Spare Parts #3 - Making A Simple Reamer From Blued Pivot Steel

Making A Simple Reamer From Blued Pivot Steel, by Clickspring

Clockmaking often involves fitting shafts to holes, where a close reamed fit is required. Often a reamer simply doesn't exist in the required size, so a custom reamer must be made to fit the job.

The main project video that this video is related to is "Making The Collets And Other Arbors":    • Clockmaking - How To Make A Clock - Part 1...  

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Dormer A190202 Jobber Drill Set, 1.0 mm - 6.0 mm x 0.1 mm Size: https://amzn.to/2DR5fdb
Dormer A190203 Jobber Drill Set, 6.0 mm - 10.0 mm x 0.1 mm Size: https://amzn.to/2ITfeTa
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Abbreviated Transcript:

0:00:11 The arbors have been made from hardened and tempered pivot steel, and I'd like them to be a close fit in the collet holes, the sort of fit you'd expect to get from a reamer. Pivot steel is supplied in a wide range of sizes that loosely correspond to the numbered drill system.
0:00:26 Its unlikely I'd be able to find a commercial reamer that would match the size I'm using today. But fortunately I don't need to. I can make a simple reamer from the steel itself, and know that the reamed hole will perfectly match the arbor.
0:00:37 Starting with a new piece of the blued pivot steel, I've loaded it into this simple holder, that gives me a quick way to index for three sides. That allows me to use the belt sander to form the 3 flats.
0:00:52 Its a 60 grit belt, and I'm keeping the angle with the belt quite shallow, about 5 to 10 degrees. I'm also keeping the contact with the belt very short. The steel is hardened, and I don't want to draw the temper beyond what it already is.
0:01:16 A quick touch to the top, and the result is this truncated pyramid. The 3 facets are then lightly honed on a fine oilstone, to knock off the burr from the grinder, and bring up the cutting edge.
0:01:37 It doesn't take much; Just a few strokes for each face, and the reamer is ready for use. The hole to be reamed is drilled slightly undersized as normal, so that the reamer has something to cut.
0:01:50 In this case, I'm drilling 2.3 mm to ream 2.46mm. And then the reamer simply follows the drilled hole; At a moderate rpm, with a little cutting fluid.
0:02:05 Now there are a few drawbacks to this sort of reamer. It has no flutes, so it needs to be backed off regularly to clear chips, particularly if using it on steel.
0:02:15 It also can't really cut very much metal, just a few thou, so the initial drill size selection is important. If the sizing is correct, the chips coming off will be very fine like this.
0:02:25 A cross section of the cutter shows that the geometry is negative rake, so its probably fair to say that it's best suited to reaming brass, although it will still cut steel. In this shot its cutting drill rod, and again, making very fine chips.
0:02:46.460,0:02:50.389
And finally, while it lasts very well on brass, it does lose its edge quite quickly on something like drill rod. When it does, just give it a quick touch on the belt sander, and you're good to go again.
0:02:58 It'll never beat the finish of a fluted HSS reamer, or be practical for high volume work, but it's a great way to get out of having to buy a reamer for a one off small hole.

References:

WR (Bill) Smith Master Clockmaker
Clock and model making construction/reference books
http://www.wrsmithclocks.com/books.htm

Making A Simple Reamer From Blued Pivot Steel, by Clickspring