4 jaw chucks

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4 jaw chucks

This topic has 31 replies, 9 voices, and was last updated 5 August 2019 at 11:33 by Arckivio Funiciello.

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6 June 2019 at 21:55 #413025
Arckivio Funiciello
Participant
@arckiviofuniciello27500
Hello all. Having got rid of the mini lathe that blew it's motor, I went mad and bought a rather large lathe from Italy. Lathe seems great & pretty accurate for the money. My problem is I want to add a 160mm 4 jaw independent chuck but don't think I'm at the skill level to make my own backplate. All the chucks I can find are either front mounting, or have the 130mm recess I need but have 4 mounting bolts & not 3. Is there a specific chuck I need to look for, or is there an easy way to mount the 130mm recess chucks, like drilling 3 new mounting holes & not using the 4? Cheers
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6 June 2019 at 21:55 #26653
Arckivio Funiciello
Participant
@arckiviofuniciello27500
Mounting
6 June 2019 at 22:53 #413028
JohnF
Participant
@johnf59703
Hello Arckivio, some more information would be useful, what make is your new lathe, what type if fitting is the spindle, screw on, DIN taper or ???

John
6 June 2019 at 22:59 #413029
Arckivio Funiciello
Participant
@arckiviofuniciello27500
Posted by JohnF on 06/06/2019 22:53:23:

Hello Arckivio, some more information would be useful, what make is your new lathe, what type if fitting is the spindle, screw on, DIN taper or ???

John

It's a CQ9332A. The chuck mount is a 130mm recess with 3 bolts on, I think a 145mm PCD. Thanks
6 June 2019 at 23:07 #413030
Michael Gilligan
Participant
@michaelgilligan61133
Arckivio

It would be most unusual to find a four-jaw chuck with three fixing holes

I think this illustration might help identify what you need: **LINK**

http://www.boltontools.net/index.php?route=product/product&product_id=2117

MichaelG.

.

Edit: Although that plate does look a little strange

Edited By Michael Gilligan on 06/06/2019 23:12:11
6 June 2019 at 23:14 #413032
Arckivio Funiciello
Participant
@arckiviofuniciello27500
Posted by Michael Gilligan on 06/06/2019 23:07:58:

Arckivio

It would be most unusual to find a four-jaw chuck with three fixing holes

I think this illustration might help identify what you need: **LINK**

http://www.boltontools.net/index.php?route=product/product&product_id=2117

MichaelG.

Ha. I never came across that because I searched UK only on Google. Even just the backing plate would do me. I also never searched specifically for the code number of my lathe. Don't want to use the brand name . Thanksas this forum has advertisers and they are not one of them lol. Thanks
6 June 2019 at 23:22 #413033
Arckivio Funiciello
Participant
@arckiviofuniciello27500
If they had a 6" chuck I'd try & order from them. If I got the 4 jaw with the 130mm recess, would it be possible to mark & drill 3 mounting holes?
6 June 2019 at 23:29 #413034
JohnF
Participant
@johnf59703
Posted by Arckivio Funiciello on 06/06/2019 22:59:34:

Posted by JohnF on 06/06/2019 22:53:23:

Hello Arckivio, some more information would be useful, what make is your new lathe, what type if fitting is the spindle, screw on, DIN taper or ???

John

It's a CQ9332A. The chuck mount is a 130mm recess with 3 bolts on, I think a 145mm PCD. Thanks

From this I assume the machine spindle has a 130mm register and the chuck backplate has a 130mm recess to mate with this and 3 studs on a 145mm PCD passing through the machine spindle fixing holes ?
6 June 2019 at 23:33 #413035
Arckivio Funiciello
Participant
@arckiviofuniciello27500
Posted by JohnF on 06/06/2019 23:29:04:

Posted by Arckivio Funiciello on 06/06/2019 22:59:34:

Posted by JohnF on 06/06/2019 22:53:23:

Hello Arckivio, some more information would be useful, what make is your new lathe, what type if fitting is the spindle, screw on, DIN taper or ???

John

It's a CQ9332A. The chuck mount is a 130mm recess with 3 bolts on, I think a 145mm PCD. Thanks

From this I assume the machine spindle has a 130mm register and the chuck backplate has a 130mm recess to mate with this and 3 studs on a 145mm PCD passing through the machine spindle fixing holes ?

Yes the spindle has the register, 130mm. The 3 jaw chuck doesn't have a backplate as it already has the matching recess. No studs, the chuck bolts through holes in the spindle. Like I said, I can find a 4 jaw chuck with the recess but has 4 holes.
7 June 2019 at 07:12 #413049
JasonB
Moderator
@jasonb
You can download the manual from the site Michael linked to. As JohnF said it shows the spindle is for direct fit of a 3-jaw. To mount a 4Jaw you need a backplate with 4 holes to it the 4-jaw and 3 tapped holes to take studs or the bolts for mounting to the flange.

