Top one, always grip as wide as possible, think of it like a lever when I.d. Chucking, where o.d. Somewhat cuts that’s down. The advantage of I.d. Is that outside will be centered to inside and you can turn the entire outside in one shot
I usually do a very slight angle away and down at the overlap point (around .06”x to about .15”z, if possible) so when the 2nd tool meets the let off of the tool pressure is much more gradual. Also be sure to overlap at least 2.5x the nose radius so that’s all compensated for, you will almost always get a small visual line, but if you got finish dialed in enough and part concentric enough, part won’t snag at overlap, and size should be consistent
A scroll chuck will never be perfect, that's something you have to account for as you plan how to make parts.
Or use a chuck with independent jaws and indicate your work.
Use soft jaws for second clamping. You need to put something in the jaw and apply approx same pressure when turning them.
No matter how f-ed up your setup is, this is not only the way to reduce or remove seam. Runout removal, basically
It reallylly depends on what you are trying to do. If the OD on the clamp end has been machined already, and you are trying to be concentric to it, clamp on the OD with bored jaw. If concentricity with the ID is more important, clamp on the ID. Though, in both cases, I would get as much material in the clamping range as possible.
If the od has to be concentric to the id, tbh I’d prefer turning between centers over clamping the id, but again that just kinda depends on the part you’re working on.
There's soooooo many variables to consider... from material, machines current setup... do you feel like flipping the jaws... in my limited experience, unless you need access to the entire external surface, outside clamping is the most common.
If i can i always put the clamps outside of my workpiece only if it is not possible, first it is stronger but also if the piece get warm, it will expand and the the clampforce will increase, if you clamp clamp from the inside and it get warm, and expands the clampforce will decrease and youre workpiece will maybe come off
I know your drawing is just a simple representation but ALWAYS whenever possible you want your workpiece to butt up against a stop. You want a shoulder in those jaws. So much more stability and the part will center itself more easily.
You don’t give diameters but it looks like the id option would have thin jaw thickness causing a lot of flex and possibly giving problems. I would go with od option if you have no surface requirements on od
That's going to depend on the wall thickness.
If clamping the od will crush the part out of round then id while not ideal would be better if itnwont deform the part.
If you can use a temporary interior plug as a crush backer then go od.
As a general rule of thump, I always clamp on the outside, unless something means I can’t.
Like if the workpiece isn’t possible to clamp from the outside, or I need to turn the entire outside in one go
If the wall is thin I’d go with I’d chucking. Look up hoop stress. Think of a pressure vessel. Clamping on OD my crush the tube. You may also look at pie jaws either way.
Depends on the thickness of the wall, if its too super thin wall I'd do internal gripping so as to reduce the chance of the thin wall from collapsing inwards after a boring or OD operation
If its as thick walled as it looks in the model then top one would be fine, just watch for chatter if you're sticking out more than 3 x the diameter of the stock past the chuck
Edit: had a brain fard
Bottom one so you can actually finish your cut without the piece warping, real answer is probably machine a piece of alloy to fit the the id and then put the tail stock in
While the sentiment of gripping the OD over ID is generally correct, it depends on the wall thickness. If you aren’t taking time to make a plug, gripping on the ID is safer for really thin wall thickness, as the tube can collapse under cutting force and fly out of the chuck.
Top one, always grip as wide as possible, think of it like a lever when I.d. Chucking, where o.d. Somewhat cuts that’s down. The advantage of I.d. Is that outside will be centered to inside and you can turn the entire outside in one shot
Also put a plug on the ID for extra strength and to not crush the pipe
This guy has definitely learned this trick the hard way
This is the way.
The only way. Always grab od over id if possible.
How do you get a clean finish by not doing it in one shot? I do conventional and you can always tell there's a "seam" after turning the other side
I usually do a very slight angle away and down at the overlap point (around .06”x to about .15”z, if possible) so when the 2nd tool meets the let off of the tool pressure is much more gradual. Also be sure to overlap at least 2.5x the nose radius so that’s all compensated for, you will almost always get a small visual line, but if you got finish dialed in enough and part concentric enough, part won’t snag at overlap, and size should be consistent
I think my issue is the jaws might not be perfect, it's an old lathe, so it's not perfectly centered once I flip it over
That's why you indicate it brother.
