turning a long hex nut

In the pic is a threaded collar and a m8 nut i just bought some 30mm long hex nuts hoping to turn 25mm down to a round bar and create the part in the pic as one piece but unsure how it will be in the lathe as will be intermittent as it hits the edges . I plan to thread a brass round bar 8mm and put the piece in the bar so i can then secure it in the chuck and a live centre

Edited By JasonB on 26/11/2017 07:26:21

You should be able to turn M8 hexagon down to around 11 mm. round (depending on how concentrically you can hold it) on any lathe worthy of the name. I think I could easily do it on my Sieg C0, which is one up from watchmaker size. If it's too harsh to do it in one cut, try 2 passes.

The main think is how comfortable you are with holding less than 5mm of the nut when taking an interrupted cut.

You could put a few ordinary M8 nuts (or one long one) on an M8 screw, align them and hold them in the chuck leaving enough thread to use as a mandrel for the long nuts.

Neil

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... with tailstock support if you want to make a job of it.

MichaelG.

I thought that was more-or-less what he said he was gonna do?

Edited By Mick B1 on 27/11/2017 10:11:58

Just use a length of M8 studding (allthread). Centre drill one end, lock a couple of nuts on the end opposite the centre. Locate in the chuck with the locked nuts up against the back of the chuck jaws (stops the mandrel slipping forwards probably not necessary)

Run the part to be machined up to the chuck jaws and it will lock in place (could put a spacer in if you don't like working close to the chuck), locate the centre and machine the corners off. Take a deep cut with fine feed to remove as much of the corner in one go to avoid the clonking!

John

Another dodge is to use a tap as a mandrel. It doesn't need to be a new or sharp tap, but it must be the right thread, of course. Taps are usually made with the shank ground from the same centres that the thread is made, so they can be more precise than studding, and firmer to hold in a collet.

So now you know what to do with all those blunt taps you have been saving up. Aunty Flo is never going to get you a fancy grinder, after all.

Cheers, Tim

cheers yes that is what im going to do and suport between a live centre i am going to leave threading the bit that goes in the chuck though i have loads of 8mm stainless rods