Advice on purchasing a lathe parting blade & block?

[PatMiles]

Thanks for the input gents!

 

[linekin]

Never tried inserts, The T style is what I use. As mentioned rigidity is key which is why I prefer a tool post over the wedge holder on the Aloris holders. Only stick them out as far as you need too.

Keith

 

[liljoe]

I bought a quality brand of HSS blades and it made all the difference. I will check to see what brand it is tonight, I can't remember.
I can part 304ss no problem with them. Lots of oil also.

Joe

 

[Canadian bushman]

When you crash with that, you can mess it up , too,,,, right there where the inset is held.............. The biggest mistakes people make are, tool tip below center, tool not square to the work, too much or too little feed/speed, blade sticking out of the holder too far, not parting as close to the work holding (chuck or collet) as possible......

Do not mis read this! This is the #1 mistake i see with machinist and part off tools.

Check with your tooling supplier when you order. My Iscar blades are supposed to be run 0-.007” ABOVE center.

Most tang grip inserted blades will give you fits below center. You will think its a rigidity issue but its not.

#2 mistake is feeding too slow. With proper sfm and feed. You should be able to bury that blade with no hesitating.

 

[carlsbad]

Your toolholder is too small for a 14x40 lathe. I use a CXA. for most parting a size 3 insert (about 1/8" wide) is used. I parting tool integrated into your toolholder like the aloris #7 will have less offset and be more rigid if you are rigidity challenged and tend to chatter. Many chinese 14x40s have the same compound as a 12x36 and that is their weak point. if you have a good heavy and wide compound you can use pretty much any parting too.

Most people try to part too slowly. Carbide like to move fast. I usually part at 300 to 500 rpms. Of course you can't do that if you get chatter and you'll ahve to reduce your speed.

--Jerry

 

[shortgrass]

I see several RPM numbers thrown out, but no mention of the diameter of the part being cut. Diameter of the part is part of the calculation to determine what RPM you should be turning. SFM x 12 divided by (diameter of the part x 3.14) Common steels, like C1018, can be cut with HS tooling @ 100-120 SFM (surface feet per minute) = RPM. If you use carbide tooling, SFM can be increased by 3+ times that of HS tooling. There are plenty of on-line resources for SFM recommendations for the material you are working with. Parting is one place where SFM really matters. You need to know how fast to turn the spindle for the diameter of the part you are parting-off/turning/drilling/reaming to get the best results.

 

[Canadian bushman]

I see several RPM numbers thrown out, but no mention of the diameter of the part being cut. Diameter of the part is part of the calculation to determine what RPM you should be turning. SFM x 12 divided by (diameter of the part x 3.14) Common steels, like C1018, can be cut with HS tooling @ 100-120 SFM (surface feet per minute) = RPM. If you use carbide tooling, SFM can be increased by 3+ times that of HS tooling. There are plenty of on-line resources for SFM recommendations for the material you are working with. Parting is one place where SFM really matters. You need to know how fast to turn the spindle for the diameter of the part you are parting-off/turning/drilling/reaming to get the best results.

Yup!
Very good advice.

With modern carbide inserts the chip should be rolling straight back and breaking off, maybe coiling up a lil inside the groove on a manual if your taking it easy.

Nice stream of flood coolant or an air blast will help chip evacuation and keep the part from getting too hot.

Slow feed as you approach center and .1-.2 dia is usually good to stop the spindle, remove the blade and break off the part.

 

[Gappmast]

The tool has to be on center and square with the part. I have good luck at 200 rpm using a acid brush to keep a little cutting oil in the grove for lubrication. It doesn't take a lot of cutting oil but you want the sides of the tool lubricated.

 

[GenePoole]

Flood coolant works nicely as well.

 

[Greg Y]

Not to dig up an old thread as a new guy, but one thing that really made life easier for me when parting was getting squared up with an indicator vs a fish or eyeballing.

Run an indicator base from the bed or chuck to the tool post. Sweep the face and get squared up.....takes no time and makes threading and parting go so much better.

I have good luck with hss AS LONG AS I make100% sure it doesn't cock in the holder and has plenty of clearance.

 

[Steve morgan]

That was where I messed up, not having enough relief.
I went back to the old school and lots of lube after trashing the insert style.

While all have an ear to this. I have a heck of time getting mine nice and square. Seems I always either go left or right with a taper or a crown.
Any tricks?
Jeff

Most times your cut off blade isn't square to the work when this happens. I cut off 4140 Heat treated bar today w,/carbide insert&coolant at 250 rpm.

 

[Steve morgan]

Do not mis read this! This is the #1 mistake i see with machinist and part off tools.

Check with your tooling supplier when you order. My Iscar blades are supposed to be run 0-.007” ABOVE center.

Most tang grip inserted blades will give you fits below center. You will think its a rigidity issue but its not.

#2 mistake is feeding too slow. With proper sfm and feed. You should be able to bury that blade with no hesitating.

Below center is death on a cut off tool. When bar grabs and climbs on top of cut off tool it's a hell of a wreck.

 

[Norton's Bench]

Use the widest insert that you can get without compromising the power of your lathe. Keep everything as short as possible. Also, never put the tool below the center line. That's the most encountered mistake. A three step process will follow. It will grab, it will break, third step is a instant BM.

 

[LVLAaron]

Carbide, on center and run it as fast as it will go. Keep the pressure on the tool. Most problems arise with too slow an rpm, off center tool, too light a feed, tool not rigid and no coolant or lube. For production work, I prefer the insert tools with flood coolant.

Run it fast and keep the feed going.

I am aroused.

 

[Greg Y]

The game changer for me and parting was to square the tool to the chuck with an indicator vs eyeballing square on the end of the work.

 

[therifler]

i grind my own out of high speed never had the need for carbide .however i do have some i made but never used them on gun work . for the industrial side of the business yes .

 

[Clark]

When I started parting 20 years ago on a 1960s Clausing lathe, I was a nervous wreck.
Now I have a 2009 Precision Matthews lathe and lots of parting tools. Lots of tool holders with cut off tools protruding different lengths.
The change in me, was "If it does not sound right or the finish is bad, stop and do something else".