Smart & Brown Sabel belt replacement Pt.2

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I offer this advice for owners of 'Sabel' lathes only and using your own manual skills and intelligence to avoid injury and damage. Since I cannot supervise your work I accept no responsibility for your own actions. I am always happy to advise with this gentle warning clearly in mind. NO force is required to accomplish anything during dismantling and reassembly.

Part 2: A request for advice on fitting a new continuous belt to a S&B 'Sabel' lathe required rather more room than I could easily add to the already long, original post on linked belts. See next Older Post. [and next NEW Post for Pt.3]

http://fullerscopes.blogspot.dk/2016/01/my-smart-brown-sabel-lathe-images.html

NOTE: YOU CANNOT USE A NuTLink LINKED BELT ON THE S&B 'SABEL'. [As seen in these images] There is not remotely enough room in the headstock casting below the iron pulleys. It will fit on one pulley but is then impossible to change gear on the pulleys. The NuTLink is considerable oversized [and expensive] compared with a standard 13mm wide 'A' belt. I understand the NuTLink WILL fit on some Boxford lathes.

After struggling endlessly with the linked belt I bought a normal "A" size [13mm wide] replacement belt from a local car spares shop. These were available in a wide range of lengths in small increments. I chose one of 1325cm after measuring the circumference of the linked belt with a cloth tape measure. Remember to measure on the same pulley size if you want to double check your own lathe.

Another reason not to use linked belts: They rub away the pulley cover speed plate inside the hinged headstock cover. I was lucky to avoid this problem. Sorry about the quality of the image. Dark and flash caused flare and the overhead lights didn't help.

NOTE: that belt this size may not match your own layshaft:headstock spacing depending whether you have the S&B cabinet stand and/or a different layshaft placement.

Removal of the pulley layshaft is very easy.
The bearing are plain bronze bushes with nothing loose to fall out. Make sure there is no belt tension first. The large lever on the right pulls forward to remove belt tension for easy gear changing. There is a screwed belt tensioner just behind the lever. Pull the lever forwards before trying to adjust tension. Turn the adjuster and then push the lever back again to check the tension. I adjust the belt tension so that the lathe can run up to the highest speeds in a couple of seconds.

Then undo the grub screw [arrowed] on the small end of the alloy pulleys, just enough to withdraw the large pulleys to the left taking the shaft with them.

Once the multiple pulleys are free you can thread your new belt around them. Then replace the shaft by pushing it back in to the right. You may choose the dismantling moment to clean the pulleys and support casting. Re-tighten the grub screw and that part is finished.

The headstock is more complicated.

NOTE: I usually leave the small 3-jaw chuck in place to balance the headstock shaft and heavy iron pulleys. I just find this easier than struggling with the bare shaft. You may not agree but you can't easily change your mind half way through the job.

Undo the two screws arrowed and remove the small tumbler gear cover.

Once the tumbler gears are exposed you will see a split lock ring with a cross screw. Loosen and remove the locking screw with a good screwdriver to avoid damage to the slotted head.

The locking ring has a fine thread but this is cut deliberately tight on the headstock shaft.

You need to insert a wedge gently into the split to free the locking ring just enough to allow it to be undone. I use a slow tapered screwdriver as a lever in the split and turn the chuck by hand to unwind the locking ring.

Once the ring has been removed the headstock shaft can be withdrawn in the direction of the chuck.

Note that the iron pulleys are quite heavy and also keyed to the headstock shaft. Replacement can be fiddly.

NOTE: There are two SPRUNG felt oilers underneath the headstock shaft within the plain headstock bearings. DO NOT damage these when replacing the stepped headstock shaft.

DO NOT TOUCH the large bearing clamping screws. It is completely unnecessary and will undo any former careful adjustment for headstock play. YOU HAVE BEEN WARNED.

The back gear shaft is held with a cross pin. Use a punch to remove the pin then wiggle the back gear knob to withdraw the back gear shaft.

NOTE: The back gear shaft is held in eccentric bushes at both ends. These must be replaced in the correct rotation relative to each other to ensure the back gear will move correctly in its eccentric bushes when the knob is withdrawn and rotated. DO NOT be in a hurry to replace the tapered pin until the shaft moves back and forth correctly as the back gear knob is pulled out and turned.The pin on the inner face of the back gear knob is the location device for each position in its rotation.

Click on any image for an enlargement.

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