Negative Rake Tooling Experience

[metaldestroyer]

Hi All; Hoping to get a discussion started regarding the subject line. I have a set of negative rake milling cutters (3/4" shank 1" cutting diameter carbide insert type) I was hoping for improved surface finish and have had some encouraging results. They do behave a lot different than positive rake tooling. 500 SCFM seems to be a good speed with high rates feed like 12" minute they remove a lot of material in a short time but with only fair to poor surface finish. At lower feed rates like 2" minute the surface finish is much improved. Right now it is just a learning experience, and I hope to get other views on this.

Jack

 

[metaldestroyer]

Well either very little interest in negative rake cutters in the group or I did a poor job of posing the question. How many in the group use negative rake carbide cutters in their mill? How about in the lathe, this I have not tried as yet. With only 1 HP on my 11" lathe it is not likely to work that well, but I have started to collect components to go 1.5 HP and VFD this will also get my lathe up to 2250 RPM, should be much better for small work.

Jack hoping to get replies.

 

[Jasonb]

I bought a set of the negative rake Little Hoggers at the beginning of december and have only tried them a few times. So far I'm not that impressed I can get a better finish and faster metal removal with either a flycutter or 40mm indexable endmill.

J

 

[New_Guy]

Lots of Industrial tooling use negative rake tools... i cant say i take much notice but i have done some hard turning with round "button nose" diamond tools, its a very different cutting action you can tell by the swarft

 

[Ken I]

I'm guessing the lack of response is because negative rake tooling requires more power and rigidity - something we hobbyists with mini mills and lathes are generally short on.

By the same token exposing small workpieces to greater stress while machining is going to diminish accuracy not to mention problems of surface finish.

Negative rake tooling (generally) only produce good finishes at high speed / feed / depth of cut typically outside the capability of our machinery or robustness of our components to stand it.

The only clearcut advantage of negative rake tooling (and that statment could open a can of worms) is the double sided tip being more economical.

I've used plenty of negative rake tooling in my industrial career - I can't say I've even seriously considered it for my mini mill and lathe which are from an industrial point of view "Toys"

After that statement I'll seek refuge in my fallout shelter.

Ken

 

[Lew Hartswick]

Good one Ken. I don't understand all the attention given to carbide tooling let alone
negative rake bits by "home shop" / model builders I see. HSS tools are so much
easier and cheaper as well as produce a better finish on nearly all machines that are
being used. ???
...lew...

 

[don-tucker]

Agree 100% Lew,I have used them in my working life and you need some heavy powerful kit.
Don

 

[Jasonb]

As I said in my reply to Jacks other post about these Little Hoggers I bought mine specifically for machining steel fabrications as my welding is not brilliant and there are quite a few inclusions which take the edge off a radius corner HSS milling cutter very quickly. And as I said here a HSS flycutter works better for me.

I agree Ken has the right point as using these cutters on my X3 does not produce healthy sounds from the head I'll definately only be using them on welded items and then its likely to only be the rounded one of the set to get that cast looking fillet on internal angles.

J