Qc-54 Spindle Gear Question

cdhknives

cdhknives

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The larger of the 2 gears on my headstock floats L-R a bit on the spindle. Eventually it moves far enough away from the cone pulley that the direct drive pin pops out. I can worry it back against the 4 step cone pulley and all is well for a few weeks.

There is a set screw on this gear. When I tighten it down, the spindle locks up. Back gears do NOT need to be engaged for this to occur. Should this set screw be left loose or is there something else going on? I know about the cone pulley oiler...this is NOT that set screw. This is on the right side of the larger headstock gear, the same gear with the direct drive pin.
 
cdhknives said:
The larger of the 2 gears on my headstock floats L-R a bit on the spindle. Eventually it moves far enough away from the cone pulley that the direct drive pin pops out. I can worry it back against the 4 step cone pulley and all is well for a few weeks.

There is a set screw on this gear. When I tighten it down, the spindle locks up. Back gears do NOT need to be engaged for this to occur. Should this set screw be left loose or is there something else going on? I know about the cone pulley oiler...this is NOT that set screw. This is on the right side of the larger headstock gear, the same gear with the direct drive pin.
Click to expand...

The larger of the two gears on the spindle is the bull gear. This is where rotational force is transmitted to the spindle through a Woodruff key. The bull gear gets rotational force either via the internal pin that locks it to the cone pulley (back gears dis-engaged) or via the back gears engages with the pin pulled back to dis-engage the cone pulley. The set screw to which you refer should be snugged up tight to keep the bull gear in position so it won't wiggle back away from the cone pulley. Tightening the set screw should have no effect on the spindle rotating in the bearings. If tightening this set screw prevents the spindle from rotating with the back gears dis-engaged then there is some hidden problem and removal of the spindle is in order.

Spiral_Chips
 
I concur. The set screw should be tight, I think on top of the Woodruff key. I can't imagine why tightening that screw could lock the spindle. Try tightening it and then confirm that you can spin the back gears.
 
I'm going to assume the woodruff key is broke or
Missing if your having this issue. And the small gear opposite the bull gear is transmitting all the load.


Sent from my iPhone using Tapatalk
 
I worried it a bit more last night. First I used the tip of a screwdriver to hold the spacing between the bull gear and the cone pulley as I tightened the bull gear set screw. The screwdriver tip ended up hard pinched between them. I then moved the bull gear about 1/4" away form the cone pulley and tightened the set screw and it all works as it should.

I think I have a divot or similar where the set screw is drawing the bull gear tight against the cone pulley. If I use something to space the bull gear well away form the cone pulley it seems to work fine...but that gap adds to stress on the direct drive pin.

Should I live with the gap between the bull gear and the cone pulley or try to fix it so I can properly locate the bull gear next to the cone pulley without them jamming hard together?
 
I went out and fiddled with the spindle and components in my 12" and need an answer to a couple of questions. When you say that the spindle locks up if you position the bull gear up next to the cone pulley and tighten the set screw in the bull gear, do you mean that you cannot turn the spindle at all, including the cone pulley and spindle belt, even with the direct drive pin pulled fully out? Or that with the pin pulled out, you cannot turn the spindle without also turning the cone pulley and spindle belt?
 
It appears to be locking the bull gear against the pulley...pin in or out it is locked together. I seemed to recall it locked the entire spindle but when I went out a couple of days ago to reproduce it I could only reproduce the bull gear locking to the pulley with pin out. I think there might have been a burr hanging up that I forced out...but the one problem remains. I have to set a significant gap or the bull gear locks to the cone pulley when I tighten the set screw.
 
OK. You can't run the lathe for very long with the set screw loose. You will wear out several things. If the set screw has in fact raised a burr, your only permanent solution will be to pull the spindle and remove the burr. Depending upon the shape and origin of the burr, a little hammer work may be desirable before filing off the remainder. For a temporary fix if you need to use back gear before you are going to have time to pull the spindle, check the clearance between the collar to the left of the small spindle gear. If there is some, re-tighten the bull gear set screw. Loosen the two set screws in the collar and rotate it about 15 or 20, deg. Re-tighten the set screws in the collar. Confirm that there is still a little clearance between the collar and the dust cover. If so, you should be able to use it.
 
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