Carbide parting off tool

[Brian Rupnow]

I have an AXA style toolpost from Little Machine Shop on my 10 x 18 Chinese lathe. I just made a bit of extra cash, designing, of all things, a Chocolate Bar Dispensing Machine!!! Now I'm thinking about one of those parting off tools that have a replaceable carbide tip. I have read good things about them on various posts. I stopped at one of my tooling suppliers in Barrie this morning, and he didn't have any in stock to show me, but said that for the blade, the carbide tip, and the holder, it would be in excess of $300, and he wasn't sure that if he ordered one it would fit my toolpost. Does anyone on here have some insight into these things, are they available for hobby machinists, is there a cheaper source, and will they fit my toolpost?----Are they really that much better than HSS???--- Any help would be appreciated.---Brian

 

[tvoght]

Brian,
I got a tool that works pretty well. You can get a glimpse of it in some parts of my Upshur engine build. In my latest posting I'm parting off a valve
with it. The holder 'with integral shank', which fits perfectly in an AXA holder, cost about 56 bucks from McMaster-Carr. The inserts are a little over 5 bucks apiece. I'm a big believer in HSS in the South Bend, but this carbide cutoff tool beats the HSS blades hands down. The inserts are a friction fit in the holder, and the holder comes with a little tool to pop them out.

--Tim

 

[tvoght]

Ok, I just checked, and what I have is a Dorian 'Shank Cut-Off tool holder RH' SGTHR9,5-2
It uses a SGTN insert.

--Tim

 

[jtrout13]

I much prefer HSS for parting tools, both on the mini-lathe and on the big SB Turn-Ado I use at school.

First, I like being able to grind and re-grind my parting tool as I see fit. I like to grind them slightly angled, depending on whether the part I'm keeping is in the chuck or is going to fall away, I'll slightly angle the grind one way or another to leave the burr on the waste piece. If I want to change the angles or I want to do some grooving, just a quick pass over the grinder and the tool's good to go.

Second, I find I can grind HSS much sharper than the carbide parting bits come. Also, unless you're really seasoned at parting off (I can part anything off on the big SB with no issue, but then again that machine's got the power to muscle through anything, so it's much more forgiving, the little motor on the mini lathe is a different story), it can be a chatter-inducing nightmare which is liable to chip a carbide tool easily.

However, if you're willing to spend the money, it certainly won't hurt to try it and it won't be worse than HSS so you're really got nothing to lose. Give it a try!

 

[Tin Falcon]

Brian when I did this stuff for a living I worked in a shop that did precision grinding We also made lots of parts on a CNC lathe IIRC 5hp motor/spindle. the obvious choice for that application was/is indexable carbide tooling. The machine did a lot of grooving with a parting tool. sometimes made scary noises. The tool was very reliable and I never had a problem with it unless I told it to do something stupid.
That said the only parting tools I use in the home shop is HSS. I have a 9" south bend and a mini lathe both fractional HP. carbide likes speed sometimes as much as 7 times that of HSS this speed requires power. home machines in general do not have 2 plus HP motors. and $300 is a lot for one tool.
Tin

 

[websterz]

I have worked in production shops on lathes up to 48" swing where big beefy carbide is the rule. Now that I am retired and running my own lathe (12x36) I have re-discovered the joys of a good HSS parting tool. I am not talking about the crappy Chinese flat blades. I grind my own out of 1/2" VASCO or Rex AAA, which ever I have on hand at the time. Somewhere I have a few pieces of Red Cut Cobalt stashed away for a rainy day. ;D I make the tools on my surface grinder and give them a slight hollow grind below the cutting surface for clearance. The tops of the tools get a shallow groove that runs the length of the tool with a Dremel and a cut-off wheel. The groove causes chips to fold inward and crumble, making for great chip clearance. Parting is the number one job I do on the lathe, up to 100 cuts a day in 9/16" 4140. I can run all day, cutting under power, without touching up the tool. Why pay for expensive carbide inserts when a $15 piece of HSS will allow me to grind literally thousands of cutting edges?

 

[shred]

I have an carbide inserted blade from Enco I use on my 12x36, The Made-in-USA blade-and-block they're always putting on sale (although not this month, oddly enough)-- much like the one Bogstandard and others have. It completely rocks over the HSS blades I suffered along with for so long. The one I have wouldn't fit an AXA toolholder however. I think you need the next size down from mine for that. Maybe if I was better at tool-grinding HSS would work better, but I'm very happy with it.

 

[ausdier]

Just my 2c
Go carbide but look around you will easily find cheaper than $300.

 

[Blogwitch]

Brian,

Ask 100 people on how to part off and you will get 99 different answers.

Buying the most expensive tooling available won't guarantee you will be able to part off any better.

During my working days, in the very beginning I started off with carbon ground up tooling, then HSS, quickly followed by brazed carbide. All had their own little foibles on how they did the job, sometimes, HSS beat carbide hands down, other times, the results were reversed. It was all to do with material and power of the machine, plus a lot of technique.

You can buy carbide tips nowadays that are just as sharp as HSS, I showed some CCGT02 tips in a post only a couple of weeks ago.
The range of tips I have picked up for my insert parting tool is awesome, from flat fronted to half round section, that allows the tool to be used for long range right and left hand turning, to those fancy 'curl the chip' types that are really good.

So what do I use now?

Any one of a dozen or so different parting off tools, some carbide tipped, some ground up from HSS blanks, it all depends on what sort of material I am cutting.
There is no such thing a a perfect tool for every job, just ones that cope with a wider range than others.

