Climb Milling

[Neil WyattModerator @neilwyatt]

[Neil WyattModerator @neilwyatt]

I've just had an email about picture 21 on page 70 of the current issue, criticising the use of a picture that shows climb milling.

Now, aside from the fact that close inspection of the picture will show this isn't the case, I'm aware that opinions on climb milling vary hugely. Mention the subject and you can be sure:

• CNC users will wonder what the fuss is about.
• Old-schoolers who did apprenticeships on manual mills will scream with horror!

The problem is, of course, that climb milling is perfectly safe and sensible if the machinery is up to the task and the operator knows what they are doing. For the unwary, inexperienced or those with machines with significant backlash or out of ajdustment, it can be a bear trap.

Now I use modest climb milling on my X2, and I know other users of benchtop machines do as well. The typical beginner doesn't know what climb milling is until they do it unawares and get problems. Sensible advice on the subject would help them work safer and get better results.

I'm sure this will trigger heated debate, no doubt some people will feel its a topic that should not even be mentioned, but ignorance is the biggest danger of all. If anyone is interested in writing a balanced article on the pros and cons of climb milling, please get in touch.

Any article should cover safety precautions, getting the machine properly adjusted, what the relative movements of cutter and work are, when it can be used to advantage and when it should be avoided.

If interested, email me at neil.wyatt@mytimemedia.com

Neil

[David Clark 13Participant @davidclark13]

Just nip up the slide locks sufficiently to introduce enough drag to stop the table being pulled onto the cutter.

[jason udallParticipant @jasonudall57142]

As a miller of little or no experience I look forward to such a reasoned treatment.

[JAParticipant @ja]

I have always avoided climb milling because I scare easily. However I know it is an acceptable and sometimes necessary practice. I would really appreciate a good and comprehensive article on the subject, please.

JA

[Gray62Participant @gray62]

Fairly good explanation of conventional vs climb milling here (and various other places on t'internet, don't really think this warrants magazine space as the information is easily available already.

I think it's plainly obvious that the slitting saw is not climb cutting. I'm more surprised that someone hasn't commented on the workholding. There's very little material actually held in the vice jaws and with a substantial slot already in the workpiece I would have thought vibration/movement of the work would be more of an issue here. That said, the author is demonstrating what can be achieved with the equipment to hand. Overall I think this is a very well written and presented article.

Edited By Graeme W on 07/10/2015 14:43:55

[JasonBModerator @jasonb]

Posted by Neil Wyatt on 07/10/2015 14:04:42:

 

Now, aside from the fact that close inspection of the picture will show this isn't the case, I'm aware that opinions on climb milling vary hugely. Mention the subject and you can be sure:

Neil/Graeme what can you see that I can't as it looks like it is climb cutting to me. Unless the blade is mounted so the spindle can run in reverse

As DC1 says just nip up the locks a bit.

Edited By JasonB on 07/10/2015 15:27:39

[Mark CParticipant @markc]

Doesn't everyone have reversible spindles? That one is going anticlockwise.

Mark

[JasonBModerator @jasonb]

But won't the blade retaining screw be at risk of comming undone.

[Mark CParticipant @markc]

Can't see what thread was used might be L/H, anyway, cutter will probably have a key?

Mark

[Stuart BridgerParticipant @stuartbridger82290]

I can't determine the tooth form to see whether that is climb milling or not. Certainly you can install a slitting saw so it cuts clockwise or anti-clockwise. May not be best practice to run it the "other" way as Jason says. Not sure I am brave enough to climb cut with a slitting saw though.

[JasonBModerator @jasonb]

Yes suppose the author may have left and right hand threaded arbors. I thought running slittingsaws with a key was more of a taboo than climb milling

J

PS can anyone confirm which way the blade is facing as the digital mag is not clear enough to see the teeth

[Gray62Participant @gray62]

From what I can determine on my ipad (and in the printed mag) the spindle must be running anticlockwise as the saw appears to be installed to cut left to right as you look at the image.

As for the arbor, it is quite feasible that it has a LH thread retaining screw. I have arbors with both LH and RH threads.

[Mark CParticipant @markc]

Tooth form can be seen but you need a magnifier unless you have rodent eyesight.

Never come across the idea of not using a key, all mine have keyways in them and climb milling is something you do if you want a nice finish but then I never was an apprentice in a tool room, I was trained as designer and only learned the theory having picked up practise from tool makers and machinists working for me.

Mark

[KWILParticipant @kwil]

Yes Mark they do have keyways in them, have you ever wondered what might happen if you had a jam?

Hence keys not used by practical people.

[David Clark 13Participant @davidclark13]

I am a practical person and I sometimes use a key. However, the key does not have to be in the cutter. Put the key on the arbor nearest the nut but not engaging the cutter. This will stop the nut unlocking whatever way the cutter is rotating but will probably not break the cutter if it has a jam up.

