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| Another Halo |
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| Darren:
I can see this is developing quite nicely...... :clap: |
| CrewCab:
Top class work Kirk :thumbup: thanks for sharing. CC |
| NickG:
Looking very smart indeed! |
| kvom:
Made a few more parts fpr the engine. First up was the crank and crank pin. I turned the crank from a piece of 1" 12L14. Faced the end of the rod, then turned .25" down to the .75" required diameter, and finally drilled the clearance hole (#43 drill .25" deep). The face needs to be countersunk to accept the flat screw. I should have used a screw to test the depth, but eyeballed it instead. I will need to deepen it so that it sits flush, else the conrods will hit the protruding screw. Before parting it off, I took the rod off the lathe, mounted it in a 5C collet and collet block, and used the mill to drill the offset hole for the crank pin. This was actually unnecessary as I had to mill the reverse side after parting off, and I could have drilled the hole then. Once I had milled the reverse to achieve the required disc thickness, I needed to counterbore the center hole 3/16" diameter and .04" deep to match the crankshaft. The crank pin was made from 3/8" drill rod. Here are the two parts: and assembled onto the crankshaft: Next up was finish boring the crankcase to 1.28". The interior finish isn't very good (using a brazed carbide boring bar). I think HSS would have been better. The holes make for an interrupted cut. I'm thinking now that drilling these after boring would be preferable, as with the thinner walls it's possible to debur the inner edges from the outside. Test fit with the cam housing: Final work for the day was to turn the push rods from .25" brass rod. This was not a difficult job, but was rather tedious as I need 10 of them. Each took ~10 minutes and three adjustments of the toolpost. First face the end, then turn to .125" diameter for a length of .465", and finally part off to .500". Once I had the 10 blanks, I mounted the shafts in a smaller collet and used a form tool to round off the heads, as shown in the plans. Had I not had the form tool, I could have also used my 1/8" corner rounding endmill mounted in a toolholder. |
| bogstandard:
Kirk, Nicely done, but unfortunately I have a bad comment to make. There are no excuses for not deburring the job as soon as it is finished. That is a very basic machining practice, even for total newbies. You will have no idea if the parts fit correctly together. As far as you know they do, but once deburred they might be as loose as anything. As for remachining the crankcase, how could you possibly hold it correctly, with previous machining burrs from ages ago still on the part. Plus the fact that you are liable to injure yourself on the rough edges. As soon as an operation is completed, and taken out of the chuck or vice, it should be fully deburred. I am not being over critical, but posts should only show a very good example to new machinists, otherwise they are liable to pick up bad habits, by thinking if you do it, they should and can do it as well. Bogs |
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