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Thread: CVA upgrade
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16th Feb 2019, 09:09 PM #1
CVA upgrade
Been thinking about my CVA no.79 mill , the spindle is the worse for wear with the morse taper end being scored badly and generally knocked about. I noticed that Tormach offer a fancy CNC style spindle cartridge with the NT30 nose , maybe I can solve my problem by adapting the new nt30 cartridge to fit into the old CVA quill ? Cost is a problem .... the Tormach cartridge ain't cheap but there is no easy fix , making a new spindle is beyond my skill level . The CVA is in good shape otherwise, I had the table ground and made a new y axis screw and nut.
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16th Feb 2019, 09:27 PM #2Most Valued Member
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Is it only the MT end that is the main problem, or are there other factors involved?
If it was only the MT, then get hold of a MT Reamer and clean up that end. If you wanted to go a bit further, it could be mounted in the lathe with a steady and cleaned up with a boring bar.
KrynTo grow old is mandatory, growing up is optional.
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16th Feb 2019, 10:15 PM #3
Hi kryn
CVA changed the spindle design in these mills at least three times during the production. Mine is a mid production 79 , it has two TRB and the MT tool end. The later CVA 79 spindle version has the NT type arbor. The spindle in mine also has damaged keyways where the pullies fit. The mill is a stout solid machine otherwise but they fitted a thin weak spindle which sort of doesn't make sense . The Lathes uk website has a CVA mill write up .
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16th Feb 2019, 11:14 PM #4Most Valued Member
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Would it be possible to open up the keyway on the shaft, and use a stepped key.
Hopefully one of the Members here will offer to help make one for you.
KrynTo grow old is mandatory, growing up is optional.
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16th Feb 2019, 11:17 PM #5Most Valued Member
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Is all you need a spindle regrind? If so I know a place that can do internal grinding that deep no issue, I have had them fix hard chromed tailstock a for me before, send me a PM and I'll get the details. Is the internal taper hardened?
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17th Feb 2019, 11:43 AM #6
Yes that would work. The spindle MT arbor has rather thin walls, there not much leeway for enlarging its inner diameter without weakening it. I'd prefer to go to a NT system if possible. The fact that they changed over to NT themselves may indicate there were problems with the earlier MT versions.Unfortunately these mills are thin on the ground in Aust. Seems to be more of them in the UK.
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17th Feb 2019, 11:48 AM #7Most Valued Member
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I'm happy to turn up a spindle blank if you provide the old one. You can then hand it to the grinder. highly doubtful you will get the result you want out of what tormach have to offer. Does the. Head casting have the meat to accommodate something bigger?
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17th Feb 2019, 04:53 PM #8
Thanks for the offer. I will upload some pics tomorrow. The spindle has a bore down its length for the draw bar. I did draw up a basic sketch of the spindle... I will have a look
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17th Feb 2019, 06:27 PM #9Intermediate Member
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CVA Toolroom Milling Machine
Looks like a nice mill,well worth repair good luck with it
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17th Feb 2019, 07:07 PM #10Most Valued Member
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Does yours have the bronze bush or taper roller at the bottom? The through drilling would have to be done with a gun drill.
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17th Feb 2019, 09:53 PM #11future machinist
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I will be interested in what solution you come up with. My CVA spindle is a little scored up as well but it's still functional.
BETTER TO HAVE TOOLS YOU DON'T NEED THAN TO NEED TOOLS YOU DON'T HAVE
Andre
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17th Feb 2019, 10:11 PM #12Most Valued Member
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If the spindle isn't really hard a quick ream will give nearly all of your taper grip back. Happy to lend a MT3 reamer.
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18th Feb 2019, 12:11 PM #13
sketch
Here is the sketch I did some years ago... the odd mixture of metric and imperial sizes is what I measured with my calipers.
I think I could machine up a new spindle myself , some trial and error would be expected !
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18th Feb 2019, 01:00 PM #14Most Valued Member
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If you swap the entire quill assembly out for something else, you are going to be left with the problem of getting a good honed fit in the old housing, this is not trivial.
On the other hand turning that spindle with the thin 10" of 15/16 diameter is also not easy.
I don't think 30 taper is going to get you that much rigidity over MT3, at least not with that quill design. I would just make the socket you have nice and clean and true.
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18th Feb 2019, 10:38 PM #15Most Valued Member
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Agree. The only thing NT30 is going to do for you is make tool changes easier due to it not being a self-locking taper. You won't transfer more power because the spindle is too lightly built - at least it is to my eye.
I'd clean it up & live with its limitations while looking for a heavier duty machine, if that's what you think you need. In which case I'd want a 40 taper as tooling is common & cheap.
PDW