I have a lead casting I need to turn. About 5” dia x 8” long. But it was sand cast so it has a 2 degree taper. I’d like to turn it to a right cylinder. Have a 12” 3 jaw Chuck. Any suggestions on holding this before I get a straight part to Chuck on??
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Holding a tapered part?
- Thread starter no704
- Start date
VR6ix
Well-known member
I'm not a machinist but my first thought was Morse taper tool holder, but that's 2.98º not 2º. Maybe there's another taper standard that's closer? These examples need some math to check.
alfadan
Well-known member
How much do want to take off it? Or just round without a specific number?
Since its lead the jaws should bite into enough to clean up one end with light cuts, then flip it.
Since its lead the jaws should bite into enough to clean up one end with light cuts, then flip it.
Beerhippie
Well-known member
Add a live end and it should be stable as hell.How much do want to take off it? Or just round without a specific number?
Since its lead the jaws should bite into enough to clean up one end with light cuts, then flip it.
Dagny
Well-known member
could you solder a shank to one side.
Actually cuts pretty nice, been running about 500 rpm.Jaws will grip it fine to take light cuts to straighten it out, then flip, lock it down and machine away.
Never machined lead. Sounds goey...
Firebrick43
Well-known member
make a shouldered plug to go inside the cylinder and center drill it so a center on the tail stock will support it. If the cylinder is open on both ends make two and use a dog to drive it off of a faceplace w/center
Regardless of taper at that length you'll need a center...Guess I’ll Chuck it up and cross my fingers. Not sure if I have a center for this lathe. I normally use the 13” for most things. Thing weighs 60 lbs!
Agreed. Just got this lathe back up and running. There is a long bolt hanging down out of the tail stock. I’ll have to figure out where that wants to be. I think it’s a MT5. Other is MT3. I think I have an adapter if not a dead center. I’ll have to do some digging.Regardless of taper at that length you'll need a center...
It’s like 5”’dia.Will collets hold it for a collet chuck in a lathe?
I edited my post.It’s like 5”’dia.
This is probably offensive, but I feel like this is one of those "if you have to ask" then you're not qualified type questions...
The fact that this is to support nuclear research and you apparently lack basic machining skills is worrisome.
The fact that this is to support nuclear research and you apparently lack basic machining skills is worrisome.
mike93lx
ALLIANCE MEMBER
It's actually plutonium, right? You can tell us
mike93lx
ALLIANCE MEMBER
You knew this going in. Why bother?This is probably offensive, but I feel like this is one of those "if you have to ask" then you're not qualified type questions...
The fact that this is to support nuclear research and you apparently lack basic machining skills is worrisome.
I go sucked in to being helpful.You knew this going in. Why bother?
Then after several people gave similar advice how to do this and the OP started talking about soft jaws I got annoyed.
That's enough Internet for me today
Me personally I'd mark out center on the big end and on the drill press put a center in the part. Grab the part by the small end and using a center in the tailstock, buy one if necessary, and turn the big end down till you have enough of a straight cylinder to flip it and turn the other end.
You don't speak of any other features or tolerances of the part so we do not know if you can drill a hole in the center and use a mandrel or pop some holes in it to bolt it to a face plate.
lg
no neat sig line
You don't speak of any other features or tolerances of the part so we do not know if you can drill a hole in the center and use a mandrel or pop some holes in it to bolt it to a face plate.
lg
no neat sig line
This was my first thought on how to approach this.Me personally I'd mark out center on the big end and on the drill press put a center in the part. Grab the part by the small end and using a center in the tailstock, buy one if necessary, and turn the big end down till you have enough of a straight cylinder to flip it and turn the other end.
You don't speak of any other features or tolerances of the part so we do not know if you can drill a hole in the center and use a mandrel or pop some holes in it to bolt it to a face plate.
lg
no neat sig line
I don’t think being careful and asking for ideas on how to grip a 60 lb hunk of lead spinning at 500 rpm is a cause to worry. I’d be concerned if I just did it without planning first.This is probably offensive, but I feel like this is one of those "if you have to ask" then you're not qualified type questions...
