First day on milling machine

[Keith MathesonParticipant @keithmatheson47708]

Hi

Day one playing on the milling machine and have started Harold's excellent milling course book. First thing I learnt is a similar lesson to the lathe. Start off with something as close to the final size otherwise you will spend an age going backwards and forwards getting somewhere near to where you should be!

Also learnt that clamping has to be more secure the more you cut ( don't ask me how I found out- one cutter chipped already!).

My question is how big a mill bit can you use? So for example I have a 1.1kw 1.5hp mill ( amadeal ama30Lv) and was using a 12mm end mill bit. I covered about a third of the area of the bit cutting and went down 2mm when I cut. If I had say a16mm bit could I cut more? Is it just a case of the cutting edges being further part on the diameter giving a worse finish, but the bit is bigger and stronger so less likely to break / go blunt, or have I missed something here?

Keith MM

[Keith MathesonParticipant @keithmatheson47708]

[Ian S CParticipant @iansc]

Keith, I have a mill of similar power, and use a 2" face cutter with 3 indexable carbide tips, The 16 mm end mill should remove material quicker, follow the suggested feeds and speeds, or a little slower until you get the feel of how it's cutting, keep the cutter feed up and don't let it rub.

All this back and forth makes one think of power feed.

Ian S C

[Ady1Participant @ady1]

Smaller cutters can be faster, more efficient and easier for your machine

Milling like latheing is a suck it and see hobby at the amateur level

[Martin ConnellyParticipant @martinconnelly55370]

There are theoretical values of maximum material removal for given power but they are best kept in production environments. What you should be concentrating on at this stage is getting correct speeds and feeds for you setups. You need to keep the chip thickness in the correct range. This involves considerations such as number of cutting edges on a milling tool, the spindle rpm and material. You do not want the tool to rub as it just reduces it's life. Spindle speed is the same as drilling speed for tool diameter. Work out feed rate for a chip thickness of 0.05mm for example and time yourself feeding to see how you compare, no need to be cutting metal when doing this. This is assuming you are working manually. If you have power feed find out the relationship between speed setting and feed rate.

Make sure you understand the difference between conventional and climb milling and the importance of minimal backlash for climb milling.

You may not be planning to use CNC but if you load Mach3 and set it up for milling it includes a wizard for calculating feeds and speeds for given materials and cutters. There are probably others available.

Martin

[EmgeeParticipant @emgee]

Keith

On a manual mill I used mainly 4 flute cutters and max DOC was equal to the diameter of cutter in use, width of cut and stepover was a quarter of cutter diameter, this was on a Victoria universal which is a heavily built machine.

As others have said take your time and experiment with different speeds, feeds and DOC but be caerfull you don't let the cutter just rub the work as it can blunt the tool.

Emgee

[Anonymous]

Keith: I'd agree with Martin on learning to understand speeds, feeds and chip loads. However, I'd disagree with him on leaving material removal versus power to production. If you have a certain amount of power available why not at least have an appreciation of how much metal you might be able to remove? After all the metal won't care, it doesn't konw if it's in a home or production environment.

A rough rule of thumb is that for low carbon steels 1hp will remove one cubic inch per minute. Personally I'd stick with the smaller cutters. As standard I use a 3 flute 10mm carbide cutter on my Bridgeport. If I was only cutting 2mm deep I'd be cutting 8-9mm wide per pass. I'd run at 1500-2000 rpm with feedrates around 300mm/min. However it is possible to cut much deeper, at reduced widths of cut. If I have a lot of metal to remove I'd be cutting 6+mm deep with a cut width of 2mm. You're paying for the whole length of the flutes on the cutter so why not use them.

Here's a 10mm carbide cutter cutting full depth, ~20mm, in steel, width of cut was 1mm conventional, 0.5mm climb:

Above all experiment, and accept that you're probably going to break the odd cutter, although it is surprisingly difficult. Unless of course you do something daft, like me, such as running the cutter into the work without the spindle turning.

Andrew

Edited By Andrew Johnston on 31/12/2015 11:08:07

[Martin ConnellyParticipant @martinconnelly55370]

Andrew, I said maximum metal removal rates are for production environment, not that people should not know what they are or work close to them. I just think that that is something to work on after the basics of feed and speed are understood. These are suggestions for a beginner to consider after all.

