Milling 101

[FIXIT]

I have a small mill/drill max 6mm cap
which seems to work well if i don't get to greedy with the cut.
I've played with this and have made a small engine with it,
as I'm about to start another i would like some advice,

When milling the edge of a piece which way should i travel with the cutter?
When cutting along the back side, from left to right with r/h rotation
i can see that the cutter would try and "climb up the face" or should i be going the other way
any advice on this and gen/milling is really wellcom.

i will post a pic when i figure how to
Steve

 

[arnoldb]

Hi Steve - Welcome to HMEM

First off, that's a mighty small mill if its max 6mm capacity ! - are you sure you have the correct specification there? ;D

Secondly, what you are seeing and describing is correct, and for the most part the wrong way to go about milling on a small mill; You never want to be putting on any significant cut by climb milling.

To make things simple, rather use the point of view of "which way should I move the workpiece past the cutter" - as the cutter is stationary, and you actually move the workpiece - unless you have a mill that is not familiar to me.

You have a nifty description with "climb up the face" - that's called "climb cutting" and is the wrong way to go about rapid material removal.
When trying to remove material rapidly, you should do it the opposite way, where the feed direction of your workpiece is against the way your cutter edges are turning when meeting the material. This is called "conventional milling".

Climb milling will try and pull the workpiece in the direction you are moving it, and if you have backlash in your feedscrews, this can cause a jump of the workpiece and very quickly cause a broken cutter or ruined workpiece. Conventional milling is more stable, as it tries to resist the workpiece moving past the cutter, thus keeping a more-or-less constant pressure against the feedscrew and nuts

If you mill a piece down using conventional milling, it helps a lot to take a finishing pass with climb milling with no additional infeed, or with a very light (0.02mm) infeed for the last pass - and that must be taken slowly. It will smooth out things, as climb milling is inclined to make a smoother finish than conventional milling.

Simply put, for cutting along the back end of your workpiece, remove metal by moving your workpiece from left to right past the cutter. Smooth off by running it back from right to left.

Same goes for movement in the Y direction; if you want to remove material off the right-hand edge of your workpiece start with it on the back side of the mill (cutter between you and the workpiece) and move the workpiece toward you. To finish, move it away from you again.

When milling a slot, you have both conventional and climb milling going on at the same time, so direction of travel is not important. If you are widening a slot, you will only be cutting on one side, in which case the above becomes a factor again.

Hope I didn't confuse you! - Looking forward to your pic ;D - there is a sticky note at the start of the "Photos and Videos" section on how to do it.

Regards, Arnold

 

[Deanofid]

Hi Steve;
I'll just second what Arnold says. I think he has it.

Check the first post in this thread by John Bogstandard. There's a picture there that shows
very clearly what is what. On a small machine, you want "Up Milling", also called "Conventional milling".

http://madmodder.net/index.php?topic=1002.0

Dean

 

[Blogwitch]

Dean,

That was one of the posts that lost all the pictures when something went wrong with my photobucket.

I now have that picture back again, and it is here.


John

 

[Deanofid]

Hi John;
That one still shows up on MM, for me, at least. We need it here, too!
It's a good one for the newer fellows to have for reference.
Thanks.

Dean

 

[Tin Falcon]

Fixit in general climb milling is to be avoided. I My USAF tech school for machining it was against the safety rules. Climb milling can have advantages in pro cnc machines but should be mostly avoided in small hobby mills. I say mostly because a light cut of a few thou in climb mode can improve the Finnish.
Tin

 

[FIXIT]

Hi- thanks for the replies, and they say "a picture says a thousand words".

after carefull reading i fully understand Arnold's explanation and it now makes sense ,
what confused me as i "climb-mill" it seemed to me wrong as it must be straining the poor little machine but the finish was better on small cuts but the help from all of you plus the drawing answers it.

What have is a axminster/chinkie desktop mini mill/drill with x/y table with max chuck capacity of 6 mm and electronic speed control
I would really like some thing bigger but no room, but that's another story,i will post pic's of my "work shop" soon
once again thanks everyone and I'm glad i found this site (you wont get rid of me now )
Steve

 

[T70MkIII]

I printed this up and stuck it onto my mill head for quick reference - feel free to use if it helps:

 

[zeeprogrammer]

Welcome to the forum Steve.
I hope you get the pics figured out soon.

 

[Troutsqueezer]

I printed this up and stuck it onto my mill head for quick reference - feel free to use if it helps:

It's early in the morning here so my brain's not fully engaged yet but it looks to me like your picture has it backwards. That looks like climb milling to me. What am I missing (beside brain cells)?

-Trout

 

[Tin Falcon]

Think you are right trout looks backwards.
Tin

 

[doc1955]

Think of the block moving not the cutter.

 

[T70MkIII]

Think of the block moving not the cutter.

That's right - sorry for the confusion. The cutter is stationary, and the arrows show the direction the block should move in relation to which edge you are cutting.

I'm new at this, so please let me know if I do have it backwards after all...

 

[arnoldb]

Richard, you have it correct for the direction your workpiece must run past the cutter.

Regards, Arnold

 

[Blogwitch]

I will tell you all now, experience doesn't stop you going the wrong way at times. I think we all do it.

I try to always work in the same direction, just to keep the mistakes to a minimum.

I always, if possible, work from the right hand side of the job. So for X axis working, I have the cut face away from me and the job moving from left to right and for Y axis work, again on the RHS of the job, I have the job coming towards me. For two reasons, I will not be climb milling and the chips are flying away from me.

Sometimes I can't have everything so simple, then I have to turn my brain on and make sure that I am going in the right direction.

When you are just starting out on the milling trail, it pays to invest in some brown corduroy trousers and a clothes peg, it is also recommended to tuck your pants into your socks.

Bogs

 

[doubletop]

When you are just starting out on the milling trail, it pays to invest in some brown corduroy trousers and a clothes peg, it is also recommended to tuck your pants into your socks.

Bogs

Now you tell me!! Where's that shovel?

 

[T70MkIII]

Thanks very much, Arnold - I appreciate the confirmation. I thought I was right having thunk it through but better to be sure, and I certainly didn't want to be propogating incorrect information here.

Bogs, I was just squaring off 2 stacked pieces in Y, so I didn't want to flip them in the vice to do the other side. I'm with you - cutting on the RHS and moving the work towards me felt much more natural. I had to think about the direction of cut on the LHS even with my little chart, and you're bang on about being attacked by chips!

Try as I might, I can't find a cords shop in Oz. I'll try eBay. Socks with thongs, however? I think not

 

[Tin Falcon]

Richard your diagram would indeed be correct your arrows are on the part.
Tin

 

[T70MkIII]

Thanks, Tin.

 

[AlanHaisley]

Steve,

This:

What have is a axminster/chinkie desktop mini mill/drill with x/y table with max chuck capacity of 6 mm and electronic speed control

concerns me. It sounds like you have the equivalent of a 1/4" drill chuck in your mill. If that's the case, you REALLY don't want to do milling with it. Drill chucks have both too much runout as a rule and also can't hold an endmill stabily (is that a word ???). Please post pictures as soon as possible so further advice can be provided if this is so.

Alan