Control Sheave Question

[algale]

What holds the control sheave (110) on the idler shaft (105) on a Mark V 520? I know a woodruff key prevents the control sheave from rotating on the idler shaft, but what prevents the control sheave from sliding off the front end of the idler shaft (if the porkchop is disconnected and the speed control is removed)? On mine, apparently nothing does.

Background: yesterday as I ran the speed control back down to slow, it went past slow to the fast position. This had never happened before so I assumed something was wonky.

This morning, I removed the speed control, which checked out fine. After reinstalling things, I went to turn it on and nothing happened. I decided to a remove the speed control again and noticed the the belt was running too low in the control sheaves. I decided to see if the control sheave was moving freely and is it ever. In fact, it slid right off the end of the idler shaft. I did not notice any obvious damage, although the woodruff key is about an 1/8 of an inch short of the end of the idler shaft as seen in the photo.

[ATTACH]20615[/ATTACH]
Normal or abnormal? Is there a set screw missing? I dropped the motor pan and found no stray parts.

[dusty]

What holds the control sheave (110) on the idler shaft (105) on a Mark V 520? I know a woodruff key prevents the control sheave from rotating on the idler shaft, but what prevents the control sheave from sliding off the front end of the idler shaft (if the porkchop is disconnected and the speed control is removed)? On mine, apparently nothing does.

Background: yesterday as I ran the speed control back down to slow, it went past slow to the fast position. This had never happened before so I assumed something was wonky.

This morning, I removed the speed control, which checked out fine. After reinstalling things, I went to turn it on and nothing happened. I decided to a remove the speed control again and noticed the the belt was running too low in the control sheaves. I decided to see if the control sheave was moving freely and is it ever. In fact, it slid right off the end of the idler shaft. I did not notice any obvious damage, although the woodruff key is about an 1/8 of an inch short of the end of the idler shaft as seen in the photo.

[ATTACH]20615[/ATTACH]
Normal or abnormal? Is there a set screw missing? I dropped the motor pan and found no stray parts.

As I advance into "old age" my memory gets shorter and shorter but I think nothing. I'll go check. I also do believe that the woodruff key is properly located. I'll check that while I am there.

When fully assembled, the belt would deter excess movement in that direction. I think. No it won't! If anything the belt pushes the sheave in that direction as it opens up with the porkchop pulling on it.

PS I don't believe you have anything wrong with the sheave or the woodruff. With the speed control mechanism removed and the drive belt removed or loose, the control sheave will slide right off the end of the shaft.

When you go to put everything back together, I suggest that you locate the drive belt on the control sheave but do not put it on the motor pulley until after you have the speed control reassembled in the headstock. The belt will tend to get down too deep in the pulley (because the sheave is unrestricted) and it can be a bear to get back out.

[beeg]

Sounds like ya might want to start with a high speed adjustment. Look here for a how to.

http://www.shopsmith.net/forums/showpos ... ostcount=2

[algale]

As I advance into "old age" my memory gets shorter and shorter but I think nothing. I'll go check. I also do believe that the woodruff key is properly located. I'll check that while I am there.

When fully assembled, the belt would deter excess movement in that direction. I think. No it won't! If anything the belt pushes the sheave in that direction as it opens up with the porkchop pulling on it.

PS I don't believe you have anything wrong with the sheave or the woodruff. With the speed control mechanism removed and the drive belt removed or loose, the control sheave will slide right off the end of the shaft.

When you go to put everything back together, I suggest that you locate the drive belt on the control sheave but do not put it on the motor pulley until after you have the speed control reassembled in the headstock. The belt will tend to get down too deep in the pulley (because the sheave is unrestricted) and it can be a bear to get back out.

Very helpful as always, Dusty.

[algale]

Sounds like ya might want to start with a high speed adjustment. Look here for a how to.

http://www.shopsmith.net/forums/showpos ... ostcount=2

Yup. In fact that was what I was about to do when the control sheave slipped off. Now that I've dropped the motor I'm going to check the poly v tension too.

[dusty]

Yup. In fact that was what I was about to do when the control sheave slipped off. Now that I've dropped the motor I'm going to check the poly v tension too.

While it is all opened it would also be a good time to blow it out and lube everything that needs to be lubed including the porkchop. The porkchop I find difficult to lub well through the inspecton port.

[algale]

While it is all opened it would also be a good time to blow it out and lube everything that needs to be lubed including the porkchop. The porkchop I find difficult to lub well through the inspecton port.

Yes. I cleaned off the old lithium grease and am debating going with graphite. Anyone had good results with graphite?

[billmayo]

If you have the speed control assembly removed from the headstock, I recommend replacing the quadrant roll pin with a #10-32 X 2 1/2" allen head bolt, 2 star washers and a nylock nut. Contact me for a free bolt kit. I will need a mailing address. I have an instruction file for this that also covers the initial high speed adjustment. I need an Email address to send the instructions. Over 300 of these bolt kits have been installed in the past 8 years without any failures noted.

[algale]

If you have the speed control assembly removed from the headstock, I recommend replacing the quadrant roll pin with a #10-32 X 2 1/2" allen head bolt, 2 star washers and a nylock nut. Contact me for a free bolt kit. I will need a mailing address. I have an instruction file for this that also covers the initial high speed adjustment. I need an Email address to send the instructions. Over 300 of these bolt kits have been installed in the past 8 years without any failures noted.

Bill, I've already done that quadrant repair/replacement thanks to you.

After a few false starts I also think I've got the high speed set correctly.

The last thing I think I need to do is to tension the poly v because I think I've got more than 1/8th inch deflection when I push on it. I have been reviewing posts on tension the poly v and watched the sawdust session. Most of the instructions and the sawdust session show how to remove and replace the poly v, not just tension it.

If I only want to tension the poly v, do I need to run it up to high speed and remove the drive belt from the motor sheaves before I adjust the eccentric?

Al

[JPG]

The quadrant gear(porkchop) is what prevents the control sheave from moving off the shaft. Ideally the button is (almost)always pressing against the porkchop.

The idler shaft is a keyed shaft, but it is not a 'woodruff' key.(they be 'half moon' shaped and the keyway has a round 'bottom').

By all means leave the motor belt off the pulley until last.

The poly-v tension is adjusted with all belts installed. If the poly-v belt is not slipping, leave it alone!(If it ain't broke, do not fix it;))

Motor belt wear will affect the 'range' on the outer dial. The position of the belt on the motor pulley will also affect that.(same reason)

Since you set the dial to 'fast' after the HS adjustment, the amount of dial movement as the speed is adjusted to 'slow' will be determined by the control sheave 'bottoming out' against the idler sheave. Actual low speed change is limited by the belt bottoming out in the motor pulley.