SB Heavy 10" Clutch Repair?

Hi! I have an older SB Heavy 10" that has the type of "clutch?" that is engaged by turning a knob. I don't believe that this clutch is working properly because the one time I crashed a tool into a work piece there was no slippage.

If this clutch is not working properly what's involved in its repair and how difficult would it be to repair it (would the saddle have to come off the leade screw, etc.)?

Thanks so much for the advice!

Hepburnman

How it looks with apron off. Fairly easy to see "knob" works a multiple disc clutch - which I suppose (?) runs in a puddle of oil

Scan from Catalog 100-F which is from August 1946

You'll have to remove the apron, but not necessarily the saddle. The apron is held on to the saddle with some large screws from the top. You can remove the lead screw support on the tail stock end and slide the apron off the lead screw. Be careful, as you will want to support the apron to keep from bending the lead screw once the bearing support is removed.

The knob style clutch is easier to disassemble than the lever type. Search YouTube and you'll find some videos of how they were taken apart and put back together.

It may be that the clutch plates just need to be dressed. I stuck some sandpaper down to my surface plate and, using some oil, lightly dressed each one.

Hi All- Thanks for the replies! Can someone tell me what the "feel" should be like when you tighten the clutch knob? Mine does not feel like you can vary the clutch's torque strength by either lightly tightening the knob, or screwing it in kind of hard. Mine has no tactile feel. It just gets hard real fast, almost like an on-off switch, if that makes sense here.

Thanks again for the replies!

hepburnman said:

Hi! I have an older SB Heavy 10" that has the type of "clutch?" that is engaged by turning a knob. I don't believe that this clutch is working properly because the one time I crashed a tool into a work piece there was no slippage.

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The clutch is not a crash safety . If you crash, you crash.

There's a better chance flat belt will slip if you crash, or dig too deep even.

If the clutch did not slip, its working good. My bitch with a star handle/knob type is it is too hard to creep up on a stop, or feather the clutch a little. Easier with a lever type. The star type grabs, and gets tighter with your hand on it, due to its natural rotation in sync with tightening.

My trick is to leave clutch engaged always. I knock it out of gear from feed engagement lever. This works by pulling and holding spring pin handle prior to bumping stop. As you bump stop, lever is forced to neutral. This only works feeding longitudinal toward chuck, going the other way, not so much.

Crossfeed, i feed by hand if its a question.

hepburnman said:

Hi! I have an older SB Heavy 10" that has the type of "clutch?" that is engaged by turning a knob. I don't believe that this clutch is working properly because the one time I crashed a tool into a work piece there was no slippage.

Click to expand...

That's not how it's supposed to work. Once engaged, the clutch is locked tight. If you want to prevent crashes, pay more attention to what you are doing - do NOT expect the clutch to do the thinking for you. Look at the clutch as being like a car clutch. If a car runs into a tree, does the clutch disengage? Of course, the answer is "no".

If you do decide to take it apart for whatever reason just remember that the screw in the center of the star wheel is left hand threaded.

hepburnman said:

Hi! I have an older SB Heavy 10" that has the type of "clutch?" that is engaged by turning a knob. I don't believe that this clutch is working properly because the one time I crashed a tool into a work piece there was no slippage.

If this clutch is not working properly what's involved in its repair and how difficult would it be to repair it (would the saddle have to come off the leade screw, etc.)?

Thanks so much for the advice!

Hepburnman

Click to expand...

What I don't understand is how do you crash something as slow as a South Bend.....

moonlight machine said:

What I don't understand is how do you crash something as slow as a South Bend.....

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You haven't watched me operate a lathe.