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I bought used 1986 Mark V 510. It would run at slow speed only due to idler sheaves frozen on shaft. I broke sheave trying to disassemble and ordered and installed complete replacement idler shaft assembly along with new style eccentric bushing. After cleaning speed control and installing I turn switch on and motor spins a few turns, starts humming, then blows circuit breaker. I recheck tension on poly belt and same thing happens. I disconnect speed control, remove drive belt, turn switch on, and motor runs fine. I have not reinstalled drive belt yet, but am thinking belt may be binding? What else should I be looking for, or is there sawdust session that describes this? thanks, Ed

I assume with the drive belt off that both the motor and the shafts all turn freely.

If so, put the belt back on, but make sure the belt does NOT drop down too far into the idler/control pulley(sheave when in high speed position allows the belt to approach the bottom of the pulley)

It is possible the new eccentric/idler shaft is not inserted far enough into the headstock????. That would cause the belt to drop further!

If you did not oil the fan sheave(motor shaft), do so.

Before turning the motor on, make sure every thing rotates freely.

I also assume you have oiled the control sheave shaft...

I reoiled again, separated motor sheaves by compressing spring to put more slack into belt, and tried powering up again. This time motor stayed on and I was able to turn speed control dial and vary output shaft speed. Finally! I did notice that the porkchop gear teeth are a little rough so that turning the speed dial is also a little stiff. However I was able to go through the full speed range. I am now putting the guards back on and will be trying my first test cuts as a shopsmith owner.
thanks for the advice and wish me luck.

Ed

edcisco wrote:I reoiled again, separated motor sheaves by compressing spring to put more slack into belt, and tried powering up again. This time motor stayed on and I was able to turn speed control dial and vary output shaft speed. Finally! I did notice that the porkchop gear teeth are a little rough so that turning the speed dial is also a little stiff. However I was able to go through the full speed range. I am now putting the guards back on and will be trying my first test cuts as a shopsmith owner.
thanks for the advice and wish me luck.

Ed

Keep in mind that adjusting from a faster speed to a lower speed needs to be done gradually. You must allow time for the control sheave closing that causes the motor sheave to open up(overcome the spring tension). This takes time, and it is possible to adjust it too fast. This puts stress on the porkchop gears. Going up is not a problem since the speed control is opening up the control sheave.

Happy saw dusting!

If you replaced the eccentric bushing, you probably overtightened the housing bolt. Once you adjust the poly-V belt tension, tighten the housing clamp just until the eccentric no longer rotates by itself, then give it maybe a quarter turn to tighten. If you over-tighten the housing down on the eccentric, you will compress the idler shaft bearing and cause the idler shaft to stall with excess friction. This is probably why your breaker blew. If it's running now, you should check it ASAP otherwise you will damage the bearing and possibly the idler shaft.

On my '57 greenie, I was missing the small washer and screw that prevents the eccentric bushing from walking out of the housing under load. I mistakenly overtightened the eccentric housing mount to try to prevent the eccentric bushing from moving, but caused myself excess heat and friction. Make sure you have the retaining washer and screw holding the eccentric into the housing!

cml wrote:If you replaced the eccentric bushing, you probably overtightened the housing bolt. Once you adjust the poly-V belt tension, tighten the housing clamp just until the eccentric no longer rotates by itself, then give it maybe a quarter turn to tighten. If you over-tighten the housing down on the eccentric, you will compress the idler shaft bearing and cause the idler shaft to stall with excess friction. This is probably why your breaker blew. If it's running now, you should check it ASAP otherwise you will damage the bearing and possibly the idler shaft.

On my '57 greenie, I was missing the small washer and screw that prevents the eccentric bushing from walking out of the housing under load. I mistakenly overtightened the eccentric housing mount to try to prevent the eccentric bushing from moving, but caused myself excess heat and friction. Make sure you have the retaining washer and screw holding the eccentric into the housing!

The new style eccentric bushing does NOT have the screw that snugs the water pump bearing into the center bore. It has a double bearing with a spacer.

JPG40504 wrote:The new style eccentric bushing does NOT have the screw that snugs the water pump bearing into the center bore. It has a double bearing with a spacer.

Water pump???

I have a new-style eccentric on a '58. Does the new-style housing no longer have the ears below the eccentric or the threaded hole for the retaining bolt/washer assembly on the outside to prevent the eccentric from walking out?

JPG40504 wrote:The new style eccentric bushing does NOT have the screw that snugs the water pump bearing into the center bore. It has a double bearing with a spacer.

I'm not sure about the water pump bearing. I don't believe I have one of those. Maybe this is just another of those 500 characteristics that I have never seen.

As far as the spacer is concerned, I believe that JPG must be referring to a feature that is provided by the shaft on the newest idler shaft assembly. The two bearings are spaced apart by the shaft itself.

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dusty wrote:I'm not sure about the water pump bearing. I don't believe I have one of those. Maybe this is just another of those 500 characteristics that I have never seen.

As far as the spacer is concerned, I believe that JPG must be referring to a feature that is provided by the shaft on the newest idler shaft assembly. The two bearings are spaced apart by the shaft itself.

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Thank You for these excellent pix. I did not realize the spacing was controlled by the shaft itself(one bearing inserted on shaft from EACH end of the shaft(that eliminates the need to secure a 'spacer').

The 'older' models used a modified water pump bearing as does the lower band saw shaft. I am guessing the water pump bearing is no longer available(radiator fans are no longer mounted to water pump shafts as in the past).

Your pix reveal some important differences between 'old' and 'new'.

1) The bearing is no longer secured in the eccentric bore by that set screw in the side of the eccentric(the one we should not tighten too tightly).

2) The eccentric is 'split' at the narrow portion of the wall. I assume this is to allow a slight squeezing action when the headstock ears are snugged up.

3) Any movement of the bearing towards the exterior end of the eccentric is limited by that NEW screw in the end of the eccentric.

4) Any movement of the eccentric(and bearing) towards the exterior end of the headstock bore is limited by the OLD screw and washer.See #5 for much older models.

5) The original greenie 'retaining clips' should be used if the old screw and washer were never used(originally they were one or the other).See comment below

6) With the new set of parts, I see no limit to inward movement of the eccentric other than the squeeze of the headstock ears, and the force of the belt in the pulley. The control sheave is 'stopped' by the pork chop, and the belt in the v shaped pulley would thus push against the idler sheave which does not move along the shaft. This is the same as with the 'older' set of parts.

The squeeze put on the eccentric by the headstock 'ears' is the same. The screw should be just snugged. Bill Mayo's recommended use of a split lock washer and tightening the screw/nut to just fully compress the lock washer is excellent advice.

Comment: Bill Mayo also recommends drilling and tapping the headstock on earlier models which did not originally have the screw and washer. As has been pointed out elsewhere, the older castings did not have as thick a boss as the more recent models having the screw and washer. I would agree with Bill IF the drilling and tapping can be accomplished accurately so as to not create a weakness in the casting. Otherwise, the original clips DO work when installed correctly. The end with the smaller 'hook' needs to go over the inner end of the eccentric(tis way too easy to get it slipped off inadvertently[check after tightening bolt]) . The clips are loose when installed correctly.

Dusty: I believe the models with the clips did indeed have two clips. I have observed them elsewhere(quite small sample however).