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Help! How much axial force from the table can a Bridgeport spindle head take?

I did some research on friction welding a couple of years ago. Axial forces can easily reach multiple tons force. There is a reason many of the larger friction welding machines have tie-rods like injection molders.
 
I did some research on friction welding a couple of years ago. Axial forces can easily reach multiple tons force. There is a reason many of the larger friction welding machines have tie-rods like injection molders.
I've seen several friction/ interna welders that had cylinders big enough to exert up to around 450 tons, andd maybe more, of force! These machines are massive in size. The machines were used to weld tool joints on to pipe for heavy wall drill pipe and drill pipe, too. The hydraulic jaws are massive, too, for holding the pipe and tool joints. Somewhere on Youtube are videos showing the process being done.
 
In my notes, I have a recommendation for 4T heating pressure per square inch, and 10T forging pressure per square inch. So we don't have to be dealing with heavy pipe for the axial forces to get up there.
US Patent 3,235,162 suggests 11HP per square inch for 4140 or 304, but this was on a flywheel inertial system. HP requirements would be less for slower direct drive friction welding.
SFM is typically 300-650. Below 250SFM, excessive torque is required. 750+SFM is considered "superspeed".
So a 1/4" flow-drill is one thing, but a 1" tool shank is a big step up for friction welding.
 
What is the difference between "heating pressure" and "forging pressure"? Do you get it warm then give it more pressure after you have a bit of a molten interface?
 
jccaclimber, yeah, exactly. Think of this as a forging process, where all the heat is generated by friction. To forge weld conventionally, the parts have to be up to welding temperature before you press/crush/hammer them into one another.
If you look at some of the promotional videos for the machinery, you can see there's a 1st stage where stuff gets hot, then a 2nd stage where axial pressure is increased and flash starts curling out from the weld zone.
I'm not an expert on the process, but presumably this produces better welds than just starting with the full axial pressure, as determined by experience making real parts.
 
Just to clarify my comment above.
Lathe type friction weld takes a lot of thrust force. Lots
Welded the CV cup onto hundreds of thousands of axle shafts this way. It is a neat process.
The pressure has to ramp just right and stop it at just the right time.
All this in the program for the machine and needs to be tweaked for differing heat runs of the incoming parts. (hello Metlab)
On B-port style friction welding is more often "stir welding". This has much lower axial force but high radial (sideways) loads.
 
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If you’re concerned about the two moveable head joints moving you could drill and pin them. It isn’t perfect but it’ll ensure they do not move until they break (which sounds like something will).
 








 
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