Cutoff/grooving problems

[july_favre]

I am having trouble doing cutoff or grooving with my maxnc lathe unless the cutter is less than .05". When I try to use the cutoff blade it doesnt cut very well and sounds like someone is killing a moose. Even at the lowest movment speed of my machine, its not cutting enough and it will catch and climb on the cutt of blade or rotate my tool holder. Is the machine just not rigid enough?

[wms]

July,

I would make sure that the edge of the cutoff tool is exactly at the center height of your stock.

Or just slightly above center. But only a couple of thousands.

And extend the blade, (If that is what it is), only enough to cut thru to center. Keep it as short as possible.

Sounds like it is below center and as it starts to cut the cutting forces "pull" it down even more and it tries to climb on top of the tool.

[CNCadmin]

I found that cutting at a slower speed works very well on alum.

[HuFlungDung]

July Favre,

"Real cutoff" takes a large machine, heavy tools and toolposts, lots of power, speed and continuous coolant.

What kind of cutoff tool is it you are using? A simple high speed steel blade?
What are you cutting off: material and diameter of material? What style of toolpost?

You must cut very close to the chuck. If you are using a 3 jaw chuck to hold small diameter stock, the grip of the chuck is poor. Use a 4 jaw chuck, or better yet, get a collet chuck to grip round stock. You can even purchase a small collet chuck which you can hold in the main chuck for some types of work.

Do not part off between chuck and tail center: an obvious binding condition will arise near the end of the cut off and bend or break something.

Use coolant on the cutoff blade.

A bit of positive top rake (its actually called back rake, but its the angle of the top plane of the blade relative to the centerline of the lathe) on the blade will help. Most HSS cutoff blades are useless for anything except cutting off brass or cast iron, where zero top rake is correct.

A friend of mine used to use old 1" power hacksaw blades for cutoff on his small lathe. He would grind a real hook shape on the top of the blade, just behind the tip. With a real light feedrate, this will not clog up (too often). For light duty machines, this is often the approach that will work.

[july_favre]

Ive been using cutt of blades, grooving/cuttoffs and grooving inserts which have been doing ok cause they are alot smaller. The .1" carbide tipped blade and .06" and .1" groove/cutoff have been giving me troubles. Ive tried all different speeds, feeds, tool heights and I only have the blade hanging as long as I need it. Ive been grooving and try to cutt off near the chuck and towards the end of the piece with the same results. My tool post is one of the mini QC type from littlemachineshop.com and Im cutting aluminum. If im squaring off the end of the work piece with not too much of the cutter digging into the work piece of a cut it cuts fine, but once I put the whole width of the cutter or anything over about .05" it doesnt want to work as well.
I think Im going to pick up a thinner cuttoff blade and see if that works any better.