Member postings for Hugh Gilhespie

Hi All, I am a complete beginner to metalwork and have recently acquired a Bridgeport Series 1 mill. I want to fit levelling feet to the mill and this involves using the mill to cut through slots in 150 by 90 parallel channel steel. My problem is that the surface of the steel seems to be much harder than the inside material. I don’t know what grade the steel is but it comes with a fairly thick layer of mill scale on the outside so presumably these are hot-formed sections.

 I have managed to destroy 3 HSS cutters so far. Everything is fine until I get to about 90% depth of cut. I am taking fairly modest cuts each time of about 30 thou and feeding slowly – around 5 inches per minute. I have been using 6 mm 2-flute cutters at about 2000 rpm – all OK according to what I’ve read.  As soon as I get near the bottom of the slot the cutters stop producing chips and if I try to force a cut the cutter overheats becoming red hot – end of cutter!

 I then thought that perhaps I should be using solid carbide cutter but when I phoned the technical support people at a good tool suppliers, I was advised not to use solid carbide on a manual machine and they are only suitable for CNC machines.

 I realise that there are other ways to do what I want that don’t involve milling but I would like some advice specifically on the milling and any suggestions of how to cut through slots successfully by milling.

Thanks, Hugh