Gib strip problem with Sharp mill

[chrismacParticipant @chrismac]

I recently bought a Sharp mill (No 706 by Town Bent Eng Co, so after 1985).   See lathes.co.uk.  Most things are well except for the gib strip (really a block) on the vertical slide.    It can be adjusted so that upward movement is fine but when the direction is changed to downward the gib strip moves upwards and jams.

The allen screws clamping the strip go into deep sockets in the strip but are not a tight vertical fit.  I can see how to remove the table to get it out of the way but what is then the best way of separating the knee from its vertical feed?   Should I support the cast part with a block of wood then unbolt the feed assembly from the knee and wind it down out of the way?

I attach pictures.

Thanks for any help, Chris

[JohnFParticipant @johnf59703]

Chris, first observations are that the Allen screws for Gib adjustment on the knee may not be original so I would check the shape & dimensions of the ends compared to the ones in the table gib [grub screws ]  It may be that the part touching the gib is wrong thus allowing movement ?

I can see on some of the photos on the lathes web site they too have standard cap screws but ???

Other than that its a strip down to see whats going on!  Separating the knee no idea but first I would remove the table which will probably reveal the knee adjustment arrangement then go from there.

John

[Chris GunnParticipant @chrisgunn36534]

John may well have the answer if the screws are not original or the holes are worn, my Bridgeport has a vertical screw as well, which is also adjustable, to maintain the gib in the same position vertically. Looking at the pictures there is plenty of meat in the gib to add such a feature to your machine if the problem cannot be solved by matching the adjusting screws to the holes in the gib.

Chris Gunn

[Dave HalfordParticipant @davehalford22513]

The dovetails look very dry in the photo.

You can remove the Gib by removing the adjusters and clamp bolt. Wiggle the knee gently and the Gib should drop out.

Yours seems to match the later Town Bent version.

[chrismacParticipant @chrismac]

Thanks for your replies.

I’d had a look at just releasing the gib.  Removing the allen screw adjusters does not release the strips, even if it did and they dropped out I would be left with a knee plus attachments no longer retained by its slides but just balanced on its feed screw, no go.

In the end I removed the table and cross slide which allowed me to clean and lubricate them.them.  I could not shift the allen screws holding the vertical feed to the underside of the knee so had to release the head to column locating pins and three of the bolts then turn it around a little to get the horizontal spindle out of the way so that the knee plus its feed screw could be lifted off the top of the slides.   Once off and inverted I could release the allen screws holding the feed assembly to the knee.

The main problem was swarf all around and under the gib strips.  The two allen screws which hold the strips to the knee and should allow some movement when adjustments are made were very loose and the bottom of their sockets not perfectly flat so the strips moved as the direction of travel changed hence the jamming.   Once cleaned up, fitted correctly, lubricated and replaced the action is good.   There is just some increase in tightness right at the bottom of the travel.

Thanks again for your help, Chris

[Author]

Posts