wobbly hubs

[Rob.A.700 306]

I just went through and put new bearings and seals in my 655s transmission, and when I put it back together I got new woodruff keys for the axles. The slots for the woodruff keys were not in bad shape. The channels in the hubs were alittle ruff but nothing I figured would cause a problem when I put the new set screws in. So what happens is now I can tighten the set screw and the hub will tighten up then one rotation or so later the hub seem loose again but the set screw is still tight. Any thoughts? 

[DennisThornton 4,769]

I think you might have some damaged threads and only part of your "tighten up" is going against the shaft and the other part is binding on the threads.  I'd be tempted to pull the hubs back off and run either a tap or the set screws you have completely though to make sure the threads are not causing your problem.  I like LONG set screws too.  Ones that take advantage of ALL the threads so you don't have to worry about damaging the threads and you can REALLY torque them down.  Or use bolts instead.

[JAinVA 4,623]

Dennis has a point and you might want to try that.It couldn't hurt.If you decide to do that while the hub is off remove the keys and place the hub on the shaft.If there is a lot of slop or wobble on the axle then that would be the problem.Time to upgrade the hubs.JAinVA

[pfrederi 17,902]

Are they new cup point set screws??  If not what does the business end look like.  It should be cupped with a clearly defined ridge around it.  That actual should dig in to the woodruff key (Leaving a cut circle in the key)  Bolts with their smooth end are not good substitutes.  Also did you put the jam nut back on and snug it down??

Edited October 16, 2016 by pfrederi

[wallfish 17,084]

All of the above but if that doesn't work....

Drill and tap a second hole in the hubs, 90 degrees of the original and lock them down with a second set screw. Cheaper, than replacing the hubs.

[pfrederi 17,902]

22 minutes ago, wallfish said:

All of the above but if that doesn't work....

Drill and tap a second hole in the hubs, 90 degrees of the original and lock them down with a second set screw. Cheaper, than replacing the hubs.

 

Great suggestion.  A word of caution if you do this.  Do not get over ambitious tightening the jam nut on the additional set screw.  WH machined a flat surface around the set screw hole you will not have that for your new hole.  You will be tightening down on a curved and sloped surface.  If you get carried away it can cause the set screw to snap off flush with the hub.  Do not ask me how I know this....

[Ed Kennell 38,719]

1 hour ago, wallfish said:

All of the above but if that doesn't work....

Drill and tap a second hole in the hubs, 90 degrees of the original and lock them down with a second set screw. Cheaper, than replacing the hubs.

John has the answer.  Yes, definitely use the square head cup point set screws with a lock nut.

 

If my hubs do not all ready have the second set screw, I add them.    The second set screw keeps more of the hub/shaft surface in contact preventing wobble in both directions.

 

Also, make sure there is not a second set screw already  in the hole.  It is common practice for some mechanics to stack the set screws.

[Rob.A.700 306]

Thanks for all the help! my set screws are just bolts unfortunately I will have to get a proper set of set screws. I will also put another set screw 90 deg. from the original. Does any one have pictures of their set up with the added set screw?

Edited October 17, 2016 by Rob.A.700

[doc724 925]

If you are going to get new set screws, don't be cheap.  Get Gr 8 set screws from a reputable source.

[Ed Kennell 38,719]

       My choice for all high strength fasteners.

Edited October 22, 2016 by Ed Kennell

[JAinVA 4,623]

Rob,

   The suggestion for better setscrews has merit.The factory used a cup point setscrew with a square head.Grade 8s are superior to almost any other fastener but keep in mind that the hubs are cast steel and be careful of the torque you put on the setscrews.The reason I suggested you check the hub fit on the axle is that if the hubs wobble to any great degree it could mean that the bore is not only out of round but in severe cases hourglass shaped.This would only be on a very high time machine but if the case then setscrews will not stop a wobble over time and with load.JAinVA

Edited October 22, 2016 by JAinVA

[lynnmor 7,356]

I would consider using Loctite 609 compound on a loose fitting hub.  As stated above, if the hub has any significant play, the setscrews will not hold for long.  Removal might be a problem, but I made a heavy puller and if that isn't enough, heat should do it.  I will be pulling a hub in the future that was mounted with the Loctite 609, so we shall see what happens.

[JAinVA 4,623]

Loctite 609 is a permanent  thread locker.If applied on something like the hub/axle combo then heat will only thing to loosen it .

Loctite also makes a bearing retaining compound that will fill the gap on loose fitting parts.Again heat will be the only thing that will loosen its hold.If the hubs don't have a lot of play new set screws may do the trick but if not some worn out parts should be replaced.

I hope your hubs are salvageable.JAinVA

Edited October 23, 2016 by JAinVA

[lynnmor 7,356]

This is from the Loctite website, but there is a typo about the 0.006" diameter.  I think that they mean .006" per side clearance.  Old information about this product stated .010" total clearance maximum.  Note the "subsequent dismantling."  There is no mention about using this product for threaded fasteners.

 

LOCTITE® 609™ Retaining Compound General Purpose is a low viscosity, rapid-curing anaerobic adhesive that augments the strength of press fit assemblies or slip fit assemblies up to 0.006" in diameter. Adds up to 3,000 psi holding power. Recommended for parts that will need subsequent dismantling, i.e., retention of bearings onto shafts and into housings. Mil Spec (R-46082B) Type I.

[Rob.A.700 306]

The hours of my tractor are unknown but more than likely high. I am going to put another set screw in at 90 degrees but before I go through the hassle while I have them off I will check the bore. I am hoping they are not hour glassed out as @JAinVA suggested. The  Once a gain thanks for the added information... 

[Don1977 604]

With the worn  key ways it will be impossible to keep the hubs tight. It allows the hub to move and will wear the cup off the setscrew. Worn key ways in the hub will do the same.  Good used parts is the best fix. My guess is that you need axles and hubs. Sorry to be a bearer of bad news.

Edited October 28, 2016 by Don1977

[R. L. Addison 299]

I have also seen a light or shallow knurl or center punch dimples used to tighten loose fits where it is not excessive. I have never used any type of Loctite in addition but might in a pinch someday.