Orac spindle nose taper

[bradders]

Customer writes ...............

I'm trying to identify the spindle nose taper on the Orac CNC lathe, and it appears that this information was never given in any of the manuals or other documentation for the lathe that I have been able to find, and despite numerous people asking the same question in various web forums no-one is any the wiser.

Would you happen to have this information? Or perhaps any left-over chuck backplates? Its a bit of a long shot, but spares for similar machines from the same era can sometimes still be sourced from other manufacturers.

[Denford Admin]

If anyone can indicate the drawing numbers to be looking at, I'll see what I can find

[Andy B]

I'm sure I remember seeing an illustrated parts list for the ORAC (possibly at the back of a user manual) in the old DO, and I would have put it with the other manuals / parts lists on top of the filing cabinets.

Should be able to identify the part / drawing number from that.
Andy

[Denford Admin]

I've found a parts illustration book - the relevant drawing would be AC100/103 - unfortunately I can't locate it in any of the drawers.
However, the beginning of this book states the spindle taper is No.3 - if that means anything ?
Tailstock taper: No.2
Tapers: 20:1-1:20


Just deciding now whether to tear this book apart in order to scan it

[Andy B]

No.3 would be 3 Morse Taper - inside the spindle.
The tailstock would be 2MT.

I'm guessing that AC100/103 is for the spindle itself.
Is there a part number shown for a chuck backplate? That should give us the taper info.

Andy

[Andy B]

I had a memory of finding the ORAC parts list on the web somewhere - its here.

It shows the spindle having number AC100/102 (not 103, or was that a typo?) - no chuck backplate shown though.

Also looked in the SK listings, and found SK803 - Orac Saddle & Spindle dimensions.
Might help.


Andy

[Denford Admin]

Yes sorry I meant AC100/102 - can't seem to locate any of that range of drawings in any case. What size paper would it be on do you think ?

SK803 dosn't show much at all - it's just showing the travels and dimensions from saddle to spindle

[Andy B]

A1 or A2 at a guess.

Andy

[EVguru]

Since the Orac is based on the Emco Compact 8, the spindle nose is probably the same and based on DIN 55021





Both images from www.lathes.co.uk

[welderfabrod]

Its definatly is not the standard Emco 8 Spindle nose the Orac nose is to small. The info from lathes.co.uk I think maybe for the Emco 8, the B dim for the Max. taper dia. for nose size 3 is 53.985mm, I measured mine at about 41.08. Dim. A is 102 on the Orac its 78. Add to that I just made the same mistake I ordered a four jaw chuck with Emco 8 back plate which arrived today and there's a large difference in the nose taper dia. and it fits like a pea on a drum. Expensive mistake £120.

Rod

[Denford Admin]

I've just added a possibly more detailed parts list here:
viewtopic.php?f=43&t=2963
hth

[welderfabrod]

Hi guys don't now if anybody is still interested in this thread but after my disappointment with my back plate and chuck yesterday I decided to check a few dimensions today. Here is what I found.
The Orac or Emco does not follow the drawings obtained from lathes.co.uk (they are similar but smaller) but are perculiar to Emco. But I now think that apart from the retaining stud holes being on a different pcd (my back plate 63mm pcd Orac 51.5 pcd) I think my back plate may be machined with an error on the tapered locating recess because the dims are too close to the Orac to be coincedence . The max taper dia. on the Orac is 41mm coincedently the parallel part of the recess in the back plate is 41mm dia which then leads out to the 7.7deg taper that should locate on the spindle nose but obviously does not because the recess is machined backwards if you know what I mean i.e. the taper is first in the recess then the parallel section, it should be parallel part first and then the taper. Or just a taper. The Orac back plate just has the taper which goes right through the back plate which is all that is needed really.

I can't see why Denford should have purchased the Emco 8 and then remachined the spindle or make their own to just a slightly different spec, seems an expensive and uneccassary thing to do to me. But I could be wrong I suppose. Don't now what admin think about this. So I now think it is possible that the Orac and Emco 8 spindle nose taper's are the same and that I may have a back plate that has been machined wrong. I have contacted PRO Machine Tools to see if they'll give me some specs for the Emco spindle but apparently they are on holiday until the 28th August so I won't hear from them until then.
Hope you could follow this ok.

Rod

[welderfabrod]

Just a bit to add to my last post. Has nobody else solved this problem yet as I need a 4 jaw and face plate for my work.

Rod.

[welderfabrod]

Hope this works.
Dims from Orac nose and purchased Emco back plate.

Rod

DenfordSpindle002.jpg (128.64 KiB) Viewed 17669 times

[Andy B]

Rod,

Are you sure about the 59.467mm PCD?

We've found a small stack of backplates that are marked ST5/108 - suggesting that they were for the Starturn machines that I understand had the same nose as the ORAC.
The 3 bolt holes measure in at near enough 52mm; 60mm PCD would give hole centres of 51.96, so this would seem a sensible 'round' dimension as designed.
O/D = 79mm
Thickness = 15mm
Bolt holes 9mm dia, C/Bored dia 14 x 11 deep
Chuck location dia = 55.5 x 2mm high.
The chuck bolt holes appear to be M5 on 65mm PCD, but you'd obviously need 4 different ones for 4jaw chuck.

Andy

[welderfabrod]

Thanks for the response Andy I'm pretty sure I've got my dims right but I've got a job set up in the 3 jaw at the moment as soon as i've finished I'll check them again and let you know.

The chuck location spigot on your back plate at 55.5mm is much to big for the Orac as its max tapper dia. is only 41mm which is why I found the plate supplied by Pro Machine Tools a bit wierd because it almost fitted but not quite if you see what I mean. On my drawing black is the Orac spindle nose and red is the recess in the supplied backplate.The mounting stud hole positions in their back plate (thats the 3 holes for mounting plate to spindle) I could have redrilled no problem but the spindle nose tapper I can do nothing about. I purchased the plate with a 4 jaw chuck fitted.

Also the Orac has 8mm clearance holes in its spindle nose to take studs fitted to the backplate.

Rod

[Denford Admin]

Drawing of ST5/108 chuck backplate is now here:
viewtopic.php?f=42&t=4106

[triac]

Thanks for the drawing but if earlier drawings and comments are correct the spindle may be to DIN55021 but be Size 1 or 2.
The table in earlier post (from Lathes UK site) starts at Size No.3, I have searched but unable to find details of Size 1 or 2.
Rgds, Emgee

[RNR107]

Hi all,
I found the solution... No more custom made back plate.... No more hammering the spindle !

I got the spindle nose re-machine to the old Boxford threaded standard 1.5" x 8 TPI BSF. (see picture attached)
Back plate for these can be bought on eBay for about £17...

Laurent

[triac]

Hi,

Nice bit of machining but my view is it is now not such a good machine, reasons:
Reversing spindle unsafe because of chuck unscrewing.
Loss of repeated concentricity when changing chucks afforded by the taper mount.

Rgds, Emgee