Pultra P type spindle

This topic has 7 replies, 3 voices, and was last updated 17 February 2020 at 12:54 by Phil P.

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16 February 2020 at 11:06 #19628
Jon Holmes
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@jonholmes92873
Unusual?
Advert

16 February 2020 at 11:06 #452483
Jon Holmes
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@jonholmes92873
Disassembling an old Pultra P type headstock I came across something unexpected (for me anyway). Inside the spindle was a standard looking long collet, but 12.7mm diameter. This particular collet was machined to accept 0 MT tapers.

First question. P type with long 1/2" collets?

Second question. Why 0 MT taper?

Photo shows (sorry about shadows!) – top left – 0MT taper, 12.7mm diameter long collet, spindle, part of collet quick change, draw bar.

Thanks in advance for any info

Edited By Jon Holmes on 16/02/2020 11:07:18
16 February 2020 at 11:26 #452485
Bob Stevenson
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@bobstevenson13909
Those parts don't look like standard pultra bits so were probably adapted for a specific task which involved MT0 tooling.

Did the headstock casting have dull black paint?……if it did then that is a pretty sure sign of 'war finish' and it's not unknown to find wartime pultras with unique features for task. PTA were quite adept at answering particular needs during the war, especially as their lathes were of unitary design so could be easily adapted.
16 February 2020 at 11:41 #452489
Jon Holmes
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@jonholmes92873
Thanks.

Yes, underneath a light grey repaint appears to be flat black.

Interestingly, the outside of the headstock indicates it has been well used (it was converted to a single V belt drive and the headstock casting had a few extra holes to secure the headstock to the bed) but the bronze (?) bearings have still almost full adjustment still left in them (easy to jam the spindle)
16 February 2020 at 12:00 #452495
Bob Stevenson
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@bobstevenson13909
Pultras were VERY well designed and made. The bearings are more or less indestructable and were guaranteed for 6 months constant use, although this was reduced to 3 months for "night and day production".
16 February 2020 at 18:12 #452540
Bob Stevenson
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@bobstevenson13909
…Strangely enough;

https://www.ebay.co.uk/itm/Pultra-10mm-rare-MT0-adapter-and-centres/124079692851?hash=item1ce3b9dc33:gvkAAOSwXBdeQoNv
17 February 2020 at 11:40 #452646
Jon Holmes
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@jonholmes92873
A 10mm collet with an MT0 adapter! Even the 12.7mm collet is a close fit for the MT0. No wonder the ad states "the correct shorter versions rather than the long type"

My LAS headstock takes a 10mm collet or an MT0 as they are similar sized.
17 February 2020 at 12:54 #452663
Phil P
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@philp
On my Putra 1770 I have two tailstocks available, the lever feed one takes standard 10mm Pultra collets the same as the headstock, but the screw feed tailstock takes the short version of the MT0. So they obviously used both in different situations.

I have never come across the setup in the original post before, I think it must be a one off.

Phil

Edited By Phil P on 17/02/2020 12:56:20
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