It should be possible to find a part machined backplate, what part of the world are you in?
7 June 2019 at 07:43 #413054
Arckivio Funiciello
Participant
@arckiviofuniciello27500
Thanks for the replies everyone. I was trying to avoid the backplate route but looks like the chuck I want doesn't exist. I have seen backplate blanks so might be easier to start with one of those.
9 June 2019 at 10:08 #413373
Peter G. Shaw
Participant
@peterg-shaw75338
For what it's worth, my lathe has a 160mm 4 jaw chuck which uses a backplate with a three hole fixing onto the mandrel.

Actually, it's worse than that as the mandrel has a set of 6 tapped holes in it onto which is bolted a chuck adaptor plate. This plate has three holes which allow for a three hole fixing 3 jaw to be directly attached to it. The 4 jaw chuck then uses a 4 hole to 3 hole back plate between the chuck and the adaptor plate. Seems to work ok. And, many years ago, I made an aluminium backplate to enable me to use an 80mm 4 jaw chuck.

Peter G. Shaw
9 June 2019 at 10:14 #413375
Arckivio Funiciello
Participant
@arckiviofuniciello27500
Posted by Peter G. Shaw on 09/06/2019 10:08:00:

For what it's worth, my lathe has a 160mm 4 jaw chuck which uses a backplate with a three hole fixing onto the mandrel.

Actually, it's worse than that as the mandrel has a set of 6 tapped holes in it onto which is bolted a chuck adaptor plate. This plate has three holes which allow for a three hole fixing 3 jaw to be directly attached to it. The 4 jaw chuck then uses a 4 hole to 3 hole back plate between the chuck and the adaptor plate. Seems to work ok. And, many years ago, I made an aluminium backplate to enable me to use an 80mm 4 jaw chuck.

Peter G. Shaw

That sounds way beyond me. I think I'm going to take the lazy, but expensive way out. A normal 4 jaw independent chuck is 70 quid, but one with a 130mm register that matches my lathe is 130 quid. Use one of the holes already in the 4 jaw and then drill and tap another 2. In my little head it's a brilliant idea
9 June 2019 at 11:57 #413395
SillyOldDuffer
Moderator
@sillyoldduffer
Posted by Arckivio Funiciello on 09/06/2019 10:14:49:

Posted by Peter G. Shaw on 09/06/2019 10:08:00:

…

… Use one of the holes already in the 4 jaw and then drill and tap another 2. In my little head it's a brilliant idea

I've wondered why bolt-on 3-jaw chucks have 3 bolts and 4-jaw types always have four. I think it's probably done to maintain balance and reduce torsional stress inside the chuck as it rotates. Turning forces are generated inside the chuck by the weight of the chuck body as it spins. If only 3 fixing points are used the forces may be unbalanced by spinning and also by unequal cutting forces via one of the jaws. I've not attempted to work out how big the forces are, but potentially quite big – trying to stop a freewheeling chuck by hand hurts.

If you try a three bolt fixing system can you report back what happens. Three possibilities:
- Works with no adverse effects (hurrah!)
- Works but finish affected by vibration (Might be acceptable)
- The chuck might burst at high-speed. (Tears before bedtime.)
Dave

Edited By SillyOldDuffer on 09/06/2019 12:00:40
9 June 2019 at 12:11 #413399
Arckivio Funiciello
Participant
@arckiviofuniciello27500
Posted by SillyOldDuffer on 09/06/2019 11:57:26:

Posted by Arckivio Funiciello on 09/06/2019 10:14:49:

Posted by Peter G. Shaw on 09/06/2019 10:08:00:

…

… Use one of the holes already in the 4 jaw and then drill and tap another 2. In my little head it's a brilliant idea

I've wondered why bolt-on 3-jaw chucks have 3 bolts and 4-jaw types always have four. I think it's probably done to maintain balance and reduce torsional stress inside the chuck as it rotates. Turning forces are generated inside the chuck by the weight of the chuck body as it spins. If only 3 fixing points are used the forces may be unbalanced by spinning and also by unequal cutting forces via one of the jaws. I've not attempted to work out how big the forces are, but potentially quite big – trying to stop a freewheeling chuck by hand hurts.

If you try a three bolt fixing system can you report back what happens. Three possibilities:
- Works with no adverse effects (hurrah!)
- Works but finish affected by vibration (Might be acceptable)
- The chuck might burst at high-speed. (Tears before bedtime.)
Dave

Edited By SillyOldDuffer on 09/06/2019 12:00:40

There's always one . I understand what you mean by the imbalance and I certainly hadn't thought of that! Wouldn't filling the holes left over with some threaded studding counteract the imbalance created by my new holes? If you're talking about creating an actual weakness, then I know studding wouldn't work and no amount of threadlocking the studs would stop the tears before bedtime!
9 June 2019 at 12:29 #413401
JasonB
Moderator
@jasonb
Dave it also has something to do with the difficulty of getting 3 holes spaced between the 4 jaws as most 4-jaw chucks are through fixing so you need room for a counterbored hole that does not come too close the the slots for the jaws. The bigger the chuck fixing PCD the less of a problem.

having work off ctr in the 4-jaw will far outweigh any slight balance issues from 3 or 4 fixings.
9 June 2019 at 12:42 #413406
GordonH
Participant
@gordonh
Arckivio,

Google d1-3 flange dimensions, they are very similar. My Myford has a BS4224 fitting, 3 mounting studs. It takes D1-3 chucks with the camlock fittings replaced by threaded studs. I bought these years ago from the old Myford in Nottingham.

