Thread: Lathe fluff cuts in steel - what tool?

G'day Chris, mate I'm honestly a little over having to fight to get everything over the line here with you. I'm not interested in arguing with you every single time a subject comes up. In this case I suggested you go out with a triangular shaped tool, and run the tool both ways to see how that makes a difference to the work deflecting. I encouraged you not to believe or trust what I say, nor what the World's largest insert manufacturer says, and instead prove it for yourself. Once you see it you will understand what's behind it. You instead dragged out your calculator. Your choice, but I'm a bit over it to be perfectly honest.

Likewise if you don't understand that chatter can be caused by the either the tool deflecting or the work deflecting, then I really have nothing more to say, that's just basic lathe work. I stated that I was testing those tools based on what I was doing, not what the OP was doing, and at the 3 mm work I was doing things like work deflection really are a big deal and it's plain to see it with by eye. I thought I'd just share what I found for the benefit of others. I then stated that it may not be such a problem with larger diameter work, never the less, with long overhangs and thin pieces, yes the work can still be deflected. On ANY lathe Anyone who has done really close tolerance work would have struck that already, and I'm frankly surprised that a person of your experience haven't seen this and instead tries to claim it doesn't courtesy of a calculator.

You're entirely free to do with your life as you please. But I'd respectfully suggest that there is no substitute for actually doing this work, and not just punching numbers in to calculators and looking things up on Google. While you were punching numbers I was bringing 3 mm shafts up to better than spec, as they turned out to need to be 2.97 and I got worst case of 2.95 mm. But hey, I guess what would I know.

Variant, I went through the same problems as you and I had trouble grinding HSS cutters so I bought the Diamond Tool holders from Eccentric Engineering and have not looked back. Some on this forum will argue I did not try hard enough, but as an Electrician who drives a computer for a living, is a part time welder, part time woodturner and part time crew chief on drag racing cars both here and in the US, I get by the best way I can. I am partially color blind and have a sight defect, but each day is a blessing.
Rgds,
Crocy

Originally Posted by Pete F

G'day Chris, mate I'm honestly a little over having to fight to get everything over the line here with you. I'm not interested in arguing with you every single time a subject comes up. In this case I suggested you go out with a triangular shaped tool, and run the tool both ways to see how that makes a difference to the work deflecting. I encouraged you not to believe or trust what I say, nor what the World's largest insert manufacturer says, and instead prove it for yourself. Once you see it you will understand what's behind it. You instead dragged out your calculator. Your choice, but I'm a bit over it to be perfectly honest.

Likewise if you don't understand that chatter can be caused by the either the tool deflecting or the work deflecting, then I really have nothing more to say, that's just basic lathe work. I stated that I was testing those tools based on what I was doing, not what the OP was doing, and at the 3 mm work I was doing things like work deflection really are a big deal and it's plain to see it with by eye. I thought I'd just share what I found for the benefit of others. I then stated that it may not be such a problem with larger diameter work, never the less, with long overhangs and thin pieces, yes the work can still be deflected. On ANY lathe Anyone who has done really close tolerance work would have struck that already, and I'm frankly surprised that a person of your experience haven't seen this and instead tries to claim it doesn't courtesy of a calculator.

You're entirely free to do with your life as you please. But I'd respectfully suggest that there is no substitute for actually doing this work, and not just punching numbers in to calculators and looking things up on Google. While you were punching numbers I was bringing 3 mm shafts up to better than spec, as they turned out to need to be 2.97 and I got worst case of 2.95 mm. But hey, I guess what would I know.

Pete, why are you making up all that nonsense? The OP just wants to take off 0.03mm form his 10mm shaft. I guarantee that he can do that by simply putting a DCGT-alu insert in his toolholder. This is a picture how these look like:
Wendeplatten Aluminium DCGT 070204 ALX TK 1210 | eBay

Originally Posted by cba_melbourne

Pete, why are you making up all that nonsense? The OP just wants to take off 0.03mm form his 10mm shaft. I guarantee that he can do that by simply putting a DCGT-alu insert in his toolholder. This is a picture how these look like:
Wendeplatten Aluminium DCGT 070204 ALX TK 1210 | eBay

Then use a piece of emery! I didn't "make up" anything, while you were at your calculator I was at my F%^&ing lathe DOING IT! I passed on my "nonsense" as it was what I was doing at the time and I thought it may assist other members.

All of this "nonsense" as you call it, is because of this statement by you:

The rule is this: you cannot take a depth of cut that is less than the cutting edge radius. Note that is NOT the tip radius that matters here - I am talking about the sharpness of the cutting edge. Or in other words, not if the knife tip is pointed or rounded, but how sharp the blade is.

