[Cydon]

Hello first of all

I am a member in this forum for quite a while now and now I dare to ask something myself:
I need to mill and grind a 30H7 hole in V2A (1.4301).

I want to pre-milled the hole with a helix. Unfortunately I never know what diameter the milling machine needs to have so that it works... it shouldn’t be too big nor too small....

Is there a general rule of thumb for Helix milling machines?


Thank you in advance...

[WarFish]

Hello

The whole lot is actually not very complicated. You need to watch out for the following:
Your milling tool’s diameter should not be smaller than the drilling radius. If the tool is too small, then residual material can get stuck in the hole centre. That could create problems e.g. when you use the cycle 208 with Heidenhain controllers.

That cycle goes back to the hole centre at the end which might cause trouble if residual material is still situated there.


If your milling tool doesn’t cut over the middle, then you must not undercut a minimum milling diameter. –> because when you mill with a helix, then residual material stays underneath the tool which can create problems with particular depths.

Your tool might touch down on the material and as you can imagine that’s not good for the machine.



If the tool that you use cuts over the middle, then the minimum milling diameter doesn’t matter- in theory.

But not in practice: you can mill e.g. a diameter of 15mm with a 12 milling machine.
But that can cause trouble with the chip removal. It would be better to use a smaller miller ( 10 or 8mm)

A smaller miller allows more room for the chips that need to come out of the drill holes.


Regards Stefan