Thread: So Who Uses Carbide Tipped Tools on Small Lathes?

I have a few carbide toolbits that I sometimes try on my Hercus lathes. Usually, I change over to HSS for final cuts, as a nice smooth finish with carbides has eluded me.

Jordan

how fast does your lathe spin? do the tip cutters have a very much radius.

there is a few great posts on this subject on this forum.

I think part of my problem with carbides is that I can't tell when the tips are worn. With HSS wear is clearly visible, not so obvious with carbides. Then again, even with a new point I don't get the performance that HSS provides. I'm sure that some patient study of the whys and wherefores of carbides would help, but HSS gives me what I want, so I don't see a pressing need to spend the time.
I guess newcomers to metal turning are attracted to a solution that avoids having to do any grinding? That's understandable, but once a few concepts are grasped, it's not difficult to make a workable HSS toolbit.

Jordan

In regard to speed I calculate the "ideal" speed for the carbide but find due to my limited speeds to choose from the closest speed is too low. So therefore I go the next highest speed and although that tends to be quite a bit higher it seems to work really well.

Cheers

Justin

The proof is in the pudding so to speak. If it works, do it. I know I am a bit late but had to include my experience.

When I first got my old second hand about 16 x 32 Nuttall lathe I bought a set of carbide tip lathe tools in a nice wooden box. The did not work very well. First there are lots of different looking tools that all seem to do the same thing. Triangle and square tips, same job. 9 tools in all but only about 5 different uses and I don't have much use for 3, 20mm square, short boring bars.

The tips chipped easily. I finally discovered I had an issue with stability of the tool post due to 2 reasons.
1. Loose cross slide ways. (Worn in middle)
2. A Previous owners crash caused damage to compound slide angle clamping rear bolt T-slot. (Circular) Cracked.

I fixed number 2.

The point is that I started using SECO tool holders and tips because of these problems and they worked much much better. After fixing number 2 problem I tried the cheap ones again and they also worked better. Stick to the good quality tool holders, and tips especially if there are stability issues such as with a smaller lathe.

The tools cost a lot more to buy but the tips are not that much more expensive and they are far better.

Dean

Originally Posted by Oldneweng

The proof is in the pudding so to speak. If it works, do it. I know I am a bit late but had to include my experience.

When I first got my old second hand about 16 x 32 Nuttall lathe I bought a set of carbide tip lathe tools in a nice wooden box. The did not work very well. First there are lots of different looking tools that all seem to do the same thing. Triangle and square tips, same job. 9 tools in all but only about 5 different uses and I don't have much use for 3, 20mm square, short boring bars.

The tips chipped easily. I finally discovered I had an issue with stability of the tool post due to 2 reasons.
1. Loose cross slide ways. (Worn in middle)
2. A Previous owners crash caused damage to compound slide angle clamping rear bolt T-slot. (Circular) Cracked.

I fixed number 2.

The point is that I started using SECO tool holders and tips because of these problems and they worked much much better. After fixing number 2 problem I tried the cheap ones again and they also worked better. Stick to the good quality tool holders, and tips especially if there are stability issues such as with a smaller lathe.

The tools cost a lot more to buy but the tips are not that much more expensive and they are far better.

Dean

Totally agree regarding the proof is in the finished job.

I use the charts and calculations to get a ball park speed and then go by feel.

If it feels ok and the surface finish is what I want then that's the best speed and feed. It's actually fairly intuative.

Cheers

Justin

Originally Posted by Jarh73

In regard to speed I calculate the "ideal" speed for the carbide but find due to my limited speeds to choose from the closest speed is too low. So therefore I go the next highest speed and although that tends to be quite a bit higher it seems to work really well.

Cheers

Justin

Inserts need to run much faster than HSS . If the spindle speed is too low then the insert tip will overheat or just not give a good finish. Finnishing times have risen 800% since the start of HSS use.
Small lathes need positive rake inserts and small radius points.

Originally Posted by Jarh73

Totally agree regarding the proof is in the finished job.

I use the charts and calculations to get a ball park speed and then go by feel.

If it feels ok and the surface finish is what I want then that's the best speed and feed. It's actually fairly intuative.

