Gear cracks:

[chris mabbott]

Here’s a quick vid on MAKING MINIATURE METAL CASTS looks easy & fun

[namonllor1953]

Hi Guys,
Paul , I placed the arbor in the lathe and cut it off. The pinion rides on a knurled section of the arbor and thus stays in place. Also the arbor being steel and the gear brass the arbor didn’t lose the knurl.
Chris, I’ve done sand casting before, so I’m familiar with that process but, I’ve never used the clay. I just figured that with the pinion being so small that there might be error in the leaves. Maybe I will give it a try sometime in the future.
I thought of soldering it but, I couldn’t close the crack down enough to make it concentric and as you can see in the photo, it’s a pretty substantial crack. I was also afraid to apply any more pressure on the pinion than I was applying, in fear of totally destroying the pinion.
William, I’m pretty lucky in that I have a milling machine and 3 different lathes (full size, mini, and watchmakers). I also have rotary tables, dividing heads and other tooling that, to be honest, up until now, I’ve never used. What I’m going to do is use some nickel silver rod to make the pinion, as it is stronger than brass and it cuts absolutely beautifully.
Since my last post, I’ve decided to record what I’m doing with photos and try to post it on a separate post, so as to not take over Richards post.
Wish me luck and

[chris mabbott]

Ren, you probably already know this, so if I’m stating the obvious….sorry 😆

To do the cast of the pinion with clay, you will need to close the break of the original, obviously, one method is to place it in a vice, apply some heat to the pinion while gently closing the vice until the gap has been closed.

Take a fine brazing rod and put a small blob of braze on the inside diameter, the hole. You can purchase the smallest diameter brazing rod then grind it down to size and use liquid flux. Then you can make the mold impression.

The blob of braze inside the hole is easy to remove from your cast piece, either by machining or with a reamer..

I think the error factor is dependent on how good the impression is and how liquid your, brass for example is. Also the purity of the material to be poured. Air shouldn’t be a problem because this can be done as an open pour, so no vent hole is needed. Air holes in a cast pour is bad. When our guys have poured new Babbitt bearings the main thing is to prevent blow holes.

As the guys have suggested, the classic method is to hand form a new one which works fine, patience is required and time to match the profile. I would go for as accurate as possible as I would want to stay within the original design specs..

The nickel rod should work fine, I’ve been looking for some at my end of the pond but here is more tourist oriented than industrial, so a problem..

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