Thread: Shaft protection.

Hi Guys,

Whilst I remember, a trick that I use to stop grub screws from raising burrs on a shaft is to insert a pellet of rubber or plastic in the hole first, though I have been known to make all brass grub screws.

The clever bit to making the pellets is to use the rotating head leather punch, the one that looks like a pair of pliers. For plastic pellets I use the plastic tape used to secure bricks onto pallets. The leather punch will make pellets from 2.5 mm to 6 mm diameter.

I like the leather punch idea. When I tried plastic I found it didn't grip very well, but found copper plugs does. The copper conforms to the shaft under less pressure than brass and seems to sort of half gall itself onto a clean shaft but it doesn't stick so much as to prevent removal. I cut and flatten out pieces of copper pipe and then use a hole punch. By then the Cu may have work hardened so a spot of annealing seems to further increase the grip.

Originally Posted by BobL

I like the leather punch idea. When I tried plastic I found it didn't grip very well, but found copper plugs sis. The copper conforms to the shaft under less pressure than brass and seems to sort of half gall itself onto a clean shaft but it doesn't stick so much as to prevent removal. I cut and flatten out pieces of copper pipe and then use a hole punch. By then the Cu may have work hardened so a spot of annealing seems to further increase the grip.

Good info from Baron as well as you Bob. I usually find a bit of brass the right diameter, or turn it down and cut it off. Fiddly with M6. I pulled the cross slide handle, dial and mount off my lathe recently. I don't remember why. The thrust is adjusted by an internally threaded cylinder that locks on the thread of the shaft with a grub screw. When I got the lathe there was nothing under the screw. I had to take it all off to undo it in the vice because of damaged threads. I then fitted a brass pellet.

When I pulled it apart recently, I dropped the brass pellet of course. I made up a new one. Whilst trying to fit it I naturally dropped the grub screw. In both cases I could not find them. They could have fallen down the cracks in the floor. I should finish caulking these. The dial has a close fit over this cylinder so the grub screw and pellet had to fit in a small depth. Fiddly like I said, grinding both to length.

One thing that comes to mind is the question of what to do with the grub screw when using pellets like these. Most have a contact ring, some have a point. I usually grind/machine the end flat. With plastic or rubber what is the chance that there will still be a mark due to cutting of the pellet etc?

I have watched Chris on "The Old Mans Shop" put epoxy on the end of a grub screw or bolt to protect the shaft underneath. I don't think this is a good idea.

I will try using copper plugs in future. I have some wad punches. This will be quicker and will allow more length for the grub screw in tight spaces.

Dean

Hi Guys,

It hadn't occurred to me that I could use a copper pellet in the same way.
As far a grub screw ends are concerned, most of the ones that I have are serrated on the nose, but a few are hollow cups. I tend to avoid using these because they do cut through thin rubber and plastic.

I'm building a single flute cutter grinder at the moment (a build thread will come when I have something to show).
It involves several clamping screws and hardened and soft shafts they clamp onto.
What are the views of this group about soft soldering copper pads to the tips of set screws (in my case screws with handles)? I figure I could then turn them on the lathe to the exact size I want and face them flat. Any reasons to leave them loose?

Joe , Could you drill the screw and press a short brass or copper slug into it, using loctite if necessary? It may need a carbide drill if you are using Unbraco or similar spec set screws, I don't know, (but I suspect an HSSCo drill bit would do it.) An, alternative may be to build a pad with silver solder on the business end of your set screw, and just face that off if you are concerned that soft solder might not cut the mustard. Good luck with it anyway whatever method you go with.
Rob.

I like both your ideas! I might try them both and report back.
Not sure if silver solder is 'compliant' enough to hold against a hardened shaft.... we'll see.
Thank you!

Originally Posted by jhovel

Any reasons to leave them loose?

Yes. The face in contact with the shaft trys to take the shape of the shaft. If its fixed to the bolt it cant.

Stuart

* tablet answer

Originally Posted by jhovel

I like both your ideas! I might try them both and report back.
Not sure if silver solder is 'compliant' enough to hold against a hardened shaft.... we'll see.
Thank you!

Hi Joe,

With reference to solder, have you noticed how it forms little balls when it drips off the work. If they are too big a few taps with a hammer, then drop one into the hole.

Originally Posted by Stustoys

Yes. The face in contact with the shaft trys to take the shape of the shaft. If its fixed to the bolt it cant.

Stuart

* tablet answer

Right, Stu, I hadn't thought of that. So on shaft, that's not a good idea - probably less of an issue on a smooth flat surface that's at right angles to the screw. I'll reconsider when I start assembly.....
Thanks!

Barron, that's a good idea for getting the right shape. Ta!

One thing though if you use a thinish soft loose plug. There may come a day when they don't work so well as they have extruded into the thread of the hole. You then need to be able to drill them out and possibly run a tap through the hole to clear the threads. Something to think about if disassembly will take some time. If you have the hole depth, maybe a longer steel plug with the correct radius into the end?

Stuart

Only thing that occurred to me is where the plug can fall. If it is a machine or casting etc, as long as the loose plug can't fall into a cavity when the shaft is removed.

On a related matter, a tip shown to me by an elderly mechanic is when there is a possibility that two steel surfaces will rust together then painting one or both surfaces with a strong copper sulphate solution will auto precipitate a thin metallic copper film on the surfaces which prevents them from binding together.

This comes in really handy when steel grub screws are used in steel pulleys/shafts etc especially in corrosive environments. Having bent and broken my fair share of hex keys on such recalcitrant buggers I remember this tip every time this happens. I clean the oil etc off the grub screws and then thrown them in a jar of CuSO4 for a few minutes.

I have also used this when mounting automotive wheel brake discs into wheel hubs. There are lots of other situations where this is useful.

Read somewhere that the brass screws from electrical appliances/plugs and sockets make good plugs. Just a matter of drilling the grub screw with a hole just under the size of the thread, and when it's tightened up, the screw is pushed up inside the grub screw, making dismantling a breeze as the brass comes out with the screw.
Kryn