How Would You Center This Under The Spindle?

kvt said:
It is nice to see you doing this one I'm still working on my #7. I wound up getting a new base cast for my #7. The fun part is now ensuring the wholes in the cylinders line up with the new cast when I drill it. Will have to work at it.
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Was the base poorly cast? I take it you mean the mounting holes? Ouch. The cylinder mounting holes are threaded. Have you considered using blind hole transfer punches? At least that is what I call them. You would also need a jig.

Billh50 said:
It is always best to blue up the casting and lay out things before any machining. Also best to take your time and make sure you start off right. It is too easy to end up off somewhere without lay out everything first.
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kvt said:
I agree with the blue up and marking things up to start with. In fact I have been putting the blue down, then mark it real light, Then If I want to change I just put a little more blue then redo it. and measure and see if things line up until I get it right. Again nice to see you working on this one.
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I'm not sure where bluing would have helped. I missed the bore by using the casting core, which was distorted, as my starting point. I think using some other reference point would have been great, I just couldn't figure out which or what or what have you. But I obviously was missing something. Any help will be appreciated.

kvt said:
How is it to do on the Sherline.
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It is a challenge for me. But, I have been machining for almost a year. Another couple of weeks and I will have a year under my belt.

I think anyone familiar with machining and Sherline sized equipment should have no problems.

Thus, I am f***ing doomed.

Cheers,

Tom
 
Your not doomed. I am, Ive been working on my #7 since about a week after you started yours. Here is what I did on my second base cast, Took at look and did some measures. Then figured what I wanted to use as a starting point In my case Flat base. and approx. center of bore for crank rod. Blued it all up and marked it out, Then shimmed the base and cut it flat. Also then shaved the front side of the base flat so that It gave me a squared reference point. maybe that would work, That was why I blued remarked, a few times till I could get what I wanted. that saved me, as then all was easy to line up after that. Seems some of their castings line up nice and some not as good, but isn't that whey they always make castings oversized.
 
kvt is right about castings. Many castings are all over the place with locations but usually have enough stock to make the part intended. There are castings that are called Investment Castings. These are so close that very minimal machining is usually required. But they are too expensive for normal use. That is why it is usually best to blue it up and lay out everything before machining. Then decide how you want to machine it. Sometimes the first thought is not always the best. So run through the machining in your mind before you start. Sometimes it is better to just clean a surface, leaving it heavy just to hold the part for machining and then go back and finish that surface. The surface does not even have to be cleaned up completely as long as you have enough surface for holding.
 
Even with production investment castings, variations from batch to batch. Made for some real challenges when cutting cast 17-4 stainless valve bodies, when the portion of the body we had been using to mount to the fixture came to us in tolerance but larger than the steel fixture used for machining them.

I have to say, the work done by members here on rough castings is quite impressive! :cheer:
 
Thanks guys. Until my new frame gets here, I am moving onto the cylinder. Looks simple. Hah, as my latest thread indicates.

Tom
 
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