How fast is fast enough

I'm looking to buy my first milling machine and have been considering a victoria elliot V1. It looks to be a robust machine. The top spindle speed is listed at 1000rpm. I'm looking to do mostly model engineering and bitsvand bobs for motorcycles and my land rover so I'm guessing at the smaller end of what this machine is capable of. Is this top speed going to be too slow for this type of work?

Hi Colin,

It depends on the milling cutters you intend to use, smaller cutters need higher speeds. Carbide cutters can run at least twice as fast as a HSS cutter of the same diameter. You would use a higher speed when milling brass than steel.
On my vertical milling machine I use mainly HSS for smaller cutters - up to 16mm. I also have a larger carbide tipped facemill, I rarely use speeds over 1500 RPM when milling steel.

Thor

Hi Colin,

Do not worry about "top speed" requirements - all cutting speeds are simply based on the "most economical speed" in commercial applications, trading off tool wear against rate of material removal. For hobby use (where you do not pay for time, but pay to replace cutters) it is normat to work at slower than textbook surface speeds, depth of cut and feed rates in order to increase tool life.

My mill is fifty years old and has three speeds (I do not know the RPM, I just call them Fast, Medium and Slow) so speed options are limited....

If you have a "slow" top speed it just me and the job might take a bit longer - looking on the positive side, this means you will have more time for that cup of tea!

All the best,

Ian

Hi Colin

I had a Victoria U1 universal mill so pretty much like the V1.

It was a very robust machine but horizontal spindle was 500 rpm, when the vertical head was fitted to the horizontal arbor position for drive the bevel gearing in the head doubled the speed to 1000rpm on the vertical spindle.
I used the mill for about 5 years and found it suitable for all ME work, even to using the slotting head to make some gears for my Bantam lathe.

So is your head drive the same arrangement ?

Emgee

Emgee

I have a U1 universal. Its max speed is 1010 rpm on horizontal. I have a vertical head as well so this may be capable of 2020 rpm if the bevel gears double the speed.

Martin

It does matter; the mill will have been designed to use relatively large HSS cutters. Of course one can use HSS, or carbide, at slower speeds than advertised without harm. Although there's little point in using coated carbide cutters at low speed. The coatings need to run hot to work. The problem comes with smaller cutters, say less than 4mm. Of course a smaller cutter will still cut at a low rpm, provided the chip load per tooth is correct. The difficulty is maintaining a steady feedrate. Slightly too fast and the cutter will break, whereas a larger cutter will just shrug and carry on.

To summarise low speeds won't be a problem unless you need to use cutters below about 4mm. Above that it's just tedious. Slowing down and decreasing feedrate doesn't always increase tool life, it can shorten it. Depth of cut has no effect on tool life.

Andrew

According to my handy sliding "calculator" device giving suggested speeds and feed rate for HSS end mills and slot 1000 rpm (ish) is fastest speed for :-

1/8" Ø cutters in stainless steel

3/8" Ø cutters in ordinary steel and cast iron

1 1/8" Ø cutters in brass and light alloy.

I rarely go over about 1,200 rpm even though my Bridgeport varispeed can get beyond 3,000. High speed means chips everywhere unless you have decent guards which tend to get in the way when big enough to be really effective. I have a good industrial quality set which just doesn't get used because I can't easily see what I'm doing. Unhitching to get in to measure becomes a pain too.

Clive

Thank you for all the replies. It looks like 1000rpm is going to be fine for me. I'm very happy with the idea that I just need to slow the feed rate to compensate as I do enjoy a cup if tea.

Although most cutters will still remove metal at slower revs it depends on how you want to use your time. If the motor bikes are your main interest and the machining secondary to getting something made so you can go out on a ride then a slower spindle will often mean a job takes longer. If you are happy just pondering along in the shed then the extra time it takes to make something may not be a problem.

My manual mill seldom come out of the high speed range of 100-2000rpm and is mostly used in the top half of that eg 1000-2000rpm The CNC mostly runs in the 4-5000rpm range as it can't go any faster even though I would like to. If I were limited to 1000rpm then given the same chip load a job would take 5 times longer so that item I made yesterday in just over 1 hour would have taken 6, I know which of the two I prefer.

As it probably has an Int40 spindle and 3HP motor there is plenty of room to make a concentric light weight speed doubler or even an ultra high speed spindle mounted in the spindle and driven down the drawbar hole.

I've no idea what these are but they sound like an ideal project to make with the mill if I buy it!!

I have just looked at the mill on "lathes UK" and it is very nice, but is an industrial machine with cat40 tooling. You will need a lot of space and as the speed is low, you will have to be patient with smaller tooling as your feed rates will have to be low. If the vertical head is included it would be a bonus, as they make the machine easier to manage for smaller jobs.

Martin

Picture courtesy of Lathes UK of the mill I had, differences are also the horizontal drive was MT3 as was the vertical head spindle, there was no quill so drilling/boring involved a lot of Z axis handle turning.
I had a 1425 single phase motor driving the original multibelt pulley so perhaps the std motor was 2800 which would fit with my 500 rpm and your 1010.

