Smoke when turning steel with HHS bits

[dbb-the-bruce]

I imagine that this could be a somewhat subjective question with wildly varying responses.....

So let me start with some parameters:

I'm turning various steels on a 9" Southbend using hand ground HHS bits.
Diameters are reasonable ~2" or less
Steels are various, from unknown & store bought bolts to O1 drill rod.
I'm confident that my bits have proper shapes and relief and that they are sharp.

Initially, I would calculate speeds and feeds but now don't bother - do to my setup and comfort level, I found that I was typically well under suggested rates found in literature.

Recently I've been turning more steel, prior experience was mostly aluminum, brass and wood.
As I've become more comfortable with steel, I've been taking heavier roughing cuts - say .03 to .05 depth of cut at moderate rpm and feed. Because my lathe is not a monster lathe, I really can't cut that aggressively without bogging down or belt slippage (old lathe with flat belt run a little loose to crashes and jams less dramatic/damaging).

I try to turn dry and occasionally use cutting oil if it helps on the cut finish. Less mess. No coolant system - I doubt I need it.

So here's the question - If I'm dry cutting how much smoke should I expect?
Clearly any cut is going to generate some heat huge amounts of smoke means that the cut is likely too heavy. Adding oil will also increase the smoke - of course.
Based on the feel of the rough cut (sound, motor effort etc) and the temp of the part after (warmed up but comfortable to handle) - I don't think the cuts are too heavy.

So my conclusion is that if I'm getting clean cuts, and the lathe seems to be handling it, some smoke is to be expected.

What are your thoughts & experiences?

-Dave B

 

[macardoso]

Some steel has an oily scale when it is manufactured into barstock. This may even be dried and not greasy to the touch when you get the material. It will smoke, sometimes significantly when cutting the first pass on the material, but the amount of smoke in my experiences gets reduced significantly as you get to fresh metal.

Trust your experience on the sound of the cut, the color of the chips, the lack of discoloration on the tool, etc. to know if you are cutting correctly. Or do the speeds and feeds to check your work.

 

[dbb-the-bruce]

the color of the chips

Yeah, didn't remember that - but of course. I'm not making blue chips or burnt metal.

My motive is too determine if I should add a little air flow / exhaust. As a woodworker, I'm pretty cautious about the air I breathe. A couple of smokey cuts is no big deal but if I'm going to encounter it a lot it's worth as small fan and exhaust - I don't need to be breathing that all day.

 

[francist]

Not all cutting oils smoke the same, some are more, some are less. I used one called TapMatic Gold at the beginning and although it was nice to use it smoked like crazy -- great plumes of white stuff. Switched to Oatey, not so dramatic. Still smokes, but maybe half as much as the first. So play around until you find something you like.

-frank

 

[Tozguy]

I also have an aversion to breathing the smoke from a cutting operation on a lathe. There is a small fan mounted on the top end of the backsplash to blow smoke away from me. For the more lengthly cutting sessions I also run an exhaust fan to the outdoors. When things get really smoky I open the garage door.

 

[Mitch Alsup]

When I was turning this die wrench:
The chips were coming off the tool and instantly turning a straw color, then about 3 seconds later the chips had turned a marvelous blue color.
{All done dry.}

 

[Bob Korves]

If you want the helping qualities of a cutting fluid without the smoke, try Anchor Lube. It is a thick, water based product, easy to make thinner by adding water to it. Comes in a plastic squeeze bottle. On the mill and the lathe, I mix it right on the vise or the cross slide with an acid brush as needed. It is very good with stainless steel, better than the few others I have tried. Very good for tapping, too.

Edit: Anchor lube is still sending out free samples:

Anchor | Environmentally friendly metalworking fluids and compounds, plus lid securing clips

ANCHOR CHEMICAL COMPANY: Half a century of experience has produced a full line of drawing and stamping compounds and other specialty products that give optimal tool life and are safe for the environment.

anchorlube.com

 

[mikey]

So my conclusion is that if I'm getting clean cuts, and the lathe seems to be handling it, some smoke is to be expected.

Sounds about right, Dave.

Other than brass and plastics, I use cutting oils with HSS. Cools, lubricates and improves chip formation but it does usually smoke more, too. I use a fan and try to have good ventilation in the shop. I also use a respirator when a lot of smoke is being generated because breathing that stuff is not good for you. As Bob said, Anchor Lube is pretty good for most metals and doesn't smoke nearly as much; I'm using it more and more nowadays.

 

[MrWhoopee]

When I was turning this die wrench:View attachment 303108
The chips were coming off the tool and instantly turning a straw color, then about 3 seconds later the chips had turned a marvelous blue color.
{All done dry.}

Hey, I have the die stock at the bottom of the picture, came with a very cheap carbon steel metric tap & die set. Both handles broke off the first time I tried to use it. Guess I'll have to make one.

 

[Cadillac]

Does anyone else have a problem with anchor lube staining your machine? It darkens where it’s been sitting?? I use a oatey mix.