The Craftmans Shop > New from Old
The Sequel - Oh Blimey I bought a CNC Lathe (Beaver TC 20)
nrml:
Ahh. I learnt something new there. I always believed that it was the taper that was the important bit and that the undercut was just relief to ensure it sits flush.
awemawson:
I have to get three features to all come together at the same time. The male and female taper, the adaptor to spindle flange (with perhaps a few tens of microns gap to pull the taper firmly together ) and the inner face where the hydraulic ports are. Again these can have the odd tens of microns gap as there are O rings squashed here to seal the ports.
modeng200023:
Andrew, with this high accuracy that you are working to does temperature of the mating items become important?
No doubt you have this in mind but I've not seen temperature mentioned in this discussion.
John
awemawson:
It does John but fortunately everything is being kept in the same environment. It was surprisingly significant when I was grinding the taper gauge and measuring how far it penetrated the female taper in the chuck. Seating tapers is a funny old business, a little goes a long way, and over shooting is only too easy!
I think the major issue is to get the taper to seat leaving just a nat's thing-a-me-bob of clearance between the chuck and it's flange, so when the bolts are torqued down the taper is pulled well home. The internal mating faces where the hydraulic ports join is marginally less critical due to the aforementioned O rings giving a bit of tolerance.
I'm pleased to say with the larger taper of the 'adaptor to lathe spindle interface', once bolted up, and then unbolted, it took a few persuasive blows from a large rubber dead blow hammer to unseat it and it's that sort of fit I want to achieve with the 'adaptor to collet chuck interface'
(A self releasing taper needs to be 16 degrees or greater - this one is 2 x 7.125 = 14.25 degrees so just on the self holding side of the line!)
awemawson:
Can't get much done today due to other commitments, however I spent some time trying to convince myself that using the 0.4 mm radius tips that are on order will produce a tight enough fillet at that pesky corner to be accommodated by the existing chamfer on the collet chuck.
. . . I think that it will but would welcome comments as usual.
I measured the chuck chamfer as reasonably accurately as I could visually at 1.5 mm, and assumed (!) that it was evenly distributed either side of the centre line of the chuck face and taper wall, which are at 97.125 degrees to each other, and drew it up, large scale, in Autocad. It seems to say I'm OK but as I say comments are welcomed!
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