EMG-12 Endmill Re-sharpening module

[Michael GilliganParticipant @michaelgilligan61133]

Posted by Neil Wyatt on 28/05/2015 13:09:02:

You obviously missed the kerfuffle about Brooklyn Beckham and Stephen Hawking.

.

Neil,

Yes, it is obvious [and almost inevitable] that I missed that.

… I generally try to avoid anything that includes the word Beckham

Thanks [?] for enlightening me.

MichaelG.

[Neil WyattModerator @neilwyatt]

> Yes, it is obvious [and almost inevitable] that I missed that.

You should listen to Radio 4

Neil

[Ketan SwaliParticipant @ketanswali79440]

Posted by Douglas Johnston on 27/05/2015 21:16:00:

The magnification of the image probably makes it look rougher than it really is. It would be interesting to know what the specification of the grinding stone /diamond is and whether there is a choice of grit size.

Doug

Doug,

This is the response from the factory:

The standard SDC wheel fitted to the module has a 220 grit – which is considered by the manufacturer to be the ideal all rounder. 150 grit wheel is available and sometimes used for larger carbide end mills =>10mm depending on the quality/grade of carbide endmill being ground, but the finish is rougher, depending on various factors. 320 grit and 400 grit are also available, to deal with smaller endmills, to give a smoother looking finish, but the working life for the finer grit wheels are shorter, again depending on quality/grade of carbide being ground, and various other factors.

The standard CBN wheel – sold as spare for grinding HSS has a 150 grit. 180 and 220 grit are available, but again, the working life of such wheels will be shorter.

The factors which could affect the finish include how much the wheel is worn or clogged.

In the factories opinion, what is installed is considered to be the best all around choice.

Under magnification, the look does vary, but as JS says, the striations are of no consequence as the finishing is done by the corners.

Ketan at ARC

[John HaineParticipant @johnhaine32865]

Given the attraction of building tool & cutter grinders I'm not surprised at the level of interest in this machine. What's interesting to me is how it turns conventional wisdom on its head. Conceptually it's like those rather duff drill grinders where you stick the drill in a collet, thrust it into a plastic housing against a grinding wheel and rotate the collet against a cunning cam to shape the end of the drill. The difference is that this works, and on cutters that are supposed to be much more "difficult" than drills.

I've got a Quorn which my father built. It took him months of his retirement and he made a load of the accessories in the book, but once built he almost never used it! I find it so fiddly to set up that I hardly ever use it either and I keep on trying to work out easier ways of sharpening end mills! So when I saw this my first thought was, how does it work, and how could I make one? I don't think I'd buy one myself but I might join an ME club that had one!

now if it had another couple of ports at angles that did 4 facet drill grinding too….!

But I hope this is really successful and good on Ketan for taking the risk to import it.

[Douglas JohnstonParticipant @douglasjohnston98463]

Thanks Ketan for that information about the grinding wheels, my earlier comment about the appearance of the ground edge was not meant as a criticism of the machine, which I much admire.

Doug

[Michael CheckleyParticipant @michaelcheckley34085]

I took a handful of 10mm slot cutters to Harrogate and John kindly sharpened them in return for a donation and lots of questions!

I have used one of the cutters for the first time tonight and I cant complain! All these cutters where telling me they werent happy the last time they were used so were put to one side for sharpening or more likely the bin.

[Michael GilliganParticipant @michaelgilligan61133]

Posted by Bogstandard2 on 30/05/2015 02:43:52:

Only people who have or are about to own one of these machines has the right to discuss what is good or not, as they are the end users.

.

A very serious question for the Motorators, if I may:

Is [Bogstandard2] John's assertion True or False ?

MichaelG.

[John Stevenson 1Participant @johnstevenson1]

Michael,

I'd love to comment as a moderator but I feel I am too close to the subject matter so will leave it to one of the others.

At the moment i am on my way out so don't have any time anyway but I will make a reply tonight as a member of this forum and not with my moderators hat on.

John S.

[Michael GilliganParticipant @michaelgilligan61133]

Posted by John Stevenson on 30/05/2015 06:44:15:

Michael,

I'd love to comment as a moderator but I feel I am too close to the subject matter so will leave it to one of the others.

At the moment i am on my way out so don't have any time anyway but I will make a reply tonight as a member of this forum and not with my moderators hat on.

.

Thanks, John

Your position is understood, and appreciated.

MichaelG.

[Ketan SwaliParticipant @ketanswali79440]

Posted by Douglas Johnston on 29/05/2015 20:38:39:

Thanks Ketan for that information about the grinding wheels, my earlier comment about the appearance of the ground edge was not meant as a criticism of the machine, which I much admire.

Doug

Personally, I didn't take it as criticism Doug. The first time I saw the results, I too raised the same question with John Stevenson, and was quickly put right by him, in his usual Ilkiston way . If not you, someone else would have raised the same point..It just happened to be another Johnston. Two Johnstons in a row may have made it look like a criticism to some – especially new comers to the thread, but I also know Andrew Johnston well enough to know that there was no criticism intended.