Emgee

Edited By Emgee on 20/12/2021 22:45:19

Hi,

It is interesting to read the views of people who find rate of removal of material an important issue (or at least a consideration).

As I stated in my earlier post, I do not consider a slow rate of material removal to be significant - I am not in the business of making large production runs, I make models as a hobby, as relaxation and entertainment. Consequentially, almost everything I do is a "one off" and so I find I spend a relatively small percentage of my time actually machining.

When considering milling jobs, I would estimate I only spend about 10% of my time actually cutting material. The other 90% is spent on the following tasks (in decreasing order of percentage time consumed):

1) Making/reading drawings and thinking about how I'm going to do the job

2) Setting up the job on the machine

3) Marking out

4) Digging out the required material and tooling

5) Cleaning up and putting stuff away

A further issue for me is that I frequently find I need to make some sort of custom jigs/fixture to hold the part I actually want to work on. Designing and making such items can often take longer than making the part I actually want....

Given all of the above, being able to remove metal at twice my normal rate would have minimal impact on my overall 'production rate'

All the best,

Ian

An interesting view Ian. As one who considers removal rates I too am purely a hobby model maker with no engineering background, Andrew 50/50. my breakdown may be a bit different. I also make a lot of things from solid or by fabrication so take something like a steam engine cylinder, I will have a lot more work in it's construction than just boring, facing a few surfaces and drilling and tapping holes

1. Yes I do design a lot of what I make but that tends to get done of a evening or if I have some spare time in the day (not retired) and I think about how I will machine the parts as I design them as little point is coming up with something that can't be made. If working from published drawings then that proportion of the overall time input would come down a lot

2. Yes there will be some setting up time, I did not include that in my example above but that will often stay constant as it takes the same time to set up a part if you then cut it in 1 unit of time of 5 units

3. Marking out seldom gets done these days in my workshop the DRO or CNC are more accurate than a scribed line and punch as well as considerably quicker

4. People have seem my workshop and its quite a quick and easy job to locate materials and tooling but there was an element of sawing from bar and roughing down to shape of that part before the main machining. I do have a bandsaw that tends to be faster than power hacksaws and obviuosly that roughing was done with as high a speed as possible.

5 Similar to above people may think I spend most of my time tidying up but if done regularly it takes little time and again is a constant not affected by cutting rates.

Yes making jigs also takes time but if you can also make those jigs and fixtures faster than that must surely be a bonus. I did make a simple holding block for the part mentioned but was able to run the 2.5mm drill at 5000rpm and feed accordingly and not have to mark out or spend time locating those marks.

So the proportion of machining time to overall time put into a component will vary depending on the individuals way of working but can certainly be less than 90% of the time.

My experience is that its not so much about rate of material removal per se.

More about appropriate feed rates to avoid breaking small cutters and choking the job with chips. Safe depth of cut is pretty limited with small cutters so its annoying when you have to reduce it even further so the chips are small and light enough to be swung clear after cutting.

About the only time the Bridgeport gets wound up to the top end of its speed range is when I have a small cutter working quite hard. Speed helps clear the chips too. With light alloy even mist coolant, along with the associated air blast, is often not enough to keep the cutter clear of edge build up and stop chip re-cutting at lower speeds. Chip re-cutting being a very bad thing. Especially in slots! Depends on the alloy and state of heat treatment. Some E-Bay "not expensive" stuff is pretty horrible at lower speeds.

That said my usual speed range is in the 500 to 1200 region. Lower end of direct drive for a Varispeed. Objectively I could manage quite well with 1000 rpm top but had I your machine it would get a VFD to perk top speed up to maybe 1500 when really necessary. Knew a man who had a V1 who reckoned an extra 500 rpm was about all it needed to make it decently right for home shop one and only machine.

I often go a bit exotic on small cutters. Three and five flute centre cutting end mills rather than common two flute slot drills for example for 3/16, 4 mm, and below for example. I do very little work needing such small cutters so the extra cost can be lived with.

Clive

Horses for courses ?

Don't be conned by "The need for speed" Colin, this is a HOBBY. Leave the high speed cleaving to industry and despite what many think, you don't need a mifford to be a muddle ingineer.

Regards Ian. (a nuvver one)

One uses a speed appropriate for the cutter. The lowest I've used is 30rpm and the highest 24000rpm. Swinging an 8.5" diameter flycutter with HSS toolbit, in cast iron, with an interrupted cut needs 30rpm:

Conversely running small endmills needs high rpm if they're not going to be liable to break:

I like my Myford, plus I don't have room for a J&S cylindrical grinder.

Andrew

I could have done with one of those 24,000rpm horses today Andrew would have saved me having to go at 50mm/min. Did not want to try any faster as the single flute 60deg pointed engraving cutters was probably only 0.1mm dia at it's deepest. Still reached teh finish line and it turned out OK even if there was a bit of thumb twiddling while it slowly did the job. 80 x 25mm small Font 2.5mm high.

Edited By JasonB on 21/12/2021 15:12:41