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Alan Gordon 408/12/2018 08:11:10
81 forum posts
3 photos

Hi All, Well I am on the final lap of completing The Whitaker "Firefly" I have to say it has been a steep learning curve, but getting there, There is however one part that is throwing me and that is machining the prop driver, The outside is not an issue but machining the internal "flat" to locate on to the crankshaft. I could secure with a grub screw but would like to learn how to machine the internal flat. Any help would ( believe me ) be greatly appreciated.

Edited By Alan Gordon 4 on 08/12/2018 08:11:41

Les Jones 108/12/2018 08:43:44
2121 forum posts
146 photos

I assume it will be made from aluminium. I would try making a broach out of siver steel. Start by machining it down to the size of the shaft that it is to fit on. (Including the flat.) Then turn it down in steps until you have got to the point where there is no flat left. I would try to make each step a little longer than the length of the hole in the prop driver. You may have to make two (or more.) broaches to do it in stages as if the steps are quite long then there will be too much length sticking out of the chuck. Harden and temper the broach.Drill or bore a hole in the prop driver the diameter of the end of the broach. You will then need to find a way to press the broach through the prop driver. An arbor press would probably be best but if your lathe is substantial enough you may be able to use that to press the broach through. A rotary broach would be another method. There was an article in MEW some time ago about making a rotary broach. I think it was by Michael Cox. I think details are also on his website.


Edited By Les Jones 1 on 08/12/2018 08:44:13

Edited By Les Jones 1 on 08/12/2018 08:45:19

Alan Gordon 408/12/2018 09:20:06
81 forum posts
3 photos

Thanks for that Les, very interesting.

JasonB08/12/2018 10:07:34
17877 forum posts
1954 photos
1 articles

I did as Les Describes here

Alan Gordon 408/12/2018 10:22:29
81 forum posts
3 photos

Wonderful this is exactly what I was after. Just another thing Jason, I also have completed cons rods as you have done however how did you over come the problem of the cutter "digging in" while turning the con rod in the chuck /rotary table.I found that "very gentle" cuts plus a good grip was required but is there another way that I need educating in ?



JasonB08/12/2018 13:12:59
17877 forum posts
1954 photos
1 articles

I can't remember there being any issue and don't tend to get a dig in when rounding other items. 10-20 thou cut should be OK.

Make sure you are not climb cutting as rotary tables can have a bit of backlash in them, conrod should be rotating clockwise as you look down on it.

Alan Gordon 408/12/2018 13:41:59
81 forum posts
3 photos

Thanks Jason You are probably aware I am still on the learning curve, however I have to say that the Firefly is coming along well, so looking forward to its first run soon

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