Most visitors online was 1660 , on 12 Dec 2020
Some folks make their own posts, but a setup can be ordered from Sherline:What kind of plate holding fixture is needed? Can one be purchased?
I assume that the spring loaded screw is screwed into the half moon to pull it up. Correct? Seems like a good idea!For those who are using a Sherline Mill for bushing, the attached photo shows My first movement holder and the Sherline holder. My holder on the left is larger and very rigid but is sometimes limited when holding plates where one would like to hold in a tight area. The Sherline holders are a little smaller and more versatile, but the half moon protective clamping block shown in the middle factory stock holder, can be time consuming in use at times. I modified mine by installing a spring loaded middle screw at the arrow shown in the holder on the right. This saves considerable time in use.
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If you choose a diameter very slightly larger than the original pivot, the gauge pin will only fit into the original center. I use a stereo microscope to watch closely how it enters the hole. If you see any deflection of the pin, you are not quite on center. I use this method only for small pivot holes of less than 1 mm. For the larger ones I use a tapered center finder. I still use the microscope to ensure that the center finder has found the largest diameter of the hole.As SB mentions, I acquired a set of pin gauges and chuck up one that closely matches the diameter of the pivot.
I then set up center by carefully aligning with the unworn side of the pivot hole.
To each his own. I use magnification and plenty of light but I don't have a microscope on hand. I do look closely for deflection. It's not hard to see.If you choose a diameter very slightly larger than the original pivot, the gauge pin will only fit into the original center. I use a stereo microscope to watch closely how it enters the hole. If you see any deflection of the pin, you are not quite on center. I use this method only for small pivot holes of less than 1 mm. For the larger ones I use a tapered center finder. I still use the microscope to ensure that the center finder has found the largest diameter of the hole.
Perhaps.I guess your eyesight is better than mine. For me, the microscope is very helpful.
Here is my set up so far. Im using the WW collet holder and trying to figure out a good way to center up on a bushing hole using a .31 gauge pin, a tapered pin, just anything to get some accuracy into the mix.
Could someone tell me what they use for centering up the plate before cutting the bushing?
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It's the metal fragments produced when you drill, mill or file anything. If even a small fragment gets between the spindle taper and the collet taper, or inside the chuck jaws, it will throw the pin or whatever you're holding off centre.What is swarf?
JohnIf I shorten things up as suggested, runout is minimal but still there. I have a good selection of collets and many of the same size so I have changed them out and checked them in my lathe first. All are true in the lathe.
I leave the plate loose and lower my centering point down into the worn bushing, rotating it by hand until it starts to push the plate around.
Then lock the plate down.
Any suggestions would be appreciated and thanks to all for your tips.
JohnI check the collets(which are a mismatch of different makers) and pins in my watch lathe. They run true. I removed the collet adapter, cleaned and polished it.
The black coating is gone. That helped and there is no wobble in the pin now.
I have been trying to get a centering tool that would work on all the bushing holes. A universal tool per say. Hoping to avoid changing out collets and pins
as you move along the plate to another bushing size. Apparently this wont work as everything tried has some wobble.
If pins are the way to go, then that's what it will be. My set only goes up to .60 so I have to figure out what to do for worn bushings above that diameter.The best set up for me now is to
mark the wear in the bushing with a sharpie, then placethe reamer under magnification with the flat side toward the wear. So far this has produced a good centered cut.
I need sherline #2118 tool post holder, to get things up a little higher so ill order that today.
Thanks for the help
Bruce mentioned my centering points in one of the earlier posts, so I guess it's appropriate to show you what they look like and how I use them. After purchasing my mill, I spent the better part of a day with a Last Word gauge, looking at the tolerances of the machine and making sure that it was set up correctly. I found near zero runout on the spindle taper and the collet adapter, but each of the collets had some runout. The 1/8" collet was most concerning because it had 0.0012 TIR runout and I knew I would be using it a lot. Another consideration was that collets are most accurate when holding a piece that is the exact size of the collet (0.125" pin in an 1/8" collet). All of the commercial centering points that I found had a larger angle on the point than I liked. The large angle on the point allows using one point for a wide variety of hole sizes, but the compromise is that it is much more sensitive to the condition of outside face of the hole. I finally decided that it would be necessary to make my own centering points to achieve highest accuracy.
I settled on a 5 deg angle for the points, which meant that I would have to make 5 of them to cover all bushing sizes.
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To compensate for the runout in the collet, I took the head off my mill and mounted it on my lathe. I then match-marked the spindle to the collet holder and the centering pins to the collet with pink fingernail polish. I turned the shank on each centering point to 0.125" dia. Then I set the head at a 2.5 deg angle and turned the tapers on the centering points while holding them in the 1/8" collet with all of the match marks aligned. Two of the points have 0.0002 TIR at the tip and the other three have 0.0000 runout.
I purchased the Sherline horological plate holders, but I found that their height gets in the way when bushing holes that are near the holder. Finally decided to make my own, which are shown below.
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Mark the pivot holes with the position of the original pivot. Place the plate on the holders, making sure that there is some room for the plate to move in all directions without binding on the hold-down clamp screws. Then plunge the centering point into the pivot hole, while holding gentle horizontal pressure between the original hole location and the centering point. Tighten the hold down screws and bore the bushing. The Sherline mill has a very sensitive "feel" and you can very easily tell when the centering point is solidly against the plate. Don't force the point down after it makes solid contact, as this just flexes the plate and potentially introduces errors.
