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CM10 Mill Gears

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Iain Downs21/11/2015 16:44:20
516 forum posts
397 photos

I have a CMD10 mill and am having a bit of trouble with it.

It started when I tried to square up a bit of steel (inch thick plate) I got from the scrapyard. The faces went OK but the edges seem to have been case-hardened. Basically, I wore out or broke 3 10mm mills and then invested in a carbide tipped end mill.

This gets through the steel (I think this may end up my favourite mill!) but I've had a series of problems.

The first thing was that the motor gear disengaged (the upper circlip rose and eventually, the key dropped out.

I fixed that and carried on milling. However, what's happening now is that the gear change gears are disengaging somehow when running. This seems to happen when the cutter hits a particularly hard piece.

I can re-engage the gears by mucking about with the gear lever, basically putting it up to high and then back (though not quite *that* simple).

I've had the assembly out and stripped it down. I can't see anything obviously wrong with it, though the slide mechanism is a little stiff.

Has anyone else had this sort of problem and if so what is the fix.

Iain.

Ian S C22/11/2015 09:26:37
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7447 forum posts
230 photos

Is the motor shaft parallel to the driven shaft?

Sounds like the bit of steel you got might have been gas cut leaving a hard area that would seem like case hardening.

Ian S C

David Clark 122/11/2015 09:48:12
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3357 forum posts
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10 articles

It might be safer and cheaper to buy a bit of steel with known qualities. Cheaper than a new mill.

Stub Mandrel22/11/2015 09:54:07
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4306 forum posts
291 photos

If it's a flame cut blank the edges may be partially hardened, it's possible to grind off the skin.

Neil

Iain Downs22/11/2015 10:59:59
516 forum posts
397 photos

Thanks for the advice above.

As to the problem, it would seem I'm a moron.

I stripped the mill again and the problem is stripped gears. The 'cure' of 'mucking about' worked because it rotated the spindle ./ gears to present some non stripped teeth which meshed and away we go. IT seems like the inertia of the spindle was enough to sort of keep the whole thing going until it hit a hard bit and got stuck.

ArcEurotrade will come to the rescue (the X1 is the same mill and ArcEuroTrade about the easiest place to get spares) and I should have it refitted by midweek.

My first stripped gears! Should I be proud or ashamed?

Mr Clarke suggests that I get some know steel and I like the idea in principle. What I'm ultimately trying to do is to make a wood lathe (I know ambitious for a bloke that doesn't recognise a stripped gear) and wanted some heavy steel to make the headstock from. I've not been able to source and decently thick plate of reasonable size. I can get something the size of my workshop at 1" thick, but nothing in the 6 - 10 inch square region (apart from a scrapyard and bits on ebay of equally unknown provenance).

Any suggestions on this would be most welcome!

Iain

Ian S C23/11/2015 09:48:31
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7447 forum posts
230 photos

Iain, a bit of hollow square or rectangular RSJ of reasonably solid size, say 100 mm sq by 5 or 6 mm thick, a short off cut should not be too hard to find. Two bits of 40x 75 mm heavy gauge rectangular tube would make a good bed, and with the 100 mm headstock, this would leave a 20 mm gap between the bed bars.

Ian S C

Iain Downs29/11/2015 16:02:52
516 forum posts
397 photos

Well an update from me.

I got the replacement gears and fitted them, but I'm still having trouble. Firstly I wasn't very happy with the sounds coming from the gear train - it seemed noisier than it used to be.

I managed to complete the squaring up of my bit of mysterious steel and re-face the big side with my new 3/4 MT2 carbide end mill. This kind of seemed to work but it seems to dig in intermittently leaving a score a few though deeper.

Now I'm trying to mill a V groove in it with a 10mm HSS end mill (taking .5mm or less off each time) and it was going OK, but under any kind of load the spindle would stop rotating, but the motor kept going.

I've stripped it down again and what I've found is that the (new) lower spindle gear is worn over half the width and about 1/6th of the circumference as if it was rotating eccentrically.

The feeling I'm getting is that the two gear's aren't meshing correctly. Is it possible that he gears from Arc Euro Trade for the Super X1L do not in fact exactly match the ones for the Clarke CMD10?

I've ordered a replacement from Arc, but I don't have a great deal of hope that this will fix the problem.

Any advice would be much appreciated.

colin hawes29/11/2015 16:25:40
502 forum posts
18 photos

I repaired a friends mini mill with metal gears from Arc-euro and was surprised that it was not as noisy as expected but at the time I noticed that the plastic gear on the motor was also well worn but it is still going after about 9 months. I did slap lots of grease on the metal gears though.

