Lathe backplate chuck help

[SillyOldDufferModerator @sillyoldduffer]

Posted by Christine Walker on 06/12/2016 12:15:49:

ps: I know I am a dumbo…. but could I not just take the 3 jaw chuck off the backplate it has? But then I guess I have to find a 4 jaw that fits that backplate.

Nothing Dumbo about that suggestion!

Undoing the 3 allen bolts should reveal the register that the chuck lines up with. This and the hole spacing should let you identify a suitable chuck to fit your backplate. Some chucks have four fixing bolts: not a problem the unused holes in your adaptor are there to allow a fourth bolt to be screwed in.

Neil's suggested another backplate for you that more chucks are likely to fit. Before going down that route, you need to confirm the thread. The manual is confusing, giving two possibilities. My guess is it will be 8 turns per inch but it's hard to be sure from your picture. If the distance between 4 threads is 0.5"/12.7mm then it's 8tpi.

Cheers,

Dave

[Christine WalkerParticipant @christinewalker32747]

Hi Dave

Thanks for the info and reply. Should I chose a 100mm 4 jaw independent chuck with a three (or four bolt mounting), would that then fit? Or is there more to it than that?

This is the measurement between the threads, sorry it's difficult holding the camera and callipers still!

http://s304.photobucket.com/user/christineanniewalker/media/IMG_3303_zpsc6c4fgcm.jpg.html?sort=3&o=0

Thanks

Christine

[Christine WalkerParticipant @christinewalker32747]

Would this one work, do you think?

http://www.ebay.co.uk/itm/100mm-4-jaw-Independent-Lathe-Chuck/260926466506?_trksid=p2047675.c100005.m1851&_trkparms=aid%3D222007%26algo%3DSIC.MBE%26ao%3D2%26asc%3D38661%26meid%3D33b893d03cb244ffa136976caf647a47%26pid%3D100005%26rk%3D2%26rkt%3D6%26sd%3D370166009118

[Christine WalkerParticipant @christinewalker32747]

Or this one perhaps? It appears to be a four hole mounting?

http://www.ebay.co.uk/itm/Sharp-100-mm-4-Jaw-Independent-Lathe-Chuck-Plain-Recess-Mount-Brand-New-/371424772878?hash=item567aa4430e:m:mawtQOBDZafV04shVHtnqYA

[SillyOldDufferModerator @sillyoldduffer]

Hi Christine,

I haven't got to the thread measurement yet.

As to the two chucks on ebay, there isn't enough information to confirm they will fit. We don't know if your backplate matches that on a C1 or not. Other posters have suggested it doesn't.

ArcEuroTrade are more forthcoming with dimensions. (This link isn't to their complete range, you may have to explore.)

Where A to N come from this diagram:

What you need is a chuck-backplate match between both G (distance from centre of the bolt holes), and H the diameter of the register indent). If H is correct, the chuck will centre automatically: if G is correct the bolts will line up with the holes.

Neil's backplate may be the answer In the event you can't find a match.

Hope that makes sense.

Dave

[Christine WalkerParticipant @christinewalker32747]

Hi Dave

The URL for the measurement is above. Here it is again….

http://s304.photobucket.com/user/christineanniewalker/media/IMG_3303_zpsc6c4fgcm.jpg.html?sort=3&o=0

It measures 12.07mm across the four threads. But it was difficult to hold the camera and calliper.

I would rather buy a backplate already drilled etc as I am not yet confident enough in my ability to do a proper job.

Many thanks

Christine

[mick70Participant @mick70]

Christine if you ring arc with info you have they will tell you if theirs will fit.

always extremely helpful when i have rung, even to point of steering me to better ( and cheaper ) item for something i wanted to do.

their indian chucks are great got some myself.

[Christine WalkerParticipant @christinewalker32747]

Dave, these are the dimensions off the back of my 3 jaw mounting plate.

http://s304.photobucket.com/user/christineanniewalker/media/chuck_zpsof6i3wkn.jpg.html?filters%5Buser%5D=142907852&filters%5Brecent%5D=1&sort=1&o=0

[mick70Participant @mick70]

the only one with 84mm pcd is their 100mm chinese chuck.

part no 040-040-00600.

there should also be a step on your back plate what is width of that?

