2mm endmill help

[Anonymous]

There seem to be three fundamental issues. Roughly in order of importance:

The new cutter shown seems to be poorly ground. The used cutter shown is badly worn with the cutting edges rounded. It would seem that these cutters are simply not up to machining steel.

Runout on the collets – it's way bigger than the chip load. So one tooth may not be cutting while the next will be taking double or more the expected cut. So the loads on the cutter are much higher than expected from simply looking at the rpm and feedrate. Varying chip load is also a recipe for vibration and chatter.

There is still quite a lot of cutter stick out. even with the shank cut down.

One and three could be ameliorated by buying quality cutters intended for cutting steel. Two is more difficult, short of acquiring a different mill. A good clean and check for any small burrs may help. Reducing the stick out of the cutter would also help.

Andrew

[Andy CarlsonParticipant @andycarlson18141]

Trawling around the net yesterday I found a couple of other places where people reported similar runout figures from the MF70. The Usovo ER11 spindle conversion is an option. Their site (naturally!) claims very good precision but I have no experience of this conversion myself.

I will drop a line to the two folks who have done the conversion and see whether they have done any runout measurements. They may not – not everyone owns a DTI.

Cutter-wise, when I bought my MF70 I asked one of the folks who had milled several chassis which cutters he used and he told me that he had always stuck to the Proxxon ones. All of my 2mm and 3mm cutting has been with Proxxon cutters. That's not to say that other good cutters can't be had of course.

I've cast the net wider for 1mm cutters and have used Cobra Carbide since breaking my first Proxxon one. These are now unavailable from the UK eBay seller so that advice is not much use now.

[Michael GilliganParticipant @michaelgilligan61133]

Posted by Andrew Johnston on 27/06/2020 08:21:29:

There seem to be three fundamental issues. Roughly in order of importance:

[…]

One and three could be ameliorated by buying quality cutters intended for cutting steel. Two is more difficult, short of acquiring a different mill. A good clean and check for any small burrs may help. Reducing the stick out of the cutter would also help.

Andrew

.

It is interesting … [‘though probably futile] to compare your excellent analysis with Proxxon’s product descriptions:

**LINK**

https://www.proxxon.com/en/micromot/27110.php

**LINK**

https://www.proxxon.com/en/micromot/28940.php

MichaelG.

[JasonBModerator @jasonb]

Looking at those Proxxon cutters I would say by the angle of the helix that they are designed for non ferrous and plastics as they look to have about a 45deg helix and could very well have deeper gullets to clear swarf making them weaker.

[blowlampParticipant @blowlamp]

How close is the fit between the parallel part of the collet and the bore it locates into in the spindle?

I found with my Dremel type hand tool that there was quite a bit of clearance here which caused significant runout of the cutter. I made new collets that fitted the bore closely and it helped tremendously in reducing runout. I used a drill shank to 'measure' the bore size.

Martin.

[JasonBModerator @jasonb]

I had a bit of a look around for the shortest cutters and it turns out our friends at ARC have a couple of cutters that look like they would be upto the job.

Their Standard length Premium carbide3-flute at 2mm dia has a 6mm flute length and their stub length 2-flute an even better 3mm flute length, both have 3mm shanks. They are a bit more expensive than the Hertel but not far off the cost of Proxxon. May be worth a try though doing so after chasing down the runout may be a better bet for the wallet.

I managed to pull Ketan away from something far more important long enough to get a couple of photos.

[Andy CarlsonParticipant @andycarlson18141]

@blowlamp: Interesting thought. Thanks. The collet mikes at 186.4 thou which seems suspiciously close to 3/16 for such a metric machine. My 3/16 brass bar mikes at 187 and is a fairly loose fit in the collet holder. I thought 5mm… My 5mm drill shank mikes at 194.4 thou (4.93mm) and won't go in. That's about exhausted my stock of things in this sze range. I might have a try making a new collet but my only slitting saws are too thick for that job so it won't be any time soon.

