Reaming hole in 45HRc steel

Hi,

I will need to ream holes made in rather hard (45 HRc) steel.

Can I use HSS for this end or only carbide reamer will do?

If I need carbide then what are the rules of their use not to damage them at first go?

Hole is to be 5mm in diameter, so should I drill 4.8 mm?

I would avoid carbide, if one of those binds up and breaks in the hole your problems will start. I spent many years operating spark erosion machines and carbide takes some shifting.

We regularly finished injection moulds to around 44/45 HRc and then did final machining.

We used solid carbide drills with through coolant to drill these type of holes in pre hardened injection moulding tooling. They were started with a carbide smaller milling cutter interpolated a short depth then drilled to size.

David

With the advent of wire erosion machines we left the holes out then used a start hole machine for the wire. All core pin holes and some ejector pin holes where finished with the wirecut machine.

I would get solid carbide 5mm drills for hard material and forget reaming.

Thanks for these comments.

With solid carbides I always have reservation about possible breaking of drill or mill in my workpiece, That due to rather low speeds of spindle at my disposal (up to 1200 rpm).

So if carbide has to be used then brazed versions are preferable in my case.

Regarding EDM - dont have it..

I would run solid carbide drills at low rpm into hard materials and use light hand pressure to feel the drill cutting.