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| My Attempt at making a A2Z QCTP Holder |
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| wongster:
Thank you Mad Jack. I just posted a new thread on the tramming and z-axis vibration problem. If its not within protocol, please feel free to move it here or remove it. I think my problem with the mill is not being able to get the z axis perpendicular to the table. The instruction outlined in Sherline's book talk about loosening the 4 cap screws holding the z axis to tilt it left or right. But when I started tightening down the screws, each will move the indicated in one direction or another. I tried offsetting the column to the side I think will result in it being "adjusted" back when tightening but it seems that I'm chasing my own tail... Maybe I'll get the accessory that allows the column to turn at specific angles to allow easier adjustments. As to the tilting of the column backwards, I'll try to use shim. Not confident enough to file it off as I may not be able to recover from mistakes. Once I can get this done, I'll be able to sweep the indicator you mentioned. When I was lowering the spindle with the xbox controller, I can hear and feel the vibration. It seems to come from the z axis lead screw. Lifting it up has no such issue. Any idea what would be the problem? What other test I can do to pin point the culprit? Regards, Wong |
| madjackghengis:
Hi Wong, I've got a question, do the cap screws holding the Z axis have flat washers on them? If they don't, put some on, and try to get grade eight washers, as they are hardened. Have you ever used Prussian Blue? If not, it is easily found in a crafts store, as oil paint for art, and it is real useful for matching up parts. Wipe a finger tip of blue on one surface in question on the Z axis, patting the blue with a finger tip to get a very thin and even coat just about the depth of your fingerprint in thickness, and put the other up against it in proper position, and then wiggle the two just a little bit, trying to stay on exactly the same plane you touched off in, then look to see where the blue transfered. This will give you a good idea of exactly where all the power of the machine is transfered through, and allow you to remove high spots until you have good say 75% blue transfer, which will equate to probably 90% when the cap screws are tightened up. The screws are merely to hold the column to the base, all the actual power should be transfered through friction between the column and the base, spreading the force evenly over a wide surface, rather than just in circles around the cap screws. The washers keep the screws from moving things by acting as "wheels" and pushing the column to the side or otherwise. The screws will slide on the hardened washers and find their own home spot without moving the column. Sometimes a simple piece of paper put between the two mating surfaces will make a big difference, particularly with aluminum on aluminum contact, you might try a square of paper with holes punched for the cap screw holes. Something like notebook paper, maybe three thousandths thick or so. It will squish and fill any low spots, and allow for any high spots less than its thickness as well as adding friction to the "joint", and dampening to vibration. Don't ever forget, the first machines were made with nothing but hand tools, and the knowledge of how to generate an accurate straight edge from nothing. I hope this helps out a bit and gets you further down the road. :nrocks: mad jack |
| wongster:
Hi Mad Jack, There isn't any washer. The 4 screws seats in the counterbore holes in the column bed. The holes fit the capscrews' head with very little gap. I'll check if I can get the mentioned washers of almost the size of the holes and trim them from there, if its possible, with a file. Appreciate you help. Regards, Wong |
| madjackghengis:
Hi Wong, most of what I've done in life has been troubleshooting the problem so it can be fixed, and much of this work done on old electronics, from the forties, in the service, or old machines from similar eras, with no source for replacement parts, so your dilema is one I am well familiar with. A lot of people think the real holding power with machinery is in the bolts or other fasteners themselves, while the truth is, they are just there to put enough pressure on the adjacent surfaces so the friction times the area is sufficient to keep things from moving. It is for this reason flat surfaces with as full contact as possible are essential, and things like shimming a side or corner to get something straight makes it easier for it to move later. If you can't get washers in the countersinks, and if you have room, you can use extra thick washers, and long bolts, so the washers are over the outside of the counterbores. The most important aspect of this is having both the base block and the column flat, square to the table, and with as full contact on the surface area as possible. A piece of paper that can absorb half a thousandth of distortion is a far more substantial bearing surface than a shim taking up the clearance, but leaving a minute gap elsewhere. Notebook paper is about three thousandths pretty consistently, cigarette papers are consistent one thousandth, and brown paper bags tend to be about five thousandths, but will take a lot of lateral pressure without giving, and also grip very well to metal. Were it mine, I'd scrape the surfaces flat and square, but I've got some experience at this, and I have a surface plate and lots of special tools for rebuilding full sized machines. If you've got a flat tool makers plate or some other accurate flat, you can read up on the art of scraping for fit, and don't be shy, it's not that hard, just takes a bit of practice, and you can get the machine exactly square and perpendicular. Wish I could just come over and visit, to take a look, but it's a long drive I think. Anything I can do to help, just ask. :nrocks: mad jack |
| wongster:
Hi Mad Jack, The Sherline distributor here commented jokingly that he "confirmed that I am only good at $$$$ matters...". Not very accurate but relative to my attempt in wiring up the Gecko G540 VFD output to the Sherline Speed Control. After going through the text 10 over times, I final have visual in my head. And the circuit diagram is a simple one.... ::) We became friends after a while. Nice chap he is. The paper solution sounds good and logical. I'll try with a piece of A4 printing paper, which I've quite a lot, in between the column block and the column bed to see if I need a washer. With the washer and bolt protruding, I'll not be able to move the spindle closer to the table. I wish that you folks are just a drive away.... Regards, Wong |
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