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Rule of Thumb.

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Stilldrillin:

Boggy`s posting & pics re.Darren`s lathe, took me straight back to my 36yr milling career, finished 3yrs ago.....

It surprised me to see the side & face cutter running at 200rpm........ :bugeye:
Until I realised it wasn`t my imagined 4” or 6” dia cutter! Probably only 1 1/2”.  :thumbup:

This set me thinking of my Rule of Thumb, which I`ve carried in my head for more years than I care to remember......

Based on 1/2” diameter = .500” = 500rpm.

Half that dia = twice the rpm.

Twice that dia = half the rpm.


RPM for drills & milling cutters, machining steel, with coolant.

1/16" = 4,000rpm

1/8” = 2,000rpm

1/4” = 1,000 rpm

1/2” = 500rpm

1” = 250rpm

2” = 125rpm

4” = 65rpm

6” = 50rpm

Proportionate rpm for inbetween sizes.

It still works!  :thumbup:

bogstandard:
Dave,

In fact, that cutter was 3" diam., so by your calcs should run at around 90RPM (using steel).

Rules of thumb are great, and a very good starting point.

I listen and look at what the machine does with the material I am cutting, and adjust accordingly. My observations suggested that I could easily have increased the speed of the cutter by about 50% (300RPM) and doubled the feed (1/2" per min to 1" per min). That was just for this job, other materials may require reducing your rule of thumb settings.

So as you say, rules of thumb work, but as you well know, the material, type of cutter and machine will tell you when you have got it spot on.

John

Stilldrillin:
John, a lot of my work included milling splines.

After several batches of these, you find the optimum speed & feed for the material......  :thumbup:



Then, on the next batch, the material changes......  :scratch:

Bernd:
Ok Dave,

What the heck am I looking at. At first I thought somebody had forgot to clean all the chips (swarf) of the part. Then I noticed numbers and what appears to be the beginings of holes. :scratch:

Oh ,and very big, by the looks of it, well at least quite heavy.

Bernd

bogstandard:
SD,

That looks to me like some sort of geological drilling head, minus it's tips.

You haven't got one knocking about anywhere? I need a bit of material for a new project. You pay the postage.


Bogs

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