[SillyOldDufferModerator @sillyoldduffer]

Hi Christine,

8 tpi is a pitch of 3.175mm (ie the gap between complete turn of the thread.

Your figure of 12.07mm over 4 turns gives 3.02mm per complete turn. This might be 8tpi, but you should take several measurements and average them to confirm it. (I'd have been much happier to see 12.7 on your caliper!) If you got the first measurement right, it could be a metric thread, but not the one in the manual. Arghh!

Are you able to post a picture of the front of your backplate, ie the side normally hidden by the chuck? Some measurements of that will enable you to have a sensible conversation with Arc just as Naughtyboy suggests.

If we can get the backplate dimensions right and find a matching chuck, it won't be necessary to do any machining, or to suss out the thread.

Dave

[John RuddParticipant @johnrudd16576]

Thread gauges will give a more positive outcome on pitch…..and dont cost the earth, will come in handy in the future…..

Where are you located? Maybe someone local could assist?

Edited By John Rudd on 06/12/2016 15:04:56

[Christine WalkerParticipant @christinewalker32747]

Hello everyone

Pleased to say, it's solved!

We made a call to Arc Eurotrade and within two minutes, a 4 jaw is on the way which will fit into the backplate off the 3 jaw as snug as a bug.

Fantastic service.

As ever, thank you everyone for your input and suggestions, and most of all, for your time to help me. It is very much appreciated.

Best wishes

Christine

[mick70Participant @mick70]

glad to hear it.

it's a great company.

[Trev67Participant @trev67]

Hi Christine

Just looked at your photo, you are actually measuring three threads there, so very close to 12mm would make it 4mm pitch.

Hope this helps

Trevor

[SillyOldDufferModerator @sillyoldduffer]

Hi Christine,

Had to go out and collect daughters car from MOT – it passed!

Looks like we may be homing in thanks to naughtyboy. The step he refers to is the register, where the male part on the backplate plugs into the socket on the chuck

On my lathe there's a backplate between the lathe and the spindle. On my old mini-lathe the chuck mounted straight on to the spindle. The socket on the back of the lathe can be quite wide and shallow, like this example:

On your 3 jaw chuck what's the measurement equivalent to the 95mm diameter above? Fingers crossed it's 72mm in which case 040-040-00600 is the one!

Dave

[Christine WalkerParticipant @christinewalker32747]

Hi Dave

Glad the car passed the MOT! The measurement you speak of was 72mm yes. I had to remove the chuck from the backplate and measure this exact part for Arc to decide which chuck was required

.

[SillyOldDufferModerator @sillyoldduffer]

Hurrah, double success.

All you have to do now is practice centring a 4-jaw chuck and finish your project!

Cheers,

Dave

[Howard LewisParticipant @howardlewis46836]

Personally, am not enamoured of swopping chucks between backplates. But, at the moment, this will get you going, and then you can search for a suitable backplate for the 4 jaw in a more leisurely way. By then you will have gained enough skill and confidence to undertake machining the register between backplate and the 4 Jaw chuck.

There's been a first time for everything, for every one of us!

Agree with the advice to buy screw thread gauges, (for Whit, Unified, and Metric threads). In the future, you will find them invaluable.

As a newcomer, DO try to find a Model Engineering Club near to you, and join. You will get a lot of help and advice, and companionship, (or you should if the club is any good). One day you may need, for a once in a lifetime job, an oddball Tap or Die, and someone will be prepared to lend it to you; or to give practical help (their shop or theirs) with a particularly difficult problem.

I can vouch for being made welcome when visiting other Clubs. Next season, (I think that you are near Gloucester?) Visit Hereford S M E at Broomy Hill. You will be welcomed (Living 140 miles away, I am not a member, and The WaterWorks Museum is next door, and worth a visit. Very occasionally, I volunteer there).

Hope this all helps

Howard

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