Insert brring bar negative rake

[AdrianRParticipant @adrianr18614]

[AdrianRParticipant @adrianr18614]

When I got the lathe it came with a Glanze S10K SCLCR06 boring bar.

It has a round shaft with two flats, that when clamped give a negative rake of 13 degrees. I just want to check I am on the right track.

I would mount this with the very tip at centre height?

Also would it be OK to machine Aluminium with a negative rake?

Adrian

[JasonBModerator @jasonb]

Yes they tend to tilt the tip so that the edge won't rub on the cut surface, more noticeable as the bar gets smaller

Cutting tip at Ctr Height.

Yes OK on aluminium with the supplied tip which was most likely a CCMT………. but you will get a better cut with an aluminium specific CCGT……… tip

[old martParticipant @oldmart]

You might run the tip a couple of thou high to compensate for the bar deflecting downwards. When taper turning or boring, the tip must be dead on centre or the taper will not be the correct angle, or straight.

[AdrianRParticipant @adrianr18614]

Ah I think I finally understand the G and M. G is solid and M is sintered so is rougher. The ones for Aluminium are polished to make them even smoother. Is that right?

Edited By AdrianR on 04/06/2019 18:49:57

[JasonBModerator @jasonb]

Easy way to remember is M = Moulded, G = Ground.

It is not so much rough vs smooth but the edge is crisper and therefore sharper on the ground inserts which means they cut better in non ferrous materials. Though the smoother surface does help stop aluminium swarf welding itself to the insert but still best to lubricate with a bit or paraffin.

[Mark RandParticipant @markrand96270]

[PEDANT MODE]

It's come up before:- M and G don't officially mean moulded and ground, even if people use the third character for that purpose. That letter position is for the insert's tolerance:-

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[/PEDANT MODE]

And now back to our regular programming.

[AdrianRParticipant @adrianr18614]

I love this site, no matter what question you have you will find someone who has asked the question before. I was just about to post my appreciation, then I saw the name of the OP DOHH!

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