using milling cutters

Tried a brand new 4 flute cutter today & with only a light cut the machine would have danced all round the workshop if not bolted down. I have not done anything with the gib strips yet as I have only just found the manual but I am not holding my breath.They feel fairly tight. I was using a 12mm HSS cutter cutting about 1-1.5mm deep * 4mm wide at 600 to 750RPM with 1 turn of the wheel every 2-3 seconds. Somehow the 2 flute one seemed just as good

Something definitely wrong. Wife has arranged for me to see a professional machinist next week ( husband of one of her golf friends) & he has offered to show me how to do this, so hopefully this will sort the problem

Sam can you post a close up of the ends of your cutters and tell us where they came from. Although they may be new they may not be good to start with.

Are you getting nice chips like in the videos that I posted or more like iron filings?

Curious problem Sam. Sounds like something is loose. Or possibly your 'mild steel' is something much harder.

I expect the machinist will work it out quickly. I guess he'll run some tests to isolate the cause. Does it do the same with something softer like aluminium, or even wood? Does it vibrate in both High and Low gear? Does it drill OK, etc etc.

Please report what happens - I'd love to know how he goes about doing a diagnosis and what the problem turns out to be.

Lots of sympathy though - it's really annoying when you want to get on and something awkward like this gets in the way.

Dave

Jason

I am really having a " bad hair day" today. Seems that I may have done some damage to the new milling machine although I do not know what.

First here are the pictures

I then went to photo the cutters & realised that the brand new 4 flute cutter now has 2 chunks out of it so i threw the piece of steel & changed back to the 2 flute cutter ( From Tracy tools)

I then remembered that I had a couple of metres of free turning steel rod & when I looked at it i found that I could get my T nuts out of the round. So I cut off 4 inches & began working on it. I have to say it was a lot better & at 650 RPM & with gib strips V tight & small cuts I was doing OK. Then I got to the top part & because I was using an old HSS cutter as a parallel the top sat below the vice so to avoid hitting the jaws I needed to run the cutter between them & take a full width cut. But as this was part of a round & only 2,8mm at the highest & only 12mm wide & as a 2 flute cutter is supposed to be ok for slots I decided to take it off in one go

Going very slow I was doing OK then as I turned to dip the brush in some oil the mill stopped dead.

When I removed the work it would only run at very slow revs & V noisy. I changed from slow to high gear & it ran OK . When I went back to low gear it now runs OK again but it may be that I have stripped a tooth off the infamous plastic cog. Will have to go on the Warco thread to ask forumites for advice on that one me thinks

Here is a picture of the offending bit of steel & you can see the cut which is by no means large. It was clamped across the width with a pack under the wide flat & the part I was cutting was below the top of the jaws hence I took the full width cut so as to miss the jaws

Edited By Sam Longley 1 on 27/09/2016 11:51:47

From the swarf colour & shape plus sizable burrs on the part I would say the cutter is blunt, I've seen this many times in the past.

Tony

Yep looks like it so a pic of the cutter would confirm

What are you holding the cutter in? Have you got a milling chuck or are you using the drill chuck that came with the machine?

Neil

Proper milling chuck with collets. Cutter has screwed end. As supplied by Warco

Sam, in the other thread you mentioned about using the side of the cutter, here is a video showing that and using the end of the cutter but at a larger width.

12mm 3-flute cutter that has seen better days, sharpened once on teh tips and used after that so showing some wear. 600ish revs for the first three cuts and then you can see I turned up te speed a bit, just put the tacho on it and says 673rpm all in low range. Probably EN3 mild steel

First two cuts are using a 10mm length of the flutes and increasing depth of cut sideways at 2mm per pass. The next two cuts use a 10mm width of cut increasing the vertical depth of cut by 2mm per pass, final cut 1mm depth.

I would say the first two cuts are a bit better as the sides of the cutter are not as worn further up as the ends but not a lot to choose between the two methods.

You will notice minimal burrs, just the couple that rub off easily and the chips are all reasonably large and bright. When your boat gets back in can you post photo of teh ends of your cutters as I'm sure that is going to be th e main problem.

Edited By JasonB on 27/09/2016 20:22:26

Jason

I really appreciate the time you have taken to do this. You are right about the cutters . It is too late to go into the workshop to photo them but the 4 flute is chipped having done less than you have done in your video from new. The 2 flute is also very finely chipped when viewed through a magnifying glass. So one can only assume they are both rubbish. The 4 flute did not cut as much as you have & was feeding slower than shown in your video.

That makes me query what sort of steel you are cutting? You made half a T nut in a few minutes whereas I spent a couple of hours fiddling & getting nowhere.

I am meeting the engineer when I get back from my trip & i will ask for his advice re what sort of cutters to purchase. Clearly cheapo ones are not worth the bother, but it may not be sensible just to throw money at it. This trip is the last one of the season( should be windy too!!!!) before I lay up so then I will spend more time in the workshop & somehow I will nail it !!!

So once again , many thanks, I now at least know what i should be aiming for

It is possible your odd bit of 25mm material was something hard and that took the edge off your cutters and once blunt they will not cut the free machining round stock.

I've posted before what I find economical yet reasonable quality for cutters.

There's also a (slim) possibility that your spindle is a bit loose. It's worth making sure it has no movement if you hold the chuck and pull it side to side.

Neil

I wouldn't be so quick to dismiss low cost cutters, particularly as you say you got one from Tracy Tools whose stuff I have found to be pretty good, as have many others on here. I have also been buying quite a lot of very cheap endmills and slot cutters off eBay sellers based in Hong Kong and have not had a bad one yet. I am very pleased with them, and rather surprised to be honest. I figure there are so many tool and die shops in China churning out plastic injection moulds and press dies for all their factories that they must be using millions of at least reasonable milling cutters in the process, hence large supply and low price for reasonable quality cutters.