The fact that this is to support nuclear research and you apparently lack basic machining skills is worrisome.
I’ve been machining for over 30 years and this is the first time I’ve done this, so yes I am looking for suggestions on the safest method to do this.
This is a machining question and should not matter if it’s for an isotope or a lawnmower engine.
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It’s good to ask questions. I’ve been cranking wrenches for 48 years, there’s always someone who has done something before me. Intelligent people ask questions, ignorant people do not.I don’t think being careful and asking for ideas on how to grip a 60 lb hunk of lead spinning at 500 rpm is a cause to worry. I’d be concerned if I just did it without planning first.
I’ve been machining for over 30 years and this is the first time I’ve done this, so yes I am looking for suggestions on the safest method to do this.
This is a machining question and should not matter if it’s for an isotope or a lawnmower engine.
RoninB4
Well-known member
-It would have been good to have been more descriptive of the finished part. Turning on a mandrel or whether centers can be added promotes better replies. Also good to include whether you have live centers for the lathe. Couple more thoughts:
-Would not touch the chips/stringers with my hands. Lead in airborne particles is toxic.
-Positive top rake on cutting tool (HSS bit or carbide insert) seems to help, so does coolant as reported by some.
-The "long hanging bolt" from the tail stock may be part of what clamps the tail stock to the bed of the lathe, should be another piece for it.
-Depending upon the cast properties, holding the part in a chuck may easily deform it due to lead being very soft
-Turning it in the lathe runs the risk of the piece being snatched by the cutter if you take an ambitious a depth of cut.
-Some report a balance of speed/feed and coolant to obtain a good surface finish, some report the finish being "fuzzy"
-Consider the lathe/tooling to be contaminated until thorough cleaning. Hope this isn't a regular thing for you.
-Would not touch the chips/stringers with my hands. Lead in airborne particles is toxic.
-Positive top rake on cutting tool (HSS bit or carbide insert) seems to help, so does coolant as reported by some.
-The "long hanging bolt" from the tail stock may be part of what clamps the tail stock to the bed of the lathe, should be another piece for it.
-Depending upon the cast properties, holding the part in a chuck may easily deform it due to lead being very soft
-Turning it in the lathe runs the risk of the piece being snatched by the cutter if you take an ambitious a depth of cut.
-Some report a balance of speed/feed and coolant to obtain a good surface finish, some report the finish being "fuzzy"
-Consider the lathe/tooling to be contaminated until thorough cleaning. Hope this isn't a regular thing for you.
I would lay out and pilot the center on the small end, chuck the large end at tips of jaws realizing you are going to put significant clamping marks into the (large, sacrificial) OD. As has been mentioned, you need to find or make a clamping shoe for the bolt hanging from eccentric locking lever shaft in the tailstock. Otherwise, no way to hold live center into anything. Once you turn your OD (assuming I read it right and you want that) from small end much of the way back down enough to make a clamping area, you need to use a piece of tubing with ID neear your target diameter, better yet take a piece of flat bar and roll it to right diameter, trimming the ends back after you get close. The end gap of your almost complete circle needs to be less than the disance between jaws of your 3 jaw. Turn your part around and clamp the ring to squeeze down on the straight diameter end you already machined. IF you are within tolerance you can work with, you can the use chuck in tailstock to drill a new center in the big end (that should be sticking out of headstock chuck pointing towards tailstock. Now you can complet the OD by turning the rest of the oversize, sacrificial material.
Why not soft jaws ? I can say I have never had a need for them before. But for this it seems like a good idea. I could mount the soft jaws and turn a matching taper into them.I go sucked in to being helpful.
Then after several people gave similar advice how to do this and the OP started talking about soft jaws I got annoyed.
That's enough Internet for me today in
Would that not be better than using straight jaws on a tapered part? I could even flip the jaws around and turn that side the other way and be able to grip either the big or little end.
I have ordered a set of Al soft jaws. Might also get set of the big pie ones.
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To me making a set of soft jaws kinda makes the most sense. The big end is the rough end of the casting. It has the spru cut offs on it.
I have ordered a set of soft jaws. But they do offer the larger pie cut soft jaws also I might get a set of them also.