@Jason: I have just bought a 1mm stub cutter from Arc Euro but so far it has not been on the machine so I'm not able to say anything much about it. Any thoughts on how the geometry compares to the Proxxon ones?

[blowlampParticipant @blowlamp]

Posted by Andy Carlson on 27/06/2020 14:20:41:

@blowlamp: Interesting thought. Thanks. The collet mikes at 186.4 thou which seems suspiciously close to 3/16 for such a metric machine. My 3/16 brass bar mikes at 187 and is a fairly loose fit in the collet holder. I thought 5mm… My 5mm drill shank mikes at 194.4 thou (4.93mm) and won't go in. That's about exhausted my stock of things in this sze range. I might have a try making a new collet but my only slitting saws are too thick for that job so it won't be any time soon.

@Jason: I have just bought a 1mm stub cutter from Arc Euro but so far it has not been on the machine so I'm not able to say anything much about it. Any thoughts on how the geometry compares to the Proxxon ones?

If you can get some good dimensions of your collet, I could CNC one up for you to try if you think yours is slack.

Just let me know if you want one doing.

Martin.

[JasonBModerator @jasonb]

Posted by Andy Carlson on 27/06/2020 14:20:41:

@Jason: I have just bought a 1mm stub cutter from Arc Euro but so far it has not been on the machine so I'm not able to say anything much about it. Any thoughts on how the geometry compares to the Proxxon ones?

If you look at the photo on ARC's site for the stub and standard length ones you can see that these cutters have the more traditional 30deg helix, compare this to one of their 45deg helix cutters for aluminium (& Non ferrous / plastic) and that looks far more like the geometry on the Proxxon ones suggesting they are more suitable for easier cutting materials.

[Andy CarlsonParticipant @andycarlson18141]

Posted by blowlamp on 27/06/2020 15:02:20:

If you can get some good dimensions of your collet, I could CNC one up for you to try if you think yours is slack.

Just let me know if you want one doing.

Thanks but I think I will need to turn some bar on the lathe myself to find out what the internal size of the holder is. I tried wrapping some 2 thou shim around the collet. That wouldn't go in but that still leaves a big band of uncertainty.

[Michael GilliganParticipant @michaelgilligan61133]

Must say: I was astonished by the modest price of the Proxxon collet set.

MichaelG.

[Andy CarlsonParticipant @andycarlson18141]

Some feedback on the Usovo ER11 spindle conversion…

The owner has clocked sub 1 thou runout on the spindle itself and on a cutter in the collet. The bearings that came with it did not find favour due to noise and suspected play and were replaced with better off the peg sealed ball races.

[Michael GilliganParticipant @michaelgilligan61133]

Interesting upgrade

**LINK**

https://www.usovo.de/shop/advanced_search_result.php?MODsid=ff390ij4amcv6lfpo3468mjn21&keywords=tuning-spindle&x=0&y=0

MichaelG.

[Dave SParticipant @daves59043]

I've had a busy weekend in the workshop:

I didn't manage to run the CNC , but I did manage to re-spindle it:

Its all assembled, and the runout on this spindle is around 2 tenths with the same end mill as the proxxon one measured 2-3 thou. Speed should be more stable (and upto 24K rpm), and with the ER16 collets I can choke down to reduce the stick out.

I still need to check/fine tune the tram, and ensure the stepper is ok with the additional weight. I did a quick check before making the parts by cable tying this spindle to the existing head, and it drove that OK, so I think it should be fine.

Hopefully Ill be able to report success later in the week.

I'll also look at getting some different cutters if this moves ok – with ER16 I'm no longer limited to the 3.2mm max diameter, so the cutter selection should be wider.

There are pictures of the build on my twitter feed : @SolutionsByDave if anyone is interested.

Dave

[Andy CarlsonParticipant @andycarlson18141]

Looks interesting. What is it?

[Dave SParticipant @daves59043]

Many years ago I needed to do some very small precision drilling, so I bought one of ARCs ER16 high speed spindles.

That project got done and as part of workshop tidy the spindle got packed away for “later”.

