Supernova 2 - how to convert from 3/4" x 16tpi to M33 x 3.5

[Random Orbital Bob]

This is likely a question for Chas but I thought I'd post in public in case other folk want to know the solution (if there is one).

Basically, I would like to convert the first chuck I ever bought for use as a spare with an upgraded lathe but of course the thread is wrong. I've been getting away on the occasions I use it, with using an adaptor from Axy but it pushes the chuck a long way out from the spindle and I'd prefer to simply change the insert so I can thread the chuck more closely onto my M33 x 3.5. The current insert is for a 3/4" x 16tpi and having just taken it off, hoping to find the supernova 2 directly threaded with M33 (fat chance) I found the direct threading to be larger than M33. This gives me slight hope there is an insert that will convert whatever the supernova direct threading is to M33???

Chas.....you're normally the encyclopedia for this kind of detail...have I got a chance? I've had a canter round the toolposts tek pages but they don't cite the detail for the SN2.

 

[stewart]

Hi Bob - i'm afraid that you are out of luck - there is no insert to go in supernova 2 to make it 33 by 3.5.... I know because I tried to do the same thing. The only way to have a 33 by 3.5 supernova 2 is to get one with the thread directly cut into the body of the chuck. I ended up selling my old 3/4 by 16 and buying a new supernova 2 as I too found the use of the adapter unsatisfactory...
sorry!

 

[Random Orbital Bob]

Thanks Stewart, I had just pretty much reached the same conclusion after having surfed through the Teknatool site. They do a blank insert and it's greatest acceptable thread dimension is 28mm, so clearly, unless directly threaded, the chuck doesn't have the girth to take an M33 insert.

Thanks for confirming it though.

 

[CHJ]

Not got a SuperNova 2 to hand to check dimensions but I doubt there is enough difference in diameters to accommodate a dual threaded sleeve if you tried to get one turned up.

I believe the SupaNova2 (insert version) accommodates spindles up to 27mm dia. (via appropriate adaptor)
Anything bigger than this up to 38mm I think has to be directly machined in the rear of the chuck.

One thing that may be possible if you have a tame metal machinist near is to get an ISO backplate as fitted to a VersaChuck and have this machined to provide a good location and fixing on the rear of the chuck body.

Would probably result in halving the overhang or better but in all honesty I don't think it's worth it, selling the Nova on and re-investing the resale value together with any parts purchase and machining costs expenditure you would need may come near a usable compatible chuck anyway.

Edit:- see you have already sorted it, teach me to answer the phone and post without checking mid typing.

 

[Random Orbital Bob]

Yes, I was pretty much reaching that conclusion Chas. In fact what prompted this is there's a chap in our club that might want to buy a 2nd hand chuck so I was mulling over which of my spares to sell. Of that list, the SN2 is the best, hence the research to see if it's convertible.

 

[TFrench]

Is this exert the same as what you already have?
https://www.stilesandbates.co.uk/produc ... 5/sn/EXN34

 

[Random Orbital Bob]

Yes, that's pretty much identical to the one I have from Axy (which I referred to above as an adaptor). It's just a tonking great hunk of steel with one end being a male threaded at 3/4" x 16tpi which fits into the insert in the SN2 and then a barrel at the end of which is a female thread of M33x3.5 which fits my spindle. You can buy others, like the one you linked from S&B where the male threaded end is 11/2"x8tpi UNC which fits in the SN2 with the insert removed. Apparently (teknatool have since responded with confirmation they don't do an insert for an M33 spindle) all their non directly threaded chucks are 11/2 x 8 UNC. It's then of course the inserts which convert that thread to the specifics of your lathe, with the exception of the threads that are too large for it to accommodate them (like M33).

So it looks like I'm up manure creek without a paddle unless I'm prepared to continue to accept having the chuck stand about 3 inches out from the register. I think Chas is right, time to chop it in and reinvest the proceeds in a directly threaded model. In fact, since this is a solution for turning small items, I might as well get the G3 instead, even more room to get to the back of the work piece at only 80mm diameter and 45mm length.

 

[Robbo3]

I suspect the manufacturers try to keep the thread machined into the chuck a trade secret to prevent everybody making their own adaptors. In addition, from the few that I've seen, they seem to be threads that are not in common use.

I did find out the thread that Sorby use for their tubular toolrests but I've since forgotten - & forgot to write it down.

When I upgraded my lathe to the APTC VS1628 I had two Axminster Woodturners 3/4x16 chucks plus additional carriers & jaws that I was reluctant to renew, so as they are not used for turning large unbalanced chunks of wood, I find mounting them on an adaptor/exert to be quite acceptable. IIRC, it only adds 20-25mm to the chuck overhang.

Not a lot of help to you Bob, but it may be to others.

 

[Random Orbital Bob]

No, you make a good point Robbo and I accept I'm being picky because even though the chuck hangs way out towards the tailstock side with the excert/adaptor, it still runs absolutely true with no run out so it doesn't affect vibration or concentricity. It just looks "wrong" if that makes any sense and I mean that from an engineering standpoint. I guess I'm just used to seeing a chuck as close to the bearings as possible and feel slightly at risk with it hanging so far out.

On the manufacturers attitude to publishing the thread dimensions as manufactured. This was what Teknatool e mailed me yesterday:

The Supernova2 is threaded 1-1/2 x 8TPI UNC as are the male side of all of our inserts. We do not offer an M33 insert

So it's certainly an odd dimension but they don't appear to be secretive about it? Also, I guess it has to be big to allow it to take as large a range of inserts as possible but still leave their manufacturing process with minimal tooling changes. Just my luck it's not quite big enough to take an M33. I wonder why they don't all make their off the shelf direct threaded dimension, M33 since that's got to be the emerging gold standard and then step down with inserts from that starting point. There cant be many spindles still widely available that are larger than M33 and for those that are, they could make those the exception. It seems to me the turning world is being dragged, kicking and screaming towards the inevitable standardisation of MT2 M33x3.5 for bigger lathes (and many smaller ones) and maybe a smaller standard like MT1 3/4 x 16. Record Power's recent relinquishing of MT1 and the move to MT2 M33 on the CL4 is yet more proof of the rolling out of that standard. Wouldn't life be simpler for lathe and chuck manufacturers if everyone used that one dimension!!! Let alone customers! But yes, I know, where would the proprietary commercial advantage be for new innovations if they were generic!!