Smart & Brown Sabel belt replacement Pt.3

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To allow more room for more images without causing slow loading I have added a third part to this series on the 'Sabel' lathe.

I have taken more images with the lathe headstock partially dismantled. I also wanted to be sure I hadn't forgotten anything since I changed the belts back in January. Now some nine months ago.

The first image shows the compete headstock shaft withdrawn after removing the threaded locking collar at the far end. [see last post for details of removing the collar screw and unwinding the split locking collar]

Note the two shoulders which will make replacement seem far more difficult.

Force is NOT required to replace the shaft. It requires that each end of the shaft is lifted to allow the two shoulders to slide through the intermediate components and headstock bearings.


The next image shows the felt oiler for the front, plain headstock bearing. The lower end of the felt sits in a reservoir of oil filled when each of the knurled plugs is removed.

The ends of each of the bearings in the casting has an oil catcher rim and drain hole for oil which leaks out from the bearing. I cleaned these before replacing the shaft. Note the white metal bearing liner with lubrication slots.

The iron headstock pulleys and back gear removed from the headstock.

Note the click spring for the back gear engage/disengage button. The button is normally pressed home to the left. When the back gear is engaged the button must be pulled out to free this gear to rotate in mesh with the back gear layshaft gears. Otherwise the headstock will be locked up solid.

A close up of the key in the headstock shaft. This key engages with the large [back gear] gear shown above. Normally the large iron back gear rotates with the main shaft without touching the teeth of gear on the back gear lay shaft. Only when the button is pulled out and the back gear knob rotated, will the back gears be engaged in mesh with each other.

Oil the complete shaft well before reassembly in the headstock.

The lower end of back gear layshaft pin is exposed by rotating the back gear knob completely. [as shown] This tapered pin must be tapped out from the underside of its normal position to free the back gear shaft. I like to use a small riveting punch with a spherical hollow in the tip to avoid mushrooming the tapered pin. There is no need for a big hammer nor any force. If the pin won't come out easily then check you aren't trying to drive it further in from the wrong end.

Both back gear eccentric bushes must be aligned with each other to allow the back gear knob to operate the backwards and forwards movement to engage and disengage back gear.

The inside of the headstock casting showing the smaller, plain, headstock bearing on the left.

When reassembling the headstock shaft it will feel as if it will not go back in. The shaft must be raised at both ends for its steps to enter the main bearings.

Note that the 3 components of the linear thrust bearing must be slipped onto the tip of the shaft just before it can be passed through the left headstock bearing. The three parts want to face each other in the same way as original to avoid causing problems. Just look for the wear tracks and arrange the rings and central ball bearing race the same way. I lay the big iron gear, the iron pulleys and the linear thrust bearing in the headstock casting before re-inserting the shaft. If you had the patience they could be packed up to their correct height. Though you'd have to be able to remove the packing once the shaft is safely back in place.

Remember that the threaded locking collar must also be slipped over the tip of the shaft just before it passes the tumbler gears. The tumbler gears can be removed but it is much easier to leave them in place to avoid extra and unnecessary work. The white washer is PTFE low friction plastic. It goes behind the collar against the headstock casting.

It feels like a real fiddle to get the headstock shaft back in but it is only a matter of patience lifting each end in turn. It must obviously be  parallel with the lathe bed to go in smoothly. Try rotating the shaft back and forth as you push the shaft gently to the left to allow the key to find the slot in the large iron gear. I can assure you that absolutely NO force is necessary to get the headstock shaft back in. Just try lifting the iron pulleys, the large iron back gear and the linear thrust bearings in turn to allow the shaft steps to pass each hurdle. Three hands may seem useful but are strictly unnecessary. I removed the rear belt shield for the photographs. You may find it helps as long as you remember to thread the belt through it or you will have to start completely from scratch!

Disposable rubber gloves are handy when working on dismantling and reassembly of the lathe. The thin rubber aids sensitivity of touch while still protecting the hands from dirt and oil.

Click on any image for an enlargement.

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