GordoH
9 June 2019 at 12:55 #413408
Arckivio Funiciello
Participant
@arckiviofuniciello27500
Posted by GordonH on 09/06/2019 12:42:16:

Arckivio,

Google d1-3 flange dimensions, they are very similar. My Myford has a BS4224 fitting, 3 mounting studs. It takes D1-3 chucks with the camlock fittings replaced by threaded studs. I bought these years ago from the old Myford in Nottingham.

GordoH

I'll look into that fixing too before I do, or buy anything. Thanks for all the replies everyone. Lots to think about and look into.
9 June 2019 at 13:17 #413409
SillyOldDuffer
Moderator
@sillyoldduffer
Posted by Arckivio Funiciello on 09/06/2019 12:11:19:
Posted by SillyOldDuffer on 09/06/2019 11:57:26:

Posted by Arckivio Funiciello on 09/06/2019 10:14:49:

Posted by Peter G. Shaw on 09/06/2019 10:08:00:

…

… Use one of the holes already in the 4 jaw and then drill and tap another 2. In my little head it's a brilliant idea

I've wondered why bolt-on 3-jaw chucks have 3 bolts and 4-jaw types always have four. I think it's probably done to maintain balance and reduce torsional stress inside the chuck as it rotates. Turning forces are generated inside the chuck by the weight of the chuck body as it spins. If only 3 fixing points are used the forces may be unbalanced by spinning and also by unequal cutting forces via one of the jaws. I've not attempted to work out how big the forces are, but potentially quite big – trying to stop a freewheeling chuck by hand hurts.

If you try a three bolt fixing system can you report back what happens. Three possibilities:

Works with no adverse effects (hurrah!)

Works but finish affected by vibration (Might be acceptable)

The chuck might burst at high-speed. (Tears before bedtime.)

Dave

Edited By SillyOldDuffer on 09/06/2019 12:00:40

There's always one . I understand what you mean by the imbalance and I certainly hadn't thought of that! Wouldn't filling the holes left over with some threaded studding counteract the imbalance created by my new holes? If you're talking about creating an actual weakness, then I know studding wouldn't work and no amount of threadlocking the studs would stop the tears before bedtime!
Well there you go – I hadn't thought of extra holes weakening the chuck!

I'm not explaining the imbalance very well but picking up on Jason's more practical point about spacing the holes here's a photo of a 4-jaw and its backplate:

Drilling new holes to match may be impossible without damaging the chuck.

Is lack of a pillar drill putting you off making a backplate (assuming one can't be bought)? Using a lathe to drill off-centre holes with a faceplate came up recently. Not as difficult as you think once you know how, especially on a big lathe like yours!

Dave
9 June 2019 at 13:27 #413412
Arckivio Funiciello
Participant
@arckiviofuniciello27500
It's not lack of a pillar drill, it's of experience on a bigger lathe doing bigger things. I've gone from a mini lathe to something quite a bit bigger! Looks like a back plate should be my first big project. I found a seller doing 160mm diameter cast iron by the inch.
9 June 2019 at 14:44 #413421
JasonB
Moderator
@jasonb
And this is how close the four fixings of a 160mm lightweight 4-jaw chuck come to the 3 flange studs on my lathe, had they been counterbored holes like Dave's they would have clashed.
9 June 2019 at 14:48 #413422
Arckivio Funiciello
Participant
@arckiviofuniciello27500
Posted by JasonB on 09/06/2019 14:44:27:

And this is how close the four fixings of a 160mm lightweight 4-jaw chuck come to the 3 flange studs on my lathe, had they been counterbored holes like Dave's they would have clashed.

The PCD of my chuck mandrel is 145mm I think so at least that isn't a problem I'll have.
9 June 2019 at 20:32 #413455
Arckivio Funiciello
Participant
@arckiviofuniciello27500
Any advice on backplate thickness? I know it has to take the 4 bolts to hold the 4 jaw so it can't be too thin. I reckon an inch might be too thin?
9 June 2019 at 20:34 #413456
JasonB
Moderator
@jasonb
About 15mm.

What size are the bolts, 1.5 x D should be OK
9 June 2019 at 20:37 #413458
Arckivio Funiciello
Participant
@arckiviofuniciello27500
Posted by JasonB on 09/06/2019 20:34:06:

About 15mm.

What size are the bolts, 1.5 x D should be OK

The bolts in my chuck mandrel are M8, not sure what the 4 jaw will have as I haven't bought it yet. Thanks for the reply
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