This is my most used one in action. I stated that this was brass in the video, but it was in fact a fairly free cutting bronze, you can tell how the chips come off it. One of these will cost at least the money you are talking about, plus some. But I wait my time on eblag and pick them up very cheaply, about 40 bucks.

[ame]http://www.youtube.com/watch?v=BG4qEw3eMcQ[/ame]


And yes, the bit I picked up was still a little hot, but not enough to cause a blister.

This is the range of tooling that the same tips all fit. I do have a few different ones.

[ame]http://www.youtube.com/watch?v=ZUwJXZEyctI[/ame]


John

 

[Jasonb]

Brian is your machine upto running a carbide parting tool. If you can't take off more than 0.010" on a 2" bit of CI then I think you will not have a ridgid enough machine to get the benefit.

J

 

[lensman57]

I have an AXA style toolpost from Little Machine Shop on my 10 x 18 Chinese lathe. I just made a bit of extra cash, designing, of all things, a Chocolate Bar Dispensing Machine!!! Now I'm thinking about one of those parting off tools that have a replaceable carbide tip. I have read good things about them on various posts. I stopped at one of my tooling suppliers in Barrie this morning, and he didn't have any in stock to show me, but said that for the blade, the carbide tip, and the holder, it would be in excess of $300, and he wasn't sure that if he ordered one it would fit my toolpost. Does anyone on here have some insight into these things, are they available for hobby machinists, is there a cheaper source, and will they fit my toolpost?----Are they really that much better than HSS???--- Any help would be appreciated.---Brian

Hi Brian,

I use an indexable carbide tip on my little Taig lathe. It works well. The tip in only 2mm wide at the cutting edge and mine is made by Glanze. It cost me about £38.00 in the UK.
I also like the P type hss tool that came with the Taig once it is properly sharpened.

Regards,

A.G

 

[Chitownmachine]

It all depends on the material you are cutting. If you are doing a lot with stainless steels, tool steel, or other hard materials, then you might wanna think about dropping some money on some carbide. BUT, if you are cutting everything else, stick with HSS. GRIND every time, and hone the cutting faces of the tool (I hone all faces of the tool, but thats just me). Sharp is the name of the game.

 

[Ogaryd]

Hi Brian,

Do to the rigidity of my machines I rarely use carbide, Super sharp HSS works the best for me.

If I had spare money I would look into indexable HSS, They look pretty nice.

Gary

 

[rkepler]

My lathe can take a GTN-3 parting tool, but often I don't care to lose that much material (.125 nominal) when I'm making small things from expensive stock. At those times I use a Nikole .040 (1mm) carbide parting tool. I think that if the Nikole inserts were cheaper I'd leave that up for anything in it's diameter range.

When the parting off length really matters I pull out the HSS .093 P-type blade and give it a fresh sharpen before parting. But it's less forgiving than the GTN carbide in a power feed and can wander if pushed too hard.

 

[rhitee93]

I use an AXA style in my old south bend. I don't use much carbide since I don't run at high speeds and feeds, but I do like this indexable cutoff tool. It fits in a normal tool holder, not the AXA cutoff tool holder.

http://www.use-enco.com/CGI/INSRIT?PMAKA=422-2880&PMPXNO=7908821&PARTPG=INLMK3

 

[Niels Abildgaard]

In the specialist section Mr Quinette has written about carbide parting of and I misused the thread to show my system that is still my favourite:Iscar Tangrip in special home modified holders.I have tried a lot of homeground HSS etc and will never be back there.Have made at least 10 parting offs on 100 mm steel and one on 125 mm alu plus myriads on smaller brass stainless etc.Have only spoiled one 2 mm insert (10 us dollars) trying to grove a 16 mm hardened piston pin.

 

[Brian Rupnow]

Thank you fellows, for all the helpfull answers. I think I was just being a Nervous Nelly, thinking about having to plunge cut the fins in that big lump of cast iron that I turned into a cylinder today. I actually managed, with a lot of breath holding, to cut all 7 fins 3/8" deep with no mishaps. Maybe I'll save my money and stick to my old HSS cut off tool for now.---Brian

 

[Blogwitch]

A good decision Brian. Only when you really need it should you look at investing money in excess tooling.

As you can see by all the replies, when I said you will get all different answers, that just proved my point about parting off.

Some people have no problems, others suffer all the time, even two people with the same machines and tooling will argue the best way to do it.

You have shown to yourself that you can cut fins with no problems, so build on that experience.


John

 

[Brian Rupnow]

Bogs---I'm just an old chicken at heart!!! ;D ;D ;D

 

[rake60]

When I was running a CNC turning center we used Iscar parting tools.

Nice design. If you destroyed one end of the blade you could flip it around to destroy the other end.
At $200 less the inserts it would be far above my hobby budget, but they sure preformed well!

You would program the surface speed for the tool and set a maximum spindle speed.
For 1-1/2" parts I'd set the surface speed at 250 feet per minute and the max at 2000 RPM.
I was nervous every time that parting sequence came up.
You would hear that spindle winding up to maintain the surface speed as the parting tool would
feed into the part. I'd program it to leave a 1/8" diameter area in the middle.
After the machine stopped, you would open the door, break the finished part off by hand and use
a burr gun to grind the nub off the end.

I did have a few tools fail in those years and occasionally a part would break completely loose at
2000 RPM. Thankful for totally enclosed machines with bullet proof glass windows.

Carbide doesn't really cut metal, it pushes it off with pressure and heat.
It needs speed and feed to do that.

At home I use P-Type HSS parting blades.

Rick