The method that I settled on for bushings is that I purchased center cutting end mills that were slightly smaller than the commercial reamers (for the smaller sizes, they are less than $10 each). Once the plate is locked in place, I chuck the mill (which usually has an 1/8" shank) and bore out the old oblong hole. I then remove the collet and drawbar and drop a custom reamer holder that I made through the spindle. Then I hand ream out the last few thousandths and drop in a piece of 1/4" round stock that I use to tap the bushing into place. If you need to trim the bushing, you are already centered up, just throw the collet back in and trim away.
Without getting into details of how I made the measurements, I checked the procedure with 4 different bushings and found that the bushings were centered on the original hole within a minimum of 0.0008" and a maximum of 0.0012".
I would strongly recommend using Jerry Kieffer's method of using gauge pins to bore the bushings to size. I usually don't pay any attention to the old pivot hole size, I just mike the pivot, select a gauge pin that is 0.0015 to 0.002" larger and bore to that size. I think you will find it to be very close to the "ideal" 5 deg lean.
I hope this helps.
Rotgut steel bar stock from Home Depot. That was a mistake because I could feel variations in hardness as I was turning the points. There is no potential for wear because there is almost no force on them and I never have the mill running when they are in contact with the plate.What metal did you use to make the tapered centers ? Centering points
I have no doubt that pin gauges would work as well or better than my method, but I was concerned about three things:Thanks for sharing your methods Dave. I was hoping that you would weigh in. I've always thought you had a good approach. At this point, I've settled into "sighting" center in with Pin Gauges whether I have them held in a Collet or a Self-Centering 3-Jaw Chuck...which works remarkably well I think. I did finally pick up a Last Word kit. Used it for the first time just this week re-centering a bent C-2 pivot on a Sonora 8-Bell movement. When I thought I had it centered by sight, I was surprised to see just how far off it still was.
I plan to go back and check both my Lathe and Mill and bushing set ups for run out as you've described. So far, as is, I think I've achieved some excellent results "right out of the box". You certainly have taken things to the next level.
On infrequent occasions, I have needed to be creative with plate positioning while using the Sherline Holders but they have not yet blocked my access to a pivot hole. Of course, if I have to fiddle around with the plate, that can eat into the clock.
Can you use your holders for a depthning setup? I wish Sherline made theirs a little taller for such use.
If you don't mind my asking, using your Tapered Centers, what would you say your average time per bushing is?
I agree. For most folks I think this is true. Of course there are the truly gifted who are always several steps beyond us before they first pick up a wrench.Doing bushing work by hand is absolutely a must learn for clock work.
That sounds very reasonable to me. I think that speed is where a Bushing Machine will excel but I'm not a professional shop doing volume work. I'd rather have the versatility of a Mill.It takes me about 15 minutes to install a bushing. Kind of slow, but my pride in workmanship is more important to me than my time.
Well, you passed that along to me so I thank both of you for your help and guidance!One more thing is that I would like to thank Jerry Kieffer for guidance on where to buy and how to use pin gauges. I couldn't live without them.
I've got a set of 1-2-3 Blocks on the way along with a couple of 3 1/2" Fasteners (Ridiculously expensive from Fastenal) which should work with the T-Nuts. I'll report on how I think they'll work out as riser blocks for the Sherline Posts. It would be nice if Sherline Made these Posts taller, especially since they specify they can be used as part of a Depthniing Set Up (It currently can for an "average" mantel clock movement). They would need to charge more for materials I suppose but I think it would be well worth it.Blocks are still not high enough
They do warn that their equipment and parts should be cleaned with Mineral Spirits (or similar) to remove their corrosion preventative, but I don't recall whether they specify or stress any one area. I think Machinists just routinely check/clean these areas/surfaces for swarf before every setup.You would think sherline would recommend a spindle cleaning before inserting any tooling.
I guess it doesn't matter if pins are metric or imperial, since you want one the same size of pivot or even slightly larger - so the pins to select from just need to have a good assortment of close sizes. Why is conversion needed? Is it because you measure in metric only?I like metric because the bushings are calibrated that way, but metric pin gauges cost a lot more for some reason, so I went Imperial with them and use a quick conversion chart that Dave was kind enough to share.
You bring up a good point MuensterMann. I need to do conversions when I'm using my Metric Collets. I also like to use a manual outside Micrometer when measuring pivots and it's calibrated in Metric. It's accurate, doesn't need batteries and is good for spotting pivot taper.I guess it doesn't matter if pins are metric or imperial, since you want one the same size of pivot or even slightly larger - so the pins to select from just need to have a good assortment of close sizes. Why is conversion needed? Is it because you measure in metric only?
If you plan to replace your digital calipers with high quality digital ones it will easy to switch between metric and imperial by a push of a button. The only issue is that the caliper will provide imperial results in decimals of an inch and the collets are labeled in fractions of an inch. So, still the need to convert.You bring up a good point MuensterMann. I need to do conversions when I'm using my Metric Collets. I also like to use a manual outside Micrometer when measuring pivots and it's calibrated in Metric. It's accurate, doesn't need batteries and is good for spotting pivot taper.
If I'm working with a 3-Jaw Chuck instead of my Collets, I could eliminate the need to convert by using my Digital. I think I'm going to replace my Digital Calipers soon and need to give it some serious thought before I do now that I'm bouncing between the two Systems.
Hey M.Mann. I checked Sherline's website and they claim that the 5400 Series 15" Extended Column upgrade increases the range from 6" of travel to 10+". For the additional $94.50, I think it's worth it.Is it a gain of 3 or 4 inches?