Need help with metal lathe!

[dliston]

Having a problem with my metal lathe. I can turn aluminum all day - no problems. Nice smooth finish - hardly needs filing to look great.

But I start turning steel and the tool chatters - really ends up giving me a bad finish - looks like I beat it with a punch. Do I have the tool set up wrong? Wrong speed? HELP!
/forums/images/graemlins/confused.gif
It's been too many years since metal shop in the eighth grade /forums/images/graemlins/mad.gif

Thanks,
Doug

 

[HomeBrew2]

Kindof hard to tell what we're dealin with without a pic or description of your setup ... is your tool bit point set just above the center of the piece you're turning? Is the tool bit pointed at an angle to your piece rather than at 90° (angled toward the headstock). What kind of steel are you turning ... "free machining" (leadloy) will look close to an aluminum type finish but anything else may not.

 

[MadReferee]

Try asking your questions in either or both of these forums. There are many home and professional machinists that can help. You will need to supply a little more info on the bit you are using and the machine setup.

Home Shop Machinists Forum

The Practical Machinist Forum

 

[gsxr1100]

I would say you have a bad tool, speed incorrect or feed incorrect. If these are wrong you could be surface hardening the metal.

 

[BubbaJr]

If it's an old lathe, it may have play in the spindle and/or chuck. You may also have the bit fastened too far from the cutting point, letting it vibrate up and down. Or your tool holder may be loose, causing vibration. Aluminum will cut a lot easier than steel, so you may not notice the problem while cutting aluminum. There are many reasons this may occur, but it's hard to diagnose from a distance.

Good Luck /forums/images/graemlins/grin.gif /forums/images/graemlins/grin.gif

 

[JerryG]

Do you have the correct relief ground?

 

[Kyle_in_Tex]

Chatter is caused by a lack of rigidity. A basic rule of thumb is to keep your length/overhang ratio at 4:1 meaning a 1" diameter bar can hang out of the chuck 4".

Your tool needs to be fairly sharp. Slowing RPM can help.

Or you turning or Boring the inside of a bore?

 

[dliston]

I'm turning - I'll try bringing the length down - that and the amount the tool is out of the toolholder.

Thanks,
Doug

 

[HomeBrew2]

Great point! If over the 4:1 ratio, center drilling and using a live-center in the tailstock should help.
Cheers!