Thread: Carbide Parting Tool

Bryan,

Good right up, any reason for not running coolant other than the mess it creates? :/

Does your spindle run double or triple bearings? I have been told that a lathe with tripple spindle bearings will have an easier time parting off due to increased rigidity?

FYI my Victor runs triple bearings on the spindle.

Cheers
Jon

Jon, yes mine has three bearings. The chatter actually made me wonder if they might need adjustment.

Apart from the mess and hassle of coolant, I'm afraid of corrosion and contamination. The sludge I found in the apron sump was evil.

Bryan, I just read your report.
I have just ordered something similar ( but smaller ) for use on my Forbes lathe. Its got me thinking if I should have bought it now.
I guess I will find out once I try it.

Bryan, do you keep the cutting area well lubricated? Assuming you're talking about steel, I find if I don't keep the part well lubed then it will chatter. I just use Tap-magic and make sure I just slowly drip it in as I'm infeeding so the blade is always cutting a lubricated surface. It's not like a flood coolant to take away the heat, the tapmagic just provides lubrication so a small amount goes a long way. I've tried dripping on other oils and also brushing them, they work better than nothing, but certainly not as well as the Tapmagic.

I'm sorry to hear the insert didn't help as I know they're expensive. But hopefully this technique will work for you too (assuming you're not already doing it of course).

Pete

Hi All,

I've been following this thread, but haven't really had anything to contribute, most of it's been said already.

I have been using one of the seco parting tools with seco inserts, can't remember chipping an insert, although I've had problems with aluminium gumming up and sticking sometimes.



I've also got some cheap HSS parting tools, but I like the carbide better.

One of these days I'll finish off one which uses power hacksaw blades.

Regards
Ray

Ray, could you expand a little on why you prefer the carbide?

Pete, I have used oil on and off. I use the Trefolex in a green spray can. I always find it seems to make the tool skate for a bit, maybe a rev or two, before it bites. I'm not convinced that's a good thing. Maybe I need more feed.

Trouble is, I don't need to part very often, and usually only once, so it's kind of hard to evaluate anything properly. If I'm purely testing I feel I'm wasting material. Possibly I should change that thinking.

Originally Posted by Bryan

Ray, could you expand a little on why you prefer the carbide?.

Hi Bryan,

I was hoping you wouldn't ask that,

Not sure really why I prefer the carbide, it works I guess, but that might be that I haven't spent a lot of fiddling with the HSS holder, and the HSS holder I've got needs a bit of work to sit properly in the QCTP, It has a slight tilt to one side so it mostly stays in the draw.

Thinking back, I think I got the carbide holder about the same time as the QCTP upgrade, and it moved up to the front of the queue, before that the HSS parting tool was used in the standard tool post and worked fine as I recall.

So, to stop waffling, I don't have a valid logical reason to prefer carbide over HSS, it's just historical accident. ( I don't normally turn hardened steel, if I did that would be a good reason)

Regards
Ray

Originally Posted by RayG

the HSS holder I've got needs a bit of work to sit properly in the QCTP, It has a slight tilt to one side so it mostly stays in the draw.

Regards
Ray

That's why you have a grinder my man

I popped mine in and ground the holder to the same angle as the tool, now it sits perfectly.

Pete

Bryan, I just popped down and quickly parted off some 1/2" steel at 400 rpm. I made a video to see if that would help, but I was trying to hold the iPhone with one hand, feed with the other hand, wave goodbye to our visitors, try to determine why one of my daughters was crying, and drizzle Tapmagic on, all simultaneously. Needless to say I don't think you'll see anything useful in it so probably no point in posting. However I could hear each time the tool was on the verge of chatter, so I stopped feeding, got some lube on it, then carried on as per normal.

Other than a really sharp tool on centre, I don't know what to suggest.

Pete

Interesting. Thanks Pete. I will do a little more testing and post results. Although this thread wasn't meant to be about my parting issues, I guess it may be relevant to others.

when i think about ive done lots of parting of on a victor. Only with hss though the only time i ever had trouble was when i didn't do it right. so you should be set mate.
when i have any trouble with parting i try the plunge and withdraw method .Instead of a constant rate of feed.

