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Does anyone know where I might be able to get specs on the ball screws on the Emco PC Mill 50? I recently acquired one of these machines and I'm upgrading the controls on it. Unfortunately, it would seem someone emptied all the balls out of the nut on the X axis. The screw itself and the rest of the machine is in excellent condition otherwise.
Thanks.
do 1/8th inch balls work?
what is the pitch and nominal diameter of the ballscrew.
1/8th is too big. These things are pretty small. The OD of the screw measures .303" (this seems odd to me). Not sure about the pitch diameter, but the minor diameter measures .275". This is why I need specs if anyone has them. These things seem odd ball to me.
They would be metric, I have one for sale it is the complete frame, all 3 Ballscrews are in place, it was a parts machine I had it is in new condition, you can sometimes get them on Ebay under Emco, here is may be a ballnut that might work for you Emco F1 & PCMill 50 55 CNC Mill & Compact 5 CNC Lathe Ballnut Ball Nut #2 0125 | eBayQuote:
Originally Posted by Nivec
Thanks for the link. I will have to contact the seller. This is just across the Detroit river from me so I might be able to go pick it up (he won't ship to Canada). The weird thing is though, this looks like only half of the nut from my machine. When I took mine apart, the nut was 2 pieces mounted inside a small block of steel. One half is press fit into the block and the other is held in with a collar. I've attached a pic.
Out of curiosity, how much are you asking for your frame?
Sent you a PM with the Price, if you remove the Nut on the front of your Ball screw assembly the Ball nut should slide out of the block and look like the Ebay photoQuote:
Originally Posted by Nivec
So I have gotten a little further with this. The balls are Ø1mm. We have some where I work so I am now going to try to re-load the nut.:( Actually there is 2 nuts on these. One is screwed into the mounting block and the other gets held on with a collar so you can adjust the pre-load on the screw. Wish me luck!
So I'm back to trying to find a replacement nut as one of the nuts is damaged and the balls don't stay in it once it is reloaded. I have learned quite a bit along the way though. First thing I learned is that it wasn't 1mm balls in the nut, but 1/16th balls. I have access to replacement balls and was able to re-load one of the nuts. There are 2 nuts on this ball screw which I believe is designed to remove backlash. As I stated the second nut is damaged and missing a little tab inside which is meant to keep the balls from getting past recirculating tube hole so when I load it back onto the screw and wind it down a little ways, some of the balls come out the other end.
If anyone out there has any more info on these, it would be greatly appreciated.
Emco probably has spares, but don't be surprised if they are 500USD+. The screw is nominal Ø8mm and I'd guess 2.5mm pitch. SKF and others make screws with nuts that look like that. The threaded ball nut is common in the small screws.
I have tried to contact Emco for replacement but hey haven't responded. Initially I thought the same, that it was an 8mm with a 2.5mm pitch, but the 1/16th balls is throwing me off. Why would they use imperial balls in a metric screw?
It's very common in bearings. Emco can be a bit slow, especially if you don't have a part number, hopefully you included a serial number.
Are you sure they are 1/16th .0625, they could be 1.6mm .06299, you would have to measure the balls with a .0001 mike to know for sure, they could be any size Ballscrews are ground or rolled, then the ball size is fitted to what the screw and nut dimensions are, so the balls can be any sizeQuote:
Originally Posted by Nivec
Tsubaki 12x5mm screws in my Compact 6 had nominal 3/32" balls. I bought balls from Baltec when I rebuilt them, 3/32", .093616", and 093413". I ended up using 3/32 and one of the others(X and Z screws used different size balls). I measured the old balls before ordering. Balls are fitted to ball screws to provide the proper clearance or preload.
It is absolutely normal to see metric balls in imperial bearings and vice versa.
Hello,
Search for SKF SH 8X2.5 R and you find immediately your ball screw.
I've also a problem with my X-screw.
It makes a clicking sound with more resistance only in one direction, if I can't
fix the problem I must spend also 74 Euros + shipping / screw.
I have already cleaned an regreased but still the same, think I must check
first with a magnifying glass for pittings, hope it isn't the recirculating tube
which blocks the balls.
Perhaps it is possible to make a new stop by unmounting the tube
and making a new one, the ends of the tubes serve for the stops.
Dieter
Found a new nut on ebay. Worked great until I blew all the balls out of that one too. These things seem too fragile, time to look at a different ballscrew I think.
You can't ignore the torque of the stepper if you've crashed the axis. Emco built all of these stepper machines with the motor not being strong enough to damage the mechanics. The little 8x2.5 ball screw is rated ~2.5kN thrust. With the 2.5:1 reduction on the axis motors, the factory ~59oz-in steppers max out the screws. Yes, these rating surely have some safety factor, but when the motors are capable of 6 times the rated torque we can see how a crash will be a problem. If running this much torque is required(is it?) you'll have to be absolutely certain the control won't crash the axes. Crashing into a fixture is a different matter.
It's a shame. The rest of the machine is built quite well. Unfortunately, in order to get a bigger screw into this thing, I'm going to have to do some major modifications which I really wasn't planning on doing. But I'm in too deep now to turn back.
Emco had a spec in mind and built these machines to that spec. These tabletop Emco are teaching machines. Imagine students crashing every session and the machine needing an axis rebuild. They often never do more than engrave a name in a few minutes. Other than some of these little machines, CNC are not built to withstand crashes any more than a car is. Software and limit switches prevent axis end stop crashes, but the rest is up to you. So, if you build an F1 car don't bump into walls with it.
I see a lot of machines "upgraded" with monstrous axis motors. I always wonder what kind of work these machines are doing that require that much axis thrust. If you put a larger screw into it, what else do you need thrust bearings? Will larger bearings fit? A new bearing support? Say you do all that and still manage to crash what breaks next? Same as tripling the HP of the engine in your car doesn't mean the rest of the car can take it.
With 2500RPM and 550W peak spindle power, it won't need to be going anywhere fast. If you have a need to make parts faster, it may be time for a new machine.