It sounds like you need to get your machinist friend to come around and have a hands on look at your set-up to give you some advice.

You might try using a small fly cutter that uses a piece of lathe toolbit HSS for a cutter to do some test cutting and get to know your machine before you start any serious projects. At least with that, you can resharpen the cutting tool just like you do with a lathe tool bit if you chip it etc.

I also have a WM-16 and I've not been able to make cuts more than 0.5mm across a 12mm cutter using 2 or 4 flute HSS endmills in mild steel. It's a different story when using roughing cutters though, much easier. I have to remember to make sure the quill is also locked to prevent the cutter bouncing off the workpiece.

Ed.

Story so far is that I am now back from sailing & have received a cutter as suggested by Jason on the video above.

Trouble is that I forgot that my chuck needs threaded cutters & ARC's ones are plain. I tried the cutter in the chuck & it just drops out as the collet does not clamp down on it at all even though both are supposedly 12mm

I do have a couple of draw bar collets but unfortunately they are imperial not metric so I still could not use the cutter.I did try another milling cutter that I already had & being brand new it did cut Ok but not brilliantly. I also had the problem that during use it decided to screw itself into the chuck a bit more so I got a tapered rebate even though I thought I had done it up to its limit of thread hand tight.

I had bought a set of small fly cutters that fit the drawbar cutters so I tried one. It cut fairly well except that the cutter moves back in the holder & as it is only held by a single small grub screw I could not get it tight enough . So that is only good enough for something soft & very light. Something to look out for if I buy again in the future. Another waste of money !!!

Oh the joys of learning !!!!

If you have any old threaded 12mm cutters slice the end off and use it as a dummy centre in the cutter holder put  plain cutter in and it will tighten up 
Nobby

Edited By Nobby on 01/10/2016 23:46:53

Edited By Nobby on 01/10/2016 23:47:32

Edited By Nobby on 01/10/2016 23:48:21

Make sure you are traversing the cutter fast enough. 650rpm on a 4 flute cutter is 2600 teeth per minute. Even at 0.002" tooth load ( and I wouldn't go any less), you need 5.2" per minute. Too low a tooth load and the cutter will rub and go blunt very quickly. Tubal Cain recommends 0.004" minimum

Did not realise that feeding too slow would cause problems -- thanks

Edited By Sam Longley 1 on 02/10/2016 07:46:50

Sam, What is your Milling machine? There is a big difference in rigidity between machines and in particular the rigidity of the column. I myself refer carbide cutters now days. Out here in NZ they are about the same price as HSS if they are 10mm and smaller and last a whole lot longer. Being as you are on a manual mill, the carbide will work very well. I don't think carbide cutters come in screw shank for Clarkson type holders though. All that aside, with you making the T nut exercise, in mild steel, 600 rpm seems about right. Depth of cut could well be on 0.5mm on your mill per pass if it is not rigid enough. If your machine has ball screws, that makes it very easy to climb mill. But a non ball screw mill, you are best to be conventional milling. If you can't make the pass in 1 go, ie you have a 12mm cutter and the part is 14mm wide, I would be cutting at just over 7mm wide pass each way at what ever cut depth that did not labour or load the machine too much. Coolant or one of those air misters that will blow the chips away from the cutting surface and cutter flutes as well. Milling on a manual mill in the home workshop is no where near the speed or feed of a substantial cnc machine. The Gibs on the X,Y,Z really need to be correct, ie there is slop in them. The gib lock or slide lock should take very little to create resistance on that slide. When we used to use old worn out bridgeport mills, we used to lock the axis we were not using, and the axis we were using used to just sinch up that axis, so it could be turned ok with a slight drag. Even with carbide cutters on your home mill, you probably will still use similar speeds and feeds and the cutters will last you 5 times longer over your HSS. Try using a smaller cutter like an 8mm or 10mm diameter cutter. They will put less load on your mill and are slightly cheaper as well.

The formula I use is (318.3 X cutting speed of material )/ diameter of cutter or work piece. For mild steel I use 25m/min eg (318.3X25)/12=663 So choose the closest to it, but I would not run 700 rpm , I would run slower with HSS cutter. Feed rate is from 0.03 to 0.1 mm per rev per tooth. In softer materials like free cutting MS the feed rate can go to 0.2mm per tooth, but the depth of cut is limited to how solid your machine is. If you are cutting harder / stronger materials, the cutting surface speeds go down and you may need a lower depth of cut. I suggest at 0.5mm depth and if all is good keep going deeper until it sounds loaded or as you have described, starts to really shake and rattle. There is no point in taking big cuts and wrecking the machine.

Neil

Well I met the engineer ( all 80 years of him) for the first time & he walked me round his shop which was full of old machines from bridgeports to myford grinders & colchester lathes. He showed me his plastics moulding machines - he machines moulds for others & himself & then produces plastic parts. I also saw the spark eroder for cutting patterns

It was interesting to see a coventry mill which he obtained 4 years old from a school that had never been used. they did not know that it needed a magnetic plate so as it had no t slots nobody could use it so it was wasted until he took it off their hands- so much for education !!

Anyway- re the milling cutter , I gave him my lump of steel & my cutter- which he proceeded to sharpen by hand ( & gave me a lesson on how to do that) . He put the cutter in a bridgeport & ran it at 188 RPM & cut the steel like butter & the feed speed was high. He felt that I was trying to run far too fast. He also felt that i did not need exotic cutters for most work & showed me drawers full of cutters which were all HSS.

So I tried what he had demonstrated at home. Sharpened a cutter. Ran at 200RPM. milled my steel & had no problems. Job done