EMG-12 Endmill Re-sharpening module

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

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).

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.

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.

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

.

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.

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

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

As Muzzer says the corners got some use during the stepped roughing operations so if there was an issue with the newly ground edge is should have shown up here. I agree with Jason that a test cut compared to that of a new cutter would be useful.

Just minutes ago the same cutter was used to reduce the thickness of the profile. I had to remove 0.55mm from the top and bottom face so did 0.3 then 0.2mm DOC at 40mm/min and then a final 0.05mm DOC at 20mm/min.

Seeing the test cuts taken by Owain some readers may like to visit my website where the process is discussed in depth. Do look at the photos, (6 and 7), of my similar test pieces, viewing them enlarged to view the results at the highest definition. The article can be seen here

Harold

Ketan

Apologies for the delay in replying.

There's no restriction on the weight of any import to NZ other than how much you are prepared to pay to get the goods shifted from one part of the world to another. So lathes and mills may as well be purchased locally rather than try in import them as a one off. The heaviest single item I've imported was 50Kg from China, it came by UPS, and it arrived without problem. Smaller items, collets, chucks, boring heads, QCTP have all been directly purchased at far lower prices than the local suppliers. Just check out some of the NZ supplier prices available online and compare them with what you charge and you'll soon see why we do it. Including buying stuff from ARC.

The other factor, which may well change, for tools and equipment GST isn't collected on a total sale price of less than $400 (200 quid) so removing the 20% VAT, including shipping and $0 import duty/GST makes small items viable. Of course that wouldn't apply in the case of an EMG-12.

regards

Pete

Thanks Pete,

To avoid taking the thread off topic, I have sent you a PM.

Ketan

Here are the results of a quick milling trial. Material is, I think, EN1A. Both slots are 1.6mm deep and 10mm width, taken in one pass. Top slot is with a worn and chipped three flute carbide cutter running at 1500rpm and 375mm/min. Bottom slot is with a nearly new, and used mainly on the side flutes, four flute carbide cutter running at 1500rpm and 450mm/min:

Clearly the top slot is rougher, and the sidewall finish is iffy. I took three surface roughness measurements in each slot. Results were:

Top slot: 2.16 2.16 3.31 Average 2.54µm Ra

Bottom slot: 3.40 2.41 3.25 Average 3.02µm Ra

Not an intuitive result.

Andrew

It's very sad when a thread descends into abuse mode. That is NOT what the Forum is about in my view.

There is a lot of interesting info supplied, and name calling does no good at all, other than putting off people, especially newbies.

I respect Ketan for his open minded and honest comments on this thread, and others elsewhere. Yes, I am a customer, but he wouldn't live for a day on the profits from my purchases!

I would love to have an EMG12, or larger, but 1) lack the space to store it, 2) cannot justify such a purchase, which leads onto my questions.

Presumably John Stevenson has an EMG 12, as has Bog Standard 2.

QUESTION 1

Whereabouts in U K are you two gentlemen? (Probably a couple of hours drive away from me?)

QUESTION 2

Would you be prepared to sharpen End Mills for folk who brought them to you, (for a consideration)?

Obviously, this would have to be either, by appointment, or on a "leave/collect later" arrangement, so as not to interfere with the "day job".

You can see where I'm heading, (probably along with a lot of others).

Howard

For those who do not subscribe to the MEW in some way, here is a link to the article on our website, published with the kind permission of John Stevenson and Neil Wyatt - editor Model Engineers' Workshop Magazine:

**LINK**

Also, a small note to say that we sold out of these machines last Friday, and new stock is expected back in around early August 2015.

Ketan at ARC

Howard,

PM sent to you, Ketan.

"What amazes me is that no-one has started to build a home brew version yet.

:0)

Martin"

With apologies to Martin Kyte but I caught delete instead of quote post, as a low level moderator I can see it but can't reinstate it, my apologies.

To answer this it would not be easy.

The holders are very easy but the cams and there are 21 different ones, would take a lot of reverse engineering. The changes between each one are that subtle. If you had a pattern and popped it on a CCM machine then you could get all the information but would then require a CNC to make full use of said information.

So by the time you have done all the cams and move onto the machine with it's many different angles it would be cheaper to buy one.

Howard,

I cannot speak for John Moore but I am situated mid way between Derby and Nottingham, about 3 miles from the M1 Junction 24 or 25 Post code NG10.

I was actually being a little tongue in cheek given our general propensity to do things the hard way rather than buying a machine. I do include myself in that statement too.

Martin

With regard to Martin's comment about a home brewed version, now to be seen in John's comments, my offer, to be seen here may be of interest to some. It is of course very much simpler but in my estimation works adequately for most home workshop tasks.

I will now be away for around 5 weeks but on my return it is my intention to start adding videos to my website and this is one of the first that I intend to attempt, my quick change lathe tool holders being another.

Harold