Upgrading chuck on 7x12 lathe

[saltoricco]

I'm a fresh owner of a Cummings 7x12, so please bear with me. I'd like to work on 6" round plastic to build landing wheels for hang gliders.

Time to find a larger chuck, I guess. My question is can the 5" chuck with the outside jaws grip a 6" rod? I'm looking at this product page. It says "The chuck can hold work up to 110 mm (4.33") in diameter.". Why would it not hold at least 5" diameter parts? Clearly, I'm not understanding something. This image here:



shows a 4" chuck (found on this page. It almost looks like this 4" chuck could hold a 6" part. If the jaws of the 5" chuck extend like they do on this 4" chuck they should reach even further.

With this soft material I'm not too concerned about overloading the machine. Of course, I'd also have to find a solution for the lack of travel of the cross slide. I didn't find anything at LittleMachineShop. Are they any for sale anywhere?

Thanks!

Holger

[ToyMaker]

Do you really have to hold the wheel by its diameter? Why not mount an arbor in the chuck and put the wheel on that?
For the cross slide travel problem I have no suggestion.

robotic regards,

Tom
= = = = =
You don't stop laughing because you grow old, you grow old because you stopped laughing.
- - unknown

[RotarySMP]

I think you will find the 5" four jaw more restrictive than the 4". You won't be able to swing a 6" blank on either as the jaws will stick out more than 1/2" on each side. Toymakers suggestion to mount on an arbor is a much better idea.

The 7x12 is really not the correct tool for the job. You can get something like this done, but turning a 6" OD is a PITA, with a boring bar turning the OD and buggar all power at the low speeds required to avoid chatter.

A 10X lathe would make childs work of this job.

[saltoricco]

Thank you, Tom and Mark! That's true, an arbor would do the trick. I haven't even thought of it - lack of experience and then the thing has a airfoil shaped cut-out in the middle, but I could put that in after I'm done with the lathe work.

I'd love to have a 10" lathe, but right now can't afford it.

If anybody has a suggestion to extend the reach of the cross slide, I'd appreciate it.

Thanks,

Holger

[pastera]

I have a 7x12 and have turned some 6"+ parts from cold rolled steel (1.5" thick). This is not something I would want to do all the time. This was done with the parts on an arbor because my 4" chuck would not open enough to hold the parts. Even if it did the jaws would not clear the bed extended that much. Going with the 5" would not help for the same reason. If you were to make your own jaws for the 4" or 5" chuck you might be able to swing it but I would not trust it to anything other than plastics. Go with a 4 jaw if you do get another chuck.

With either the 5" or 4" chuck, you will not be able to part off a 6" part. The lathe simply too small to do this (the stock would hit the cross slide). If you just want to turn the diameter and add some simple grooves, the 7x12 will work.


Aaron

[saltoricco]

I have a 7x12 and have turned some 6"+ parts from cold rolled steel (1.5" thick). This is not something I would want to do all the time. This was done with the parts on an arbor because my 4" chuck would not open enough to hold the parts. Even if it did the jaws would not clear the bed extended that much. Going with the 5" would not help for the same reason. If you were to make your own jaws for the 4" or 5" chuck you might be able to swing it but I would not trust it to anything other than plastics. Go with a 4 jaw if you do get another chuck.

With either the 5" or 4" chuck, you will not be able to part off a 6" part. The lathe simply too small to do this (the stock would hit the cross slide). If you just want to turn the diameter and add some simple grooves, the 7x12 will work.


Aaron

A very helpful response, thank you Aaron. If I can find affordable Delrin 6" round stock or 2" thick disks I may not have to do anything to the outside diameter. Maybe I can also do it on the drill press. At 5" diameter I have to step down the thickness toward the center and hope I can do this with the lathe. I think I'll upgrade to the 4" chuck.

Thanks all for the great help!

Holger

[pastera]

If you don't need to turn the periphery, then the 7x12 will do what you need but you will have get imaginative to hold the stock.

Check out ebay for some 6" black Acetal (Delrin is a name brand): 190192018096

McMaster has black Acetal for ~$153 per foot.

Aaron

[rustamd]

enco has acetal at $146.71 per foot with free shipping(need shipping code)

[saltoricco]

Thank you two for the Acetal pointers! Jeez, they're producing this stuff for somebody richer then me. Maybe I'll just get two cutting boards at Target and stick them together. I'll post a picture of the wheels when they're done. From 6000ft

Holger

[rustamd]

most cutting boards are HDPE i believe. you can also buy acetal by inch(28.91) at onlinemetals.com if all you need is few inches.

[saltoricco]

most cutting boards are HDPE i believe. you can also buy acetal by inch(28.91) at onlinemetals.com if all you need is few inches.

I think you're right, and HDPE will probably do the job. These wheels are only needed in a rough landing, and if they break I can make new ones.

Thanks,

Holger

[pastera]

HDPE in 6" is about $64/ft at McMaster
If UHMW is enough that's even cheaper

Aaron