The Home Machinist!

Really looks interesting please keep the pictures coming. CB

Very nice!

I too am building John's shay, I finished machining my cross head guides and Im now working on the crank... well, actually working on my 3rd crank. the first two didn't come out too good. lol

Keep the pictures coming! I'd love to see more.

Brian

About the hard spots: notice they are in the corners of the base. Many times in foundry pratice, the pattern is set up without a 'hard' corner like that, and use a radias in proportion to the thickness of that base, to eliminate the 'chilled' corners that are white iron. That tends to eliminate most if not all of the problem. If that was cast in Bronze the chill factor would not come into play, since Bronze does not work that way. For the most part, some patterns run in iron, were once run in Bronze, or the corner mistake would not appear. The guides in Bronze would probably wear well, compared to iron, and be a bit easier to machine.

Obviously, having to grind a base (corners) is not as desirable as a full cut. But, this is clearly an example where getting it done is an important part of progress. Other thant a bit of a gap in the fitup, surely the part is strong enough, and has enough base to avoid rocking in service.

IMHO perfection is always the goal, and rarely attainable, as Murphy's Law always applies.

Edit:
Several of the posts regarding this thread were deleted, including the pictures. Some of the remaining posts may not make sense as a result.

Harold

Funny you should mention that, Big Dave. I took note that the base had been ground, but figured it was done when the castings were cleaned up. I've had that happen to me before, with feet cut off a cone mold. Sort of annoying when you wish to have a full surface, although it appears the part is still quite functional.

Maybe ng_2-4-2 can address the grinding, so we'll better understand why it has occurred.

Harold

Harold_V wrote:Funny you should mention that, Big Dave. I took note that the base had been ground, but figured it was done when the castings were cleaned up. I've had that happen to me before, with feet cut off a cone mold. Sort of annoying when you wish to have a full surface, although it appears the part is still quite functional.

Maybe ng_2-4-2 can address the grinding, so we'll better understand why it has occurred.

Harold

On the picture discreption he says "I ran into a small problem with the casting. If you notice the upper left corner of the casting it is shiny. This is a hard spot due to the iron being too hot when poured. This spot is so hard that the cutting tool rides over it instead of cutting. The only way to work around this is to grind the spot down below the machining line."

David

srrl5 wrote: On the picture discreption he says "I ran into a small problem with the casting.

Thanks, David. Don't know how I missed that, but I sure did!

Harold

My understanding is that the hard spots occur when the iron cooled too quickly, not because it was poured too hot. It makes sense that a thin section at a sharp corner would cool more quickly than the body of the casting and would be more likely to be hard. As Big Dave Suggested above, a radius would help. In the days of iron freight car wheels the hard parts were intentional An iron "chill" would be used in the tread area to intentionally cool it quickly so it would be hard and wear well. As far as I know they were operated with the treads unmachined.

Yep! Chilled cast iron. While it may not always respond, if the correct grade of carbide is used, it often will machine reasonably well. It's a huge mistake to use a C5 or C6 grade in such an instance, something I learned the hard way. By using a C2, edges that fail readily with the other grades will cut with relative ease.

Some folks think that a steel grade is proper for cast iron, but it isn't. Same goes for stainless. Pick the carbide grades properly and you'll achieve much better results.

Harold

I received the engine base yesterday. Worked on most of today.

More pictures.

Wow, I guess this makes three people on the forum building John's shay. I started on the frame, and am now working on the trucks. My build thread is still over in the live steaming forum, I'll look in to getting moved. Having run John's shay, its a beast of a locomotive and runs great.

Started working on the crankshaft today.