My 63mm diameter boring head accommodates 10mm diameter boring bars and accessories. I have no 10mm bars and so far I have made do with modified indexable carbide bars which have a minimum boring diameter of about 20mm. I also have a bitty boring head which will bore a maximum of 12mm. It uses 4mm diameter boring bars.

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With the desire to reduce the minimum boring diameter of the larger head in mind I spent $8.26US on an ER11 chuck. https://www.ebay.com/itm/C10-ER11A-1...53.m2749.l2649

I opted for the ER11 because the head of an ER11 chuck is shorter by about 6mm than the head of an ER11M chuck and with a mill bereft of Z, the millimetres count.

So today, with the chuck's arbor suitably shortened and flatted, I had reason to use it. I needed to bore what I hoped would be a well finished 14mm diameter hole in a 14mm thick piece of 1045. With a 0.01mm cut at 600RPM and the power feed of 11mm per minute, the 4mm dia. carbide bar produced an extremely (IMO) neat hole. Well worth the expenditure. I might lash out and buy an ER16 chuck to further expand the head's usefulness.

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BT
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