What's the primary benefit of the adjustable 3 jaw scroll chuck?

[Jimsehr]

I mostly use 3 jaw chucks . I like the chucks with top jaws and the ability to mount soft jaws to bore to size if I need them . It is also nice to be able to bore soft jaws to hold a washer like part. Like 1/8 inch thick and have part run true with a built in stop ( back side of bored jaws ) to hold part. I have also turned a regular 3 jaw chuck into a set true chuck. If the back plate register fits into the recess of the chuck you can turn the register down to give the chuck some slop
them put 4 set screws thru back plate to adjust.

Also I have other types of set true chucks that work same way .

 

[skcncx]

I like the chucks with top jaws and the ability to mount soft jaws to bore to size if I need them . It is also nice to be able to bore soft jaws to hold a washer like part. Like 1/8 inch thick and have part run true with a built in stop ( back side of bored jaws ) to hold part.

I have yet to comprehend the all the great benefits of boring soft jaws. If they are reversible, stepped jaws ("top jaws"??) that seem common, wouldn't reversing them and holding a washer like part accomplish the same thing? I ask out of ignorance. Maybe if the part's diameter is too small, you would have to bore soft jaws in that case.

I have also turned a regular 3 jaw chuck into a set true chuck. If the back plate register fits into the recess of the chuck you can turn the register down to give the chuck some slop
them put 4 set screws thru back plate to adjust.

I may give that a try on the economy chuck included with my lathe. Worth a shot before I spend $700. What's the point of set true if it's that easy... maybe the internal mechanism of PM's adjustable 3 jaw is more sophisticated. It seems like it does the same thing though, except your screws to lock it down are on the face, so maybe easier to do....

 

[Jimsehr]

This is an couple examples of set true chucks. Not spindle chucks but same idea.

First pic shows a ring with 4 set screws bolted to back plate with tight fit. Front set of screws used to adjust center part true.

Pic 2 is different tool made to set true center body of tool. These tools are made to inserted into turret lathe or automatic machine. To center cutters true.

I also have more of this type of tool.

 

[Larry42]

Aren't we supposed to have both lathe and mill?

"Depends" on what you intend to do! Some milling can be done on a lathe. BUT having both is a much nicer set of tools. And all the tooling, accessories etc. turns into an expensive rabbit hole.

One thing I've noticed with my D1-4 spindle is that it makes a difference how I tighten the cams. Not much difference but I can measure it. So I always do the same sequence.
Both of my collet chucks are "set-tru" types. If the work fits my 5C that's what I'll use. If I'm just turning parts from a piece of round stock any 3 jaw is good enough. If a second operation is needed by reversing the part the level of accuracy required will govern my choice. Putting the 8" 4 jaw on and centering each part can get very good tolerances. But it is time consuming for me. I finally made a second shorty chuck key so I can use it on the back side at the same time as the key on the front side. Speeds up the process.

I did finally buy a nice Taiwan 8" 3 jaw. Not set true, but it repeats much better than the 6" included in the box, 3 jaw.
The finest chuck in the would would not make me a master machinist. The only place I find it really important for dead on sizing is for press fits. For press fits both parts need to be the same temperature to measure accurately. Loktite can be your friend.

 

[mmcmdl]

I have yet to comprehend the all the great benefits of boring soft jaws. If they are reversible, stepped jaws ("top jaws"??) that seem common, wouldn't reversing them and holding a washer like part accomplish the same thing? I ask out of ignorance. Maybe if the part's diameter is too small, you would have to bore soft jaws in that case.

Can't live without soft jaws . Maybe a hobbiest can , but in an industrial setting where TIR needs to be spot on , soft jaws are the bees knees . If they are on a set true type , they are even better . Bore them once and you can remove them and re-install them as long as you need them . They are simple to make out of round stock aluminum so no need to buy expensive sets of jaws .

 

[skcncx]

"Depends" on what you intend to do! Some milling can be done on a lathe. BUT having both is a much nicer set of tools. And all the tooling, accessories etc. turns into an expensive rabbit hole.

Ha, I don't have a lot of pre-made plans/intentions, other than I really enjoyed using my Atlas 618 for some tractor parts, shop parts for band saw upgrade, few other projects for friends... but wanted to do some threading and realized, I'm gonna stick with this so might as well upgrade to something with a decent QCGB.... that got the snow ball rolling. Then, what tooling should I get, and.... should I just get a mill when I go pick up my lathe, save another round trip. So far, every time I have tried to save I end up spending more . The PM728VT or the PM833T or TV models are looking good... my responsible side should kick in.... but I have really no justification for any of this.

 

[mmcmdl]

Once I get caught up around the house , I'll have a few pieces of equipment going out depending on what you're looking for . They'll be posted on here .

 

[skcncx]

Can't live without soft jaws . Maybe a hobbiest can , but in an industrial setting where TIR needs to be spot on , soft jaws are the bees knees . If they are on a set true type , they are even better . Bore them once and you can remove them and re-install them as long as you need them . They are simple to make out of round stock aluminum so no need to buy expensive sets of jaws .

These things? You make those out of round stock?

I think I'm not picturing what you have in mind... no answer needed, I'm just soaking all this in these days. I'll do some googling.

 

[mmcmdl]

Yes , those things .

 

[skcncx]

Once I get caught up around the house , I'll have a few pieces of equipment going out depending on what you're looking for . They'll be posted on here .

Sounds good... I guess there is a place to sell... but I have yet to find it on here. Manual flat bar angle bender, rolling bender possibly, mill stuff interested in.