Parting tool trouble

[Bustednuklz]

Good day to all
I am having a chatter problem while trying to use my parting tool(cut off tool) on a mini lathe. It is a 7x10 lathe. The tool is a 1.5 x 5mm with the matching holder. The tool cuts well for a couple of seconds and then chatters, until the lathe shuts itself down. This is on 6061 aluminum. I have not tried it on other materials as of yet.
I have tried setting the tool on centre, slightly above or slightly below centre, all with the same result.
I have tried to use various rpm and feed rates, with little luck.
Almost no backlash in the cross feed (haven't measured it but is less than 2 thou on the dial)
Tried sharpening it a couple of times but no real difference.
Thought that a wider tool might be different but only have the one tool
Any thoughts?

Thanks in advance
Steve

[EdK]

Steve,

Are you using plenty of lubrication?

Ed

[Bustednuklz]

Hi Ed
I thought I had covered it all...... But ......
Yes I have tried using WD40 (by the gallon) and kerosene minimally.
The WD40 seemed to help a little, but still enough chatter to shut the lathe down

Thanks again
Steve

[Mayhem]

Are you locking the z axis?

Generally you increase the feed when the tool begins to complain. However, it sounds like you are stalling the lathe when you do this. Belts tight?

[EdK]

Sounds like a dull cutter or not presented at the optimum angle. But I'll let the experts chime in since I've already made a fool of myself today and like to limit it to once a day.

Ed

[DaveH]

Steve,
Sometimes a picture of your set up may help.

Something to try: your cutter is 1.5mm wide, so push the ali bar in to the chuck so only 20-30mm is sticking out. Then cut (as you would in parting off) 0.75mm off the end of the ali bar. So you are only using half the width of the cutter.

DaveH

[DaveH]

(04-05-2013, 08:20 PM)Mayhem Wrote: Are you locking the z axis?

The z axis? which one is the z axis?

DaveH

[f350ca]

Steve
If it starts out cutting fine, it may be binding. Is the tool perfectly square to the work, and perpendicular, ie the bottom is going directly into the cut? Is there any chance the tool has a tapper in it, thinner at the tip. Try feeding faster right from the start, I'm not familiar with smaller lathes but sounds like you'd stall the spindle before anything broke.

[Hopefuldave]

The non-other Dave has a point, how far from the chuck are you parting off? If more than twice the work diameter it could be the work flexing, not the tool... Also make sure the parting tool is dead square to the spindle axis - I either use a square against the work or run the blade/holder against the face of the chuck then lock the toolpost down.

Something I've noticed, a lot of new turners pussy-foot a bit when parting off - chatter's often down to too small a depth of cut, so if you're not slowing the lathe, wind it in harder and faster and see whether it stops chattering! I usually part off as close as I can get to the chuck with the power cross-feed, 10 thou" / rev or more works well (admittedly on a heavy and rigid lathe with 3hp) for me... A lot of people advise against power feed when parting, I know, but it's important to have a consistent depth of cut rather than allow the tool to rub!

Dave H. (the other one)

[Mayhem]

(04-05-2013, 08:51 PM)DaveH Wrote: ...which one is the z axis?

The z axis is defined as being parallel to the spindle. So, on a lathe, moving the saddle toward or away from the chuck is moving along the z axis.

So, locking the z axis will reduce the risk of the tool flexing whilst in the cut.