Edited By David Clark 1 on 07/10/2015 17:02:05

[Steve PaveyParticipant @stevepavey65865]

Neil – can you reproduce the picture here for us to look at?

Like many, I was taught not to climb mill unless absolutely necessary. Same applies to woodworking machinery (routers, spindles etc), though it's potentially more dangerous than with milling. I don't think it is good for any machine to be dragged through the workpiece by its' cutter, so I would still avoid it with a new machine with little backlash. I'm not sure about cnc machines and their feed mechanisms – possibly a ball screw is capable of withstanding the extra load of a climb cut, but it is still counter-intuitive for those of us who like to look after a machine.

[MuzzerParticipant @muzzer]

Even with climb milling, there is a depth of radial cut above which there is no longer enough net force to pull the work into the cutter. If you achieve this or slightly exceed it, you are in little danger of rubber pants moments and will have to actively feed the work to the cutter. This applies mainly when using an end mill to remove stock off the end of a work piece. I'm guessing it's something like 2/3 of the cutter diameter.

[VicParticipant @vic]

I use climb milling because it saves time to cut in both directions and sometimes you get a better finish. I can't however recommend doing it on a machine with worn lead screws/nuts however tight the gibs are. I'm not a trained machinist just someone who had to learn the hard way on an old machine!

[AjohnwParticipant @ajohnw51620]

I was taught not too either unless the work needs it but wouldn't scream in horror. Just laugh if I saw some one doing it and it messed the work up. It's no good saying tighten things up as the degree of that needs some intuition relating to the size of a cut. The grab goes once the lead screw play is taken up anyway.

No key ??????? Any well designed miller will have a shear pin some where. Best hope some one has not replaced it with welding rod etc and that it is annealed brass. Belts would slip on some unless they are over tightened.

Actually some where from the days when masses of people descended on motor factories daily to the sound of a hooter and parts were made by hand I have read arguments that horizontal climb milling is more efficient. However they wouldn't have been using noddy Bridgeports. Not even sure these even have a horizontal attachment.

John

–

Edited By John W1 on 07/10/2015 17:41:03

[Mark CParticipant @markc]

KWIL, thinking as a practical person, you have a tool steel cutter with a sharp edged keyway located against a soft (ok, it's probably a bit tough if it is a real key) key located at about a 1/4 or less of the working outside diameter. If it decides to stop turning because you get excited with the handle there is a very good chance the excitement will be in the form of a bang and a sheared key? Apart from very thin saws all my horizontal cutters are big and need a key or they will not cut, just spin on the arbour and jigger the shaft and spacers up. The spacers on my machine are all lapped square so I really don't want that to happen!

Mark

[Mike PooleParticipant @mikepoole82104]

The only factor against climb milling is the existence of backlash in the table drive, the use of ballscrews usually solves this at a stroke but other solutions are available, anti backlash nuts can be spring loaded or hydraulically loaded to eliminate any lost motion, I even worked on an NC mill that used hydraulic rams to move the axes. Unfortunately serious backlash solutions are not often fitted on home type equipment, my humble VMC has a crude pinch screw to tighten the nut but any wear in the screw will soon result in tight or loose spots. I often do light climb milling for a finish cut and adopt Davids suggestion of using the locks to provide more resistance to the axis being dragged by the cutter but this relys on having some feel for the cutting forces versus the table drag. Backlash elimination tends to wear the screw but converting to ballscrews could be done even if CNC is not the final goal but costs a bit just to eliminate backlash. If backlash did not exist I think climb milling would be the mode of choice as all the theory is in favour of it.

Mike

[Neil WyattModerator @neilwyatt]

Posted by JasonB on 07/10/2015 15:23:30:

Neil/Graeme what can you see that I can't as it looks like it is climb cutting to me. Unless the blade is mounted so the spindle can run in reverse

Exackertaly!

Neil

[Neil WyattModerator @neilwyatt]

I was hoping you would all rush out and buy a paper copy!

Right click and view image if it's a bit small.

Someone has shared a Sandvik document with me that details why cutters last much longer when climb milling –

Conventional cutting gives chips that start thin and end thick, climb milling makes chips that start thick and end thin. The thickness on entry doesn't matter as the cutter is in compression but the shock of reaching the end of a thick chip causes rapid erosion of the cutting edge. Sandvik have the photos to prove it and the effect although worst for carbide also applies to hard metal cutters as well.

I had never realised that climb milling was better for cutters and always assumed it was a bit worse!

Neil

[AjohnwParticipant @ajohnw51620]

It certainly may start thick when the cutter engages Neil, much thicker than intended.

Sounds to me like Sandvik diidn't have any feed on as that will always tend to make the end thick.

John

–

[Author]

Posts