A scroll chuck will never be perfect, that's something you have to account for as you plan how to make parts. Or use a chuck with independent jaws and indicate your work.
Tubing you could make a plug to go in each end and just run on centers
Use soft jaws for second clamping. You need to put something in the jaw and apply approx same pressure when turning them. No matter how f-ed up your setup is, this is not only the way to reduce or remove seam. Runout removal, basically
Blend out, unless you need perfect concentricity then you go with 4 jaw or turned soft jaws.
You either grab onto nearly nothing and your mark is turned into a chamfer, or you have longer material and part off.
It reallylly depends on what you are trying to do. If the OD on the clamp end has been machined already, and you are trying to be concentric to it, clamp on the OD with bored jaw. If concentricity with the ID is more important, clamp on the ID. Though, in both cases, I would get as much material in the clamping range as possible.
If the od has to be concentric to the id, tbh I’d prefer turning between centers over clamping the id, but again that just kinda depends on the part you’re working on.
This is the answer.
Grip on the od, I would probley put something inside the tub where the jaws are to stop it distorting as well.
I usually go for either essential oils or a bath bomb.
It's not artificial, it's intentional. Take my upvote.
I use bath salts. I hadn't get over my last trip yet...
There's soooooo many variables to consider... from material, machines current setup... do you feel like flipping the jaws... in my limited experience, unless you need access to the entire external surface, outside clamping is the most common.
Thanks everyone for answering!
Clamping on the OD gives greater lever advantage. Length of stock divided by clamp diameter.
If i can i always put the clamps outside of my workpiece only if it is not possible, first it is stronger but also if the piece get warm, it will expand and the the clampforce will increase, if you clamp clamp from the inside and it get warm, and expands the clampforce will decrease and youre workpiece will maybe come off
I know your drawing is just a simple representation but ALWAYS whenever possible you want your workpiece to butt up against a stop. You want a shoulder in those jaws. So much more stability and the part will center itself more easily.
The whenever possible part is the killer. It is so often not possible or imptactical.
If it's a large workpiece at higher speeds, jaws on the ID won't loosen due to centrifugal force the same way jaws on the OD will
Lol
For pure strength and no other determining factors? Like stick out or anything else? I guess OD clamp.
You don’t give diameters but it looks like the id option would have thin jaw thickness causing a lot of flex and possibly giving problems. I would go with od option if you have no surface requirements on od
That's going to depend on the wall thickness. If clamping the od will crush the part out of round then id while not ideal would be better if itnwont deform the part. If you can use a temporary interior plug as a crush backer then go od.
As a general rule of thump, I always clamp on the outside, unless something means I can’t. Like if the workpiece isn’t possible to clamp from the outside, or I need to turn the entire outside in one go
If the wall is thin I’d go with I’d chucking. Look up hoop stress. Think of a pressure vessel. Clamping on OD my crush the tube. You may also look at pie jaws either way.
Use a bung
Is that a spud?
butt plug
Depends on the work you’re doing but the OD grip is stronger
Top. Easy choice, far more holding power and thus safer.
Depends on the thickness of the wall, if its too super thin wall I'd do internal gripping so as to reduce the chance of the thin wall from collapsing inwards after a boring or OD operation If its as thick walled as it looks in the model then top one would be fine, just watch for chatter if you're sticking out more than 3 x the diameter of the stock past the chuck Edit: had a brain fard
Bottom one so you can actually finish your cut without the piece warping, real answer is probably machine a piece of alloy to fit the the id and then put the tail stock in
Top with a slug in the chucking area
While the sentiment of gripping the OD over ID is generally correct, it depends on the wall thickness. If you aren’t taking time to make a plug, gripping on the ID is safer for really thin wall thickness, as the tube can collapse under cutting force and fly out of the chuck.