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2019 in the workshop
 

2021 Spinner backplate V2

November 2021 In August of 2020, I made a backplate to fit the RO-Jett 67 that I intended to put in my new plane. The most critical part of that project was to get the angle of the cone to 18°. I start a new project to make a new backplate and set the toolpost slide to 18°. <div style="Font-size:5.0pt" November 2021 I decide to make a new cone first and to leave the toolpost slide set throughout the complete machining process. Actually, machining a new cone is harder than it looks so I abandon the idea. Original cone is on the left. Later, I find some free machining steel which is much easier to use. At some future time, I'll try this idea again. <div style="Font-size:5.0pt" November 2021 I put the 4-jaw chuck in the lathe and retrieve my lump of 60mm alloy. I indicate it to set the workpiece centrally in the lathe's jaws. <div style="Font-size:5.0pt" November 2021 Even though it is set centrally in the jaws, the workpiece is out a bit on the end. <div style="Font-size:5.0pt"
November 2021 A few light taps with a hammer straightens the lump along its length. <div style="Font-size:5.0pt" November 2021 I fit a live centre to the tailstock to support the alloy and stop it from moving around. Then the machining starts. <div style="Font-size:5.0pt" November 2021 I turn the end of the bar down until it is slightly larger than I need. <div style="Font-size:5.0pt" November 2021 Then I turn the engine side of the work to the correct size. This time I machine a larger diameter than before as I have changed the design slightly. <div style="Font-size:5.0pt"
November 2021 It is time to separate the bit that I want from the bar. Parting is always a sweet sorrow but I manage to cut most of the way through without incident. I use a 4mm wide parting tool and then cut the rest with a hacksaw. <div style="Font-size:5.0pt" November 2021 I reverse the workpiece in the chuck and indicate it again. <div style="Font-size:5.0pt" November 2021 "Indicate" is a term I picked up from watching machinists on YouTube where they make a verb out of the noun "dial indicator". I've always been uncomfortable "indicating" a 4 jaw chuck but I keep repeating to myself a little mantra that I've picked up on YouTube, "Tighten the highs, loosen the lows." <div style="Font-size:5.0pt" November 2021 I bore a 1/4" hole all the way through the workpiece and then wind the tool post in (set to ~18°) to bore out the tapered cone. It is set at too great an angle so that the cone touches only the bottome edge of the hole. I use engineers blue to do this. <div style="Font-size:5.0pt"
November 2021 I keep adjusting the tool post angle until I finally get the cone angle right. By the way, the change in design is visible here: there is now a shroud at the very rear so that the shroud covers the engine and does not stop short like before without the shroud. I don't think I'll bother doing this again. <div style="Font-size:5.0pt" November 2021 I remove a little bit of metal in the hub (at 18°) to lighten it a little. I also have to leave a little more metal at the hub than I would have liked because I need to reverse this in the chuck again to machine the spinner side of the work. <div style="Font-size:5.0pt" November 2021 I switch the piece around and indicate it again. I finish the machining on the propeller side. The large round divot is a mistake - bugger. <div style="Font-size:5.0pt" November 2021 The carbon fibre propeller cone is a snug fit and stays there unsupported. <div style="Font-size:5.0pt"
November 2021 I take the backplate over to the mill to cut some grooves to stop the propeller from spinning on the polished hub. <div style="Font-size:5.0pt" November 2021 I drag a starting drill through both sides of the hub and the advance the indexing head by 5°. This should have been simple but I muck it up a little: I don't have the hole exactly centralised so it's off a bit. I have since bought another dial gauge made for centralising the hole. Next time better. <div style="Font-size:5.0pt" November 2021 Back to the lathe but this time I use the 3 jaw chuck which has returned to its rightful home. All I need to do now is to remove the burrs. <div style="Font-size:5.0pt" November 2021 Burrs removed and polished. I also take the opportunity to remove the sharp edge on the engine side of the backplate. <div style="Font-size:5.0pt"
November 2021 Screw it all together and job done. <div style="Font-size:5.0pt" November 2021 It's 2grams heavier than my earlier effort at 30 grams (about 1 ounce). I'm quite pleased with the way this turned out. <div style="Font-size:5.0pt" November 2021 And outside the workshop it's raining. <div style="Font-size:5.0pt" November 2021 Oh joy! End of this project &nbsp; Click to go to home page <div style="Font-size:5.0pt"
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