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Milling for beginners

Please use this thread to ask questions of make suggestions about the series in MEW

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Ketan Swali03/08/2018 08:27:47
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Posted by Ron Laden on 03/08/2018 08:20:58:

Thank you Jason, I enjoyed those, very informative.

If as you advise, using a small amount of Maxsyn cutting fluid, would that be neat fluid..?

Regards

Ron

Ron,

Maxsyn is generally to be used 1:20 dilution.

Ketan at ARC.

JasonB03/08/2018 10:02:33
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As Ketan says it's 20:1 on the bottle but I usually mix a small amount a bit stronger around 15:1 and dab a bit on with a brush.

SillyOldDuffer03/08/2018 10:15:14
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Posted by Ron Laden on 03/08/2018 08:20:58:

...

If as you advise, using a small amount of Maxsyn cutting fluid, would that be neat fluid..?

...

May be worth knowing that there are two types of cutting fluid available, those intended to be used neat and those intended to be mixed with water, (which can be used neat).

The 'mix with water' type create an emulsion like milk containing globules of lubricant evenly dispersed in water. Water is exceptionally good at removing heat and preventing cutter damage. Also, a good way of blunting a cutter is to have it re-cut old swarf rather than cut clean metal. An effective way of removing swarf is to wash it away by flooding the cutting area with coolant. Therefore, though it can be dabbed and splashed, emulsions are typically used with a tank, pump, hose, and recovery system.

The neat type are intended for use when heat removal and swarf clearance aren't a priority, like when tapping. The lubricant is applied as needed with a brush or spray.

Some metals like cast-iron and brass are best cut dry. Aluminium is cut with a neat light oil lubricant like paraffin or WD40.

It's not clear in my amateur workshop which approach is 'best':

  • Carbide is 'all or nothing' because splashing hot carbide with cold liquid is likely to crack it. You either flood cool carbide or cut dry.
  • HSS is less likely to crack and it's safer to apply lubricant with a brush or spray, using the brush at the same time to clear swarf as well as lubricate the work.
  • Neat cutting fluid can be used on everything, including Aluminium, which is a convenience.
  • The big problem with cutting fluids, especially flood cooling is they make a MESS! I suspect for many reducing mess is the most important consideration. Mostly I potter about doing light machining and don't stress my tools. That means I can get away with a minimalist approach to cooling. All that's normally needed is strategic dabs of lubrication and swarf clearance. Cleaning up is straightforward. Anyone cutting metal more intensively than me would likely put more effort into cooling and cleaning up.

But there are many exceptions. Always lubricate when thread cutting. Despite, not bothering normally, I flood cool my milling machine to protect expensive HSS cutters whenever removing largish amounts of steel.

In an emergency many ordinary substances can be used. Milk, bacon fat, soap and similar all work. Beware of serious disadvantages though. For instance, although Fresh Milk is a good cutting fluid, it decomposes. Apart from the stink, you don't want to get it in a cut - not even in the age of antibiotics. Usually better to buy the real thing.

It's possible I'm 'special'. How do others use cutting fluids?

Dave

Involute Curve03/08/2018 10:44:35
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I use flood on both mills, I have flood on both lathes, but 90% of the time run dry, although I do use flood for stainless or deap drilling on the lathe, and Rocol tapping and cutting fluid applied by brush on the drill press and or tapping arm, I also keep a small container of suds next to the grinders, I dip drills, lathe tools ect into it when hand grinding, to stop the fingers getting too hot.........ouch

Shaun

Andrew Johnston03/08/2018 11:34:48
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Posted by SillyOldDuffer on 03/08/2018 10:15:14:
How do others use cutting fluids?

Centre lathe: fitted with flood coolant - mostly turn dry except for drilling steel with HSS, and when parting off

Repetition lathe: fitted with flood coolant - always run flood coolant except for brass and cast iron. All tooling is HSS and I run the tooling hard, after all it is a production machine!

Vertical mill: fitted with flood coolant - almost never use it, as I don't have a drip tray, and it gets thrown everywhere

Horizontal mill: fitted with flood coolant - always use it, except for cast iron, as all cutters are HSS and are working hard

CNC mill: fitted with flood coolant - always use flood coolant, except plastic, brass and cast iron, primarily for washing swarf away, not so worried about cooling.

Cylindrical grinder: fitted with flood coolant - always use flood coolant, seems to give a better finish

I use a multi-purpose soluble oil, Castrol Hysol XF, formulated for hard water areas.

