Hi Terry, Ronan,

Not wishing to contradict but my Tom Senior M1 has a 1" horizontal arbour without a keyway and I have no trouble clamping horizontal milling cutters sufficiently just using the nut, which, does not have to be more than just nipped up to drive the cutter. Admittedly I mostly use fairly thin section cutters i.e. slitting saws etc and this has the advantage of letting the slitting saw slip (tongue twister) rather than breaking the saw blade.

Alan

Surely, sawing stainless steel stock several slightly slack slitting saws should sometimes slip safely, substantially saving some shattered saws – circumstances suggest skimming surface slows slicing.

Now that is as fine an example of alliteration as you will ever get in the model world. Surely superflous to suggest otherwise,Top marks Stub

What Bazyle says is quite right and some cutters are not chamfered at the ends of their bore which exacerbates the problem if they slip; however many horizontal mill arbours don't have a keyway.The main problem here is that if the cutter does slip due to excessive overload it can tighten the nut and make it very difficutt to undo,largely because some arbours that are driven by taper friction have no spanner flats at the taper end to grip it tightly enough to make good use of a long spanner at the nut end.

If you have a keyway some of the spacers need a keyway too to enable their use on thin cutters. Colin