I don’t think they still sell them, but similar spindles can be found out of China.

it runs of an invertor, 750w and 4-24k rpm IIRC

Bit overkill for this mill I suspect, but already in the workshop and should solve the runout issue.

Seemed worth a try for the time investment

Dave

[Andy CarlsonParticipant @andycarlson18141]

Thanks. I had a shufty on fleabay and found several variations. I suspect this option will only be attractive if you already have one of those kicking around.

My next step will be to try making a better fitting collet for the Proxxon spindle. It's not top of the 'to do' list though and I need to sort out a skinnier slitting saw before I can do it.

[Dave SParticipant @daves59043]

Good news!
My CNC failed to snap my last 2mm endmill last night
The Job started:

and then it progressed some

As it was all looking good I even went and sat in the garden with a beer, keeping an ear out for the noise.
I was back to watch the pocketing process, as the rest of the cuts were small width, and this was the full width, after all the other milling.

took just under 2h20.

End result of the roughing pass:

Somethings gone wrong here, the pocket is supposed to be a curve:

Turns out the recycled bearing on the X Axis has collapsed/ jammed.

Must have happened pretty much at the end, as the other shapes look OK.

That's why I took the stock off – cant run the finish on it until the leadscrew is sorted, which means stripping the table out…

Still, massive progress, and the new spindle seems to have made a difference.
I think its now in the 'tune' stage, rather than the throw things at it stage

Thankyou all

Dave

[JasonBModerator @jasonb]

That looks a big improvement, did you have a similar amount of tool stick out or have some of the flute inside the collet?

It will be interesting to see how the raised features measure up once the final cut has been run.

[Dave SParticipant @daves59043]

I stuffed the endmill into the collet further – as I could do now its ER16. This spindle is loads quieter, both cutting and idling.

I'll run the job from scratch once the bearings are sorted, but I am also interested – that should allow me to tune which is where I started this whole thing.

Dave

[old martParticipant @oldmart]

6mm is a good size for solid carbide for a machine like that and can use the speed.

[Roger BParticipant @rogerb61624]

I also have an MF70 and decided to check the play and runnout. Measuring on the shank of a 3mm endmill I got a play of around 0.02mm and runout of around 0.04mm.

**LINK**

So far I have only broken one 1mm end mill when cutting a keyway in a silver steel shaft. This was mostly my fault. The first cut just put a flat on the shaft and the second cut was a full slot and was too much with the depth of cut I had chosen. Reducing the depth of cut resolved the problem.

[Andy CarlsonParticipant @andycarlson18141]

Cheers Roger.

Sounds like you are doing better than Dave or myself, you have about half the runout that we have measured. I think I've broken three 1mm cutters, one of which was from a stupid mistake. Dave has broken several 2mm cutters prior to his total spindle transplant.

I'm waitiing for a thinner slitting saw to arrive and will try making a new collet to see if that improves the runout on my MF70. If not then I will consider my options again – my rate of breakage is manageable for the work I want my MF70 to do but it would be better if it didn't happen and I could consider running sub 1mm cutters to get into tighter spots.

[SpurryParticipant @spurry]

As I only have a cnc router, not a proper milling machine, a little job came up utilising a 2.00 diameter cutter. The requirement was for square 7.00 and 7.50mm sockets to suit a 1/4" drive ratchet. They do not seem to be available anywhere, so decided to make some from brass (as it was a plumbing job).

Having made a small fixture, the brass blanks 20mm long x 15mm diameter were mounted after through-drilling 5.50mm. A single flute carbide router cutter was used at a feed of 0.5m/min, depth of cut 0.50mm, step over 50% , rpm about 22,000 to machine the square holes 8.00mm deep.

The 1.00mm corner radius was not a problem for the plumbing drain tap, nor the ratchet, so there was no necessity to over-cut the corners.

Pete

[Michael GilliganParticipant @michaelgilligan61133]

Posted by Spurry on 02/07/2020 23:12:19:

.
As I only have a cnc router, not a proper milling machine, […]

.

Very impressive result, Pete

MichaelG.

[Author]

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