I rarely use lubricants when hand tapping, or machine tapping on the vertical mill. For coarse threads or tricky materials like stainless steel or bronze I use Rocol RTD. Works well but is a PITA to remove.

Dabbing coolant on with a brush is a complete waste of time. It doesn't really cool or lubricate and just creates a sticky mess. If you need to get rid of swarf when milling use cheap brushes dry.

There are stories about soluble oils going off. That may have been true in the past with natural oils, but is certainly not true of the newer formulations. My coolant can sit in the tanks for months or even years and never seems to go off. Mind you I do have a poor sense of smell.

Andrew

Neil Wyatt03/08/2018 11:44:55
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Posted by SillyOldDuffer on 03/08/2018 10:15:14:
  • Carbide is 'all or nothing' because splashing hot carbide with cold liquid is likely to crack it. You either flood cool carbide or cut dry.

I've never had problems with brush application of neat cutting fluid to carbide tooling. Stop start dribbling of suds might be riskier.

Muzzer03/08/2018 11:57:58
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Don't see the point applying coolant by brush to carbide tooling (or any, other than hand tapping for that matter). Seems to be essential behaviour in the US - but on this side of the pond?

Neil Wyatt03/08/2018 11:59:21
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Posted by JasonB on 03/08/2018 07:27:16:
I hope Neil did not have to reach for the sick bag too much

He appreciates your concern

The problem is not a moving camera, it's combining a moiving camera with automatic stabilisationon interior shots so it causes weird perspective changes.

Bazyle03/08/2018 12:23:59
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School machines were fitted with flood coolant because it made more profit and the salesman justified it as training for industrial practice which was true. When these machines got sold off amateurs started to get the impression that it was necessary. Before that virtually no modellers used flood, just a can and brush or a simple drip as shown in some ME articles to be 'advanced'.
When the company I was at still had about 50 machinists in the prototype section they never used flood (nor any lubrication on Al) because like sensible hobbyists they were not in a tearing hurry.

Soluble oils still evaporate water and can stain/rust when not in regular use. Do you really want to spray your workshop with a hosepipe? I think there are some waterless products for use in volume on CNC machines if you really want flood.

Neil Wyatt03/08/2018 13:06:44
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Posted by Muzzer on 03/08/2018 11:57:58:

Don't see the point applying coolant by brush to carbide tooling (or any, other than hand tapping for that matter). Seems to be essential behaviour in the US - but on this side of the pond?

I see an improvement in finish on some materials.

Also makes a big difference when parting off aluminium alloys under power cross feed. Stops welding to the insert. Affordable uncoated parting inserts are like rocking horse poo.

Neil

Edited By Neil Wyatt on 03/08/2018 13:08:04

JasonB03/08/2018 13:18:17
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Although I apply soluable oil with a brush it is not used as a coolant, more a lubricant/cutting oil and I do seem to get a noticably better finish when using it with both carbide and HSS. I don't often drive the carbide really hard so it does not get to a temp where adding more liquid could cause the problems that it is said to.

I use soluable on steel when both turning and milling, CT85 for tapping/threading/reaming.

CI and Brass don't use anything

Bronze I use soluable when drilling applied to the drill both in lathe and mill otherwise all dry

Aluminium is machined with paraffin and tapped/threaded wih CT-85

Wood and plastics dry

Matthew Sugden23/10/2018 16:13:56
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Hi Jason,

I've been reading your Milling for Beginners series with interest on Ketan's recommendation.

After also reading the flute-number-related comments above, I was wondering if there is any general 'rule of thumb' regarding cutter flute number to make things simpler in selecting a cutter?

I have some aluminium edge cutting to do (upto 25mm) and want to cut a long groove (70mm wide, 13mm deep) and I was planning to do these with a 20mm dia. 4 flute cutter after reading your comments in Part 6...

My current thinking is that the number of flutes are chosen based on the desired chipload and cutter strength and thus this is why a 4 flute is more suitable for edge-cutting (greater strength and smaller chips for lower forces).

But I was also wondering if there might be other considerations - such as any vibration issues when edge cutting with a 2 flute?

Any clarification/correction to my thinking will be most welcome!

Matthew

JasonB23/10/2018 17:30:35
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The chip loading is not affected by the number of flutes so a 4 flute cutter won't make chips half the size of a 2 flute.