Cheers

Justin

The problem with that method is if you start a carbide insert too slow it does not take much to rub the point and damage it at a slow speed. By the time you decide that the speed needs to rise it may be too late and the insert will have a shortened life.

Originally Posted by Retromilling

The problem with that method is if you start a carbide insert too slow it does not take much to rub the point and damage it at a slow speed. By the time you decide that the speed needs to rise it may be too late and the insert will have a shortened life.

Fair point but in my breif experience and my limited number of speeds available you realise that its too slow before you even start cutting.

On a side note the carbided tipped boring bar leaves fantastic finish and looks very professional. My Step Father manages a injection moulding and CNC maching business and he has cast his eye over various items I have machined and he thinks the surface finish i get is pretty good. (of course he could be biased)

Cheers

Justin

Originally Posted by Jarh73

Fair point but in my breif experience and my limited number of speeds available you realise that its too slow before you even start cutting.

On a side note the carbided tipped boring bar leaves fantastic finish and looks very professional. My Step Father manages a injection moulding and CNC maching business and he has cast his eye over various items I have machined and he thinks the surface finish i get is pretty good. (of course he could be biased)

Cheers

Justin

If you select a suitable surface feet per minuet right from the start then there is no problem . What I was talking about was when someone machines away at a very slow spindle speed for too long before recognizing that it is too slow. For a HSS cutter the worst that could happen is dull the edge or chip it and a regrind is needed but for a carbide insert it could reduce the working life of that point quite dramatical and they are too expensive for that. On most older lathes the spindle speeds are a bit on the slow side for more modern tooling and most new lathes the oposite is true. I have trouble on my lathe getting slow enough spindle speed for some jobs .
HSS cuts the steel but carbide inserts push the steel off. So you need some HP , spindle speed and a rigid setup to use them at peak effecientcy . Run them too slow and they just don't work well . Large rigid lathes can use Negative rake inserts and gain some economy from using both sides of an insert and larger radius points but small low power lathes have to stay with Positive rake inserts and sharper points .

Originally Posted by Retromilling

...small low power lathes have to stay with Positive rake inserts and sharper points .

How small is too small for carbide tooling. I've got an AL 330, 900 BC's about 400kgs, is this too small, or are you talking about really small bench lathe weighing 80Kgs??

Even small lathes can run carbide,the results may not be impressive.

Generally carbide tooling (the indexable type 0 would be considered overkill in a blokes backyard.
In industry on manual lathes they work well,still not to there optimum.

Cnc machines are where they are best suited but tip life is usually noted by minutes.

In the backyard most blokes will get hours out of tips.

As long as the cutting tool is harder tougher than the material being cut theres no problem.

The only thing I would suggest is that you dont purchase the sets of several indexable tools.

They mostly seem not to be interchangable with industry standard and they also appear to have a fairly big nose radious,something that you dont want on a small machine.

Small machine in this instance would relate to HP,even some of these small machines have trouble with HSS.

An AL 330 should be able to run a solid Positive rake insert something like a TPMR 11 03 04 ( TPMR 221 USA ) for finnishing and TPMR 11 03 08 (TPMR 222 USA ) for intermittant and roughing with light cuts .
Or smaller inserts with center hole like a TCMT , TCGT, There is quite a few different applications like sharp turned up cutting edges for non ferrous in small inserts .
The main thing is identify that the insert is the right size for the tool and that it is a positive rake and the tip radius is suitable . Anything with N in the code is most likely a Negative rake insert . Then if you have a choice choose the correct grade of coating for the metal you want to cut. In general most coated carbide tips will turn ordinary steels including free machining stainless fairly well.
When choosing an insert for Aluminium go for the one with the sharpest up pointing edges as it will behave more like a HSS steel cutter and have less trouble with edge buildup .
If the lathe is light then don't overtax it with hard materials and heavy cuts and run the inserts as fast as possible. The limiting factor is usually swarf control . When I run my lathe flat out at 2000 RPM the inserts cut like crazy but the chip control can be darn right dangerous on long chipping steels as I don't have the correct chip breakers at the moment . So I have to back off the speed to 1200 and then the chip is a bit more manageable .
Not ever job is so well balanced that you can run at those speeds anyway , especially intermittant cuts.