Originally Posted by Jon_77

Bryan,

Good right up, any reason for not running coolant other than the mess it creates? :/

Does your spindle run double or triple bearings? I have been told that a lathe with tripple spindle bearings will have an easier time parting off due to increased rigidity?

FYI my Victor runs triple bearings on the spindle.

Cheers
Jon

hello
parting off with a carbide is a bitch when you have a fair depth to get through. I find that I can run at about 1000rpm for k1045 70mm dia. (practically always run at 1000rpm for parting off) I always hand feed, and use water based coolant. I think the trick is to actually set your tool up so that you are above center height (slightly, and depending on depth) because these tools will load up your tool post on only one direction and that is down. Bring your blade out only as far as you need to. Load it up when parting off. I know its scarry, but getting the hot ribbons curling up on themselves shows you that you are feeding correctly. Considering parting is a fast process you shouldn't get much spray from your coolant.
The problem with parting off at a great depth is the surface fininh. get a nice finishon the od and then its poo bum closer to the center as it tears the steel. Usually end up with a tit too. Face off to clean up. It sounds backyardish but thats how I do it at work.

I did some more testing after adjusting my spindle bearings and thought I would add a post script, this time with some actual numbers. Of course the usual disclaimers about different machines etc apply. I grabbed a chunk of 40mm 1045 and turned it down to 35 so my tool would reach centre. It was quicker than drilling a hole.

I started at 260 rpm and the recommended .003" feed. I was using imperial because that's what the tips where spec'd as. The cut started to sound rough and I backed out just in time to stop a jam. I removed a hot compacted wad of chips from the top of the tip. Twice that happened. By the end of the cut the insert had chipped away below the edge. Must have happened on one of the nearly-jams. I hadn't noticed as I was looking at the top. It kept cutting though!

With a new insert I tried 400 rpm, same feed. Chatter. Reduced feed to 2 thou. Better but still the chip compaction. Tried hand feeding and got it cutting nicely. Found a feed that looked like my hand feed rate, which was 1 thou. At 400 rpm and 1 thou feed I did a complete cut without incident.

My next speed is 620 rpm so I tried that, still with 1 thou feed. It cut pretty well, with chips coming out the prettiest purple I've seen (little if any colour till now). But again it wanted to wad up.

That was where I'd had enough. I have no real need to go that fast. I guess it's handy if you can use the same speed you turn at. With that thought I went back to 260 rpm with the .001 feed. It didn't cut as smoothly as 400, and I once pulled out for a discretionary breather. So I found one notch up from turning speed (HSS) worked better. 35mm @ 400 is about 44 m/m - a tiny fraction of the suggested 190! What I didn't do was try to compare with HSS.

All cuts were dry, and there was no real difference in finish - not great but quite acceptable. The good news is the spindle adjustments have virtually eliminated the chatter. Just the occasional soft moan in the background. Which I think underlines the point about machine setup.

Manofaus, thanks for sharing your experience too. Could you tell us what sort of machine you're using? As you can see, 1000 rpm @ 70mm would be scary on mine. I wonder if coolant alone can make that much difference. I don't want to try that but I might try your above centre trick. How much above would you say - with the 35 mm example? And backyardish is what we're mostly about here. (Hope that doesn't put you off - it's great to have a few pros around.)

Bryan, did you try it with copious amounts of lube as suggested? I find as soon as the cut begins to dry out I'll start to get early signs of chatter when parting. When I get plenty of lube in there the pre-chatter stops and it will slice off no problem at all. I think I mentioned previously that I currently use Tapmagic and a few drops consistently dripping in does the trick. For this very reason, on my new lathe I intend running pure cutting oil. Soluble coolant would possibly be better, and I'm sure it's no coincidence it's used so much in industry, however I have various reasons not to go down that path. Inserts are expensive and you shouldn't be damaging them each time you part something off.

Pete