New Chucks

[Roger B]

I thought that the Pratt Burnard 4 jaw independent chuck that came with my Hobbymat was a little light for some of the abuse I give it. I found a TOS 85mm front fixing chuck of somewhat heavier build and with a 62mm recess at an acceptable price.
To be able to use it I had to bore the recess out to 63 mm and make some rear fixing holes. I carefully trued the chuck onto the lathe flange and bored the recess to match the one on the TOS 3 jaw sc chuck. The fixing holes were set out using a protractor on the chuck jaws. Result a nice smooth fit with no discernible play 

I will now make 2 new backplates to use the PB 4 jaw and the TOS chucks on my RT. I have a length of 90mm cast iron for this (but I will cheat and take it into work to cut some slices  )

I also have a TOS 4 jaw sc on order.

[Jo]

I thought that PB was a steel bodied chuck. 

I also have a TOS 4 jaw sc on order.

I knew you would realise you needed one in the end.

Her original is doing a very nice job on my BCA table 

Jo

[fumopuc]

....... (but I will cheat and take it into work to cut some slices  )

Hi Roger, highly recommended.

[Admiral_dk]

I never occurred to me that you can put the chuck on the lathe "in reverse" as you did 

Enjoy your new "toys" 

[Meldonmech]

 
Hi Roger,

                 A Job well done, I fitted the same chuck to my Myford ML10. The TOS  is still going strong after many years.
                                       
                                                                    Cheers David

[Roger B]

Unfortunately this project has been a little delayed as Parcel Force has lost the package with the TOS 4 jaw SC chuck and the M14x1 taps     

I had a couple of slices of the CI bar cut at work and am roughing them out.

[Jo]

  The Register on the back of the TOS chuck and the mounting holes are a dead fit for the Hobbymat spindle.

Jo

[Roger B]

These backplates are to fit to my RT which has an M14x1 adaptor, the thick one for the 'Hobbymat' chucks and the thin one for the front fastening Pratt Burnard.

[Roger B]

The replacement chuck and taps finally arrived (Thank you Rotagrip  ) So I could continue with the backplates.

The bore was drilled 6mm then 12mm and bored out to 13mm. There is a 4mm deep 14mm counterbore to match the RT adaptor. I decided to start the thread with a singlepoint tool and just use the taps for finishing. On the first screwcutting pass there was a crack and the tool flipped over, maybe 0.2mm was too deep    The point on the tool had chipped off so I roughly reground it by hand and had another go, this time with a cut of 0.1mm. This worked so I cut to a depth of 0.3 mm and then finished of with the taps.

I went to repeat this for the second backplate but during drilling 12mm the drill snatched violently and went off center. I withdrew the drill and there was a large blowhole      I will need to get another slice cut and start again.

I then put one of the MT2 -M14x1 adaptors in the lathe and finished the chuck face. Just 4 M8 threads to do.

[Roger B]

I had another CI blank cut at work and started again  This had a small blowhole but luckily I could turn it away 

As I had a suitable chuck on the lathe I parted the boss off the original blank to see if it could be salvaged as a flywheel. Maybe if I can fit a large boss it will be usable, but this will have to be bolted as I don't think that shrink/press fitting will be sensible with CI 

As a trial I mounted the backplate on the RT adaptor to drill the three 6mm fixing holes.

[Jo]

Roger why are you not mounting that 4 jaw TOS chuck directly on the hobbymat register.

or are you only checking the fit of the chuck for when it goes on the rotary table 

Jo

P.S. Not impressed with the quality of that Swiss CI, it seems to be pretending it is a piece of cheese 

[Roger B]

Yes it was just a trial fit as I had not Loctited the studs into that chuck yet.

It's actually Luxembourg (RC) cast iron. It's the first bad bit I have had from them.

When I said at the beginning that the PB chuck was a bit light I wasn't concerned about breaking it but the TOS one is slightly larger diameter and has deeper and wider jaws which makes a difference when you stretch (overload) machines as I tend to