Lathe parting

[Acsr]

This picture is of the parting tool I have been using. I need suggestions on what parting tool would be better because all I get is chatter!!!! I have adjust the speed of the lathe with no correction. Any and all suggestions are greatly appreciated. Thanks, acsr

 

[Terry]

The tip of your tool is broken.

 

[Preacher]

That aint gonna part nuffin.....

 

[mram10]

I bought these off eBay

4pc 3/32 x 5/8 x 5" HSS CUT- OFF BLADES, BEVELED

I part at 300ish rpm with lots of oil. I’m new, so I’m sure there are better ways, but this works for me

 

[carlsbad]

Assuming your tool is sharp and set at the right height, then parting is all about stiffness of your setup. Mram parting at 300 rpm tells me his lathe is performing very, well. If your lathe will part well, then the big problems are solved. When looking at a used lathe, parting is a key test.

Check your gibs, minimize overhang. If that doesn't work, try to find an experienced machinist to put eyeballs on it for you.

--Jerry

 

[ridgeway]

It's all in how you grind the HSS tool. You can get the one pictured to cut. I always grind a nice sharp up sharp on the blade so it cuts. 300 RPM is a bit fast for my taste. Kick her down to 200 or slower and feed in slow and consistent as possible...don't stop to regrip the handle...pleny of oil. You want a nice curl coming off the cutter...

 

[Roeder]

This picture is of the parting tool I have been using. I need suggestions on what parting tool would be better because all I get is chatter!!!! I have adjust the speed of the lathe with no correction. Any and all suggestions are greatly appreciated. Thanks, acsr

That set-up can be a problem if you are using a Chinese lathe. The tool hangs off the tool post and makes a less than rigid set up so much worse. Try to get your tool closer to the center line of the compound. Plus, use a properly sharpened blade, no wider than necessary, and do make sure gibbs are adjusted properly. The reason the smallish ChiCom machines have so much trouble parting is that the spindle tubes tend to be thin and the apron is small and light weight, so the set up can not be as rigid as it should be.

 

[Cloudrepair]

Just a hair below center on the tool.
About 110 to 150 rpm set on the slowest feed in so it is consistent and constant pressure. then a constant oil drip or brush on.
The feed that usually works great is about 3 ipm or about .0015- .005 per rev
this is all with a sharp tool at right hight and a fairly rigid setup
And it changes with diameter
This almost always works with small manual lathes in my experience if it doesn't there could be issues somewhere else
Ridgeway has shown a good tool profile.
I would go a little less chip breaker with harder material.
if setup is good flat should work for most all material.

 

[liljoe]

I have the same style holder and had lots of issues with chatter. I bought a good cutoff blade and it made a huge difference.
I think they are Empire brand. I can part a piece of 304ss easily.
Joe

 

[Acsr]

Thanks for all the feedback. Keep it coming. Thanks, acsr

 

[hogpatrol]

On HSS, I grind a radius and set the tool a skosh below center. Chips roll off smooth. The problem with parting is proper surface speed goes awry the closer the tool gets to center. If you have a machine with variable speed, increase it as the tool nears center. If one isn't adept at sharpening high speed bits, use carbide and run it at high speed.

 

[carlsbad]

Hog,
The importance of running carbide at high speed is greatly exaggerated. Sure, best surface finish is at higher speeds, but that is after you have all the other issues resolved. Parting is generally not a surface finish important process. Chatter can almost always be reduced or eliminated by lowering surface speed (note once you have chatter, you have to get rid of it before changing surface speeds will help.).

If you're having trouble with chatter parting, use your slowest speed. Also, don't use power feed. Use feel to feed to tool at the tool pressure that keeps it biting at a happy cut.

--Jerry

 

[hogpatrol]

Hog,
The importance of running carbide at high speed is greatly exaggerated. Sure, best surface finish is at higher speeds, but that is after you have all the other issues resolved. Parting is generally not a surface finish important process. Chatter can almost always be reduced or eliminated by lowering surface speed (note once you have chatter, you have to get rid of it before changing surface speeds will help.).

If you're having trouble with chatter parting, use your slowest speed. Also, don't use power feed. Use feel to feed to tool at the tool pressure that keeps it biting at a happy cut.

