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 Post subject: How to Cut the Crown?
PostPosted: Sun Apr 14, 2019 10:21 pm 
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Hi, I have an old unkeyed ultra Tec and the crown always seems to give me trouble. Also the problem increased after I added some oil to make the dops easier to remove. Any tips to facet the crown or getting the table adapter perfectly aligned. Thanks!


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 Post subject: Re: How to Cut the Crown?
PostPosted: Mon Apr 15, 2019 3:38 am 
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Your problem may lie in the use of worn dops and the set screw that holds them in the chuck. It can push the dop slightly off axis. The answer is to ensure that your dops fit very snugly in the chuck and to tighten the set screw only just enough to hold the dop. I see you are looking for new dops. As long as they fit really snugly that may solve your problem. Old worn dops should be discarded. On my old Ultra Tec I had the chucks modified to self-centering three-jawed with a threaded tightening collar. This solved the problem with the set screw but tended to rotate the dop slightly when tightening the collar, which required compensation with the cheater. Buying a new Ultra Tec solved all these problems.


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 Post subject: Re: How to Cut the Crown?
PostPosted: Mon Apr 15, 2019 8:20 pm 
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Thanks, I'll try to make sure that the dip fits tightly when I cut my next crown, where would you buy an unkeyed table adapter if the dop is worn?


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 Post subject: Re: How to Cut the Crown?
PostPosted: Mon Apr 15, 2019 11:32 pm 
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Couldn't you send your head to UltraTech get it refurbed, converted to a keyed dop head, and buy a bunch of dops from them directly?

Also, don't the UltraTech keyed dops work just as well in an unkeyed quill?


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 Post subject: Re: How to Cut the Crown?
PostPosted: Tue Apr 16, 2019 2:28 am 
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1bwana1 wrote:
Also, don't the UltraTech keyed dops work just as well in an unkeyed quill?
Yes, they do.
Zhufaceter, why do you want to replace your table adapter? If your crown is tilted because of the set screw pushing against one of the jaws in the two-jaw chuck, then when you get to cutting and polishing the table you can adjust for that with the cheater and/or mast height.
Your crown problem could also be in the transfer process. Check that your transfer fixture is in proper alignment by sliding a straight 1/4 inch rod from one side to the other. It should not catch on the inner edge of the opposite block. The old UT transfer fixtures have one of the blocks adjustable to change the gap. Make sure there is no dirt under the foot of that block and that it fits snugly in its groove.


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 Post subject: Re: How to Cut the Crown?
PostPosted: Wed Apr 17, 2019 5:29 pm 
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Ah, after researching what you said I realized we were talking about different machines. My machine isn't a V2, it older when ultratec wasn't using its current system, they don't even have my serial codes in their system, it doesn't have a two jaw chuck or set screw and is rather basic. I literally just screw the chuck until I can't go any more and there is no locking mechanism. Also how can I make it sure the table adapter is meeting up correctly with the chuck so that it is 90 degrees? I just can't tell right now with my machine and dop.


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 Post subject: Re: How to Cut the Crown?
PostPosted: Wed Apr 17, 2019 8:45 pm 
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This for checking, and aligning your table dop and the accuracy of protractor.

https://www.amazon.com/Wixey-WR300-Digi ... B001PTGBRQ


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 Post subject: Re: How to Cut the Crown?
PostPosted: Thu Apr 18, 2019 2:26 am 
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Zhufaceter wrote:
Ah, after researching what you said I realized we were talking about different machines. My machine isn't a V2, it older when ultratec wasn't using its current system
Is yours an original Howard E. Stanley machine? A photograph of your machine, and if possible of the dop/chuck and table fixture would be interesting. Here is a photograph of Ultra Tec table fixtures. The older one on the right (dating from 1971) fits into a Morse tapered quill; the more recent one on the left slides over the quill. The flat bases allow you to align the fixtures on a lap.
Attachment:
Table fixtures 001.jpg
Table fixtures 001.jpg [ 24.36 KiB | Viewed 102 times ]


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 Post subject: Re: How to Cut the Crown?
PostPosted: Fri Apr 19, 2019 10:14 pm 
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Yeah this is an original Howard E Stanley machine here are some pics


Attachments:
File comment: Original Machine
image.jpg
image.jpg [ 1.93 MiB | Viewed 27 times ]
File comment: Chuck and table adapter
image.jpg
image.jpg [ 1.52 MiB | Viewed 27 times ]
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 Post subject: Re: How to Cut the Crown?
PostPosted: Sat Apr 20, 2019 2:11 am 
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Looks OK to me. If I were you I would buy a new set of brass dops from Ultra Tec (part 2283.3 for US$260).

Out of curiosity, what is the serial number on the base of the mast?

I am still not sure what your problem is with cutting the crown. Perhaps you would like to describe it in more detail. With unkeyed dops you need to use a girdle facet cut before transfer to align the stone after transfer, or judge it by eye and make small adjustments with the cheater to get crown and pavilion facets to line up with each other if you don't want to cut girdle facets. When you cut the table, position the flat base of the table adapter on a lap before tightening the chuck. Or have I misunderstood your problem?


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