Initially, there were some concerns and eyebrows raised near the beginning of this thread, but that I would suggest was partly my own fault for adverting in ME before the review came out in MEW, as I have mentioned before.

When John 'Bogs.' called to purchase the machine, (prior to the two Johnstons comments ) he was aware that I was worried at the time because I did not know how the product would sell. A culmination of events may have resulted in certain comments made by John 'Bog.'. To John Bogs I would say – thank you, relax and please don't worry, all is well.

Again, to the two Johnstons I would say, don't worry, I took your comments as observations – not criticism.

Regardless of anything, this is an open forum, and I respect that everyone has and should have the right/ability to express their own opinion.

John Bogs is a friend as well as a customer, who has his own views. Similarly, there are many other people who have contributed on this thread who have their own views – be they positive or negative or perceived negative or questions, buyers or non-buyers, who I know as customers and friends, or people I don't know.

I do not take any comments as personal. I would politely request that we all relax and carry on with any questions, regardless of the poster being a buyer or not.

Ketan at ARC.

[JasonBModerator @jasonb]

I will also defer this one to Neil and Diane.

As a Personal view I think all the questions and queries raised are quite justified and not made to critisise the machine. For all we know the people asking about grinding wheel wear, size of cutters catered for and the ground finish may well be interested in making a purchase and would like some more details before parting with the cash.

I too thought the ground edge looked quite coarse from the early photos and would still be intetrested to see how the cutters perform when plunged as that is when the end is doing the work.

J

[Douglas JohnstonParticipant @douglasjohnston98463]

John,

I rather feel you want to close down all discussion of the machine from people who don't own one. The point I raised about the grinding elicited a very polite and helpful response from Ketan, which I much appreciated ,and would also be helpful to others who are considering the machine. Surely this is what the forum is all about. I think we should call a truce on this one, life is too short to argue about who has the right to speak.

Doug

[Douglas JohnstonParticipant @douglasjohnston98463]

It is always the same with Johnstons, you wait for ages to hear from one then two come along at once.

Doug

[Neil WyattModerator @neilwyatt]

I have no problems with people discussing a machine like this. the reason I wanted an 'exclusive' on the machine was exactly because I thought it was different enough to create a lot of interest and discussion, which it certainly has. I was under no illusion that it would be anything other than a niche product, but I could also see that there would be a reasonable market.

As for only owners or prospective buyers having opinions on things, then we would have very little left to talk about in here…

Neil

[JasonBModerator @jasonb]

Posted by Michael Checkley on 29/05/2015 20:39:59:

I have used one of the cutters for the first time tonight and I cant complain! All these cutters where telling me they werent happy the last time they were used so were put to one side for sharpening or more likely the bin.

Michael would it be possible to say what depth of cut and proportion of the cutter was used on this part.

To my eye and looking at the length of the swarf the finish we can see on the part was a full depth cut possibly climb cut as is common on CNC machines so little of the resharpened tip would have come into play. The only part that the tip may have affected is where the tool ran out into the ali plate where there is a burr that can be seen on the first photo on the nearest edge where a climb cut would not have been applied.

Just curious as to which part of the cutter has actually done the work.

[Michael CheckleyParticipant @michaelcheckley34085]

Hi Jason, it’s a valid point which I think I can answer with another photo. Out flying at the moment and can’t upload from my mobile…

[MuzzerParticipant @muzzer]

It looks like a well executed piece of kit and seems to do what it says it will. I have no strong views about whether or not people should buy it – or should have bought it. Personally I don't feel drawn to invest in one as there are quite a few purchases I would prioritise ahead of it. Very few of us actually need to buy tools – it's something we choose to do and there's no law against it yet.

With an and end mill, virtually all of the cutting is done with the side edges, not the end face, and that has been clearly stated and understood. From my viewpoint, the wear on an end mill's cutting edges is progressive and is a function of speed, feed, temperature and duration – as well as the material and quality of the tool itself. For cutters in our application that get a variety of work over their lives, the wear rate is going to tend to be greater as you approach the tip / corner of the tool. So, regrinding the end of the tool is going to help to improve the cutting performance a fair bit – but only by removing the worst worn areas.

I like to think I take this view of tool wear into account when setting up and using milling cutters. Wherever possible I try to take a deep cut that uses as much of the side edges as possible and if the work permits, allow the cutter to extend beyond the workpiece so that the corner is not used. It's not always possible of course but the job that Michael C posted looks like an example where the precious corners of the tool could have been relieved of their duties by use of a spacer under the work – and conversely an opportunity to make use of a cutter with a blunted corner. Setting the work up to make use of the side of the cutter rather than the end (where possible) not only makes more use of the cutter's edges but also gives a better finish, as shown in Michael's photos.

When the tool is overworked and the corner becomes severely blunted, I see that particular cutter as only fit for use where the corner edge is not required. Not all jobs require a corner / step but I recognise those as situations where a good / new cutter (and extra care!) is required. The cost of a snazzy grinder equates to a lot of cutters, hopefully quite a few years' worth in my case, notwithstanding my current armchair confinement!

Murray

[Neil WyattModerator @neilwyatt]

I think that, just like turning, milling by hand (not CNC) is a very personal thing, with much variation in speeds, feed rates, approaches.

