Hi Gents,
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Thought I'd let you know what I ended up doing here.
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I took a punt on this 20mm boring bar: http://www.ebay.co.uk/itm/RDGTOOLS-2...E:L:OU:GB:3160
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Clamped a milling vice to my cross slide and then the tool in the vice and took things very slowly <0.5mm DoC per pass and other than a couple of hard spots where the tool "dug in" and stalled, everything worked out OK to a depth of 160mm. I was very naughty having the tool oriented in the vice so it could have slipped downwards as that 's the direction of cutting force and its certainly not something I would have tried in steel for sure.
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I must see if I can find a suitable vertical slide for this machine, as then the tool would definitely be better clamped and would also be handy for the milling head, which I use for light, quick and dirty manual milling.
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Cheers for the advice chaps.
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Chris