I have commented before about how the Sherline CNC mill is not powerful enough to do large scale production work, but it still amazes me that I can afford a tool like this!
I did have an odd failure last night. The Y axis was suddenly not going where it should. The coupler that locks the stepper motor to leadscrew had disengaged. This was easily fixed, but one more thing to check before starting the mill.
Generally, you do not want to hang a part out of the side of a vice like that. One, it is difficult to get even, parallel, holding force when the part is not centered in the jaws. You can damage parts trying to get enough holding force. The other problem is that parts tend to migrate from their starting location, unless you are using a very expensive, precision vice. Which that isn't. One work-around is to clamp up an identical size piece in the other side of the jaws, so the vice jaws stay even.
ReplyDeleteUsing parallel bar sets under the part in the jaws helps to support it, and makes positioning the part faster and more repeatable.
I would suggest moving the part to a centered position, and raise it high enough for the bit to just clear the top surface of the jaws at the lowest position that will be cut, when those cuts extend beyond the part edge. That, of course, depends on the clamped sides being parallel. Actually, being co-planer. The more surface area over the longest axis that gets clamped, the more stable it stays.
Of course, the smaller engagement the milling bit takes, the less force there is that wants to shift the part, but that is a bad habit to get into. It tends to bite you when you can least afford it. Sometimes the vibration can cause the part to shift, and it may not be noticeable by eye, until it is late in the process.
Sometimes you leave extra material for clamping purposes, that gets removed last, after an orientation shift.
I forgot to add:
ReplyDeletelike this: http://www.amazon.com/Anytime-Tools-pairs-MACHINIST-PARALLEL/dp/B000MCG2W6/ref=sr_1_1?s=industrial&ie=UTF8&qid=1442901178&sr=1-1&keywords=parallels
Will: thanks for the suggestion. I will center in vise and use parallels.
ReplyDeleteWill: Centering workpiece in vise seems to allow higher feed rates without pulling the workpiece out of vise. Thanks.
ReplyDelete