RDG Tools indexable boring bar

Hi all,

Back in October I bought a 6mm indexable boring bar from RDG at the Midlands show.

This sort of thing...

https://www.rdgtools.co.uk/acatalog/8MM-Indexable-Boring-Bar--TCMT-09---4537246.html

I had reason to dig it out in the past few days and I'm a bit puzzled. The shank is a sort of rounded off square shape. I guess I was expecting round or (less likely) square but this is both.

Placing it on the flat produces a quite negative rake angle.

I guess I can forget the flats and make myself a holder for the diameter of the rounded parts but how are these things intended to be held?

Regards, Andy

Andy

As far as I'm aware (I asked the same question) it is held by the flats, and the rake gives clearance in the bore.

David

These are deigned to to locate on the flat. Centre height is at the cutting edge of the insert.

Jim

To go in a round toolholder & the flat at the top so your grubscrews grip it. Just been on ebay trying to find a holder to point you to, but cannot find one. I asked the question about the rake on the cutter. It should be like that.

Steve.

Holding by the flats gives a reasonable rake but you can get square holders that allow angle tweaking and may be more convenient. These from Arc Euro Trade.

Dave

Thanks - so the downward pointing angle is intended

The flats seem kinda small to be reliably 'hit' by the toolpost screws TBH.

I have one of those Arc holders which is in theory the right diameter so will give that a go.

Regards, Andy

You don't need to hold them in a round holder just let the flat bottom sit in a standard toolholder or post and the grub screws onto the top surface. As said the angle gives the edge of the tool clearance and usually gets less as the dia of the bar and therefore minimum hole size goes up.

Edited By JasonB on 28/03/2020 13:02:10

I knew you would explain it Jason.

Steve

I am guessing that Jason has put these bars into holders to show the negative angle and would pack the front of that small one if intended for use so that the grub screw has more tool to tighten onto.

Thanks. I will definitely need packing in my toolpost.

No, I had been using it for something that needed it set at an angle to the toolholder lengthways for clearance just before taking the photo. usually just set directly below the screws. I've got 5 or 6 holders all with their own bars so just picked them up for the photo.

J

Edited By JasonB on 28/03/2020 13:18:55

With these round/flat bars in a round holder I find it helpful drill a hole for a tommy bar perpendicular to the flat at the non-cutting end of the bar so that the design angle can be eyeballed.

Edited By ega on 28/03/2020 14:12:04

Ahh ok.