At a guess, it is merely pressed in. You should measure both ends just in case there is a shoulder, otherwise some sort of puller should be made, or use a press if you have one. If you are still concerned about the possibility of it being screwed in, then either turn up a piece of metal that just fits the bore nicely, with an end the same size as the interface between the bronze and cast iron. That would prove the presence or absence of a thread. You could also measure the interface diameter at several angles to see if it is round or not.

Hi Andy , Your insert is so close to the bottom of your cross slide ,Just like mine was at the top which was why I made my replacement the way I did fear of breaking the top of my cross slide , Yours very little room to play with i will watch this operation of yours with interest. I wonder if this has just been pressed in does not like this could have been screwed in . Before i had a lathe. I had a small pulley made for a motor when collected was told this will not fit your motor shaft . Put the motor in the freezer for 24 Hrs Then push the pulley on do not use for 24 Hrs . This I did and it ran for years without any further problem the machine was eventually scrapped with the motor still OK

Good luck Brian

You mention the deep recessing of the other end, I would then expect any threads in the cast iron to be visible. The only time I have seen nuts like this in threaded housings is if there are two in the hole and there is backlash adjustment. The Smart & Brown model A tailstock has screwed in nuts to Adjust the backlash. There are slots in the outer nut to turn it.

Edited By old mart on 23/06/2020 20:40:12

If the hole is blind I'd pump it full of grease and wind the screw into it. If it's a through-hole I'd wind the screw right in then punch it out with an aluminium drift against the end of the screw.

Andy,

There is a solution of thread repair by drilling out the original diameter, tapping a larger diameter thread and placing an insert.

If it is allowd to mention trade names:

Helicoil applies an insert which is some kind of shaped wire that follows the new tapped thread.

Time-Sert applies a thin walled solid insert of which internal thread and external thread have the same pitch.

The latter seems to me more suitable for thread repair where the spindle has to move more or less freely.

Thread for spark plugs is often repaired with the Time-Sert or equivalent solution.

You need special tooling to place the insert and there is also a tool to replace an insert which means that, once you tapped the larger diameter thread, you can easily replace the insert when it is worn.

I have not seen inserts made from brass or bronze.

I have thought of repairing the thread for the spindle in my Emco Compact 5 saddle with a Time-Sert insert.

Edited By Jouke van der Veen on 23/06/2020 21:52:01

Edited By Jouke van der Veen on 23/06/2020 21:56:07

Just some guesses!

As the thread takes a fair amount of stress as the saddle is worked, I believe it must be well fixed. I don't think there's enough room for another thread. So I suspect a shrink fit, ie a tight insert was forced into a hot saddle sized to give a really strong friction grip when the saddle cooled down. In which case it will have to be bored out.

Another possibility is age related corrosion. This can be better than superglue, and the grub-screw being damaged removing it could be a clue! Heat cycling is a good way of breaking gunged up joints, plus penetrating oil.

I suspect the grub-screw is a crude backlash adjuster, not a fixing. As the insert wears, the grub might be tightened to crush the insert down on the leadscrew. If so, the deformation would also make it hard to get the insert out.

Dave

Edited By SillyOldDuffer on 24/06/2020 09:19:55

The edge of the casting adjacent to the bush at the 10:00 to 11:00 position looks like it is proud of the surface like the start of a thread being pushed out. This might mean it is threaded. As this is a spare I'd suggest a semi-destructive investigation. If you have a mill start to cut away the end of the bush at it's thickest point. Use an end mill bigger than the thickness of the bush but less than half th diameter. It should be obvious if there is a thread as ou will hit cast iron. A drill or even slitting at an angle with a hacksaw blade (with the height reduced by grinding) would also do.
When removing by whatever method, applicatin of heat will help a lot. A paint stripping type hot air gun is a useful heat source and safer than an open flame.

Robert G8RPI.

While heat cycling may loosen crud in the joint it requires cooling to loosen the insert – yellow metals have a considerably higher ceoff. of exp. than cast iron. I expect, if it were shrink fitted, it would likely drop out if immersed in liquid nitrogen.🙂