Byzantine Sundial-Calendar - Part 2 (Make Your Own 'Cycloidal' Cutters) (Patreon)

Byzantine Sundial-Calendar - Part 2

Byzantine Sundial-Calendar - Part 2, by Clickspring. Making your own cutters is a valuable trick to have up your sleeve - So in this episode I go through the process in detail, and also provide a handy calculator that you can use to crunch the numbers. Download the calculator here: https://www.patreon.com/file?h=7965761&i=813598 If you'd prefer to buy the commercial cutters, you can now get them directly from PP Thornton at their website: http://ppthornton.com/ Required cutters for the BSC build are: 1 x 0.85M Wheel Cutter 1 x 0.85M 7 Leaf pinion Cutter 1 x 0.85M 10 Leaf pinion Cutter 1 x 0.85M 12 Leaf pinion Cutter ________________________________________________________ A very special thank you to Patrons: Mitchell Collins Sinking Valley Woodworks (http://www.sinkingvalleywoodworks.com) Daniel Cohen Larry Pardi Sean Kuyper Samuel Irons Dan Keen Florian Ragwitz Matthew Middleton ________________________________________________________ Abbreviated Transcript: 0:00:44 The easiest, and fastest way to get to the finish line, is by using a turned fly cutter like this, made from drill rod. They cut brilliantly, are cheap to make, and once you get the hang of it, you can knock them out in a matter of minutes, with no special tooling required. 01:28 OK, so now a word or two about the geometry of the modern horological cutters generally referred to as cycloidal gear cutters. The first thing to point out is that they are in fact not cycloidal. They use circular curves at the addendum to approximate a cycloid, and this is for us, a huge bonus. Because it makes their construction a lot simpler to replicate. 02:08 But as helpful as those sources are, nowhere have I seen the necessary data that links the cutter geometry, to what you need when you're standing in front of your lathe, ready to make a cutter. To the things that you can control, like the crosslide, carriage and topslide positions. 02:55 But as the module of the gear gets smaller, the button gets a bit impractical to both make and use. Far more convenient, is to grind the radius directly into a HSS blank, using a simple shop made gauge to confirm the radius. It's not as accurate as a turned button, but it's definitely accurate enough. 04:04 We can just turn the stock down until we measure that diameter, and we know we're there. The Z axis position is given by facing off the work, and locking off the carriage. Now of course it's not quite as simple as that in practice, so here's the approach that I take: I take up the backlash on the top slide, and zero the handwheel collar. 05:04 I work towards the zero position set on the cross slide a moment ago, making the cut by feeding out the with the top slide. This is probably the trickiest part of the job. Since I'm going past the cross slide zer indicator more than once on my way towards that final diameter D. It takes me a bit of time to get my eye in, to spot the actual zero point that identifies the minimum diameter. 06:23 With a wheel cutter the flank angle is quite shallow, so a rough check can be made to confirm the final tooth tip width. The section being measured is of course tapered which compromises the measurement, but I can see that I'm in the ballpark with the final dimension slightly oversized to allow for polishing and stoning. And with the turning complete, the cutting face can now be formed. The cutter is milled to a few hundredths less than the half diameter, again as an allowance for stoning. 07:27 And as a final step I think its a good idea to stamp in some identifying marks, so that it can be easily identified in future. The cutter is then hardened in the usual way, quenching in oil, and then very carefully tempered. With the tip taken to a pale straw color, by slowly running the colors up the shank from the blunt end. 07:53 I should point out that this step is critical. If the cutter remains brittle from the quench, it'll snap off on the first attempt to cut. With the heat treatment complete, the cutter can be polished and have its cutting edges sharpened. Which brings me to the first of a few limitations. First of all, its not a constant profile cutter, so the profile will change as its sharpened. 09:50 You can of course simply purchase the cutters for this project if you prefer, and I'll put a link in the description box to show you where you can get them. But it's there for you as an option, and also worth keeping in mind if you ever need to replace a single clock wheel one day, and don't want to shell out 70 quid for a single use cutter. References: "Gear Cutting in the lathe" Model Engineer Commenced June 1949, Duplex "Wheel And Pinion Cutting In Horology", J Malcolm Wild https://www.amazon.com/Wheel-Pinion-Cutting-Horology-Historical/dp/1861262450 "Gears and Gear Cutting", Ivan Law https://www.amazon.com/Gears-Gear-Cutting-Workshop-Practice/dp/0852429118 M-P Brochure Byzantine Sundial-Calendar - Part 2, by Clickspring.