Sedgwick MB rise and fall damage

[J-G]

So, current threaded bar is M20x2.5mm, and has an unthreaded portion which passes through the bottom planer casting and receives the retaining collar above and driven gear below. It's not bent but it is worn, major diam varies from 19.97mm in the virgin section to 19.30 in the middle, and the thread is a little deformed with some rough bits.

Looking at leadscrews, 20mm would typically have a 4mm lead, meaning a significant increase in the gearing of the thicknesser lift. Also, I'm not finding any stock leadscrews with an unthreaded portion. I could turn down one end of a larger leadscrew but then the gearing would be even higher. Am I missing something?

The 'Standards' for Trapizoidal threads do have both a 'Fine' & 'XFine' - for 20 mm OD they are 3 & 2 respectively.

As @Fitzroy has suggested though, a standard M20 with 2.5mm pitch would be the way forward.

 

[Housey210]

Thanks, hadn't thought of looking at imperial sizes.

Yes the indicator is just a pointer, and yes it was the effort I was concerned with - that and the rather flimsy-feeling plastic crank. The lathe does screwcutting, though it remains to be seen whether I can...

Right, I now have several workable solutions, thanks - enough analysis paralysis! My next post will probably be about lathe problems

simple fix, comments OMG what drama

 

[Fergie 307]

simple fix, comments OMG what drama

And If the OP wants to spend north of £500 on buying new parts, then that is up to him.
The very fact that he has started the thread suggests that that is not his preferred choice, for whatever reason.
The point of threads like these is to help the OP by suggesting other approaches, and saving him some money.
Some of the ideas might also help others in a similar situation.
If the approach were invariably "just buy a replacement part" then it would be pretty boring, and not really very helpful at all.

 

[jetsetwilly]

And If the OP wants to spend north of £500 on buying new parts, then that is up to him.
The very fact that he has started the thread suggests that that is not his preferred choice, for whatever reason.
The point of threads like these is to help the OP by suggesting other approaches, and saving him some money.
Some of the ideas might also help others in a similar situation.
If the approach were invariably "just buy a replacement part" then it would be pretty boring, and not really very helpful at all.

We could extend it to 'just go to a furniture shop' and dispense with most of the forum

 

[jetsetwilly]

To turn the end of your threaded rod you will need to protect the threads from the jaws of the chuck. Best to use a four jaw independent chuck if possible.
Then get a suitable length of copper plumbing pipe and split it with a hacksaw to make a copper sleeve for your threaded rod. This will protect the thread when you tighten the jaws.
Reason for the four jaw chuck is that you want any machined section on the end of the thread to be concentric.
Most videos etc will show setting up a four jaw chuck using a dial gauge. Ideal, but not strictly necessary. You can do it by just putting a piece of rod in the toolpost, with the end ground to a point like a pencil. Bring it up to the workpiece and adjust the jaws until your pointer is at the same distance all the way around as you spin the chuck. You can move the pointer in a bit at a time as your clearance gets finer. Useful to put a sheet of white paper under the chuck while you are doing it so everything can be seen more clearly.
Most three jaw auto chucks don't hold the work sufficiently accurately, unless you spend loads of money on a very high quality one.
You will enjoy yourself, and learn new skills.

Thanks, I def will need the concentricity if I'm machining over 3/4 because that's the bore of the lathe So far though I've only managed to roughly level it and get the blasted b*ggering drive belt threaded (it had to be split to get in the cellar - or Tool Room as I'm now calling it). I think there might be some soft jaws somewhere, but split pipe is a much easier solution, thanks.