Thread: BONHAM SC assembly advice please

Well Richard, seeing no one has answered, I will have a go. This is going to be long winded. I have not seen a Bonham chuck, but they are all similar except on some the scroll goes the opposite direction. Pull the chuck apart and lay the scroll down with the grooves upwards. Then place all the jaws into the grooves and keep rearranging them until they touch each other in a circle at the closed up position.
Call this ACW. If the groove in the scroll goes inwards when rotated anticlockwise, mark the jaws 1 to 4 anticlockwise with a felt pen, it is not critical which is number 1 at this stage.
Call this CW. If the scroll goes clockwise, reverse these instructions.
Clean the chuck, I give mine a lick of heavy moly grease, that bit is up to you. Reassemble the chuck, mark one of the jaw slides with a heavy dot with a felt pen and while looking into it if it is ACW, rotate the scroll ACW until you see the lead in of the scroll thread, reverse it slightly and insert jaw number 1. Keep rotating the scroll ACW and when you see the lead in of the scroll in the next slide insert jaw number 2. Keep doing all 4. If they don't contract into the correct shape of a circle remove them all, go back to the marked slide and start with jaw number 2, then 3, 4 then 1. You may have to do this 3 times till you get the correct jaw to start, but it will work.
If its CW, do all this the other direction.
When you get it to work you can mark the slide you marked with the felt pen with a small center punch mark or engrave it number 1 and then do the jaw as well and then all the others in the correct order and direction.
Hope this helps.
Rgds,
Crocy.

Well Richard, I don't see how you could go wrong with Croc's detailed instructions. I did it that way with a Nova G3 once, and also with a large machinist chuck once. ........ After you figure out #1, it's a piece of cake from there. ............ Jerry (in Tucson)USA

The jaws and slides on most scroll chucks are typically numbered. If the Bonham slides and jaws aren't its a good idea to mark them for future reassembly. Simply use a centre punch and stamp 1, 2 , 3 & 4 small spots on each jaw face and slide end face.

Scroll Chucks and Their Maintenance AAW - 29.3 p20–23.pdf

Hope this helps

Many thanks to Crock and Mobyturns for your assistance and the printed article ( that will go into the Mens shed maintenance handbook )
Luckly the slides and jaws are numbered - looks like at time of manufacture. I have had the slides scroll into the centre BUT when the jaws are mounted at least 1 does not match as the slides need to be wound back to allow for the greater diameter needed.
Tried starting the CW scroll into the slides from each number - again 1 usually does not mate.
Now with the printed word and another dose of patience, I will have another go - The good thing is the scroll is in good condition as are the slides & jaws. Will need a new stop pin & some dry lube.

Thanks again - an interesting learning curve that is for sure

Richard

Rob McKee gave me the handy tip on removing a set screw with a damaged socket, unfortunately his credit was edited out of the final article.

Originally Posted by UPO

Morning All - I have a Bonhan SC that I have been asked to re-assemble correctly - someone it would seem has unwound the scroll and when replacing the jaws has missed the sequence and 1 is out of sequence / place. At one stage I had 3 jaws correct !! Anyone have either advice as sequence to start the scroll or a handbook ?

Before asking - No one has attempted to mount that chuck AFAK , just found it in the back of a shed drawer, so the fix is to ensure no disaster happens and regain a usable chuck. Also what is used for the stop pin ? seems too small diameter for a thole pin ?

Many thanks

Richard
PS - I did a search on Bonham and quite a few references but none about re-assembly - maybe no one has tapped the stop pin down far enough to unwind fully

One flaw of the Bonham chuck is no stop screw to stop it happening..
I have not been on here in a long while,
Have you got it sorted