indexable lathe tools

[Gary Brooke]

Help please.
When machining in the four jaw chuck with interupted cut the torx screw works free causing the cutting insert to work free. this makes getting to size more luck than good practice. It can vary from 2 thou to 20 thou out. Am i using the wrong style off tool? should it be a ridged tool. the problem is only with the 4 jaw i can get within a thou every time when using the 3jaw.
Thoughts from learned members please.
Rgds Gary

[Vixen]

Hello Gary,

What material are you cutting? What feed, speed and depth of cut? Also what inserts are you using, is the lathe rigid enough for the job?

A photo of the work and the set-up may give us some clues.

Mike

[Jo]

When machining in the four jaw chuck with interupted cut the torx screw works free causing the cutting insert to work free. this makes getting to size more luck than good practice. It can vary from 2 thou to 20 thou out. Am i using the wrong style off tool? should it be a ridged tool. the problem is only with the 4 jaw i can get within a thou every time when using the 3jaw.

Is there any dirt under the tip? If you have a bit of swarf under there the knocking would dislodge it and instant loose screw... any oil on the bed where the tip goes or down screw hole?

Tools should always be ridged. Has your cross slide or top slide got any play in it? Tool post well clamped down.... 

Jo

[Jasonb]

I've never had a screw come loose, is it a decent holder and screw or a £2 jobbie from afar?

As Jo says nice clean seat and thread, make sure there is no swarf in the torx socket and that you are not using a rounded off key or mashed screw socket. Also is it teh correct screw for the holder & insert as the angle of the CSK can vary.

[Stuart]

Plus one on Jo and Jason

I would bet a penny on the seat being bad and the insert is moving

One tip though if you buy the shanks cheap replace the tork screw with a quality one the ones normally fitted to the cheaper shanks are not that good ,or up to speck

But as is the case others mileage will vary
Stuart

[Gary Brooke]

Thank you lady and gents for your advice plenty to look at there.
A bit more information its a wm 180 lathe nearly new the slides are solid with no play as for the tool it came with the lathe so ive no idea of the quality or tip.
The job is to face to length 3/8" square EN1A not critical that they are all but it would be nice. depth off cut 5 thou speed 750 ish rev and feed  ing in at asteady rate. Ill post some photos when cameras charged.
Rgds Gary

[Jasonb]

Should not have a problem on such a small piece or big bits for that matter will wait for the pics

[john mills]

check that when you do the stew up the insert feels tight  ,don't go past the centre.sound like the insert ,the tool holder ,and screw don't match .For what you are doing a piece of high speed steel ground to a suitable shape would work .

[Gary Brooke]

Sorry its taken so long that nasty work got in the way.
Rgds Gary

[Jasonb]

Screws don't look right to me as they seem to have a raised button type head. Usually they have a steep countersunk head and sit flush or below the top of the insert

[Stuart]

By ekk Jason thou lamps are good ,yes it does look like a button head .

Goes back to prev posts insecure tip

[Vixen]

They say a picture is always worth a thousand words.

As Jason says, looks like you have a standard button head allen screw instead of the correct torx insert holding screw.

Mike

[Jasonb]

Should look something like these

http://www.arceurotrade.co.uk/Catalogue/Cutting-Tools/Lathe-Turning-Tools-Indexable/ARC-Indexable-Turning-Tools/ARC-Insert-Locking-Screws-and-Wrenches

[bent]

FWIW - I have one 1/4" bit holder that has suffered a lot of abuse (lots of heavy cuts, interrupted cuts, and a few involuntary contacts with moving lathe chuck jaws), and the bed where the insert lays is no longer flat.  It's usable for light cuts now, but will chatter horribly if I get aggressive with it.  I've been on the lookout for good replacements...

[Gary Brooke]

Thanks for your views gentlemen. Think I knew that I'd have to get some decent tools at some point so is it best to get a set or separate ones ? Also which tips TCMT09 or CCMT06 best.
Rgds Gary