using milling cutters

[Tony Pratt 1Participant @tonypratt1]

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

[JasonBModerator @jasonb]

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

[Neil WyattModerator @neilwyatt]

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

[Sam Longley 1Participant @samlongley1]

Posted by Neil Wyatt on 27/09/2016 13:23:14:

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

[JasonBModerator @jasonb]

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

[Sam Longley 1Participant @samlongley1]

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

[JasonBModerator @jasonb]

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.

[Neil WyattModerator @neilwyatt]

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

[HopperParticipant @hopper]

Posted by Sam Longley 1 on 27/09/2016 21:03:55:….

i will ask for his advice re what sort of cutters to purchase. Clearly cheapo ones are not worth the bother,

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.

[Ed DuffnerParticipant @edduffner79357]

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.

[Sam Longley 1Participant @samlongley1]

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 !!!!

[NobbyParticipant @nobby]

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

[duncan webster 1Participant @duncanwebster1]

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

[Sam Longley 1Participant @samlongley1]

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

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

[Neil LickfoldParticipant @neillickfold44316]

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

[Sam Longley 1Participant @samlongley1]

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

[Ken Price 1Participant @kenprice1]

I read all the above comments most of which is accurate and helpful. What must be appreciated is that the machine must be adjusted so that all slides move smoothly without vibration. Then you come to the question of cutters. This to the beginner can be a minefield but does not have to be. As you have experienced there are 2,3 and four flute cutters all of which have their place for different applications. The 2 flute is primarily for cutting slots hence why it is referred to as a slot mill. If you used a tri cutter or 4 flute to do a slot you would find that it would cut oversize. The reason for this is that with a 2 flute cutter there is more room for the cut chips to be evacuated which would not apply to both 3 and 4 flute cutters. One then has to take into account the cutting load being applied to each edge of the cutter. For example if cutting steel at say 500 rpm with a feed rate of 30 mm per min with a 2 flute cutter you change to a 4 flute cutter using the same speeds and feeds, then the force on the 4 flute would be twice as much. You then have to take into account the cutter you wish to use. Is it a new cutter or a used one. Is it a HSS one or is it a carbide one. The speed and feed for a carbide cutter will be significantly higher than for HSS. Do you propose using cutting oil using flood coolant or occasional brush applied coolant. You can now see that there is a lot of considerations regarding tooling. The other factor to be taken into account id the material you are going to use. This will have a great bearing on the tooling to be used. Again this is a difficulty when materials are purchased at the shows not knowing exactly what it is. I hope that this will guide you and feel more confident with your future machining operations. I am more than happy to answer any questions you may have.

Ken Price.

[EmgeeParticipant @emgee]

One then has to take into account the cutting load being applied to each edge of the cutter. For example if cutting steel at say 500 rpm with a feed rate of 30 mm per min with a 2 flute cutter you change to a 4 flute cutter using the same speeds and feeds, then the force on the 4 flute would be twice as much.

Ken, with the same speed and feed rate wouldn't tooth load be halved if doubling the tooth count ?

Emgee

[Neil WyattModerator @neilwyatt]

Something I have never seen written down, but that is blatantly obvious when you think of how a cutter works when making a slot:

When a 4-flute cutter is used to make a slot one flute is cutting across the end of the slot (and tending to pull the cutter to one side while pushing the work the other way) this deflects the cutter right at the moments the other flutes should be sizing the slot.

With a 2-flute slot drill there is no flute cutting the end of the slot (and therefore pulling the the cutter to one side) when other flutes are cutting the edges of the slot.

With a 3-flute this effect is negligible and in my experience most 3-flute cutters will make slots to size.

Neil

[Anonymous]

Posted by Neil Wyatt on 12/11/2016 15:18:36:

When a 4-flute cutter is used to make a slot one flute is cutting across the end of the slot (and tending to pull the cutter to one side while pushing the work the other way) this deflects the cutter right at the moments the other flutes should be sizing the slot.

With a 2-flute slot drill there is no flute cutting the end of the slot (and therefore pulling the the cutter to one side) when other flutes are cutting the edges of the slot.

With a 3-flute this effect is negligible and in my experience most 3-flute cutters will make slots to size.

Exactly, I've cut slots with both 2 and 3 flute cutters and they're accurate to better than half a thou, as measured with gauge blocks.

Andrew

[Paul FallertParticipant @paulfallert28101]

Sam wrote "Well I met the engineer". RPM @ 188 aka = 1/3 plus fast feed. Cutter sharpened by hand!!! Same lump of steel.

Job done". Several posters here suggested steel might be hard-tough.

1) Does anyone else think Sam's lump of steel was hard-tough steel? I ran the FS-Wizard and consulted the Presto chart.

Both assume coolant and suggest reducing rpm by 1/2 if no coolant. That gets me to around 200 rpm. Sam's tool likely blunted-chipped by too much rpm on hard-tough steel, right-away.

2) Any suggestions on how to identify hard steel before blunting tools? How did Sam's new friend identify the steel?

3) Sam: Will you share your hard-won secret on how to sharpen endmills by hand?

Paul

[Phil PParticipant @philp]

Posted by Neil Wyatt on 12/11/2016 15:18:36:

Something I have never seen written down, but that is blatantly obvious when you think of how a cutter works when making a slot:

When a 4-flute cutter is used to make a slot one flute is cutting across the end of the slot (and tending to pull the cutter to one side while pushing the work the other way) this deflects the cutter right at the moments the other flutes should be sizing the slot.

With a 2-flute slot drill there is no flute cutting the end of the slot (and therefore pulling the the cutter to one side) when other flutes are cutting the edges of the slot.

With a 3-flute this effect is negligible and in my experience most 3-flute cutters will make slots to size.

Neil

Neil

If you look at chapter 6 of the Model Engineers Workshop Manual by George Thomas, he explains this in great detail.

Phil

[Neil WyattModerator @neilwyatt]

Posted by Phil P on 27/10/2018 16:38:57:

Posted by Neil Wyatt on 12/11/2016 15:18:36:

Something I have never seen written down, but that is blatantly obvious when you think of how a cutter works when making a slot:

When a 4-flute cutter is used to make a slot one flute is cutting across the end of the slot (and tending to pull the cutter to one side while pushing the work the other way) this deflects the cutter right at the moments the other flutes should be sizing the slot.

With a 2-flute slot drill there is no flute cutting the end of the slot (and therefore pulling the the cutter to one side) when other flutes are cutting the edges of the slot.

With a 3-flute this effect is negligible and in my experience most 3-flute cutters will make slots to size.

Neil

Neil

If you look at chapter 6 of the Model Engineers Workshop Manual by George Thomas, he explains this in great detail.

Phil

I probably have I have seen it mentioned there then, I just don't recall it.

Neil

Edited By Neil Wyatt on 27/10/2018 16:48:53

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