, so probably didn't need a steady or live center. But, if you were insistent on eliminating the squeal, they're worth a try.

- Which alloy? Lots of different with stainless allows. Remember the old machinist' saying, "303, that's for me, 304, she's a Who*** (rhymes with 4)".

- Did you work harden it? Stainless is nasty about that, especially when you take little tiny cuts like you were doing. Carbide is also funky about depth of cut. It's good to get in the habit of being able to know your machine's accuracy and foibles well enough that your finish pass can be 0.005 - 0.010" on a small lathe, or even more if you have decent rigidity.

- I can't see what type of inset tooling you're using, but different inserts have widely varying performance in my experience, especially on small lathes. That's why I keep several things on hand:



Note that I started with a 3/8" shank set of CCMT turning tools and then bought 1/2" shanks. The latter are DRAMATICALLY more rigid and cut down the chatter.

As I said, the squeal, or chatter, is a resonance. All these things I mention can affect the resonance. Experienced machinists even talk about putting led on a boring bar to damp or move the resonance band.

In fact, there are really sophisticated high end technologies that analyze the sound and tell you exactly what to do with your feeds and speeds to get rid of it.

Cheers,

BW

[ImanCarrot]

Many thanks for the replies. That is a LOT to think about and I'll certainly experiment with speeds and feeds etc. Thinking about it... it did make more noise when feeding slower- I was too scared to go faster It was also making more noise when I was machining towards the chuck than away from it (the tool was at 45 deg to the diameter).

Much food for thought, thanks for the tips!

I was using these little things- it says carbide on the box (apologies for the poor pics, my camera is on the way out I think)

[cjmerlincnc]

This might just apply to me but I though I might mention it as I was on the verge of tearing all my hair out, I cut 316 stainless quite frequently and use a tipped tool holder that has a 12mm shank, the largest I can fit in the toolpost. I was plagued with tool chatter (squealing) to the point of very bad chatter (leaving large spiral lines on the billet) with horrendous noise.

I spent weeks trying to reduce the problem which ended up as months with no result. I changed speeds and feeds, tool height, I tightened up the head bearings to a point that I lost alot of top speed on my VFD controlled spindle.

To cut a long stort short, An idea came to me to place a bit of bar longways under the tool holder right under the cutting end and wedged the other end on the saddle.

Immediatly all the squealing stopped and the tool cut properly. So experiment over and the problem seems to be that the actual tool holder was flexing.

I found an old file that was thin enough for a packing piece and cut it to fit under the tool holder to support the whole tool holder length and voila, problem solved.

The moral of this is avoid buying cheap no-name tool holders on Ebay.



Cheers.