I find that the corners are the only parts of my mills that get significant wear, but also rarely use set-ups where the end isn't cutting – for example when making toolholders and milling a 1" face, I do it as a series of steps before taking a very light full depth climb-milled finishing cut.

Mostly I am either shaping things or thinning them down, both of which require the end to cut. When they blunt the increase in force required (and decrease in finish) are very obvious.

I also use them to make pockets, such as blind keyways – these need an end-cutting cutter.

There's not a lot here that wasn't milled with the corner or end of the mill:

(I really must finish some projects…)

To get a mill cutting again I sharpen the facets on my very basic T&C grinder or I just grind relief on the corners. Both approaches work but the latter obviously leave corners with a small fillet (which is good for some jobs).

[Enough!Participant @enough]

Posted by Neil Wyatt on 30/05/2015 09:56:40:

As for only owners or prospective buyers having opinions on things, then we would have very little left to talk about in here…

Not to mention that this is an open forum and should not be commandeered to limit discussion about a particular product or vendor to suit one individual's sensibilities.

[Michael CheckleyParticipant @michaelcheckley34085]

Home now after a morning at the field .

The slot cutters I took to Harrogate all had the corner "ruined" (by me) about 1mm on the side and across the face. I went through a spell of running my spindle speed to fast when milling steel and took out a few cutters before the penny dropped. Having fairly light weight equipment my DOC tends not to be more than 0.5 to 1mm for steel.

For the operation shown in my previous post I milled about 1mm in and about 3mm deep. The shoulder looked good and this is the area of the cutter where the wear was. I used both climb and conventional milling when roughing out (depending on which side I was milling) and then climb milled 0.05mm off full depth to finish off.

For my use the cutter was brought back to life as the blunt corner was ground away. Now that there are a few machines out in use it would be good if someone could do a comparison of a new cutter and a sharpened cutter on the same material, parameters e.t.c and publish the results on the forum, this kind of testing I have seen more on a forum rather than a magazine article.

[Owain SamuelParticipant @owainsamuel55325]

For your consideration, may I draw your attention to the above photos? Material is unknown mild steel, cutter is a 10mm HSS, spindle speed 510rpm, feed 4"/min (aprox, but was the same for both cuts). DOC is 60thou. In all photos 1 is the cutter as found (second hand, used), 2 is after grinding.

Your comments are invited.

Owain

[Michael CheckleyParticipant @michaelcheckley34085]

No.1 looks like the deeply scratched finish I get when the cutter is blunt and No.2 looks much cleaner cut?

[Michael GilliganParticipant @michaelgilligan61133]

Posted by Michael Checkley on 30/05/2015 18:49:01:
No.1 looks like the deeply scratched finish I get when the cutter is blunt and No.2 looks much cleaner cut?

.

Agreed … But I would also suggest that the spindle is perhaps not perpendicular: Even on No.2, I can see no evidence of the 'trailing' cutter-tip doing any work … It's nicer to see overlapping circles.

MichaelG.

[JasonBModerator @jasonb]

Certainly an improvement but still a bit ragged at the edges.

Michael C. thanks for the additional imformation which does go to show its as much the removal of the blunt areas that makes the difference as it is the shaprness of the tips. As a get me out of jail option I have at times simply ground across the whole end of a blunted cutter at a very shallow angle, provided one flute is at the bottom the "new" cutter will cut very well when its side is used but absolutely useless when plunged.

As a lot of ME work is usually fairly shallow cuts then the small amount a shaprening takes off will no doubt work, but if a cutter were mostly used with a large amount of its side cutting then a lot more material would need to be removed to get back to a sharp side as well as just touching up the ends.

What would be an ideal test is to take two identical cutters one new and one that has seen a lot of use and then been resharpened, take these two cutters and do some side by side tests much like Owains and compare the results. Ideally on a CNC so feed rates etc would be identical and also some plunge cutting so maybe a pocket, and if the tester was able to measure surface finish RA values would be better than a photo

[MuzzerParticipant @muzzer]

Posted by Neil Wyatt on 30/05/2015 14:29:16:

I find that the corners are the only parts of my mills that get significant wear, but also rarely use set-ups where the end isn't cutting – for example when making toolholders and milling a 1" face, I do it as a series of steps before taking a very light full depth climb-milled finishing cut.

There's not a lot here that wasn't milled with the corner or end of the mill:

I hear what you are saying but there are many occasions eg when pocketing or profiling where you can go down to near full depth and then machine around the profile and I see various such operations on your engine parts. For instance, there seem to be quite a few examples in your photo of outside profiles, deep slots and pockets – did you make lots of shallow passes or did you drill / plunge to depth and then open them out? First instinct may be to take lots of shallow cuts in layers, gradually working down to the required depth.

The last photo from Michael suggests that he actually roughed out the part in several layers, so this part gave the corners a good workout all the way up to and including the finishing cuts. Coming in from the outside at full depth (with a gap between the work and the table) would have avoided any wear at all on the corner. His machine looks to be up to the job and produces nice swarf in that mode.

Murray

[Author]

Posts