--Jerry

Jerry, Disagree with the slowest speed. If you have to do that, you have something else going on. Chatter is a result of too slow rpm (surface speed), improper rake, off center, insufficient clearance, slop in the headstock, cross slide or compound. Check CNC parting programs, speed increases as diameter decreases. Carbide is made for higher surface speeds. It's production tooling. The problem with most of these Asian machines is they don't have enough ass to take what carbide is designed to do. The ones I've used, at high speed, hop all over the place and are usually out of balance and have too much slop in the headstock bearings, compound and cross slide. On top of that, their gearboxes are total weaklings. This goes for the small Grizzlys and the other imports. From my experience, these lathes are just plain lightweights and that is their main problem with parting. Take a G&L, Clausing, Hardinge, Monarch or other lathes with big gearboxes and horsepower and high speed carbide parting is a piece of cake. Before I retired, I had job parting off three inch diameter cold rolled with carbide. Insert tool was hanging out inch & three quarters. I ran the lathe as fast as it would go and hand fed the cross slide as fast as the tool would take it. It cut like butter, a nice blue ribbon with no chatter and no coolant. Carbide needs speed to function as designed.
I'm done.

 

[carlsbad]

I agree that if you have to go that slow, you have something else wrong. But on a borderline machine, slower will help. I've never seen faster help a flexible setup.

I like indigo blue swarf.

 

[hogpatrol]

I agree that if you have to go that slow, you have something else wrong. But on a borderline machine, slower will help. I've never seen faster help a flexible setup.

I like indigo blue swarf.

Yep, that's the color of money.

My modified parting tool, in need of touch up, radiused with positive rake. Hold the tool parallel, carefully, against the grinding wheel to impart the radius. Fifty other machinists will say it's crap and theirs is better. No one said we were easy to get along with.

Notice the radius on this tool for facilitating chip removal. Also, the increase in tool feed (difficult to see RPM increase) to maintain surface speed.

 

[mram10]

I’m glad you brought this up, OP. I’m learning a lot and need to try a little slower. Keep us posted

 

[Cloudrepair]

One thing I found is it isn't always easy to feed it in by hand and keep a consistent feed rate.
So it has been good in my experience to find a feed rate that works with the material and speed. Now I get good results with carbide or hss at slow speeds.
I don't run them hard though to preserve tooling.
I only have a couple years cnc lathe experiance much more manual.
most my time has been with cnc mills.

 

[carlsbad]

Cloudrepair,
I find I have good feel by hand parting but prefer to use power feed. My current lathe is stiff enough I can pretty much part however I want but I've been thinking I'll work on improved choice of feed rates. What speed and feed rates do you like in steel with a 3mm carbide parting tool? I've been using 135 rpm and .002 to .003 in/rev.

--Jerry

 

[hogpatrol]

Cloudrepair,
I find I have good feel by hand parting but prefer to use power feed. My current lathe is stiff enough I can pretty much part however I want but I've been thinking I'll work on improved choice of feed rates. What speed and feed rates do you like in steel with a 3mm carbide parting tool? I've been using 135 rpm and .002 to .003 in/rev.

--Jerry

Jerry, are you versed in surface speed? RPM is calculated off of optimum surface speed, not the other way around. On those videos, they show surface speed, not RPM. They're running a feed rate of .011. .002 to .003 is WAAY to slow. You want that chip thick enough to roll out, not bind up in a jammed up mess.
This is one of my pet peeves with those trying to learn machining. Study surface speed, it's the foundation, and everything else falls easily in to place.
Example: Ever see someone break a small diameter drill? The problem is not RPM, per se. It's too slow of a surface speed.

 

[Cloudrepair]

Cloudrepair,
I find I have good feel by hand parting but prefer to use power feed. My current lathe is stiff enough I can pretty much part however I want but I've been thinking I'll work on improved choice of feed rates. What speed and feed rates do you like in steel with a 3mm carbide parting tool? I've been using 135 rpm and .002 to .003 in/rev.

--Jerry

That sounds about the same what I use for most but I will feed a bit faster for stainless. I don't have a coolant/oil pump on my lathe at home so I take it easy and brush it on.
I used to calculate everything off of surface speeds mostly run thing from feel and memory.
now we use a lot of Walter tooling at work and that I use there recommedations mostly because they work and are pretty agresive.