LOGAN 9X38 CHUCK HELP

[riversidedan]

just picked up a logan 9X38 lathe that has only a 4 jaw 6 in. chuck, really dont care for that type and needing a 3 jaw. dont know very much about the machine yet
so reaching out here hoping someone can set me striaght on what to get...........pix below>>>>

 

[markba633csi]

I would get a Pratt-Burnerd or a Bison if you can afford it- they are excellent chucks
A 5" would be a good size for that machine

 

[Firebrick43]

That is not how you remove the chuck. the face of the chuck should stay attached to the back plate and it unscrews. There is a spindle lock of sorts, you put it in back gear but not pull the center pin. Then use a crescent wrench on the jaw of the chuck and unscrew the back plate CCW. A much better way so you don't end up breaking teeth off the back gear set is to get a spindle lock like this

Ebay spindle lock

You then by a new back plate machine it flat and to diameter for your new chuck and then mount the new chuck to it.

Shars back plate

5" 3 jaw chuck

 

[riversidedan]

That is not how you remove the chuck. the face of the chuck should stay attached to the back plate and it unscrews. There is a spindle lock of sorts, you put it in back gear but not pull the center pin. Then use a crescent wrench on the jaw of the chuck and unscrew the back plate CCW. A much better way so you don't end up breaking teeth off the back gear set is to get a spindle lock like this

Ebay spindle lock

You then by a new back plate machine it flat and to diameter for your new chuck and then mount the new chuck to it.

Shars back plate

5" 3 jaw chuck

so in other words the face plate has to come off and I have to replace the existing face plate??? why cant I just use the existing plate and get a 3 jaw that fits the plate////

 

[mksj]

Face plates can have different hole patterns and registration steps, the latter is often chuck specific. At the cost of a back plate, it pays to setup each one for the intended chuck, and you can easily switch chucks by unscrewing them from the spindle. You probably would do fine with a less expensive chuck, you need to check that the mounting hole pattern matches the chuck. You cut the registration step if needed with the back plate mounted on the spindle,

 

[markba633csi]

The old backplate probably won't fit the new chuck without re-machining, which means it won't fit the old chuck anymore. Usually, the backplates are machined to fit the chucks they are mated with and won't interchange.

 

[Firebrick43]

so in other words the face plate has to come off and I have to replace the existing face plate??? why cant I just use the existing plate and get a 3 jaw that fits the plate////

Others mentioned the registration steps. They are critical to having a chuck that is true. Otherwise you have lots of runout

And its a backplate, not a faceplate. Similar but different structure and purpose.

 

[riversidedan]

ok I know the back plate unscrews from the spindle which involves locking the gears from moving .....so in otherwords id need to get a matching back plate and chuck? or is thier a 3 jaw that will fit the plate?? if so where available??

 

[WobblyHand]

You may be able to find a matching back plate, but most require some final machining to exactly fit your chuck. This is particularly important if you get a 3 jaw chuck. The registration feature is what gives you low(er) TIR. The back plate is machined right on your lathe. You have to sneak up on the final fit. If the fit is too loose you either start over with a new back plate, or you can bump it into position and tighten it up. It's best to machine it right the first time. It's actually not that hard to do, just take your time and do a fit check often.