As always I appreciate all of the great insight you guys offer. Lots of great input.
I have ordered a set of soft jaws. But they do offer the larger pie cut soft jaws also I might get a set of them also.
As always I appreciate all of the great insight you guys offer. Lots of great input.
I'm not a machinist, but I'm pretty sure any soft jaws would be harder than lead. The soft jaws I have seen machinists use have been aluminum, brass or copper. All of these are harder than lead.Why not soft jaws ?
In context of everything I've done, Soft jaws refers to the fact that they aren't hardened, and are therefore machinable to suite your application.I'm not a machinist, but I'm pretty sure any soft jaws would be harder than lead. The soft jaws I have seen machinists use have been aluminum, brass or copper. All of these are harder than lead.
Personally trying to match taper in a casting for a few parts seems like a fools errand. I would just machine it in steps, getting enough of a round surface in the first step to clamp it and finish machine.
Without any additional context on final shape and tolerance to sure what else to offer.
You missed the point, and are taking "soft" too literally.I don't disagree, but he is machining lead. What would be used as a soft jaw in this instance, rubber?
He's buying a set of jaws that he can machine a 2 degree taper into.
I just can't get past the fact he is trying to hold lead. Any pressure with the chuck jaws will deform the lead casting. I'm sure I'm mistaken as I am not a machinist, but I am thinking any jaws he would have to machine to hold it would damn near have to surround the casting as to not deform lead and be of sufficient thickness not to deform the soft jaws with the chuck jaws. Then there is the issue of castings not be true to begin with, unless he has a really good casting.You missed the point, and are taking "soft" too literally.
He's buying a set of jaws that he can machine a 2 degree taper into.
This has been explained, in a couple different ways, buy a couple different people. "Hard" parts deflect if the cross section is thin, so dealing with "soft" deformable material isn't that unusual.
I'm not machinist either, but I can run a lathe in a pinch, and work with multiple pros daily.
Every one of them would as "WTF do you want that for?", then shrug their shoulders at the explanation and come back a few hours later with a sample based on what they had on hand.
I'm not machinist either, but I can run a lathe in a pinch, and work with multiple pros daily.
Every one of them would as "WTF do you want that for?", then shrug their shoulders at the explanation and come back a few hours later with a sample based on what they had on hand.
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I’ve made one set of these parts using lost pLA casting. Turned out sort of ok just had an actual foundery do them using a pattern. Pattern was made with a 2 degree taper for the sand casting process.
I’m going to see if moving forward we could possibly use a lost foam casting method to cast closer to finish dimensions.
I might know a guy that cncs foam but would love any recommendations.
I’m going to see if moving forward we could possibly use a lost foam casting method to cast closer to finish dimensions.
I might know a guy that cncs foam but would love any recommendations.
Why did they do taper on a sand cast, just for the pattern to release?I’ve made one set of these parts using lost pLA casting. Turned out sort of ok just had an actual foundery do them using a pattern. Pattern was made with a 2 degree taper for the sand casting process.
I’m going to see if moving forward we could possibly use a lost foam casting method to cast closer to finish dimensions.
I might know a guy that cncs foam but would love any recommendations.
American Locomotive
Well-known member
I would say turning a set of jaws to match the part would be a good idea, especially with the softness of lead.
If you have a 6 jaw chuck, that'd be even better.
If you have a 6 jaw chuck, that'd be even better.
Machining one-off jaws is par for the course for machining. Often making the work holding and fixtures takes longer than the actual machining of the product.Personally trying to match taper in a casting for a few parts seems like a fools errand. I would just machine it in steps, getting enough of a round surface in the first step to clamp it and finish machine.
Thanks to everyone that have made suggestions. Many great ones. This is why I ask here. I have a set of aluminum jaws on order that I’ll turn to match the taper of the part. I also plan on flipping said jaws and turning them to that negative taper. This should allow me to get a good grip on either end of the part.
Yes. And I’m looking into doing a lost foam process to be close to finish dimensions. I’m not against this current process as it makes nice useable casts. Higher ups want it to be pretty also!Why did they do taper on a sand cast, just for the pattern to release?