Machining 50mm hole in inconel 625

[Kpnuts]

Im in need of some help with manufacturing coursework, so hoping someone might be able to help.

I want to machine a Ø50mm hole in a short (30mm long) cylinder using a CNC lathe/turning centre.
I assume the quickest and most efficient way to achieve this is to use a Ø50mm drill head (I have found an insert type drill in the sandvik catalogue that can do this) But im not sure if I need to go up in step sizes? i.e. can I go straight to 50mm, or do i need to go Ø5, Ø20 then Ø50 for example? I cant really find any information on this on the web! What are the advantages/disadvantages of step drilling and would you recommend it for this application?

Any help would be much appreciated!

[runangolee]

Depends on what kind of machine you have.

I wouldn't even attempt to push a drill that size into inconel with less than a 30hp machine.

Also, I usually avoid step drilling like the plague.

[prasadsge]

We are using Inconle 625 Material 70 MM Dia * 940 MM Length. Want to do 31 MM I.D in it. Please let me know what is the procedure for it.

We also have done annealing & rite now the Hardness is 20-21 HRC.

What type (Grade) of tool it should be used ?


Thnk's Regard's

Prasad Kulkarni.

[Khalid]

Why not to use simple HSCO drill with that low HRC inconel?
I will suggest you to do Step drilling , start from Centre Drill, then 8mm drill, then 15mm drill then 20mm drill and so on... We have done a similar job for high temperature Thermowell manufacturing out of Inconel 800H and we have done that hole by Lathe.. For that long you need to precisely Align the Stock on Lathe and drill both side..

[prasadsge]

Why not to use simple HSCO drill with that low HRC inconel?
I will suggest you to do Step drilling , start from Centre Drill, then 8mm drill, then 15mm drill then 20mm drill and so on... We have done a similar job for high temperature Thermowell manufacturing out of Inconel 800H and we have done that hole by Lathe.. For that long you need to precisely Align the Stock on Lathe and drill both side..

Hey Khalid thnk's for ur quick reply.
Me trying with the same procedure with 16 MM Drill & Simultaneously modifying with Sandvick carbide drill. Hope that work's on.

Again Thnk's for your imediate reply.

[uli12us]

If you have the tool for it, I think its much better to recess turning axial up to 0,01" of the end of your part, then use a hammer to remove the middle part. If you must do this with a drill bit, than you need a lot of power and a special drill for that material. Generally in stainless Steel an Nickelalloys you should grind your Drill to 130°