Chip load is worked out for a single tooth lets say 0.1mm as that is a nice round number. So for a 2 flute cutter one revolution of the cutter needs for it to advance 0.2mm ( 2 x 0.1) to give the desired chip loading. If on the other hand you are using a 4 flute cutter that will need to move 0.4mm per rev (4 0.1) to give the same chip loading. Or looking at it another way the 4 flute can remove twice as much as a 2 flute in one rev and it does this by being fed along at twice the rate.

As the revolution speed is set to suit the metal being cut and the cutter material and cutter diameter that is fixed and the same for any flute number of the same given diameter. You would have to run a 2 flute faster than optimal speed to remove the same amount of material.

Generally a 4-flute will have a larger cross sectional area than a two flute so will be stiffer but you may find that with the large volume of swarf that can be produced when working with aluminium can start to clog a 4-flute unless you have coolant or air to help get it away from the cutting edge. For this reason an aluminium specific cutter may be a better bet as you won't risk blunting it or getting a poor finish by recutting swarf.

Having a larger CSA the 4-flute should vibrate less than a 2-flute of the same diameter and also using a short series will vibrate less than using a standard or long series, though with edge cutting you can use the area of flute nearest the shank to get the same results as a short series.

I'm trying to picture what you intend to cut. Sounds like you have upto 25mm thickness plate and want to cut a 70mm long groove going 13mm in from the edge is that correct?

Matthew Sugden24/10/2018 17:26:49
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Hi Jason, thank you for that answer - it helps put my mind more at ease and will save me umming and arring over 2 vs 4 for aluminium! I think I'll be better sticking with 2 flutes for now - I don't have coolant or air system set up and will just be lubricating/cleaning as I go. I have a 12mm 2 flute long series from ARC but I wanted to push it to 20mm preferably for the extra rigidity and to take fewer passes. I have the bigger brother of the machine in your article (SX4) which I think should cope amicably.

I think we're saying the same thing regarding chipload, feed, speed and number of flutes but from slightly different perspectives. I built a CNC router a few years ago and spent some time trying to get my head around the relationship between the variables and used the relationship "Feed = Flute number x chipload per tooth x RPM" to base a lot of my logic around. For different combinations of cutter material and workpiece material I figure that these variables are essentially adjusted to compensate for the relative difference in hardness and heat generated.

I've attached a picture of the of the piece with the 70 x 13mm channel I'm going to cut (as well as trimming the edges of the rough/plate sawn aluminium pieces). This is the thickest piece I'll have to edge-cut at 25mm deep.

capture.jpg

JasonB24/10/2018 18:50:53
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the 12mm should be fine for doing round the edges if you do as I said above and let it overhang the bottom of your plate so you are using the flutes closest to the shank.

For the groove work down on say 3 full cutter width passes and then start cutting sideways full depth maybe 2.5-3mm at a pass depending on how the tool sounds.

The other option to get faster removal rates is to use a carbide cutter for ali which can be run faster so faster feed and ARC do them in standard length, give a good finish too.

Matthew Sugden25/10/2018 12:01:41
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Thanks, I think I'll do that with the 12mm - saves buying more for now.

I do apologise though, I'm not sure I understand the procedure - are those 3 full cutter width passes next to each other and in the middle or to one side of the groove? I'd originally considered cutting the groove edges first accurately and then just working across the remaining at 2/3rds of the cutter diameter at a depth of cut that sounded OK.

JasonB25/10/2018 13:00:46
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I would do the three full width (of the cutter) passes just clear of the edge to take you down to the 13mm depth then a 13mm high by 1mm deep finishing pass to define one edge of your slot and then a series of 13mm high cuts working your way across the work until you get to the other side.

70x13 groove.jpg

Ron Laden27/10/2018 08:59:38
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Seeing the ARC premium cutter above, the 10mm 2 flute Std Al length carbide, I have just orered one as I have a fair bit of aluminium cutting to do. I have used my 10mm 4 flute TiN coated HSS cutter at around 750- 800 rpm which it seemed quite happy at, what speed increase for the carbide..50%..?

Ron

 

Edited By Ron Laden on 27/10/2018 09:00:13

Edited By Ron Laden on 27/10/2018 09:06:59

JasonB27/10/2018 09:22:44
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Will depend a bit on what depth of cut the machine can handle but 1500rpm will be fine, more for light cuts.

Andrew Johnston27/10/2018 11:17:02
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I run 10mm coated carbide cutters at 2000rpm in steel and 10mm uncoated carbide cutters at 3000rpm in aluminium.

Andrew

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