Parting Tool 101

[tclaunch]

I have an old vintage South Bend H10, and have been using Arthur Warner HSS .062" parting blades. Just to reduce time, I'd like to see if anyone has positive results using carbide on an old manual machine. Thank you.

 

[Walt Krafft]

Rigid setup is key to cutoff tools. Carbide needs a faster speed and feed making it even more important to have a rigid setup. How tight and rigid is your old machine?

 

[tclaunch]

I have learned on this lathe been using it since 2012. I have not run anything other. So nothing to compare to. A retired machinist called it a cherry. It has served me very well, but I don't want to over work it.

 

[X Count]

Some would say Iscar make some of the best parting tools and this is what I was recommended. I'm using a 3mm insert in a manual lathe and have been very impressed. Im parting all sorts of fun stuff like 316 stainless and PH 4150 and it's eating it. During cutting the insert is forced down into the strongest part of the holder instead of being "levered" out like many of the double ended inserts.

My machine is quite rigid but if I had a small machine I would run one of the 1.6 inserts. 416 barrel steel is really soft as long as you keep it cutting.


https://www.iscar.com/eCatalog/Family.aspx?fnum=2272&mapp=TG&app=0&GFSTYP=M&fr=1

 

[tclaunch]

I hope I can figure out which one and how to order, being my age has its limits....lol
Thank you for commenting and offering the link, quite helpful!

 

[linebaugh]

What speed do you run your HSS at? I run HSS and have not used a carbide yet but like you I have considered the same.
200 RPM with a reasonably sharp or freshly sharpened bit has worked well for me. I keep things wet with dark cutting oil and maintain pressure by hand or with the power feed.

 

[gunsandgunsmithing]

Speed is your friend with carbide Tim.

 

[tclaunch]

What speed do you run your HSS at? I run HSS and have not used a carbide yet but like you I have considered the same.
200 RPM with a reasonably sharp or freshly sharpened bit has worked well for me. I keep things wet with dark cutting oil and maintain pressure by hand or with the power feed.

I used the middle belt position in back gear. 70 or so fps. I got chatter way back when first attempting faster speeds
I can say it is an easy 10 minute cut the way I'm proceeding now on 1.250" barrel.

 

[Jud96]

We use nothing but carbide at Pierce, and same for the other shops I’ve worked at. We use 3mm wide Iscar inserts in our parting tools in the CNCs and our Clausing manual lathe at Pierce. I can get the part number Monday if you’re interested. On a manual machine, I run 240-350RPMs, and feed slow by hand. On a CNC, depending on material, I run 300-700RPMs with .002-.0035 IPR feed rate. I generally only let the part off blade stick past the tool holder 5/8” or so. That keeps it rigid but will let you part off up to 1.250” material.

Also, make sure your tool is on center and your tool post is square and actually cutting straight in and not on a slight angle. Lock your carriage down as well on a manual when parting off.

 

[59FLH]

Carbide CAN run faster, doesn’t have to.

 

[LVLAaron]

 

[mike mccormick]

The carbide parting tools are typically a chip breaker design, the additional speed makes it easier to break the chips.

 

[xr650rRider]

I like these with a GTN-3 insert in an Aloris BXA-7 holder.
https://www.shars.com/11-16-retrofit-gtn-cut-off-and-grooving-blades-bxa

 

[Walt Krafft]

I used the middle belt position in back gear. 70 or so fps. I got chatter way back when first attempting faster speeds
I can say it is an easy 10 minute cut the way I'm proceeding now on 1.250" barrel.

10 minutes doesnt make sense. I am doing it in about a minute with a hss blade. What feed rate are you using?

 

[Hal]

I read somewhere if you got chatter when parting off , try raising the cutting edge to just above the center.

Hal

 

[X Count]

Yeah if your talking 10 min it's doing a lot of rubbing / work hardening.

With carbide, depending on the diameter, I'm running about 250-350rpm and using power feed at about .001 from memory. Frees up a hand to apply cutting oil.

 

[X Count]

The carbide parting tools are typically a chip breaker design, the additional speed makes it easier to break the chips.

This doesn't matter as much with a parting tool because the plunge tool doesn't typically make a bird's nest. At low speed the Iscar sort of folds the swarf into a U shape, to give it clearance in the cut, and coils it up like a snail. Even at low speed the biggest snail Ive seen was about 1.5" diameter and they just quietly fall off into the chip pan.

 

[boltfluter]

Most high speed blades are horrible a set-up. They grab, squeal, and chatter. Basically everything except cut! I have a very nice Iscar holder for reversible carbide inserts. I can easily part off a 1" piece of barrel steel in 30 seconds or less. Carbide likes rpm's and pressure!. For me anywhere from 300 to 900 rpm's and a descent feed works like a champ. This tool just does not grab, and it makes parting off a non event. The key is that the insert is bolted in place and does not move. Period. Still on the same box of inserts I purchased 20 yrs ago when I purchased the holder. You just can't kill these inserts, as God knows I have tried! I can get a part number if anyone is interested.
Paul

 

[jackieschmidt]

I do a lot of parting, we have switched over to carbide parting tools for just about all parting operations.

Surface feet per minute is the key, that means RPM increases as size gets smaller.

As a starting point, when parting off 2.5 inch 316 stainless round bar to make steering pins, 500 rpm is about right with your typical carbine insert parting tool with coolant.

IMHO, when using older plain bearing machines such as your little South Bend, just stick with HSS and take your time.

This is what we use for most parting

 

[std7mag]

We use a Walters at work in everything that uses a parting tool.
HAAS, Mazak, Okuma CNC machines, and the 4 different manual machines.
We also use it as just an OD groover at times.

You can cut slower with a carbide. But if it took us 10 minutes to part a 1.25" piece of 4140, we'd be looking for a new job.

Key with part off tool is to make sure it is as perfect to 90° as possible. Otherwise they don't tend to last long.