Convensional vs climb milling

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Convensional vs climb milling

This topic has 18 replies, 13 voices, and was last updated 15 October 2017 at 10:20 by Martin Connelly.

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28 October 2010 at 01:59 #57631
GoCreate
Participant
@gocreate
Hi

Came across this link

convensional vs climb milling

which I thought would interest those new to milling.

I often use climb milling with light cuts to get a better finish but you have to be very careful about backlash in your leadscrew, graet care is needed,

Nigel
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28 October 2010 at 01:59 #5254
GoCreate
Participant
@gocreate
an interesting link
28 October 2010 at 07:33 #57633
Bogstandard
Participant
@bogstandard
Nigel,

A good link, and a thing all new machinists should inwardly digest at a very early stage.

Unfortunately, I think the link is geared towards industry rather than home machining, because there wasn’t any warnings about backlash, which on large industrial machines doesn’t really need to be considered, as they normally have some sort of backlash elimination ie.ball screws, whereas home machines invariably don’t.

For the beginner, climb milling is really a no-no and no-go area until you know the full limitations of your machinery, and the full meaning of the two types of cut are fully understood, and even then, must be pursued with great caution.

OK, it it can give fine finishes (but with care you can achieve the same thing with conventional milling), but also it causes more broken tooling and damaged work pieces than any other thing when the unwary encounter it by accident. Usually ending up with a big question mark hovering over their head, and rather smelly trousers, plus of course the damage caused.

If at all possible, I keep away from climb milling like the plague, even on small cuts and a largish machine as I have. But sometimes you can’t avoid it, in which case I do a slight tighten up on my gib locks and take things very steady.

Bogs
28 October 2010 at 09:29 #57637
KWIL
Participant
@kwil
The condition of the cutter has a great effect as well. Do not climb mill with a dull cutter!
28 October 2010 at 10:04 #57640
GoCreate
Participant
@gocreate
Hi Bogs and kwil

Thanks for your additional input all of which I fully agree with.

Yes, on reflection I don’t think beginners should try climb milling but rather be aware of the two conditions in order to avoid it.

I must confess to having broken cutters by accidently climb milling and when I live dangerously and do it deliberately a little pressure on the table locking screws is used. So it may increase slide way ware a little but I doubt if I will be around long enongh to worry.

Cheers

Nigel
28 October 2010 at 11:08 #57645
GoCreate
Participant
@gocreate
Here is a more appropriate link that explains why you should not climb mill when backlash is present, as will be the case with all convensional hobby milling machines.

Climb milling and backlash

Hope this clarifies the situation

Nigel
28 October 2010 at 11:27 #57647
Anonymous
Hmmm, I think we’re being a little pessimistic! Climb milling is a useful ‘tool’ to have in the armoury. Here are a few notes, based on my experiences:

1) I find that climb milling gives a better finish on soft metals, such as aluminium, albeit I do limit it to a small depth of cut on the manual mill, say less than 1mm

2) On harder metals, such as stainless it seems to have less of an effect, but there are other reasons for climb milling on materials that work harden

3) On plastics, such as uPVC, climb milling does not give a better finish, conventional milling is best

4) On my CNC mill I always finish by climb milling, roughing is usually a mixture of climb and conventional, whatever gives the shortest machining time.

5) If you do climb mill with an end mill, don’t use a radial depth of cut near 50%, it will be likely to chip the teeth, especially with carbide cutters. Use much less or much more.

Tongue in cheek; if a beginner shouldn’t use climb milling, how do they try new things, and learn, so that eventually they’re no longer a beginner?

Regards,

Andrew
28 October 2010 at 18:00 #57688
Mark Dickinson
Participant
@markdickinson21936
Daft question time…

If you are using a fly cutter or a face mill do you still have the issues withe climb milling?
28 October 2010 at 18:30 #57692
KWIL
Participant
@kwil
You can answer your own question by looking at the state of the surface after the cutter has passed
28 October 2010 at 19:45 #57697
chris stephens
Participant
@chrisstephens63393
Re Andrews tongue in cheek, I just copied this from another site;

“I believe it was Einstein who said, “It’s a miracle that curiosity survives a formal education.” “

chriStephens
10 October 2017 at 22:45 #320947
C J
Participant
@cj88518
Hi,

I am new to milling and want to cut a 60mm hole out of a 1.5mm plate using a small end mill and a rotary table, can someone tell me which way should I rotate the table.

