Roughing Mill Bit or Indexable cutter

Briank · May 31, 2013

Hi all,
I haven't found a discussion of this issue and please pardon me if it has already seen thorough treatment.

I have a Micromark Belted R-8 Mill of recent vintage. Most of my work is with Al and Brass, but occasionally I work with 12L14 steel. 1018 and 1045 are more accessable in square and plate dimensions but that brings the problem of removing metal. I generally use a .500 HSS Roughing Mill and would like to explore other options such as a 2- Insert Indexable Milling Cutter. My question concerns the suitability of a 2-insert cutting tool of say, .750" or so, given the limited ridgity and power of a small mill. Would there be any advantage to making the investment and what performance improvment might I expect?

Many thanks,
Brian

xpylonracer · Jun 1, 2013

Hi Brian

I take it your HSS roughing cutter has 4 flutes and you are cutting to the limit of your machines rigidity so going to a 2 tipped cutter will reduce your metal removal rate even at the larger diameter cut.
I believe you will be better to change to a solid Carbide 4 flute cutter for the tougher materials rather than a 2 Insert Indexable cutter, kinder on the machine.

Emgee

jwcnc1911 · Jun 1, 2013

Metal removal rate will be determined by several factors...

What's your spindle capable of? do you have power feed so you can set a constant feed rate? A bigger tool does not always mean more efficient metal removal. You may even try a 6 or 8 flute specific roughing tool if you can feed fast enough to use it. Otherwise your just burning your tool any way. Which I honestly figure your doing with your HSS endmills. Where is your mill? If you can stand the smell of burnt cutting oil, throw some tapmagic on it.

BobH3852 · Jun 1, 2013

Hi Brian,
With the smaller diameter indexable tipped cutters, they are designed for faster feed rates and small cuts, and give the best results on CNC machines, however depending on the type of tips you select, and what are available for the type of cutter you purchase, you can do some great things with these cutters, some you can plunge with (centre cutting) some will cut down parallel faces, there are so many to choose from, and most brands have a general purpose one that can be used on small manual mills, talk to the suppliers and the reps, and they will let you know the power requirements.
Hope this helps

Cheers

Bob

Briank · Jun 1, 2013

Thank you for your kind responses. I have favored HSS 4-flute roughing mills for steel until now but I doubt that I have pushed the tool as much as I could have, as Emgee queried. I guess I need to find out where 'empty' is before I plunge into another direction. I do monitor chip color and speeds to avoid burning up tools, but I think I'm going to try carbide for a comparison before anything else. The idea of beating my machine to death with a 2-flute indexable cutter is definitely a turnoff. Thanks again!

Brian

Wizard69 · Jun 1, 2013

Briank said:
Thank you for your kind responses. I have favored HSS 4-flute roughing mills for steel until now but I doubt that I have pushed the tool as much as I could have, as Emgee queried. I guess I need to find out where 'empty' is before I plunge into another direction. I do monitor chip color and speeds to avoid burning up tools, but I think I'm going to try carbide for a comparison before anything else. The idea of beating my machine to death with a 2-flute indexable cutter is definitely a turnoff. Thanks again!

Brian

You won't beat your machine to death with a carbide tool, indexable or not. Like any other tool you will only be able to achieve the metal removal rates the machine allows.

If you go carbide insertable tooling is a advantage in at least one respect. Carbide can chip easily, especially when used manually. An insertable tool allows you to change cutting edges when required. The question then becomes is this actually economical. If your goal is large metal removal I'd say go carbide in one form or another, however you need to buy tooling your mill has the power and stiffness for. I'm not sure about the specifics of this mill you are talking about but my guess is it wouldn't handle a 3/4" mill of any type well.

As for feed rates and metal removal rates find some on line calculators to see where you stand. None of these calculators are perfect but they should give you an idea as to what power is required for a specific tool removing metal at a set rate. Of course manual machining is a different ball game but generally manual machinist feed carbide on the slow side. This is one big advantage of CNC, you can set very specific feed rates and get a good idea about how your machine handles those rates.