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For a long time I’ve always felt that to do the best possible job on something mechanical, my favorite approach is to break a task down to their separate steps, and have a systematic method for performing each step. So with repivoting, I kind of started with an assortment of different diameters of blued pivot wire, and went from there. My idea is that since I have a wide range of diameters to pick from, one of them ought to be the next size thicker than the pivot I want to duplicate. That’s because I like to make a pivot slightly thicker than my final diameter and machine it down to maybe a couple thousandths larger than my final destination diameter. Then I can just stone & burnish to destination diameter.
This first photo shows how I keep my pivot wire organized. I made a cheap wooden stand and drilled for plastic test tubes for each wire diameter. I get my plastic test tubes from Lake Charles Manufacturing in Louisiana. You can find them here: http://www.lcmlab.com/Vol_10ml_Round_Bottom_Plastic_Test_Tube_16x100m_p/w-206u1.htm?1=1&CartID=0 . You have to scroll down to the size I used for pivot wire…16x150mm. I bought item #58A2 for a pack of 25.
In my wooden stand I drilled holes for three rows of plastic test tubes…the back row has the pivot wire. I got little adhesive round labels for the blue caps, so I printed out the wire diameter for each tube, makes it easy to quickly select a needed piece of pivot wire. In front of the pivot wire row is two rows for smaller plastic test tubes, which I use to hold ONE carbide printed circuit board twist drill. I know twist drills aren’t the ideal drill for pivot work, but they’re so cheap they’re easy to replace and besides, I peck at the spinning arbor so lightly that I haven’t broken a drill bit yet. But, I drilled the stand for two of each drill bit to go with each wire diameter. As you can see some of my wire sizes only have one drill bit, but my more common wire diameter have two bits in front of it, in case I break one (and I probably will someday).
Here’s another view of my pivot wire organizer. This shows the little labels I made for the drill bits. The top number in bold matches up to the pivot wire diameter behind the drill bit. The middle number is the actual drill bit size, whether it’s a metric, wire gauge or fractional or whatever. The bottom number is the drill bit size expressed in thousandths. I picked each drill bit size to be just one or two thousandths UNDER the pivot wire it goes with. That way I can file down the pivot wire piece to just fit tightly into the hole in the arbor.
Here’s a closeup of the little test tubes I bought for the drill bits. They’re really cheap, only $11.02 for a pack of 500 of them. I don’t know what I’ll do with them all. Guess what – you have to buy the caps separately! You can find the tubes here: http://www.lcmlab.com/12mm_Polypropylene_Test_Tubes_p/w-206m1.htm?1=1&CartID=0 Look for item #51A3 – you can also get the caps in bags of 25 for $2.00 or so…they are item #51A2. The caps I got for the tubes are item #88A3 (pack of 25), you can find them here: http://www.lcmlab.com/12mm_Two_Position_Caps_Natural_for_Plastic_Test_p/210-0001w.htm?1=1&CartID=0
Here are two more shots of the organizer. The first one shows the diameter labels on the pivot wire blue caps, and the second shot shows a construction detail. The organizer is made from three pieces of plywood with only the top one drilled for holes.
OK, now here’s how I hold the drill bits in my tailstock. One thing I like about PCB drills (besides the fact that they’re carbide so they cut great) is that all the shanks are perfectly 1/8″, or 0.125″ diameter. I use a special runner I had made for the tailstock in my Rivett watchmaker’s lathe. I took my actual tailstock and a 36″ piece of “S”-sized O-1 drill rod to a company in Phoenix that does centerless grinding for the aerospace industry – I figured if they can make little parts that go on the Mars rover, they can make me a tailstock runner! They ended up grinding me 3 separate runners, but the one shown here is drilled with a less-than-1/8″ drill hole, then bored with a tiny boring tool just to the point that the shank of a PCB drill just made a nice slip-fit. I also had three tiny holes drilled and tapped for very small allen set screws. The holes are spaced 120-degrees apart so all three set screws are equidistant from each other. Just lightly tightening down on the set screws effectively locks the drill bit very firmly.
Here’s two shots of the little knob on the end of the runner. The knob was turned from Delrin.
