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Turning long thin walled tubes

jsimon

Plastic
Joined
Oct 10, 2014
I am looking for some advice on inserts, tool holders and speeds and feeds for turning 6" OD x (.25" to .50") wall 1026 DOM steel tubes 70" to 100" long. We have a Fryer ET30 lathe. What would work best?
 
That is way to much info to begin to tell you. You should call a machine tool company in and date them. tell them your current machine isnt cutting it and you'll need a turn key setup. They'll quote you everything that is needed.

Plan b would be hire a competent turning guy.

Proturn
 
Proturn - I agree with your plan B. Easier said then done.

Mtndew - We have been using VNMG style inserts at 250-400 rpm .01-.015 ipr. turning the part between centers.

I know that I need to call a tooling rep. I was just curious if anyone on this forum had any experience doing this. Thank you for all the reply's.
 
Stuff the 1026 DOM tube with bicycle inner tubes fill with steel shot. You might even get by with heavy heater hose all folded up and inserted in the bore. This should eliminate any chatter from OD turning. As for tooling follow the above comments.
Ken
 
Proturn - I agree with your plan B. Easier said then done.

Mtndew - We have been using VNMG style inserts at 250-400 rpm .01-.015 ipr. turning the part between centers.

I know that I need to call a tooling rep. I was just curious if anyone on this forum had any experience doing this. Thank you for all the reply's.

The first problem I see is the N in your vNmg. This is a neutral tool designed to give you 4 cutting edges but is not the most free cutting tool avalible. If you are profiling and need the shape of the v*mg stle insert maybe try a vcmt with a positive 7 deg rake, it has has 2 less cutting edges but may do a little better due to putting less force on the work piece. If you are straight turning and are not profiling maybe try a tpgt, 3 edges are better than 2.
 
Even if you turn the between center the od and the id are usually not concentric and if you remove more material on one side or the other the tube is going to bend and youll fight hard to get it strait again. I also agree that the N is not free cutting ans some tool would work best.
 
If you think that sounds silly, I've gone as far as using those pool noodle floats and shoving them in bores. If the ID is to large, wrap some duct tape around the diameter of the noodle every so many feet. Get the ones that have the hole through them and use a piece of bar stock or all thread to add weight. I use a Kennametal Top Notch VPGR3305 at about 350/500rpm and .006/.01 feed depending on the surface finish call out.
 
The first problem I see is the N in your vNmg. This is a neutral tool designed to give you 4 cutting edges but is not the most free cutting tool avalible. If you are profiling and need the shape of the v*mg stle insert maybe try a vcmt with a positive 7 deg rake, it has has 2 less cutting edges but may do a little better due to putting less force on the work piece. If you are straight turning and are not profiling maybe try a tpgt, 3 edges are better than 2.

I agree with this. Whatever insert you use, it should have a "C" as the second letter. TCMT inserts will give you three edges. I've had the best luck with Sandvik inserts for chatter free turning.
 
DOM should be quite uniform in wall thickness, and straight enough to use a steady rest near the half way point. That should take care of chatter problems. Feed aggressively during roughing, to prevent establishing a chatter wave pattern on the surface which will want to replicate on successive passes.

I'd try the Iscar cutgrip style tooling for finishing, as you can obtain a nice smooth surface with a very aggressive feed rate compared to conventional lathe inserts. You have to be of an experimental attitude, because setting the holder to get the insert to clear at just the proper angle to avoid wide nose chatter issues, is critical to success, if it will work at all in this instance.
 
OP, you didn't specify how much material you're removing, and the finish that is needed.
As said above, a positive rake insert for finishing would help with vibration and chatter.
Is this being done on an Okuma lathe with a P200 or P300 control? If so, there is a simple macro to fluctuate the spindle to eliminate chatter.
 
Leaving the tube stationary in a fixture and spinning appropriate TOOLING instead of the flexible and less-predictable tubing is what works 'best'. Think it through. Make it happen.

Bill
We do not have a machine to do this. But thank you for the response.
 
OP, you didn't specify how much material you're removing, and the finish that is needed.
As said above, a positive rake insert for finishing would help with vibration and chatter.
Is this being done on an Okuma lathe with a P200 or P300 control? If so, there is a simple macro to fluctuate the spindle to eliminate chatter.
Removing .100" at most with a 100 to 125 finish. We are using a Fryer ET30 lathe.
 
Removing .100" at most with a 100 to 125 finish. We are using a Fryer ET30 lathe.

oops, I guess you did specify the lathe model in your 1st post. disregard my inability to read lol.

Since you're removing only .100, I would say 1 rough cut leaving .01" per side for finishing with a positive insert would easily do the trick.
125 micro shouldn't be a problem.. IF.. you have a steady rest. If not, then you may have to play with the speeds and feeds a little to get the chatter out, at least with the 100" long tubes.
I used to turn stuff like this all the time,it can turn into a nightmare pretty quickly :)
 
Chatter and Resonance Damping

Stuff the 1026 DOM tube with bicycle inner tubes fill with steel shot. You might even get by with heavy heater hose all folded up and inserted in the bore. This should eliminate any chatter from OD turning. As for tooling follow the above comments.
Ken

Many thanks 4GSR for the steel shot tip. My problem was relatively mundane - aluminium alloy (5083) tube 1.375" (35mm) dia. with 0.08" (2mm) thick walls to be turned down to 0.040" (1mm). The tube was 16" (400mm) long and would not stop chattering and ringing, spoiling the surface finish, waking the neighbours and making accuracy difficult. I'd tried a wide variety of speeds, cutting rates, tools, tools cutting angles, lubricants and nothing really worked. Just beginning to put it down to my 1938 IXL lathe, then went on line to see if others had a solution. I came onto this forum, saw your post, then stuffed the tube with shot (actually lead shot as I have loads, used without the inner tube) rammed it down hard and the problem completely disappeared. Thanks again.

Dave
 








 
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