That is, quite frankly, complete crap. Please provide any credible source that supports your "rule". Now while anyone who actually uses a lathe would know that's crap , there are a lot of people on this forum who are reasonably new to machining. Yes, absolutely, sharpness is critical, as I keep reiterating, but so is the geometry of the tool to ensure the work isn't pushed away, and part of that geometry is the nose radius. Did you dust the cobwebs off your lathe and actually try what I suggested? Run a triangular tool one way, then back the other and compare the deflection for yourself.

With that I have to say I'm done with this! I've tried to pass on what I was actually doing at the time, on my lathe, as it was reasonably similar to the OP's question and hope it may have been of some assistance to somebody in future. However I'm not going to waste hour after hour illustrating how these seemingly endless streams of bizarre statements of "fact" from one person in particular are just not true. ...and it doesn't seem to matter what the subject is, out pops another bizarre statement This is time that I would much rather be enjoying making things than swapping out tools, or researching credible industry sources to support. So Chris, as my little niece would say ... "whatever!"

Hi Pete,

I stand by that rule:

"The rule is this: you cannot take a depth of cut that is less than the cutting edge radius. Note that is NOT the tip radius that matters here - I am talking about the sharpness of the cutting edge. Or in other words, not if the knife tip is pointed or rounded, but how sharp the blade is."

It is also what Harold Hall suggests. I highly commend to you his "Workshop Practice Series #34" as today's bedside read on this subject.

Also, always keep in mind that the Original Poster just wants to take off 0.03mm from his 10mm shaft. He did not ask how to change seasons or turn Lead into Gold. So we should aim at getting a reponse to his question. We got a few good answers together, use DCGT-alu inserts in his existing toolholder, or use a freshly sharpened HSS, even the tangential tool was offered as a solution making sharpening simple and foolproof. The key is always tool sharpness of the cutting edge and positive geometry. A tool tip as rounded as possible helps getting the best surface finish. Whilst tool shape is utterly irrelevant at such shallow depths of cut.

If the information supplied by the OP is correct he is trying to remove .03mm from a 10mm shaft over 100mm, that is .015mm (.00059") per side. I doubt that the shaft would be running concentric within these limits at each end and in the middle to allow full clean up on a lathe anyway, I would stuggle to do this on a cylindrical grinder. So lets be realistic here and just recommend the use of some wet and dry paper backed up by a nice flat piece of steel, I use 400 grit and a little WD40 for this purpose with excellent results usually within a couple of tenths.

Polish it with emery.
Using carbide would leave an undesireable surface finish.
And you can machine a depth of cut at less than the nose radius and achieve excellent results.

Given the vigor in this thread, I thought I had best respond with the results. After all that I got my cut fluffed. I might have even learned something in the process. The shaft now sits at a nice 10mm with a deviation of +.003mm along the length. I achieved this with the "high positive rake ally tips" as suggested first by Ew (a hair trigger). I was surprised I did not wreck the part. The finish was not as nice as with the Mitsubishi steel inserts (the shine!). The AL tip performed well with fluff cuts. I found that when the shaft deviated (slight taper towards the chuck), I wound the carriage back towards the tailstock, seeing it take off the lightest dust and checked with the mic. Then I did a few 1/3rd the way along the shaft slow runs without adjusting the cross slide, and watched it just dust. That is how I ended up with the good uniform size.

IMG_3531.jpg IMG_3530.jpg

Originally Posted by variant22

IMG_3530.jpg

Where did you get that blue PB scraper from?

Originally Posted by cba_melbourne

Where did you get that blue PB scraper from?

They came from Michael Merta - A nice guy to deal with. Much like Jens-Putzier (where the Hazet came from) - the Germans really know service.

Amazing result Variant, what lathe were you using? Who needs a Hardinge or other high precision machines hey.

Originally Posted by Techo1

Amazing result Variant, what lathe were using? Who needs a Hardinge or other high precision machines hey.

Yeah, I am very pleased! At first I was a bit shocked at how well things went. All in all, it is about as perfect as I think I could ever get it. I reckon it was about 98% luck and 2% skill on my part.

I am running a near new AL960b (Taiwan). I could still do with a Schaublin however..

Originally Posted by variant22

They came from Michael Merta - A nice guy to deal with. Much like Jens-Putzier (where the Hazet came from) - the Germans really know service.

Thanks. I am a big fan of all PB tools.

Originally Posted by cba_melbourne

Thanks. I am a big fan of all PB tools.

Aside from the picks, I have a couple of sets of their screwdrivers. They grip extremely well. Some screwdrivers tend to twist out but these things really grip.