I am guessing at anti-clockwise when viewed from above as the metal on the right side of the end mill is travelling ever so slightly faster than on the left side of the end mill which whilst effectively climbing is always lagging behind the right in speed.

Edited By C J on 10/10/2017 22:50:05

Edited By C J on 10/10/2017 22:51:04
10 October 2017 at 23:09 #320949
not done it yet
Participant
@notdoneityet
I doubt it makes much difference. Ease of turning the table at a constant rate would likely be more imortant.
10 October 2017 at 23:21 #320950
C J
Participant
@cj88518
I hadn't thought of that but I splashed out on a 6" Yusa table with a very nice action.

Edited By C J on 10/10/2017 23:24:45
10 October 2017 at 23:36 #320951
Mike Poole
Participant
@mikepoole82104
As Bogs says backlash is the enemy of climb milling. Ball screws do a good job of minimising backlash but you can also have anti backlash nuts or hydraulic eliminators. A balls screw conversion can be useful even if you do not intend to convert to CNC but is quite a bit to spend just to climb mill. Mechanical elimination by nuts tends to wear the screw and as wear tends not to be even along a leadscrew it will not have a constant performance, more complex nuts can compensate but wear will still be an issue. Hydraulic eliminators are not really going to be found on hobby machines. I suspect we all snug the locks down and hope a sneaky light cut will not overcome the drag but get it wrong and you will wonder what the bang was. I have seen apprentices learn the hard way and drag the job out of a vice on quite a powerful mill. Maintaining the buttock clench can be quite tiring aswell if hand feeding.

Mike
11 October 2017 at 05:56 #320959
Paul Lousick
Participant
@paullousick59116
Hi CJ

The direction which you turn the rotary table depends on which side you are cutting your work.

Which ever side it is I would suggest that you use conventional milling so the work is pushing agains the cutter. The rotary table will have an amount of backlash in the worm and gear and will the cutter will try and turn the table and cause vibration when climb milling unless it is adjusted up tightly with brakes on. But hard to turn like this. Even with conventional milling, I would slightly clamp the table with the brake levers.

The teeth on the crown gear in some of the rotary tables are faily small and will not withstand hard knocks, which Is how I broke the teeth on my 6" Yuasa RT.

Paul
11 October 2017 at 06:12 #320961
Alan Charleston
Participant
@alancharleston78882
Hi,

One situation where it is definitely better to climb mill is when cutting gears in plastic such as acetal. If you cut the teeth using conventional milling you end up with a hairy finish on both the top of the teeth where the cutter exits, and the side of the gear the cutter exits on. If you climb mill, the hairiness is confined only to the side the cutter exits as the cutter enters the top of the teeth. It's easy to remove the hairiness on the side of the gear using a razor blade but very difficult to trim the top of each gear individually.

Regards,

Alan
11 October 2017 at 08:19 #320969
C J
Participant
@cj88518
Paul,

I am not going to cut from a side as such but cutting a continuously curved slot to make a large hole in the plate, or that’s the theory anyway.
11 October 2017 at 08:57 #320974
Mick B1
Participant
@mickb1
My experience has often been that the middle diagram showing cutter deflection doesn't show what really appears to happen.

You can run a 'final' counterfeed cut across a surface with the flutes of an endmill or slotdrill, and then find when you return across the same surface with a climb feed that you're still taking a spring cut.

Sometimes you can take advantage of this to get a good finish, although probably more often you have to add a thou or two to the cut to get out the last little digs from the previous one.
15 October 2017 at 10:20 #321536
Martin Connelly
Participant
@martinconnelly55370
C J, cut out about 59mm diameter first then clean up the edge to 60mm diameter. To finish to size turn the plate anticlockwise viewed from above to cut conventionally for the reasons given by Paul earlier. When the centre is close to coming free take care as it can be flicked into the tool or out towards your hand.

Martin C

Edited By Martin Connelly on 15/10/2017 10:21:35
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