So how does the runner perform? Like this:
Hey Doug, FANTASTIC
I have been thinking of how I would organize pivot wire for some time now, I think Paul and I have talked about it in the past, WELL, now I can put my mind at ease because of your ingenuity and kindness in sharing your idea…now I dont have to think about it anymore….I can feel a bit of emptiness in my head right now 🙄
I especially like keeping the drill bits with the wire. Do you think you can put a bit of oil on the shank of the drill bit to “hold” it while drilling yet slip if the bit were to bind, I believe Daryn had mentioned somewhere that he does that. thanks. William@willofiam wrote:
Hey Doug, FANTASTIC
I have been thinking of how I would organize pivot wire for some time now, I think Paul and I have talked about it in the past, WELL, now I can put my mind at ease because of your ingenuity and kindness in sharing your idea…now I dont have to think about it anymore….I can feel a bit of emptiness in my head right now 🙄
I especially like keeping the drill bits with the wire. Do you think you can put a bit of oil on the shank of the drill bit to “hold” it while drilling yet slip if the bit were to bind, I believe Daryn had mentioned somewhere that he does that. thanks. WilliamThank you William. Feel free to copy whatever you want, if you make improvements to it then all the better!
I don’t think putting oil on the drill shank would be a good idea – that would defeat the purpose of holding the drill bit in securely with the three set screws. What I do is set my belt tension between lathe & motor so the belt will slip if anything binds. Machinists do that all the time on their large lathes – in fact, I got that idea from a machinist friend of mine. Basically I just move my motor toward the lathe *just* enough so that it will still run, but I can easily stop the headstock with my fingers.
Hope that helps a bit…
…DougHi Doug,
Funnily enough I made myself a drill runner today for my 6mm Wolf Jahn Geneva lathe. My teacher, Daryn, made his own drill runner for the carbide bits and made it so as not to be a snug fit and oiled as William pointed out in his earlier post. as you know with these carbide bits they break easily so I thought it would be a good idea to try one for myself after seeing Daryn’s perform so well. I had two re-pivots to do, a fly from a french clock and a 4th wheel. The pivot on the fly is .33mm (a third of a mm!) so this would be a good test. It worked flawlessly but I didnt once notice the drill bit grabbing and making use of the liquid clutch system. The next pivot was .62mm, this one did grab twice and this works beautifuly, the drill bit just spun with the work. Both pivots turned out dead true and I am very happy with the runner. Considering I have an old lathe and I remember someone commenting recently about how a lot of these lathes are not accurate I sure am happy with mine!
Those carbide drill bits are in a collet and my home made tailstock runner and they are .33mm – All lines up well for an old machine
Paul.
p.s. I am stealing your tube idea for the pivot steel, its brilliantI too, have a dedicated tailstock runner for those 1/8″shank drill bits. I didn’t bother with more than one set screw, but I have never had any problem with things not being centered.
Incidentally, and old machinist friend of mine told me how to check a used lathe (or one with a moveable tailstock) for center. Hang a double edged razor bade between center points in the head and tailstock. If they are centered, the razor blade will hang perpendicular in both vertical axes. Also, if you want a rough idea how far out of center they are, pinch the blade between the two centers, then rotate the headstock or the tail stock runner by hand. The blade will wobble. Knowing the length of blade sticking out from the centers, and the distance of the wobble, and that Oscar Has A Hairy Old Ass (Opposite/Hypotenuse= sine, Adjacent/Hypotenuse =cosine; Opposite/Adjacent = Tangent of unknown angle in a right triangle), you can easily calculate how far off center they are.
Here is a photo I took, where I shimmed one side of one center, to show how the blade hangs when they are not aligned.If you find that your headstock and tailstock are not centered, all is not lost You can still do pivoting, by making a dedicated bit holder. Turn a piece of brass stock to fit the tailstock runner. Place it in the runner, and lock the runner. Chuck a standard twist drill (or spade drill which a shank the same diameter as the drill bit) and drill a hole in the brass piece, by sliding the tailstock on the ways. Reverse the bit, and secure it in the holder with a bit of Loctite. Chuck the arbor to be drilled, and, again <u>without unlocking the runner</u>, drill the arbor by sliding the tailstock on the ways.
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