Nigel McBurney 129/11/2015 16:33:16
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623 forum posts
3 photos

I think you are being very unkind to your small milling machine,I would be very reluctant on my industrial Adcock and Shipley 2E to to try to mill inch thick steel plate which has been cut with some sort of process which produces hardened edges, even if it was decent mild steel it would still be too much for a such a small mill as yours, why not try another material e.g. aluminium alloy and cut with a fly cutter which is a lot easier on small machines. When milling ,if a high speed cutter fails or is damaged then do not approach the problem by using carbide ,small gears will not stand up to this treatment.

Ketan Swali29/11/2015 16:37:45
1124 forum posts
91 photos

Hello Iaian,

The gears and their form are correct. The CMD10 = X1 and the SX1L share the same gears. They are both made in the same factory.

If you are stripping gears, your problem may be elsewhere, ranging from correct and full engagement or not, in the hi/lo setting, through to the type of use/abuse (unknowingly), through to the material being milled, feed and speed. Be also aware the forces being put on the gear train by use of a 3/4" Indexable Carbide Endmill, especially if they have two tips? resulting in intermittent cut and the force this generates, plus depth of cut into the unknown material you are milling. Bigger the diameter of cut, the lighter the depth of cut, based on known material being milled.

If you are breaking gears so quickly, it is not normal for X1/SX1L and it suggests abnormal forces being put on the gear train, if it is not down to full engagement of the gear train in the high or low setting. Be careful, as if this continues, you could soon be calling Clarke or ARC for an new control board. Please remember that the plastic gears are a kind of fail safe - sacrificial - to protect the board, but if this happens regularly, the board could blow.

Unfortunately I cannot guide you on feeds and speeds. It is not a subject I am entirely comfortable with. The tests I do are usually abusive in nature.

Ketan at ARC.

Edited By Ketan Swali on 29/11/2015 16:38:52

Iain Downs01/12/2015 21:47:35
516 forum posts
397 photos

IThanks for all your comments. I've ordered more gears from Ketan ( smiley  but won't be doing much until they arrive. I'm planning to have a look at how they engage with an inspection mirror just to make sure everything is OK mechanically.

I should note that all the nasty stuff appears to have been milled off well before these issues started and I seemed to get really good results from the carbide cutter for a while with no sense of the machine struggling. Being aware that it was steel and a bigger radius, I've only been trying to take a few though off a time (probably around 5 thou tops) with a relatively low speed.

I did want to ask NIgel about his comments on the fly cutter. I've no experience of the fly cutter and was wondering why it would produce less strain that the carbide end mill I've got which appears to be pretty similar in makeup to a fly cutter. It's got two tips and it's true that one is slightly lower that the other. This seems to me to be pretty much how a fly cutter works, except the fly cutter has one tip and mainly with a wider radius than my paltry 3/4 diameter cutter.

Would I be better off with a fly cutter for facing than the (smaller) carbide tipped end mill? I would guess I'd have no trouble with aluminium but I do want to build some things in steel.

As always in this hobby, you want to have bought a bigger machine....

Thanks

Iain

Ian S C02/12/2015 11:28:49
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7447 forum posts
230 photos

A carbide cutter needs much more power from the mill to operate correctly. A sharp HSS fly cutter at minimum speed, and at as smaller radius as possible should handle the job, your not on a production line, just take your time, but make sure that the cuts are positive, not rubbing, your bit of unknown steel may work harden if the tool is allowed to rub.

Ian S C

Martin Connelly02/12/2015 12:52:13
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893 forum posts
111 photos

The specs for the CDM10 mill include end mill capacity of 10mm. Using a 19mm cutter that is close to double this diameter puts double the torque on all the gearing and results in double the force on the gears. This will break the weakest part every time. There is a reason the max diameter in the specs is 10mm, don't overload the drive train by trying to use the mill beyond its capacity. Since Ø10mm is the maximum you may be better off using something like Ø6mm and accept the limitations of the machine you have in terms of speed of metal removal.

Martin

Iain Downs02/12/2015 17:49:01
516 forum posts
397 photos

The specs indicate a 'face mill' capacity of 20mm. as I'm trying to face the piece of steel with the carbide mill and not take big chunks out of it this seemed reasonable. By face I mean remove irregularities so it is flat (and parallel to the opposite face) rather than actually shape it.

I'm not still not entirely sure that I understand the essential difference between my carbide end mill used to face, a 'face mill' and a fly cutter.

