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Milling for beginners

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not done it yet01/07/2018 13:02:02
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Both will do the same basic job apart from the end mill does not have cutting edges which cut to the centre on the end. That means that if you try to plunge cut there is a central area left uncut, preventing any plunge. Basically as simple as that.

Ron Laden01/07/2018 13:17:13
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Thanks, Now I,m probably being stupid here but what is the point of an end mill, why not use a slot drill for everything..?

 

Edited By Ron Laden on 01/07/2018 13:18:08

Edited By Ron Laden on 01/07/2018 13:18:35

JasonB01/07/2018 13:19:59
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Sorry I can't agree with that old way of thinking, many "end mills" produced now have centre cutting edges and would now be better named "4-flute milling cutters" as they can plunge cut. Ok this is a rougher but same applies you can plunge, ramp and side cut with 4-flutes

2-flute cutter also tend to cut a lot closer to their nominal size where as a 4-flute can cut over width if it deflects in a heavy cut.

Have a read of part 4 of my series for a bit more info

Not the best photo but the 4-flute on the right will plunge cut

imag3096.jpg

 

 

Edited By JasonB on 01/07/2018 13:46:21

JasonB01/07/2018 13:44:50
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Posted by Ron Laden on 01/07/2018 13:17:13:

Thanks, Now I,m probably being stupid here but what is the point of an end mill, why not use a slot drill for everything..?

- If you were to slice a 4-flute cutter across the flutes the cross sectional area would be more than that of a similar diameter 2-flute one so they are more rigid handy for long deep cuts or when using a lot of the cutters side.

- for the same optimum speed and tooth loading you will be able to remove twice as much material with a 4-flute than a 2-flute so job takes half the time.

- For the same cut a 4-flute will remove twice the metal of a 2-flute before the cutting edges are worn to the same extent so cost and time savings

Ron Laden01/07/2018 13:58:56
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Thanks Jason, appreciated, I can understand that.

Ron Laden01/07/2018 14:10:35
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Posted by JasonB on 01/07/2018 13:19:59:

Sorry I can't agree with that old way of thinking, many "end mills" produced now have centre cutting edges and would now be better named "4-flute milling cutters" as they can plunge cut. Ok this is a rougher but same applies you can plunge, ramp and side cut with 4-flutes

2-flute cutter also tend to cut a lot closer to their nominal size where as a 4-flute can cut over width if it deflects in a heavy cut.

Have a read of part 4 of my series for a bit more info

Not the best photo but the 4-flute on the right will plunge cut

imag3096.jpg

Where do I find your series Jason, I,m probably missing the obvious.

Edited By JasonB on 01/07/2018 13:46:21

JasonB01/07/2018 14:20:51
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In Model Engineers Workshop mag, alternate issues with Neil's Lathework for beginners in the other issues

Nige01/07/2018 14:23:00
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Ron. The series Jason is referring to runs in the magazine Model Engineering Workshop.

Gas_mantle.01/07/2018 15:40:42
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Where do 3 flute end mills fit into all this ?

At the moment none of the 4 flute mills I have are centre cutting so I use a 2 flute for the odd plunge job and 4 flutes for everything else but was curious as to the pros and cons of 3 flutes ?

Ron Laden01/07/2018 16:09:20
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Thanks Jason and Nige

Ron

JasonB01/07/2018 16:37:01
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Posted by Gas_mantle. on 01/07/2018 15:40:42:

Where do 3 flute end mills fit into all this ?

They fit in the middle! Good all rounders particularly in the smaller sizes.

Most of my cutters 1/4 or 6mm and below are 3 flute, I keep a few 2 flute for things like keyways and valve slots and the odd special, material specific or extra long one but as you can see the rest are 3-flute. They work out quite economical on price and I don't see a lot of point in having all sizes in 2 and 4 flute.

dsc02891.jpg

Edited By JasonB on 01/07/2018 17:14:59

Andrew Johnston01/07/2018 19:41:42
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Posted by Gas_mantle. on 01/07/2018 15:40:42:

Where do 3 flute end mills fit into all this ?

At the moment none of the 4 flute mills I have are centre cutting so I use a 2 flute for the odd plunge job and 4 flutes for everything else but was curious as to the pros and cons of 3 flutes ?

