Chris,

That sounds fine … 'though I think a single [axial] screw at the end of the bar would probably do the trick.

MichaelG.

I,v got one a little bigger than you need, but it could be scaled. It's just a bit of 3/8" bar(scrap bin), with a chip off a broken industrial power hacksaw blade brazed on the end, I needed it for a one off job, and its been used for a number of jobs since. Ian S C

Did some about 10 years ago for 1/4" bore out of a 6mm HSS engraving cutter blank on offhand grinder and angle grinder held in a vice. Material was 316. Neutral rake worked just fine. Job's been working (dymamic, not static) 40 hrs a week ever since. Diameter is the critical dimension with O rings, width is more about type of duty but anyway is less important. Surface finish must be adequate but nothing special. It's easier than first appears.

Edited By jonathan heppel on 25/04/2014 22:56:02

I have just acquired a lovely 6mm ISCAR Boring bar kit that would do this.

You don't want to be buying one for a one off. Lovely bit of kit though.

I would go with Neil's suggestion.

graham.

Edited By Oompa Lumpa on 26/04/2014 06:32:57

Hi Chris

I did just as you say.

The tool on the right I ground up from an old No.1 centre drill and held it in a holder like the one on the left – which is nothing more complicated than a end of square bar cross drilled for the centre drill and with a hole tapped in the end for a grub screw. Just a few minutes work and it works fine. Mine was for the same job as Steve – eccentric straps. I guess that in a 5/16 bore though you might have some rigidity problems as everything will need to be pretty small so I think Neils method is favourite. ( Well he should know – after all he did get the job!)

Regards

Norman