Martin

[MuzzerParticipant @muzzer]

As Andrew says, experiment to see what your machine can do. You are more likely to be limited by the machine rigidity (judder) than by the power of your machine and even then, changing (increasing?) the speeds and feeds may help bring you out the other side. My machine is almost identical to Andrew's ie 1.5hp motor like yours, so hardly a monster

This shows what 1.5hp can do. It's a 5/8" tee slot cut in 4 passes using a 12mm HSS end mill. 2 passes to get down to full depth, one to open out to 15mm / 5/8" and then one pass with the tee cutter. As Andrew says, make use of as much of the side faces as you can otherwise the ends and corners will wear out prematurely.

For prolonged cuts like this, the coolant is necessary to avoid the tool overheating. You have the power – now see what it can do! Power feed is a bonus, as it allows a consistent and safe feed rate.

Have fun!

[VicParticipant @vic]

It's handy to have a couple of roughing end mills to hand, they can remove a lot of material.

[Keith MathesonParticipant @keithmatheson47708]

Hi

This is all really useful. Looks like I am being very cautious and I can mill much more. However, my two mistakes (so far) stem from inadequate clamping. I have discovered why people use a milling vice not a drill vice and why there have been articles about removing the' rocking in the drill vice for improved clamping! Anyway, as I make more of the clamping pieces in Harold's book I should be better positioned to clamp things better and explore the full range of cutting speeds. On another note I seem to be taking many many hours to mill the simplist of bits – however, I am learning so much it is a great experience-I'm really enjoying it. . I'm sure as I get more competent ( and have better clamping options) my output per hour will increase!

Thanks again for your input

Best regards

Keith MM

[Ian S CParticipant @iansc]

I rarely use the mill vice(it's a bit rough), but clamp directly to the table, or the angle plate.

Ian S C

[Ketan SwaliParticipant @ketanswali79440]

Andrew,

I would politely advise that Keiths machine is a far more 'lighter' machine in size, weight and rigidity in comparison to the mill in your picture.

Murray,

I am uncertain about what your machine is, but if it is similar to Andrews, then the comment made to Andrew applies here too. However, as an additional note: I would question the output power of Keiths machine. The marketing blurb says 1.1kw, but fails to say – input or output power. To the best of my knowledge, the power being stated for his machine is input power, and the output power will be lower, and then there will be the torque, which is governed by other factors, along with rigidity of a lighter machine. (Nothing wrong if output power is lower than that specified, but it has a direct bearing on the question being raised in the opening post. However, I am not in favour of such marketing practice of sellers stating input power without stating if it is input or output, for obvious reasons, a concern which has been growing over the past year.)

Keeping the above in mind, it would be wrong to draw conclusions about feed, speed, depth of cut for Keiths specific machine. I would be more inclined to support Martins comments in this respect.

Keith's machine is a hobby machine, and I would be more inclined to use the quote borrowed from another thread even though it applies to a lathe, namely: "Lots of engineers reference books give tables of cutting speeds for various metals. You can turn over quickly – they don't apply to you and me. In home workshop machining you can only go by the feel, sound and appearance of the job".

The above comments are being made with the greatest of respect for the knowledge of all concerned, and my intensions are to try and be helpful to a beginner, rather than to create an argument or slag off any machine. I have seen plenty of beginners – almost on a weekly basis breaking gears or end mills or whatever on light duty/hobby machines as a result of failing to follow 'the quote'. The principal remains the same – be it a mill or lathe.

For clarity: ARC states output power for the SIEG machines it sells.

Ketan at ARC.

[JasonBModerator @jasonb]

Keith I have just posted on the Workshop progress Thread, this will show what a similar mill to yours can do.

J

[MalcBParticipant @malcb52554]

Martin Connelly has highlighted one of the essentials in that is very important to recognise the difference between climb milling and conventional milling.

Conventional machines ( i.e. None CNC ) have varying amounts of backlash and this can be climb millings downfall.

Aim to do as much as possible on your particular mill using conventional milling to start with as it is more forgiving where backlash is present. Even if your machine is new, check your jib strips on all slideways and take up any play that shouldn't be there as you should seek to maximise rigidity whilst cutting.

Also lock the two axis's that you are not using for your cutter feed. You sound as though you have already encountered the need to maximise the rigidity in your clamping arrangements. Speeds/feeds and depth of cut already covered.

Choice of using soluble cutting oils even if applied from squirt or spray bottle can help with cutter life and finishes just as with lathe work.

As with anything, protect your eyes and enjoy.

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