Industrially 3 flute cutters are used on aluminium alloys where high feedrates and large chips need large gullets to avoid jamming, but metal removal rates need more that 2 flutes. I don't get too hung up on the number of flutes. I mostly use 3-flute cutters but also have 2 and 4 flute ones. Generally the 2 flute cutters are small (less than 2mm), the 3 flute cutters are uncoated and the 4 flute one are coated and so get used on high carbon and stainless steels.

Despite being centre cutting it is usual to follow a ramp or helical path with centre cutting tools (at least on CNC) as when plunging the centre is, in theory, cutting at zero speed. And hence is quite inefficient.

Another thing worth noting is that some far eastern suppliers don't seem to know how centre cutting cutters work. So the grind pattern on the end is a joke and gives a poor finish.

Andrew

Ron Laden18/07/2018 09:37:02
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I have not looked at mini mills yet in any real detail but a question, do they follow the minilathes in that they are all very similar and coming out of two or three main factories in China. The minilathes (in the same price bracket) dont differ very much in features from one to another, is this the same with the mills.

Ron

Edited By Ron Laden on 18/07/2018 09:37:39

Neil Wyatt18/07/2018 10:23:36
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Generally true, but there is less variation in the mill specifications.

Look for a brushless motor and large table.

Neil

Ketan Swali18/07/2018 10:45:23
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Posted by Ron Laden on 18/07/2018 09:37:02:

I have not looked at mini mills yet in any real detail but a question, do they follow the minilathes in that they are all very similar and coming out of two or three main factories in China. The minilathes (in the same price bracket) dont differ very much in features from one to another, is this the same with the mills.

Ron

Edited By Ron Laden on 18/07/2018 09:37:39

Ron,

Mechanically, they are 'broadly' similar. Things start changing mainly in the headstock with type of motors, belt or gear drive. Also, be careful when comparing wattage. Most state input power but WILL NOT say that it is input power.. Machines on our website state OUTPUT power.

The minilathes and minimills no longer come out of two or three main factories. There are plenty of smaller operations selling less than acceptable product via known shopping platforms. It is difficult to explain this to new people entering the hobby without making it sound like sour grapes, and the marketing which supports such products doesn't help either. Also, unfortunately the presumptions you make about 'coming out of the same factories' are quite common. As a result, all the problems start coming to light once the user needs electrical spares.... as they are not all the same.

ARC sells SIEG products, and we field queries on a daily basis - requests for electrical spares to fit a machine which did not come out of the SIEG factory.

Ketan at ARC.

Edited By Ketan Swali on 18/07/2018 10:46:43

Edited By Ketan Swali on 18/07/2018 10:47:45

Ron Laden18/07/2018 10:52:44
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Thanks Ketan,

Belt drive or Gear drive....pros and cons...?

Ketan Swali18/07/2018 10:58:15
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Posted by Ron Laden on 18/07/2018 10:52:44:

Thanks Ketan,

Belt drive or Gear drive....pros and cons...?

Realistically, for this size of mill, very little, depending on where you get it from.

Key points: brushless with belt - quieter than anything gear driven.

For gear driven, plastic gears less noisy than metal, but if they break (plastic), more time needed to figure out and change. The plastic gears are 'usually' a fail safe.

Ketan at ARC.

Ian S C18/07/2018 15:21:11
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Not quite on topic, the other night I was reading up on Medding drill presses, they recommend belt drive as best for production drilling over gear drive.

Ian S C

JasonB03/08/2018 07:27:16
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With the next issue of MEW about to hit the virtual door mats of those with a digital subscription here are the videos that show the SX2.7 from ARC being used for some basic cuts with a 4-flute cutter. I used a piece of EN3 steel for these rather than the 6062 aluminium used for the magazine photos, 10mm 4-flute cutter from a budget range as that may be more representative of what a beginner may buy. Cut dry for a clearer view buy would suggest a small amount of something like this to give a better finish and prolong the life of the cutter. If you click "Youtube " along the bottom it will show at a larger size or the icon bottom right for full screen.

Also not all the text was deleted from last months title so no marking out in part 6.

 
 
 
 
 
I hope Neil did not have to reach for the sick bag too much but using a tripod would have been a problem as I needed to show different parts of the machine, also cranking one handed with the camera in the other does not bode well for steady shots.
 
This is the finished steel test piece.
 
dsc02958.jpg
 
 

Edited By JasonB on 03/08/2018 07:53:55

Ron Laden03/08/2018 08:20:58
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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

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