1mm deep with a decent 3mm cutter in Ali should be OK though for now you would do better to stick to the 1/4 times diameter as your max so 0.75mm depth.

You say an "end cutter" by which I will assume end mill or 4 flute cutter. Really for slots you want a two flute cutter or 3 flute as a compromise. Not only will the 2-flute give a more accurate flute width it will also clear the swarf better which may well by why you snapped the cutter.

What grade of aluminium were you milling and did you use any lubricant?. Some grades can be soft and sticky which will build up on the cutter and cause problems. This can be helped with a cutting fluid, on Ali use paraffin or WD40

Sets of cheap cutters can be of variable quality

Higher speed would help.

The aluminium may have melted a bit and stuck to the cutter, 'it happens. Also with that sort of size of cutter any looseness in the set up, slides etc can cause problems.

Plus as Jason mentioned a slot drill would be a better option than an end mill.

I usually work on a max depth = the diameter of the cutter but a fine feed is needed and I doubt if I would use that on a cutter under 6mm dia – that's end mills too. Slot drills have less flutes so would need an even finer feed or a much shallower cut. Jason's rule is safer.

John

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Make sure the x and y slides (and the quill) are locked and also slightly nip up the table lock so that there is no backlash. Use plenty of WD40 etc to prevent swarf sticking to the tool, make sure the swarf is cleared from the slot – and calculate speeds and feeds using something like FSWizard. It's also critical to feed consistently to prevent overloading the tool.

Hi Sam,

Difference between end mills and slot drills and their use were discussed here. You also mention in your first post running at 1125 RPM, that is quite a bit slower than I use on aluminium alloys. Have you tried using the top range of your milling machine?

Thor

Edited By Thor on 30/07/2016 18:18:45

Use a bit of paraffin or neat cutting oil and it will help stop chip welding, a major cause of cutter death.

You can salvage the end mill by grinding the end at an angle to give it one cutting corner. It's not as good but it may get you out of a hole some time.

Neil

I've seen chucks in particular that get a brown patina due to suds but people should clean up their lathes and wipe over with oil fairly regularly and also try and keep it on the work not all over the machine. I've only been involved with suds at work and it doesn't seem to cause any problems there – the machines were generally looked after.

I generally just use neat cutting oil from Morris Lubricants for problem jobs or if I want an exceptional finish. Just a smear via a lightly loaded kiddies paste brush. 5L of it will probably last longer than me.

Having posted about suds though I have ordered a bottle but don't intend to flood things with it. I just suspect that it will be better for some things and again will just use a brush. When people see video's of pumps chucking out huge streams of the stuff it might be worth pointing out that even grinding doesn't need that high a flow rate.

John

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Edited By Ajohnw on 31/07/2016 00:50:20

For milling I think this thread has gone a bit bonkers. I suspect Jason hit the nail on the head early on. The feed rate was too high for the speed the cutter was running at. There is no should be as far as cutting speed go other than problems can crop up of various sorts if it is too high. The type of problem will depend on the material that is being machined and the material the tool is made of. There is no too low really other than maybe chip breakers but in my opinion that is more related to feed rate.

Also slot drills must be used when a milling cutter is plunged into something. End mills aren't very good at doing that – try drilling a hole with one. A slot drill will do that easily. End mills are for surface milling.

John

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I have a feeling of despair every time the cutting speed thing comes up. People just wont realise that the quoted figures all relate to tool life – some one opinion of how long it should be and time to do a job and nothing else and that there can be all sorts of reasons for working well out of them.

Maybe if they looked at old figures based on hardened tool steel cutters they would but I suspect that the myths would still persist.

John

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Edited By Ajohnw on 31/07/2016 18:05:05

.

Given Jason's 'denial'… I will revise my response:

[ I only included the reference to Jason as a courtesy ]

Exactly that ^^^

It's the relationship between the two that's important.

MichaelG.