Climb milling

[bogstandard]

It seems that a few members don't fully understand climb milling.

Unless you are fully conversant with the dangers of climb milling, it can easily become a major safety issue, with bits of metal and tooling flying in all directions.

My advice is that if you don't need to do it, then don't, but if there is no other way, then only takes very small cuts and do it with a slow feed with the gibs tightened up.

As they say about a picture, I hope the one at the bottom explains it all.

John

[John-Som]

I remember struggling to get a grasp of the difference between standard milling and climb milling. In my case I now relate it to shovelling coal (or snow if you live in Alaska). In other words you scoop it along the ground then lift rather than hacking in from the top - well the analogy works for me !

JohnS

[Divided he ad]

I lost count of the shattered cutters I went through when i first got my mill'      


I was pointed in the right direction by Boggie and all has been pretty good since then..... 



Hi Mr S

Coal!! Snow!!.... I'd rater not shovel either   .... But the analogy works for me 




Ralph.

[usn ret]

I have a Tiawanese mill made in the early 70s' which has been converted to XY CNC with recirculating ball lead screws.  When I first got the mill to do a climbing cut was taking your life in your onw hands. With the recirculating ball lead screws climbing cuts give me an execellent  finish without jerky grabbing feeds. It loads the cutter differently than standard feed.  The recirc ball takes all looseness from feeding.  The one I have to watch is the rate of feed which is controllable using the power feed. It works ok for me. My  $$$.02 
Cliff

[bogstandard]

You are quite right Cliff.

Climb milling does give much superior finishes, and in industrial machines, they have anti backlash nuts like you have, so that manual machines can take advantage of it. CNC machines usually have ball screws as standard.

I suppose with a bit of research, thought and work, most of our machines that we use could be fitted with them, at a price.


John

[George Greer]

OK...

As I am a beginner, and before I go and break my mill, or cutters........or hurt myself.

I will ask a few questions..

Link to a video for milling a simple part...start to finish?

If a part is machined from Left to right, then front to back and then right to left, Then,,, back to front....down, climb milling? On what face's ?

All this that I have been reading about, the dangers of it, has quite acutally got me a bit reluctant to begin.....

 George

[Dean W]

Hi George;
Look at the picture in the first post of this thread.  It shows the difference very clearly.

Dean

[BobWarfield]

The way I finally got through my head the difference was to think of the cutter as a pinch roller that's trying to move your work along.  With conventional milling, that pinch roller is working against you.  With climb milling, the pinch roller wants to pull the work deeper into the cut.  Think about it that way as you are feeding--does the pinch roller pull in the direction of feed or push against?

The safety is a function of your backlash, and the ability of the "pinch roller" to overcome your machine's friction.  If there is no backlash (for all intents and purposes) as with a ballscrew on a CNC, it doesn't matter.  If you can successfully increase the friction enough (by running with very tight gibs, for example), you MAY create a situation where the "pinch roller" (your trusty milling cutter) can't generate enough force to overcome the friction, in which case you can climb mill there too.

If you are unfortunate enough to climb mill with significant backlash and not enough friction to offset the cutter force, what will happen is your work can get "sucked" into the cutter a distance equal to the amount of backlash.  Depending on the machine, cutter, workpiece, how well it is clamped, etc., etc., this can result in problems ranging from a requirement for new underwear to serious bodily injury.   Have you ever seen a surface planer in a woodworking shop throw a plank?  Or perhaps a table saw with a nasty kickback?  Well, a bad incident here can have that drama plus shrapnel from the cutter.  No fun.

Something else to consider is reducing the force the "pinch roller" can create.  Use a smaller cutter and MUCH less depth of cut.  Hopefully you are only contemplating a risky climb cut because you're in search of a nicer finish anyway.  So if you are using a very light depth of cut commensurate with a finer finish, your pinch roller won't pull as hard. 

Or, consider a heavier mill with a heavier table.  There is a lot more to get moving there with a light cut.  Add tightened gibs and you're getting there.  Is it worth it when the handwheel is so hard to turn that it's hard to get a good finish for that reason?  You gotta wonder.

OTOH, having the ballscrews and CNC on my machine, gosh you can get a nice finish.

Cheers,

BW

[Baldrocker]

www.cnccookbook.com/MTCNCDictCADtoCycle.htm
I too had great difficulty  gettig my head around it  until I found the above page
It has one of the best illustrations I've seen, scroll down to get to it.
br

[George Greer]

Baldrocker...

That sums it up quite nice.

I had it backwards in my way of thinking..

I am going to print that photo and hang in my workshop...

Thanks.

 

George 

[andyf]

It's a bit like a circular table saw for wood, really, where you feed the wood against the top of the blade, against the direction of its rotation. If, with the blade rotating in the same direction, the table was such that you fed the wood into the bottom of the blade with the rotation, it would immediately snatch the wood from you and try to take enormous bites out of it, breaking the blade in the process.

That said, even on my rattly old machine I do sometimes take a very light (less than three thou) climb milling cut with the side of a slot drill no more than 1/2" dia, to get a better finish.

Andy

[BobWarfield]

I am going to print that photo and hang in my workshop...

Thanks.

 

George 

LOL, I had it taped to the side of my mill head for more than a few months!

Cheers,

BW

[Rob]

is there 'climbing' when you're fly cutting a surface?

[Stilldrillin]

is there 'climbing' when you're fly cutting a surface?

Hi!

Welcome to the Collective! 

No climbing, when your cutter is central to the workpiece. But, off to one side could be a different story....... 

David D