Back Gear selection on smart and brown lathe When I momodelA mark 1

[john walker 5Participant @johnwalker5]

With the lathe stopped I engage The out position on the back gear selector lever but when I then try and restart the machine the spindle won’t turn. Return the lever to the in position and the spindle  turns . I don’t know what to do I am a novice and any help would be appreciated

Thank You

John W 

[john walker 5Participant @johnwalker5]

[John OlsenParticipant @johnolsen79199]

Usually with a back gear there are two things to do to engage it.

 

One is that you move the actual gears into engagement…that will usually be something like a lever with two positions, and will be the one you have been trying.

 

The second thing is that you must disengage the direct drive on the spindle from the drive pulley to the spindle. I don’t know the Brown and Smart, but for example on my Myford ML7 there is a small allan screw on the bull gear of the back gear. That screw has to be loosened and moved radially outward. That disengages a little drive dog between that gear and a smaller gear that is attached to the pulley. So the pulley turns on the spindle, drives the small gear, that drives a large gear on the backgear shaft, the small gear on the backgear shaft drives the bull gear on the main spindle, and the main spindle goes around slower than normal. Depending on accessability, you might be able to see how it is done on your lathe.

 

If you don’t disengage the normal drive on the spindle, when you engage backgear it will lock the spindle. This is sometimes used as a way of locking the spindle, but be cautious with it as using it to get a stuck chuck off will put a very big load on the gears.

 

Hope this helps.

 

regards

John

[Dinosaur EngineerParticipant @dinosaurengineer]

I strongly recommend that you join the “smart_and_brown_lathes” group on “Yahoo! groups”. There are lathe manuals, operating instructions, etc for most Smart & Brown lathes on this site. I’m not familar with the model A but do have a S and B 1024 roundhead. There will be group members who have Model “A”s who I’m sure will be happy to help.

Good choice of lathe ! 

[john walker 5Participant @johnwalker5]

Thank You I’ve got it sorted now

John Walker 

[Author]

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