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External screw thread

External screw thread

External screw thread

I need to make a male thread on the tip of an hydraulic rod. The diameter is 64mm and I need to machine M64x3,0. Lenght= 80mm
Is there a way of doing this job without disassembling the rod? Maybe with a hand die?

RE: External screw thread

M64 = 2-1/2 inch = very, very difficult to hand-tap threads that large. Worse, you have an interference below, so you're going to be trying to use a loooong lever arm on a the thread die that has to be continually reset and started over. (Yes, a ratchet is possible, but that too is a start-stop type of machining. Easy to foul up and cut crossed threads.)

Rather than ruin the part, take it apart and cut the threads properly on a lathe with a good, steady, aligned drive motor and steady rest.

RE: External screw thread

Don't know where you are, but when I had problems with tasks like that, I would try the nearest shipyard or repair company, they might just have a way of doing it.

Otherwise it's a strip down, as you are certainly going to have to strip it down after it goes wrong!

RE: External screw thread

You could weld on a threaded piece.

RE: External screw thread

Or machine the (external male threaded) piece so it creates an interference fit with the 64 mm round section. That means the ID = 64 mm (minus a few thousanth for the interference fit), and the threaded OD becomes 70 or 75 mm. Changes the configuration, so the idea may not work.

RE: External screw thread

thanks to all for your replies.
I like Compositepro`s idea. I will have to change the thread to M74 or M75 but it could work. The piece that is going to be screw to the rod is a "cilindrical head" made of nylon.

Those 6 holes that can be seen in the picture are now used to hold the Head. The idea is to discontinue the use of the holes and hold the head by a center thread. Obviously we will make a new nylon head without the holes and with a single big female thread

RE: External screw thread

Might be easier to drill and tap a female thread in th end of the rod. Especially if you are going to make a new nylon head.


RE: External screw thread

What is the purpose of the "cilindrical head" ?

I envision threaded nylon loosening over time if the nylon acts as a snubber and gets bumped from time-to-time.

RE: External screw thread

Not sure what you mean by "disassembling the rod," but if you can remove the entire cylinder from the machine there's no need to remove the rod from the cylinder. Hydraulic shops do this regularly. Personally I'd set it up on the boring mill and use a geometric die head in the spindle to cut those threads, but there's many ways to fixture this and do similar on other machines.

RE: External screw thread

Tmoose: the purpose of the nylon head are 2.
1. to thermically isolate the load (welding flux) from the heat of the rod coming from the oil and 2. to minimize the wear of the load cylinder by sacrifice the nylon material. We change the nylon head once a month

CWB1: The hydraulic cylinder can not be remove. It is a one piece cast. The rod can be remove from the end side of the cylinder but we dont have the time to stop the machine for more than a few hours

RE: External screw thread

What about cross drilling through the rod tip and nylon?
Then drop a bolt in and your done.

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