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Milling - Crash course.

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Nick_G13/10/2014 19:47:59
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1808 forum posts
744 photos

.

Well hopefully there will not be 'too' much crashing going on.! laugh

I have a mill being delivered this week and what I know about milling can be written on the back of a postage stamp in capital letters. So a few basic questions :-

2 or 4 flute end mills for.

1) En3 / En1 etc.

2) Brass

3) Cast iron

4) Phosphor bronze / gunmetal etc.

What region of spindle speeds for above.? I am presuming these will vary if using a 3mm or a 20mm tool. But I am just after a bit of guidance on a starting point.

Like a lathe I know that feed rates are also important but that will be another issue. I just wish to buy a few tools for arrival of this mill so I can dabble.

 

Cheers, Nick

Edited By Nick_G on 13/10/2014 19:50:02

JasonB13/10/2014 20:47:20
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2 or 4 flute will depoend on the type of cut to some extent. 2-flute is better suited to cutting a slot where there is metal on both sides of the cutter, a 4-flute is better when cutting from the side. Same applies for all the materials you list. The bronze and brass will benifit more from a sharp cutter

If you are going out to buy some cutters then a good start would be some 3-flute "FC-3" type cutters which wil do for most things to start with.

Speed will vary depending not only on dia but also depth of cut and material, I'm of the suck it and see school rather than working it out, you will soon get to know what sounds right on your machine and what does not.

Michael Gilligan13/10/2014 21:33:51
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16638 forum posts
725 photos

Nick,

Predictably wise words from Jason ...

I would just add a couple of comments:

  1. You obviously understand speeds & feeds in relation to the lathe ... it all translates to the mill, provided that you take account of the number of cutting edges.
  2. Buy, or make, a nice rigid flycutter for your mill ... use it in preference to end-mills wherever it is practical to do so,

MichaelG.

Rufus Roughcut13/10/2014 21:47:58
83 forum posts
20 photos

Mike

Some of these are a good range to start

**LINK**

GaryM14/10/2014 00:05:22
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314 forum posts
44 photos

Nick,

Here's a thread on MadModder that will give you a start.

**LINK**

Don't be tempted away though, there's lots of bike related stuff on there. devil

Gary

Thor14/10/2014 06:25:54
1294 forum posts
39 photos

Hi Nick,

much good advice offered, if you want a couple of books to read I would suggest two books from the Workshop Practice Series :

Vertical Milling in the Home Workshop (#2, by A. Throp) and

Milling A Complete Course (#35, By H. Hall)

Thor

Nigel McBurney 114/10/2014 14:46:59
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762 forum posts
3 photos

I would start by using 2 flute cutters,and a fly cutter for flat surfaces,a flycutter costs nothing to regrind so why use an expensive end mill to produce flat surfaces, for cast iron ,mild steel, phos bronze use as a guide about 240 rpm for a 1 inch (25mm) dis cutter so a 1/2 inch cutter would run at 480/500.for brass and alloy 2 or 3 times faster. for a light finishing cut on brass with a 2 inch flycutter and HSS cutter ,500 rpm can produce a very good finish.

Jack Foreman 114/10/2014 15:12:27
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99 forum posts
17 photos

I shall be following this thread with great interest Nick - as what I know about milling is significantly less than you proclaim to know emotion
Thank you for asking the questions.
Do please let us know how you get on, when your mill arrives.

Edited By Jack Foreman 1 on 14/10/2014 15:13:24

Russ B14/10/2014 15:49:30
597 forum posts
26 photos

As per the lathe, the rigidity of your setup is key, spend plenty of time stripping and cleaning the machine before finally re-greasing/oiling and assembling, don't expect results right out of the box, do expect to run in to the odd thing that needs a touch up or file down.

I found the "suck it see" worked best as JasonB said, just because you have calculated the perfect speed and feed rate to hit the magical numbers quoted somewhere doesn't mean your machine,work piece or work holding is capable of achieving it without deflection. (same as a lathe I guess?)

I found milling mild steel easier than aluminium since the spindle speed for cutting aluminium with small cutters was well out of my range (upto 2500rpm is my limit). I could actually drop down to the low speed high torque gear range for steel and work the mid range speeds of the motor which felt like the sweet spot.

Edited By Russ B on 14/10/2014 15:51:21

Howard Lewis15/10/2014 07:31:50
3766 forum posts
3 photos

As an Apprentice back in the late 50s, we were given charts quoting cutting speeds for Milling , and feed rates (in terms of feed per tooth). These referred to Industrial machines, such as Cincinnati mils. the lightest machine that we had in the Training School was a Theil Universal. (Wish that i had it now!).

All the rates quoted are depending upon hardness, slower for harder materials, obviously.

AND UNDER IDEAL CONDITIONS (Machine power, rigidity, Clamping security, sharp cutters)

The charts indicated that Carbide Tipped tools could be run about 3 times as fast, as HSS/Tool Steel.

It quotes CAST IRON, 55 -70 ft/min Roughing, 65 - 110 Finishing

STEEL , 35 -70 Ft/min Roughing, 50 - 100 ft/min Finishing

BRASS, 150 - 300 ft/min Roughing, 200 -700 ft/min Finishing

BRONZE 100- 125 Roughing, 150 - 180 ft/min

Feed Rates in Feed/Tooth (INCHES)

FACE MILLS

Cast Iron 0.013 -0.018; Steel 0.004 -0.012, Brass and Bronze 0.008 -0.022

SLOTTING DRILLS

0.008-0.013. Steel 0.010-0.003, Brass and Bronze 0.008-0.03

END MILLS

Cast Iron 0.008-0.006, Steel 0.002-0.008, Brass and Bronze 0.005-0.011

SAWS

Cast Iron 0.003-0.004, Steel 0.001-0.003, Brass and Bronze 0.002-0.005

Calculate feed by multiplying No.of Teeth by Spindle RPM .

Then use the nearest that the machine can provide, (try hand feeding at start of cut, certainly the first) if blessed with power feed.

If, like my machine, the feed is "mandraulic" you have to try to match your hand speed to the above!

And, of course, in all cases, watch and listen to the machine. If it struggles/objects/chatters, then slow down!

I NEVER use a key with Slitting Saws. It it jams, no damage is done, just stop, back out and go in again more gently. (I did break a 0.020 saw, to my shame, on a machine with a 3/4 hp single phase motor, this is the only damage so far.) Forcing a thin slitting saw will cause it to flex and wander, even if it does not jam.

Lubricant does help, both cutting and the surface finish.

Hope that this will be of some help.

Howard

Nick_G15/10/2014 07:42:32
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1808 forum posts
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Posted by Howard Lewis on 15/10/2014 07:31:50:

Hope that this will be of some help.

Howard

That's pukka. laugh

Thanks, Nick

Bob Brown 115/10/2014 07:44:03
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1016 forum posts
127 photos

When milling for the first time I would not recommend climb milling as unless there is very little to no backlash in the slides then the tool will grab, I only use climb milling on light finishing cuts.

Robbo15/10/2014 09:41:38
1504 forum posts
142 photos

If you go to "Workshop" on the black menu bar at the top of the page, then click "Processes" you will find that Neil has included a cutting speed table.

 

Phil

Edited By Robbo on 15/10/2014 09:42:01

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