Author Topic: Horizontal Milling - Speeds and Feeds  (Read 3365 times)

Offline Jasonb

  • Full Member
  • *****
  • Posts: 9466
  • Surrey, UK
Re: Horizontal Milling - Speeds and Feeds
« Reply #15 on: December 17, 2022, 01:23:23 PM »
Jo, I can't see anywhere in those pages you have posted that includes cutter diameter in the feed rate calculation, could you highlight it for me if I have missed it.

From what I can read he says feed rate is number of teeth cutting per min (74 x 20) multiplied by chip load (Say 0.003") = 1480 x 0.003 = 4.440" which is what I posted earlier but I did not have to go and look in a book to see how to calculate feed rate. I also instinctively new that some rates mentioned were too high. You don't have to own a horizontal to  know how to calculate feed rates are they apply just the same with milling cutters in vertical machines be they manual or CNC

Brendan, I'm not sure why you are having a job cranking the handle, assuming 0.100" pitch on your lead screw one turn per second is 6"  which should be easy enough to manage.

Offline jadge

  • Full Member
  • ****
  • Posts: 503
  • Cambridge, UK
Re: Horizontal Milling - Speeds and Feeds
« Reply #16 on: December 17, 2022, 01:45:39 PM »

...which photo you are referring to with regards to dust? With the plain S&F cutter or shell mill cutter?


The shell mill - Andrew

Offline Jasonb

  • Full Member
  • *****
  • Posts: 9466
  • Surrey, UK
Re: Horizontal Milling - Speeds and Feeds
« Reply #17 on: December 17, 2022, 01:48:48 PM »
Andrew mentioned a video of his mill fitted with an 80mm, 7 insert facemill chomping it's way through some low carbon steel which was posted on ME forum following another thred about running a similar cutter on a typical imported bench top hobby machine. It illustrated well that with a powerful motor and a solid/rigid machine a lot of metal can be removed in short time. More details in description under video.

<a href="https://www.youtube.com/watch?v=-lJcsCRBoew" target="_blank">http://www.youtube.com/watch?v=-lJcsCRBoew</a>

You can see chips not dust in this video and mine too, though Andrews are a lot more impressive



By way of contrast these are a couple of videos of a Sieg SX2.7 which has less power available due to electronic speed control and is certainly not as rigid as even Brendan's small but solid machine. Doing some calculations (using the right formulas) the facemill was the quickest option for removing a similar amount of metal to flycutting or muptiple passes with a 12mm milling cutter and also faster than the person asking about the facemill own lathe could do it

<a href="https://www.youtube.com/watch?v=ABLBkBl6inA" target="_blank">http://www.youtube.com/watch?v=ABLBkBl6inA</a>

<a href="https://www.youtube.com/watch?v=QK3AgOPvr4A" target="_blank">http://www.youtube.com/watch?v=QK3AgOPvr4A</a>

For those interested the two threads on ME are

https://www.model-engineer.co.uk/forums/postings.asp?th=184130

https://www.model-engineer.co.uk/forums/postings.asp?th=184183
« Last Edit: December 17, 2022, 02:23:31 PM by Jasonb »

Offline Jasonb

  • Full Member
  • *****
  • Posts: 9466
  • Surrey, UK
Re: Horizontal Milling - Speeds and Feeds
« Reply #18 on: December 17, 2022, 03:47:16 PM »
Ah I see where jo is confusing the issue and not helped by showing images of pages from a different book.

The attached shows the book by Tubal Cain where I have underlined in red where he says that feed rate is the product of rpm, number of teeth and tooth LOAD which is what I said.

He then goes on about an "F Factor" which is related to the diameter of end mills and slot drills when used on a Myford Size lathe, the chart showing that the very smallest dia cutters will have a lower Factor than anything over about 7/16 due to them being less rigid. Not really relevant to horizontal milling unless you count holding a milling cutter in the lateh spindle as horizontal ;). This F factor seems to just be a guide for what can be safely cut on a Myford size lathe.

Offline john mills

  • Full Member
  • ****
  • Posts: 417
Re: Horizontal Milling - Speeds and Feeds
« Reply #19 on: December 17, 2022, 07:29:09 PM »
try using narrow side and face cutters 1/4" does not load the machine as much .think of the width as the depth of cut on the lathe
if the cut can be deep enough to have teeth in contact and so load on the machine all the time.if you use the lowest speed the cutters will last longer .when you feed buy hand you will feel how it is cutting and you will be surprised how much feed you can use if more teeth are in contact and cutting is constant.your machine is light and low power but will work well with narrow smaller cutters slitting saws that are narrow are much easier to drive for cutting slots the smaller side and face cutters are easier too.helical teeth help with sallower cuts.
The larger wider cutters  were more suited to use on much larger heavy machines .

