Beyond Milling Speeds and Feeds

Harold Hall has written much useful advice beyond feeds and speeds. Width of Cut, Depth of Cut, Step-over, etc.

My milling machine has a bit of backlash and I must use conventional milling.

Are modifications to the Walter On-Line Calculator, FSadvisor etc. or textbook formulas for radial width, (axial depth, stepover, chip load etc) required or a different approach needed when conventional milling?

Paul

ps I know the Pros on these Forums use Walter and FSadvisor etc. because they mention them. If it saves broken carbide or HSS end mills or worse, then they are worth it.

Edited By Paul Fallert on 13/03/2018 20:45:27

Hi Paul,

I mostly use conventional milling (Warco WM-16) and would never consider myself to be a pro. I have learned to feel what's more or less right by 'doing' and sometimes getting it wrong. If I use climb milling, it's usually trying a finish pass and if it looks better than conventional then I stick with that, but only for finishing passes, never for bulk material removal.

To get technical I suppose it's all to do with chip-load for the various materials and cutters being used, but when I think about those parameters I personally believe they are more within the realm of the CNC world.

Regards,
Ed.

+1 for Ed's comments. I tend to use a hogger for large removal of material then finish of the last cut to size with climb milling for finer finish...

George.

That's not terribly logical; the cutting process at the interface between cutter and material is the same whatever the machine. The process has no knowledge of whether movement is created by a servo motor, a stepper motor or a manual handlewinder.

I don't use speed 'n' feed programs; they seem to be more trouble than they are worth. I have a pretty good idea of what I want in terms of speeds and chip loads and I either do generate the numbers in my head or use a calculator.

I climb mill on a regular basis on my manual mill as I'm too idle to waste half my time winding the cutter back without it cutting. If the WOC is greater than 50% then it's not really climb milling anyway. For smaller WOC I may just nip up the table lock, but it is quite surprising how big a cut the cutter will take without breaking. I've got about 15 thou of backlash in X. If the cutter does pull the work in, along with the table, it just coughs and moves on. Just goes to show how big a chip you can use in normal milling.

Andrew

I think the main constraint on climb milling is how rigid the machine is. Climb milling puts more force on the machine which is OK provided the machine can handle it. The advantages of climb milling are that it removes more metal faster for a given amount of power and leaves a better finish.

You are unlikely to get good results climb milling on a lathe or a lathe/mill combo. They're just too wobbly. It's also a dubious proposition on a light hobby mill designed to keep cost and weight down. I have a WM18 - a large light hobby mill - and, like Ed, do most cuts conventionally before doing a moderate climb cut for finish. Although a new WM18 can climb mill, it complains on deep cuts. I can tell it's not happy!

Something like a Bridgeport is a better bet; the construction is altogether beefier. But I've seen criticism that they're not hefty enough for continuous production climb milling where machines remove metal as quickly as possible all day every day. They're also too big for my workshop!

Even if you own a heavy stiff mill, it has to be in good order and set-up correctly. Backlash isn't the main enemy, it's loose gibs and anything else that allows vibration. A worn machine may be hopeless.

All this tends to discourage climb milling in a home workshop. But it's a useful technique if your kit can stand it. As always it pays to experiment.

Dave

And the main downside of ‘conventional’ milling is likely that of tool wear. The initial cutting edge engagement is very close to zero depth of cut and can reduce tool life by rubbing - especially if the operator is at all ‘overly shy’ of providing a sufficient feed rate.