Negative Rake Tooling

[ddickey]

I bought this https://www.banggood.com/WWLNR1616H...p-1062955.html?rmmds=myorder&cur_warehouse=CN
after watching this review.

I thought I'd give it a try ten inserts and a holder for just over twenty bucks. It is a negative rake tool.
From what I've read here and other places you need a rigid machine. Not sure if mine is or not, (13x40 Acra-Turn). Negative rake tools are good hoggers for hard materials, correct? Not good for soft materials? Can leave a nice finish?
Might try it out today.

 

[benmychree]

When I started my apprenticeship in 1964, positive rake tools, other than brazed on type were unknown in the shop, in fact there was a prejudice against them because they had half the usable cutting edges as compared to a negative rake tool. A negative rake tool requires more power to drive the cut and puts more pressure against the machine's moving parts. They are a good deal better than pos. rake tools for interrupted cuts, as the cutting edge is stronger. I mostly use positive rake tools, but do have negative rake as well for the rougher sort of work; in my experience, you can achieve nicer finishes with positive rake tools. I expect that a neg. rake tool would finish better on harder materials, but will preform OK on softer materials, but not give the shiny finish as on harder materials.

 

[ddickey]

Probably won't be trying it out today.
My water heater is leaking so it's getting replaced, still under warranty. That means the garage door will be open for a few hours. Even though it's warm today 42°F to cold to work out there.

 

[benmychree]

Agreed; too cold! It is 55 here, borderline too cold.

 

[Buffalo21]

I’ve bought the same BangGood tool and inserts, about 6 months ago, I’ve had very good results with it. I use mine on a Jet 14” x 40” (2HP) lathe, I was very surprised by the quality of the inserts, I’m still on the first corner of the first insert, With over 20 hrs. Most of the work is on 1018 and aluminum, good cutting and good finishes.

When I ordered it, I was hoping for a 300 series (size) insert, but it was a 400 series, a standard WNMG 432 insert.

 

[mksj]

Negative rake takes more Hp and rigidity, but I have been using WNMG 300 series holder and inserts on a 1340GT with great results. You can take both light and medium heavy cuts, I have mine setup primarily for aluminum with very sharp positive rake carbide inserts. You may have more difficulty with deeper cuts, but a 0.050 DOC/0.10" diamter is done easily. The finish is great. On steel and harder or mor difficult alloys I use a neutral rake CCMT insert holder. The type of insert you use can make a big difference.

 

[Buffalo21]

about 90% of the time, I use negative rake tooling, using TNMG, WNMG or VNMG inserts, the rest of the time I primarily use CCMT insert (unless threading). It all depends on the material being machined.

 

[Jimsehr]

Maybe I am too old school but in the old days negative rake meant no back rake. But in my mind the new molded negative inserts have a positive rake built in to their chipbrakers. Maybe that is just me.

 

[Ray C]

I decided to buy the L and R set of these toolholders and they've been sitting in the shop for a couple of weeks waiting for the lathe to free-up. I was pleasantly surprised. In terms of strain on the machine, they did not seem significantly different from any of the other inserts I normally use.

1.5" dia barstock. 1045PH (PH = pre-hardened. apprx 28-30 Rc). approx 600 RPM. 0.012ipr. The larger OD was 0.020 DoC (40 total). That made 1" long tight spiral chips that were manageable. Test cuts on the smaller part of that shaft showed that between 30 to 50 thou DoC produced "perfect chips" and made a clean finish just like the left side. The final pass on the smaller OD was a 10 thou DoC which produced ribbon swarf and also left visible lines from the birdnest that tried to strangle shaft. The picture looks worse than real life. The actual finish is pretty good. All testing was done with no coolant.



Here's another piece of 1045 (HR, as-is condition), 3.5" dia spun around 500 RPM with a very slow rate of about 0.002 on the crossfeed. It is beautifully smooth and has a perfect neutral sheen. DoC was the full depth you see there, about 0.050". Because of the point angle of the cut, it produced ribbon swarf.


In a nutshell, they seem just fine -and now I have one more type/size of inserts to babysit.

Ray