Rough Milling

[mickParticipant @mick65121]

This is why I was reluctant to post, as the original post mentioned cutter direction. The photo shows different areas cleaned up, rather than cleaning up the whole area in a continuous series of cuts, starting at the bottom left hand corner, looking at the machine. Then with only half the diameter of the cutting in contact, feed from left to right, until the bottom R/H corner is reached, then up to the top right hand corner with 50% cutter step over then, to top L/ H corner and back to the start, where the cutter is stepped over by 50% and the conventional milling pattern is repeated until the cutter reaches the centre. I've always understood this to be a conventional milling pattern. If the cutter was started at the bottom R/H corner and fed to the bottom L/H corner, this would be climb milling, as the cutter is trying to climb over the work piece, imagine yourself sitting on the cutter and look at the direction of cutter rotation, you should see what I mean. Feeding the cutter backwards and forwards is alright as long as you have the ability to correct any error in the Y axis, which on some hobby mills you can't. Any error in the Y axis would manifest itself as a series of small ridges in the direction of cut, which will only get bigger as the cutter diameter increases. That's why a spiral pattern will always clean up a face on any type of machine. I hope that clears things up a bit, so beginners will see the advantages. You can learn a lot from books, but when your teaching yourself, understanding the effects of climb and conventional milling, along with correct speed and feed for different materials and the importance of sharp cutters and coolant has to be the foundation.

 

Edited By mick on 02/08/2012 13:23:15

[blowlampParticipant @blowlamp]

I feel I have to take issue with some of the advice against climb milling as I think it does have significant advantages when employed on smaller machines and is used with consideration.

I would almost certainly climb mill Wolfie's steel block on any size of milling machine.

My aim would be to 'spiral' in from the outside and go around the periphery in a clockwise direction with the cuts overlapping by about 75% of the cutter diameter.

This allows the teeth to take a clean bite straight into the material without the cutter being dragged into the cut and also has the beneficial effect of avoiding the rubbing (hence, blunting) action that happens with conventional milling as the the cutting edge starts to engage.

I find the tendency for climb milling to snatch the cutter is with deep(ish) cuts combined with a small overlap ratio to cutter diameter. So an example might be say a 16mm diameter cutter at 0.5mm (or more) depth of cut, but with only 5% overlap (0.8mm).

Even here though the technique can be employed if the machine is well adjusted and the slide lock is used to introduce a little drag on the moving axis.

Martin.

[WolfieParticipant @wolfie]

Heres a couple of pieces I did this aft after checking that the spindle wasn't oscillating and making sure the bolt at the top was extra tight. The round bit is brass.

I was careful with the steel, didn't rush things and used coolant. Lot better isn't it. Its not perfectly square to the sides but I'm not 100% sure I got it absolutely square in the milling vice as its dim and difficult to see.

If I run my fingernail over the block I can feel very tiny ridges in places but only just.

 

Edited By Wolfie on 02/08/2012 18:21:20

[MICHAEL WILLIAMSParticipant @michaelwilliams41215]

Splendid result Wolfie – much better !

Michael Williams .

[Ketan SwaliParticipant @ketanswali79440]

Wolfie,

Please read the private message I have sent you. Thanks, Ketan.

[Michael GilliganParticipant @michaelgilligan61133]

A great improvement Wolfie … it looks like the machine is not very far out, after all.

Time to start experimenting with Speeds & Feeds, and various Cutters.

MichaelG.

[mickParticipant @mick65121]

Martin.

As this is a beginners question I would be interested, purely for balance, to know which milling operations you feel would not be suitable for climb milling to be used and at what depth of cut climb milling wouldn't be the first choice for facing operations.

Well done wolfie, working in the dark you'll probably turn out to be a better engineer that the most of us.

Regards.

Mick.

[blowlampParticipant @blowlamp]

Wolfie.

Congratulations on the outcome of your experiments

Mick.

For me, climb milling is almost always my first choice regardless of the depth of cut, as I tend to find cutters stay sharp for longer and I usually get both a better finish on the wall of the job, as well as finding it easier to turn the feedscrews due to what I consider to be a more natural cutting action i.e. not feeding against the rotation of the tool.

As soon as the infeed overlap starts to drop significantly below 50% of the cutter diameter there becomes an increasing tendency for the cutter to drive the work, so I find climb milling is most likely to grab the backlash in the slide with a combination of a large diameter cutter and a shallow infeed, at a large depth of cut.

A safer way to climb mill on a machine with appreciable backlash and small infeed, is to bias (push or pull) the slide to ensure the 'lash is removed before the tool engages in the cut, at which point the feedscrew is kind of used to regulate the pass rather than drive it.

Having said all that, using this method when machining the walls of a pocket should be done with care, particularly as the cutter engages in the corners, because this is where the backlash in the stationary slide can suddenly beome apparent if it hasn't been accounted for by locking that axis or biasing out the 'lash

Martin.

[WolfieParticipant @wolfie]

Eventually mainly to put my mind at rest I took it down to Arc Euro and had them do their checks on it. Turned out it was badly set up but not too much else wrong with it so I now have peace of mind and can get on with my grinding rest.

I have to commend Arc Euro by the way, a very efficient set up, knowledgable staff and a quite decent mug of tea. Much recommended.

[StovepipeParticipant @stovepipe]

Posted by Wolfie on 27/08/2012 16:14:08:

I have to commend Arc Euro by the way, a very efficient set up, ……….a quite decent mug of tea. Much recommended.

The really decisive criterion – the shop tea.

My experiences by mail order from them confirm that they are an efficient outfit, and a pleasure to deal with.

Dennis Franklin

[Author]

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