There is no direct imperial cutter, the nearest would be 9/16" which is 14.29mm

What is it you ar edoing that needs that specific size particularly an end mill as that is not use dfor slots which may have a width or half round end that determines the diameter.

If it is just a through slot use something narrower say 12mm or 1/2" to mill down the middle and then offset each side to bring your slot to width

Margaret,

You will need a slot drill if you want to plunge cut a hole, They have two cutting faces. You can get a cutter with three cutting edges that can also do a plunge cut. You are better off with a slot drill to cut a slot as it will cut to size, An end mill will cut oversize.

Andrew.

Edited By Andrew Tinsley on 18/07/2023 14:42:54

Edited By Clive Brown 1 on 18/07/2023 15:25:12

I would centre drill and then drill, say 6mm diameter, to just short of final depth. Then one could use a ~10mm centre cutting endmill and finally the 9/16" slot drill. Personally after drilling I would use a short HSS boring bar. That way one gets a hole exactly to the size wanted and with a truly flat bottom. Slotdrills and endmills are ground slightly concave on the end.

When using a slotdrill as a "drill" in brass one needs to be careful in case the tool grabs. They are better than normal twist drills (due to a slower helix) but not as good as the slow helix drills specifically for brass and bronze.

Andrew

Though I often use a cutter to open a hole as you suggest this would be a much better way to achieve what you intend. There is no guarantee that an endmill or slot drill for that matter would give you the exact size you seek – you will only know after you have machined the hole – using a boring bar (if used carefully) will.

A small boring bar can be made from a worn slot drill – I have an image somewhere so will try to find it for you.

Tug

It took a while to find –

The flutes on a slot drill are ground back to leave just one tip and that is then used as a short boring tool.

(The reason this is cutting backwards is that the part being turned is screwed onto the rear part with the inlet tube)

Old slot drills and three flute end mills make ideal 'home made' cutters if you are up for using an off hand grinder

Hope that helps – Tug

Bill, It's held in a Myford QC holder for boring tools – the type that has a vee groove machined in the lower face.

Margaret – Good luck with your task If you can learn how to use an off hand grinder to shape HSS then you will have a huge 'extra' to call on in future. Just bear in mind you won't necessarily get it right at first but keep trying and you will. Also bear in mind it's only the very tip of the tool doing the cutting that has to be right – what's to the side and behind it is just support

Best – Tug