Offline Brendon M

  • Full Member
  • ****
  • Posts: 229
  • Melbourne, Australia
Re: Horizontal Milling - Speeds and Feeds
« Reply #20 on: December 18, 2022, 02:14:40 AM »
This is going better than I was expecting

Brendan, I'm not sure why you are having a job cranking the handle, assuming 0.100" pitch on your lead screw one turn per second is 6"  which should be easy enough to manage.

That will be because one hand is trying to squirt the workpiece with oil and the other is cranking  :-[ I need some sort of drip setup

However, I just repeated the test and found I could go at 4 inches per minute, each crank of the handwheel is 5mm and 4ipm is turning the handwheel 1/3rd every second. Yeah probably more manageable with both hands. 6 ipm sounds like a workout though : P

Just a reminder the original question was: is there a way to reduce the feed rate that won't result in the cutter getting blunted as a result, or will I just have to accept that I will need to sharpen frequently, or get used to cranking quickly (or come up with a powerfeed).

Unfortunately in this test I managed to destroy the 20 tooth cutter  :facepalm: several of the teeth are now chipped

The chatter on entry from the side is terrible, I guess that's because the little Hercus vice is both small and tall allowing too much flex, and the table has too much play in it (can vibrate back and forth) but that can be compensated for by slightly tightening the table lock - which I know you are NOT supposed to do as it will cause long term damage.

The only way I could  get the cut going without chatter was to plunge from the top and center of the vice, after that I was able to get the 4 IPM mentioned above. I was getting rectangular flakes instead of curls so I was definitely going faster than last time.

I thought maybe it stops chattering because plunging ensured that all the teeth engaged, but that didn't work when plunging to the left of the vice. The flex in the vice is allowing the workpiece to vibrate, and I assume it gets better after going past the center because the teeth are now not able to grab and pull the workpiece into it.

The thing that gets me is the original cutter supplied with the machine is 3/8ths but with angled cutters and it has no problem engaging the workpiece and maintaining a nice cut regardless of depth, and that is with some of the cutting edges not in great shape either. I guess the angle of the cutting edge goes a long way to gradually introducing the cut unlike the straight tooth cutter.

Conclusion: too much play in the table and too much flex in the vice, sound about right?


...which photo you are referring to with regards to dust? With the plain S&F cutter or shell mill cutter?


The shell mill - Andrew

Thank you Andrew

This shell mill came with the machine and pre-chipped on one of the teeth however it still has no trouble cutting - on that part it made a nice "slicing" sound.

Aside from the dust what about the other chips that are essentially long curls formed into tubes, do they indicate the cut was going OK? I was perhaps being a bit cautious I'd once managed to jam the machine by taking too much of a cut. Have to remember this is basically a bench-top machine.

try using narrow side and face cutters 1/4" does not load the machine as much .think of the width as the depth of cut on the lathe
if the cut can be deep enough to have teeth in contact and so load on the machine all the time.if you use the lowest speed the cutters will last longer .when you feed buy hand you will feel how it is cutting and you will be surprised how much feed you can use if more teeth are in contact and cutting is constant.your machine is light and low power but will work well with narrow smaller cutters slitting saws that are narrow are much easier to drive for cutting slots the smaller side and face cutters are easier too.helical teeth help with sallower cuts.
The larger wider cutters  were more suited to use on much larger heavy machines .

That might end up being the answer for the straight tooth cutters however this same machine has no problem with staggered tooth cutters almost as wide, and Hercus only list a max diameter on the cutters, so I presumed the limit of DOC is the 1HP for each cubic inch of steel removed. In other words.

The intention for the wider cutters was for doing cleanup on large surfaces in one go, not to go really deep. However maybe I need to start looking for those helical slab cutters instead.

Thanks again everyone :)
« Last Edit: December 18, 2022, 02:18:13 AM by Brendon M »
(This signature intentionally left blank)

Offline Jasonb

  • Full Member
  • *****
  • Posts: 9466
  • Surrey, UK
Re: Horizontal Milling - Speeds and Feeds
« Reply #21 on: December 18, 2022, 07:23:30 AM »


That might end up being the answer for the straight tooth cutters however this same machine has no problem with staggered tooth cutters almost as wide, and Hercus only list a max diameter on the cutters, so I presumed the limit of DOC is the 1HP for each cubic inch of steel removed. In other words.


There are three factors to arrive at MRR (metal removal rate) so for one cubic inch/min you need three dimensions to arrive at a cubic one.  Ap x Ae x (Zf x Z) per min

Ap - Depth of cut is the first and the easiest to adjust to suit the available power of the machine

Ae Width of cut this may be limited by wanting a slot X width so you have to use a cuter of X width or as John says use multiple passes of a narrower one to reduce the MRR and therefore reduce the load

Total Chip load, given that we now know you have a small machine then anything over 0.001" or 0.025mm per tooth is expecting a bit much from it and anything less runs the risk of rubbing. so you are really fixed with that one.

