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How To Machine a Crystal Retention Ring


jmb

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Now that Lani came through with a loaner MBW 5513 retention ring I can make a couple to replace those of Kurt's that the postal service swallowed! I priced some 316L and decided that there was absolutely nothing wrong with 303 in this case since nobody will see it.

I first measured the loaner ring and made a working drawing (attached in PDF format). I then chucked up a scrap of 1 7/16" round 303 in the lathe and turned about 1/4 inch to proper OD:

ring 1.JPG

Then drilled a hole that a small boring bar would fit through:

ring 2.JPG

After the hole was drilled through it was time to bore the ID to size. This needs to be held pretty close tolerance as this dimension determines how much squeeze is gonna get put on the crystal to case junction:

ring 3.JPG

I chose to machine this .001" undersize as I have noticed varying diameters in aftermarket crystals. If too tight then the ID can be sanded a bit until you have a perfect fit:

ring 4.JPG

ring 5.JPG

I then mounted the cutoff tool and machined in the "step" and parted off the ring:

ring 6.JPG

Here is the finished product. Original ring on the right:

ring 7.JPG

ring 8.JPG

I probably won't machine the rest of them until I finish the toolholder for my carbide cutoff blade as it will leave a better surface than the "flexy" cobalt steel blade and be easier to control precisely. I feel that I just got lucky on this one with the cobalt blade!

Well, that's all there is to it. Small Chinese lathes are not all that expensive and with a couple mods and upgrades can hold pretty fair tolerance so go get one and have fun!! :thumbsupsmileyanim:

MBW 5513 Retention Ring.pdf

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It's a cheapie Chinese 9x20. This one is a Harbor Freight branded one but you can get the same one branded as Grizzly, Enco, Jet, etc. The stock compound clamp needs to be replaced with a beefier one (homebrew) and I then installed a quick-change toolpost and a 1.5 HP variable speed DC drive motor. I got it on sale several years back and I think with all the mods still have under $1k invested in it,

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Here is the finished product. Original ring on the right:

ring 7.JPG

Notice in this picture (above) ... the ring on the right has a gap between it and the table. There is a slight bevel from the undeerside that allows the bezel to rotate when pushed down.

ring 8.JPG

Justin,

Thanks so much for taking on this to help me and others out.

Note: Look closely at the loaner underside. There is a slight thinning or bevel on the edge that allows the bezel to turn freely when pushed down.

You may have it but in your pictures it is hard to tell. Use a micrometer and measure fron the inside(nearest the crystal) and pull it outward toward the edge and you should notice a thinning right at the very edge.

Thanks again and thanks To Lani for the loaner.

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The detail in the corrected drawing shows the bevel I measured. I've sent some to a respected source to see if what I have done so far will work with the bezel as I don't have one to try them with...

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  • 2 weeks later...

Crap, OK! Hell, I wuz fixin' to e-Bay it!! :rofl: This weekend I'm going to try to turn out a couple more this weekend and I'll return the loaner and a couple spares for your trouble first of next week.

Remind me not to forget to make a couple for Kurt! ;)

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