Incidentally, I've got a couple of alerts for posts in this thread, but although I can read them in my email, I can't see them here. Any ideas why?

Iain

Ian S C03/12/2015 09:13:44
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7447 forum posts
230 photos

If you go alerts, go up to the Green line and the inbox envelope should be open, click on it, and you'll find your message.

Ian S C

Martin Connelly03/12/2015 09:27:51
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893 forum posts
111 photos

A face mill usually has inserts that only make contact with the workpiece at a corner or the bottom of a radius with the surface they are producing. An end mill has contact over the whole of its bottom face. This large contact area can produce drag or recutting of swarf so results in the reduction of max diameter for an end mill compared to a face mill. Also the face mill often has more cutting edges so the chipload is lower per tooth and the load on the drive train is not so variable, you get nearer to a constant torque and less like an intermittent cut.

Using the mill at its maximum size of 10mm for an end mill or 20mm for a face mill is like running any machine at flat out, likely to find a weak point and cause failure. These machines are made to a price and not for industrial use. Keep away from using them at their specified maximums to get decent use out of them.

Martin

Iain Downs03/12/2015 13:05:47
516 forum posts
397 photos

Hi, Martin. I get the point and I must say I've mostly being milling Aluminium so far.

The 'end mill' I've been using is this one from ArcEuroTrade

You will see that it has relatively little cutting area - more like the point of a lathe tool or a flycutter than a normal end mill.

The reason that I'm been awkward about this is that I love this tool! Not for cutting chunks out and stuff, but it gives a much better surface than any of my end mills.

When I get my new gears I will have another go. If I keep getting problems then I will regretfully reserve this tool for Aluminium.

Would a flycutter like this one be a reasonable choice for a small mill? I would have thought it would actually load the mill more than the carbide cutter I've been using - especially as it's a single cutter and the radius, would be larger than the 19mm of the end mill.

Cheers

Iain

Andrew Johnston03/12/2015 13:35:27
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4938 forum posts
560 photos
Posted by Martin Connelly on 03/12/2015 09:27:51:

An end mill has contact over the whole of its bottom face. This large contact area can produce drag or recutting of swarf so results in the reduction of max diameter for an end mill compared to a face mill.

I don't understand? An endmill is not centre cutting, so the bottom teeth do not extend over the whole radius. I was also under the impression that endmills, like slot drills, are ground slightly hollow, precisely to prevent rubbing. If an endmill is advancing by 'x' per tooth then surely it will only cut on the side at the depth of cut and along the bottom to distance 'x'?

Andrew

Martin Connelly03/12/2015 14:50:32
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893 forum posts
111 photos

Lots of end mills are able to plunge/centre cut. The mill manufacturers are not going to get into an argument about was the end mill in use flat bottomed or not so they just put a spec on the machine that covers all end mills. The ends of most are flat or very close to flat and the outer ends of the cutting edges are where most of the torque will be generated. A small degree of hollow grinding will not stop recutting of swarf or small particles getting in the gap and dragged around. A face mill is more likely to push swarf away from the cutting area than an end mill because there is somewhere for it to go.

Iain, the carbide inserts in the links you posted are zero top rake. Probably not designed for steel and a small hobby mill. If these are what you are using try getting some inserts with the same shape and size designed for steel and with a chip breaker edge and see what the difference is when they are used to cut steel. The flat faced inserts are designed to be tough for a long life but need a machine that is high torque and stiff to make good use of them. For a small hobby machine you want inserts that have "light cutting geometry" as Sandvik call it. The inserts really need to be matched to the material they are being used on.

Search on Ebay for TNMG and you will see a lot of inserts with a chip-breaker edge which will probably suit your machine better than those shown on the ArcEuroTrade site. I don't think the holes in the centre will be a problem for clamping as shown in your link.

Martin

Derek99903/12/2015 19:11:10
10 forum posts

Iain

I have suffered exactly your problems, and ended up fitting a larger motor driving the spindle through a 2 speed belt drive, using a spare KB controller. I had been working on this conversion in any case, but I was finally driven to finish it more quickly than planned.

However, the problem in my case turned out to be a badly worn oilite type bearing on the top of the countershaft.

This was sufficiently worn to allow marginal meshing between the countershaft and spindle gears, which was both noisy and ultimately destructive, Fortunately the motor and controller survived and are now for sale, complete with all new gears etc.

If you have not already done so, check for any play in these bearings, and replace them if you find any. They take quite a heavy load and are quite cheap. I noticed a vast improvement all round when I did this.

I hope this will help, and wish you good luck with sorting it out.

Regards

Derek

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