Large dia cutters will often sound unhappy on entry and exit as there is very little tooth engagement, think of turning a piece of square or hex stock in the lathe it may not sound happy at first but as you get closer to turning the full AF things become a lot smoother

Offline jadge

  • Full Member
  • ****
  • Posts: 503
  • Cambridge, UK
Re: Horizontal Milling - Speeds and Feeds
« Reply #22 on: December 18, 2022, 11:43:10 AM »
The curled swarf indicates proper shearing of the metal.

Even on entry there shouldn't be any chatter. Certainly a thunk, thunk as each tooth cuts, but not chatter. I agree that the biggest issue seems to be lack of rigidity. Although I have a large machine vice I prefer to clamp the work direct to the table wherever possible. I note that the vice is use is a swivel vice; unfortunately that reduces rigidity. Swivel vices seem to be one of those things that everyone thinks they need, but never actually use. I don't have a swivel vice and have never missed the facility.

There isn't any way to slow the feedrate without slowing the spindle speed. The chip load is the important factor. When I first got my horizontal mill I had trouble with vibration. Doubling the chip load from 2 thou per tooth to 4 thou per tooth solved the vibration problem in an instant. It all comes down to the fact that cutters need to cut,  not rub. So small feedrates are a real problem if they lead to small chip loads. With shallow depths of cut the feedrate really needs to be increased to allow for chip  thinning.

I recall a thread on another forum talking about similar problems with a comparable size machine. The conclusion was that with a lowest speed of around 200rpm the machine simply wasn't capable of utilising larger diameter, and wide, side and face cutters.

Andrew

Offline Brendon M

  • Full Member
  • ****
  • Posts: 229
  • Melbourne, Australia
Re: Horizontal Milling - Speeds and Feeds
« Reply #23 on: December 18, 2022, 11:55:51 AM »
Thank you JasonB I have had a chance to review your attached image

So chip load of 1 thou as a minimum and slow RPM = somewhere between 1 to 2 inches per minute, quite manageable while hand feeding, but I should aim to feed faster if I can.

On reflection of all my testing, even with the allegedly blunt cutters, the chattering always stopped once the cutter was past the center of the vice but I didn't notice this because I had usually altered DOC or RPM by this point, so I thought one of those two had the effect; this is why you only alter one variable at a time  :facepalm:. I should have tried this test with something solid bolted directly to the table but until now I wasn't sure if it was the second hand cutters being dull.

I also need to sort out the backlash in the table which I can imagine is also a major contributor to cutter entry being entirely unpleasant since it allows the cutter to vibrate the table back and forth.

In the meantime, I can confirm that simply taking a smaller width of cut is fine, at least with the test piece and vice as shown in the above photos, I get nice curled chips and no chatter, but that same cutter chatters horribly if I try to take more than half of the width of the workpiece.

I have to state it plainly that this is my first mill - horizontal at that - and things like judging the rigidity of a setup I am still learning. But now I know, and knowing is half the battle.

@Andrew I just saw your post, and yes I have since realised most of this trouble I have been having was with the rigidity of the work holding.

Thank you both for your input
(This signature intentionally left blank)

Offline jadge

  • Full Member
  • ****
  • Posts: 503
  • Cambridge, UK
Re: Horizontal Milling - Speeds and Feeds
« Reply #24 on: December 18, 2022, 12:43:11 PM »
Backlash shouldn't be a problem, unless you are climb milling. However, badly adjusted gibs on the table may allow the table to bounce around under the influence of the cutter.

Andrew

Offline Jasonb

  • Full Member
  • *****
  • Posts: 9466
  • Surrey, UK
Re: Horizontal Milling - Speeds and Feeds
« Reply #25 on: December 18, 2022, 01:05:51 PM »
If you can remove the vice from it's swivel base that will help with rigidity and also gain a bit of extra head room.

I think I have only used the swivel base on mine Once in 15years, the rest of the time it lives in the back of a cupboard. On the odd occasion I do want the vice at an angle I just use one of the lugs over a tee slot and clamp the other down where ever it ends up.

If you are plunging the cutter down into the middle of the work and then moving it both left and right then you will be climb cutting in one of those directions which is probably best avoided.

