Machining Hardened Steel On Mini Mill - Speed And Feed Advise Please

[T Bredehoft]

Back to basics, two flute vs four flute:

Two flute will cut a slot to size, because only one flute at a time is cutting
Four flute will cut a slot oversize because while one flute is cutting ahead of the center, one is also cutting on the side.
For non-slotting functions, a four flute generally has more than one flute cutting at a time, thus reducing vibration.
Of course, this is not limited to Carbide, but is true of all materials.

 

[edojan]

Thanks guys. Any advise on how to start the cut (i.e. bringing the end mill into the work piece) to reduce the chance of carbide breakage (all other things being equal)?

 

[countryguy]

Just wondering how this turned out? I have cut 1045 on my 3:1. Carbide 4 flute with a corner radius. Nothing bigger than 3/8. I also learned about annealing and how to soften it. Do what you need done. Then run a heat treat again. Recipes are very specific. Need to also know the steel type. No guessing there. Just a note on something my son and I tried as a learning project. Worked out great. The 1045 was so soft I could bend a 2" wide 1/4 gauge over my knee. Rc value was much better than as purchased when we did the harden run. Anyway. Just noting that with the small mills you can get things done in different ways. I'd you want to see a great post on HT and DIY search on a post from Ray C and heat treat. My 3cents.

 

[edojan]

Just wondering how this turned out?

I ended up buying the carbide end mill (actually I have also bought a 4 flute 3/8) and taking light cuts of about .4-.5 mm at a relatively low feed rate. I could not possibly use annealing because it would be a terrible idea for a rifle bolt. On my next project, however I am planning to spot anneal areas of a hardened angle plate in which I need to machine some groves and drill some holes. I would appreciate any tips on spot annealing from the members.

 

[T Bredehoft]

I worked as a Tool and Die maker for nearly 30 years. never heard of selective annealing. If this is case hardened, there is a layer of high carbon steel on the surface. To anneal this you heat it cherry red and let it cool slowly, packed in ashes or lime, or some such. Not something you can do in one place.

 

[John Hasler]

Here's a discussion on another forum: https://thefiringline.com/forums/archive/index.php?t-247057.html

 

[T Bredehoft]

Thanks, John, spot annealing seems to be done often. My loss. I hope I never have to tap hardened steel with a 6-48 tap. 4-40 in aluminum is scary enough.