Hi all! I wanted to share the process to make a Copper Buffalo FlatTop. I took some pictures of the various steps along the way to give you an idea of how one is made.
First we start with a piece of copper round stock, in this case it is 1.5" diameter, and chuck it up in the 3-jaw chuck on the lathe. Copper in particular is quite expensive in the larger diameters and also quite heavy.
Once in the chuck we need to measure how much "stick-out" we want. It is better to do things closer to the chuck, as you are less likely to get tool chatter and it's less likely things can go unexpectedly wrong. Once we have the desired amount protruding from the chuck, I'll score a line with calipers where I want to machine up to. Then we'll turn the outside diameter, removing just enough material to ensure that the material is actually round. "Round stock" is a relative term...it is generally not exactly round coming from the supplier. After turning the outside, we can "face" the end of the material to ensure that we have a flat and perpendicular surface on the end.
Next, we'll apply the knurling to the outside of the material. This is done using knurling wheels, and is easier said than done. Copper is usually fairly easy to knurl, as it is very ductile and forms quite well. Knurling is not a cutting process - the material is actually formed into the pattern, rather than cut.
Next comes the drilling of the hole for the silicon nitride bearing on the bottom of the top. The bearing is a 1/16th inch bearing, so the hole is just slightly undersized to allow for a press fit. The first step in drilling a hole on a lathe is usually using a center drill. A center drill is a very short and very inflexible bit that allows for a hole to be started without the bit 'wandering' and creating a hole that is off-center. In this case, we'll just 'kiss' the material to create a dimple with the center drill.
Then we use our bit to drill the hole.
Once we have our bearing hole, we can cut the bottom profile of the top. This is done using a hand-ground High Speed Steel (HSS) cutting bit. This bit in particular is quite handy - I use it all the time for many things.
Next we'll sand the bottom. I like using 220 grit sandpaper cut into rectangles and folded over on itself. For copper, I like the paper to be partially "used up".
After sanding comes polishing. I use a polish called "Blue Magic" that can be found at automotive stores. It turns black during polishing.
At this point we're finished with the bottom side. Now we need to part the piece off and work on the top side. To part it off, I use a carbide tipped parting blade. The blade is fed into the material slowly until it is almost completely cut off.
Hanging on by a nub....at this point we can just twist it off. We don't want it falling off and getting scratched or dented.
Once it's parted off, we need to do the top side. To do that we'll switch the chuck from the 3-jaw to the collet chuck, and insert a custom collet specifically cut for FlatTops.
We'll insert the FlatTop and tighten the collet down. The first operation is to face the top of the 'top' to make sure we have a flat surface.
Once faced, we can cut the pocket that the Buffalo Nickel will sit in. Each Buffalo Nickel is slightly different, so each pocket is cut specifically for the nickel that it is going to hold. The pocket is approximately .080" deep and .835" diameter.
Pocket has been cut and sized for this particular nickel.
Next we'll cut to grooves to give the top some more texture. These are cut using a small, hand-ground HSS bit with the profile of the groove ground into it.
After the grooves are cut, it's time for sanding.
And then polishing...
At this point, we're done with the machining process. The nest step is to clean the top. I use a plastic container filled with Acetone and a toothbrush to clean the top. Acetone is great for removing any oil or residue from the machining process, and the toothbrush is needed to get down in the grooves of the knurling to remove any black polish, oil, etc.
All clean!
Now we have to press in the Buffalo Nickel. I use delrin to hold the top so as not to scratch it or damage the nickel.
Once on the press, we can gently press in the nickel.
The last thing we need to do is to press in the bearing on the bottom.
Done! We have a brand new FlatTop ready for a test spin!
Thanks for reading! I hope you found it at least interesting if not informative. If you are interested in seeing more "behind the scenes" on a regular basis, follow us on Instagram at Butterfield Machine!
You can check out our collection of FlatTops and other spinners here!
Thanks for your support!
Chris