Thread: Carbide tooling help !!

Jack, that was 38 dia @ 960 rpm (100+m/m). Feed .2 mm, doc 1.1 mm. Deeper cuts worked, shallower didn't. Try it with powerfeed. There's no way I could have hand fed that fast. And that was at the slower end of the range given: .17 - .45.

Thanks Bryan, I was running 38mm diameter at 600RPM. I'll up the revs and engage power-feed.

Did you use coolant?

No I don't have coolant set up.

Edit: But if I did I would use it for this.

Bryan,
I just checked the manufacturer's data and they actually advise against using coolant on FC, MS and even 4140. I had another go with a piece of 32mm MS using the power feed. Holy s**t, it absolutely tore thru the metal! I had metre long coils of dark blue swarf all over the place. 1200RPM, 0.1mm feed and 1-2mm DoC seemed to work well. The recommended 3mm DoC at 0.2mm feed just stalled the 260.

The finish was good, but not as good as yours.

I like carbide.

Yeah it's a bit scary when you're not used to it. I tried heavier feeds and they worked great but it was just too fast and too hot for me. I couldn't dodge the chips quick enough. Interesting that coolant isn't recommended. I thought I was doing it all wrong by working dry.

Edit: Metre long chips is not what you want. You may get them to break by fine tuning your settings. I'll let more experienced carbide users advise on that.

Increase your feed rate to get the swarf to chip,but do not exceed your nose radious,1200 RPM is ok but try around 800 RPM,try these at 2mm cut.

OK will do. Radius is 0.8mm. Am I right that higher feed equals rougher finish? What's the aim here- do I shoot for the minimum feed that results in swarf chips rather than coils?

Your feed rate is well under the optimum,the max you can run is .8mm.
.8mm tips for a 260 are a bit too big,if possable look for .2 or .4 mm tips.
What you should find is that if you increase the feed rate you may experience vibration .
Higher feed wiill not give a rougher finish as long as you dont exceed the nose radious.
For your .8mm tip I would suggest to try it on a .4/.6mm feed,you will probably find that this will possably stall your lathe.
If these are the only Nose Radious tips you have at the moment you will need to play with feeds speeds and depth to achieve a reasonable finish.

sometimes you can increase your speed to get the chips breaking.

i'd say a .6mm/rev feed on a hercus 260 would probably stall it.

usually my roughing feeds on large diametre jobs ( 200mm plus ) are about .2 to .3, depending on my set up, finishing about .1 to .15. speeds on this job get up to around 400m/minute, this relativly low feed creates a lot less force trying to rip the job out of the jaws, even with a 10mm cut

for small diametre work ( ie they have given me a peice of bar and i have a small overhang out of the chuck, full length grip on the jaws, very rigid set up, i run at the highest speed the lathe has ( 1350 rpm ) and up to a .5 feed, with 5mm deep cuts.

both these combinations result in chipping shavings, in fact i have a notebook with all my speeds and feeds for good finishes, getting chipping shavings etc that i have written up just from experimenting

i never rough with coolant ( except maybe on 15mm doc's at .6 feed )

always finish with coolant

my point after this rant is that you should just experiment with your speeds and feeds, try anything from .1 feeds and 500m/min speeds all the way to 100m/min speeds with a 1mm feed

and look out for those long stringy shavings, i copped a VERY thick VERY hot one to the face once and my face looked like it was attacked with a knife, not pretty

Received the carbide tools, tested the boring bars on a small job.
bored out a short piece of mild steel, from 20 to 22mm.
the bar is left handed, set the insert tip to center height e.t.c.
was not impressed with the results, the bars flex easily, tested both the 12mm and 16mm bar, must be vibrating as it constantly sqeels,
using the CCMT09T304 korloy inserts from CTC.

must be doing something very wrong, ran it at different speeds up to 650 rpm, still sqeels, feels like a blunt hss tip when cutting,
even a 0.5 mm deep cut causes the bar to visibly flex.

Originally Posted by lather

Received the carbide tools, tested the boring bars on a small job.
bored out a short piece of mild steel, from 20 to 22mm.
the bar is left handed, set the insert tip to center height e.t.c.
was not impressed with the results, the bars flex easily, tested both the 12mm and 16mm bar, must be vibrating as it constantly sqeels,
using the CCMT09T304 korloy inserts from CTC.

must be doing something very wrong, ran it at different speeds up to 650 rpm, still sqeels, feels like a blunt hss tip when cutting,
even a 0.5 mm deep cut causes the bar to visibly flex.

650rpm still sounds too slow to me for a start, I would have said about 1500rpm for that bore diameter in mild.

may test at higher RPM, though prefer to keep it on the low speed belt, had queried about carbide and speeds earlier in the thread, and assumed that 650 rpm would still give a reasonable performance, due to using the positive rake inserts.

it seems to grind more than cut, could the insert be the wrong type for boring, due to the downward tip angle of the boring bar, causing more of the upper lip of the insert to make contact when cutting or does the bar need to sit lower than center height ?

using the same inserts for all the holders, the insert was recommended for the boring bar.

The tip of the tool needs to be on centre.
You say you have a left hand tool,I take it you are running the lathe in reverse.

the lathe is run in reverse, the insert has a 7 degree positive relieve angle,
when viewed from the front of the bar, 1 bar angles downwards 10 degrees the other 12 degrees,
wouldn't this affect the overall cutting angle, as it has a 7 degree positive relief angle (when the top surface of the insert is in a horizontal position,same as when used in the turning tool holders),
the boring bar is angled downwards x degrees, doesn't this expose more of the upper tip of the insert into the surface of the material