Offline john mills

  • Full Member
  • ****
  • Posts: 417
Re: Horizontal Milling - Speeds and Feeds
« Reply #26 on: December 18, 2022, 08:49:59 PM »
if you are plunging down and any tenancy to climb mill it is not good on light machines with ordinary screws even with adjustment an
minimum back lash there is sufficient spring for climbing into the material very quickly.plunging may be necessary for cutting slots but should only be done with all backlash taken up and only with thiner narrow cutters. eaven on heavy machines climb milling is not good .as an apprentice they would not show climb milling on a good sized heavy mill equiped with backlash eliminator but did not work last time it was
tried it took the vice off .and that was a heavy machine.when you feed from the side it should take up the load gradually.on a small machine use smaller cutters as you find what the machine will handle .
john

Offline Brendon M

  • Full Member
  • ****
  • Posts: 229
  • Melbourne, Australia
Re: Horizontal Milling - Speeds and Feeds
« Reply #27 on: February 03, 2023, 11:57:23 AM »
Hello, apologies for the late reply, since December I haven't had much of a chance to get down to the shed. Thank you all for your help so far.


With the same now probably busted cutter, I did some more testing, this time with a piece of 20x20 solid bar about 2 inches long, so minimal overhang of the vice jaws to eliminate any possible vibration from cantilever effect. Here are my results:

  • Using the original Hercus swivel vice without the swivel base - 5mm DOC - chatter and pins and needles for swarf. I hate this because they really are needles and one way or another end up embedded in your hand.
  • Attempted to clamp work piece directly to table, but unfortunately the arbor couldn't clear the clamping arrangement. I would need some of those fancy low profile clamps that bite from the side.
  • Out of desperation, tried a crappy certain hardware store vice bolted very firmly to the table - 5mm DOC - again, chatter and pins and needles for swarf.
  • Just for kicks, tried a 1mm DOC. Machine stopped complaining, starts generating "flakes" for swarf. Not great but at least no chatter and pins and needles. Repeat this several times with similar results.


So while in principle a 1mm DOC at 12.7mm wide is technically not near the 0.5 cubic inches per minute this machine is theoretically capable of, the combination of straight teeth and machine rigidity limits how much of a DOC I can take. I wonder if that relationship is linear i.e. a 1 inch wide cutter I can only take a 0.5mm DOC. I suppose I should repeat the test with a cutter that isn't potentially blunted from all my earlier idiocy.

I just want to stress that a 3/8th staggered tooth cutter is able to take a 5mm DOC in mild steel even in the swivel vice.

Conclusion: I think I need to buy more staggered tooth cutters and a better vice ;)
(This signature intentionally left blank)

Offline Mcgyver

  • Full Member
  • ****
  • Posts: 394
  • Toronto
Re: Horizontal Milling - Speeds and Feeds
« Reply #28 on: February 04, 2023, 01:37:53 AM »
Agree with the conclusions....that vise looks like a drill press vise!   :o

Straight tooth cutters can hammer, as you say, you need the staggered tooth as they have a helix to the cutting edge.

Of course you can't surpass the machine's or set up's rigidity, but 1mm seems like a cray light cut....especially for a horizontal. What I try to do is go full depth of cut, and slow the feed down to point where the machine can take it.  Also slow rpm down to the point that at said slow feed rate, its making chips not dust.  Its still obeying all the rules, but it is an entirely different approach that would for say a 1/2" end mill.  RPM is set last after the result of the heaviest DOC at the feed the machine can handle.

You get a lot better results burying the cutter, within the above guidelines.  You end up with more than one tooth in the cut which reduces the hammering, and the whole system gets kind of preloaded, system being cutter, arbour, arbour support, bearing etc

Here's some examples at full dept.  These are all done with a vise, for heavy cuts these set ups are more solid.










Offline Brendon M

  • Full Member
  • ****
  • Posts: 229
  • Melbourne, Australia
Re: Horizontal Milling - Speeds and Feeds
« Reply #29 on: February 04, 2023, 06:39:45 AM »
Hello McGyver

You have an industrial sized machine, I have a 1/2hp 150kg "bench top" machine that also does horizontal milling ;) http://www.lathes.co.uk/hercusmiller/

Unless there are other parameters I have not yet accounted for, at the moment 1mm DOC with a 1/2inch wide straight tooth cutter was the best I could manage. That might be because the cutter is damaged, mind you. I might try again with a brand new cutter but making mistakes gets expensive. Perhaps that is just the cost of learning.


I will say that this Hercus mill had no trouble at all slotting directly through 10mm mild steel flatbar with a 1/4inch slot mill, or using a shell mill to take a 7mm DOC at 1.5inches wide; it is just straight teeth cutters it seems to struggle with.

And yes it is a drill press vice  :facepalm: I used it because I wanted to try and clamp the work piece as close to the table as possible. I need some neato clamps like what you have.

Thank you for your time :)
(This signature intentionally left blank)

 

SimplePortal 2.3.5 © 2008-2012, SimplePortal