Jointer Sounding Bad

dusty · Post by **dusty** » Sat May 01, 2010 4:11 pm

I started out the day with a jointing job scheduled. It is a good thing by schedule is not demanding right now.

It has been a while since I used the jointer so when I turned it on and heard this unusual sound I was surprised. But then when I turned it off, as it slowed down it sounded really strange and was rough. I happened to have one hand on the headstock as it slowed down.

I pulled the headstock away from the jointer to hear/feel the headstock by itself - smooth and quiet (naturally noisy).

Must be the jointer. Then when I went to reconnect the power coupler I realized it did not fit right.

[ATTACH]8735[/ATTACH] [ATTACH]8736[/ATTACH]

Check without the coupler.

[ATTACH]8737[/ATTACH] [ATTACH]8738[/ATTACH]

Obviously out of alignment. Could see that better after I changed the hub on the headstock allowing they to come together.

Manipulating the eccentric on the jointer is probably my least favorite set up procedure but I got it done.

The bad noises and the rough rotation is now smooth and as quiet as ever. It is hard for me to understand how this small misalignment could have such a dramatic effect on the jointer cutter head.

dusty · Post by **dusty** » Sat May 01, 2010 4:15 pm

After thought to the previous post. Why is the power coupler plastic?

Actually, the real question: What risks would one be taking if the plastic coupler was replaced with a coupler milled from aluminum or brass?

horologist · Post by **horologist** » Sat May 01, 2010 4:37 pm

Dusty,

Aside from financial reasons, I suspect that the coupler is made from nylon for two reasons.

1. To act as a fuse, making it from a stronger material (metal) would allow other more critical areas to suffer should something cause a jam. Sort of like replacing an old fashioned fuse with a penny.

2. To make it more durable, any slight misalignment between the two hubs would cause flexing in the thin flanges that could result in fatigue failures, especially with aluminum.

Troy

JPG · Post by **JPG** » Sat May 01, 2010 5:21 pm

It is both 'flexible' and a sloppy fit intentionally so as to accommodate slight mis-alignment. I am surprised your example created an alarming amount of noise.

Perhaps extended dry environment has 'stiffened' the plastic. The older Zytel plastic ones were more 'flexible/durable' than the current variety.

Was the headstock pushed tight against the coupler thus eliminating all possible movement between the headstock hub and the spt hub? A slight amount of clearance helps when some misalignment exists.

dusty · Post by **dusty** » Sat May 01, 2010 6:17 pm

JPG40504 wrote:It is both 'flexible' and a sloppy fit intentionally so as to accommodate slight mis-alignment. I am surprised your example created an alarming amount of noise.

Perhaps extended dry environment has 'stiffened' the plastic. The older Zytel plastic ones were more 'flexible/durable' than the current variety.

Was the headstock pushed tight against the coupler thus eliminating all possible movement between the headstock hub and the spt hub? A slight amount of clearance helps when some misalignment exists.

I don't know for certain if there was some slack in the coupling or not. I hardly ever get it real tight so I would bet there was some slack.

The noise, JPG, was not not loud - just unusual. The jointer makes very little addition noise.

These couplers are likely twenty years old. I don't recall every buying additional couplers and they have lived much of their life in this climate which is hard on plastic and rubber.

JPG · Post by **JPG** » Sat May 01, 2010 8:42 pm

Dusty: Have you by any chance adjusted the poly-v belt tension since previous alignment of the shafts(or loosened the tie bar or 'rest')?

dusty · Post by **dusty** » Sat May 01, 2010 8:52 pm

JPG40504 wrote:Dusty: Have you by any chance adjusted the poly-v belt tension since previous alignment of the shafts(or loosened the tie bar or 'rest')?

I have not knowingly done anything with the tie bar or rest but I have done a retensioning of the poly-v belt. I was inspecting the eccentric to see if it had a set screw (it does not) and therefore had to reset the eccentric.

JPG · Post by **JPG** » Sat May 01, 2010 9:18 pm

dusty wrote:I have not knowingly done anything with the tie bar or rest but I have done a retensioning of the poly-v belt. I was inspecting the eccentric to see if it had a set screw (it does not) and therefore had to reset the eccentric.

When you move the eccentric, it changes the location of the 'auxillary' shaft. It moves in a circular path. At minimum tension, the shaft is at its highest location. as you rotate the eccentric clockwise, the shaft moves down and to the right and after 90 º moves down and back toward the left.

I believe you have less tension than before, but the left/right shift has me confused unless you had moved the eccentric CCW from minimum tension previously or it was adjusted past 90 º(9 o-clock).

dusty · Post by **dusty** » Sun May 02, 2010 6:13 am

JPG40504 wrote:When you move the eccentric, it changes the location of the 'auxillary' shaft. It moves in a circular path. At minimum tension, the shaft is at its highest location. as you rotate the eccentric clockwise, the shaft moves down and to the right and after 90 &#186]had[/B] moved the eccentric CCW from minimum tension previously or it was adjusted past 90 º(9 o-clock).

Very keen observation. After all these many years I had not thought about the fact that when the eccentric is adjusted the drive shaft changes relative position. After thinking about this for a while, I now realize that adjusting the eccentric can change the relative location ofthe drive shaft (used by the jointer) almost 3/16".

This almost necessitates that the SPT eccentrics be adjusted.

Thanks JPG.

JPG · Post by **JPG** » Sun May 02, 2010 11:45 am

dusty wrote:Very keen observation. After all these many years I had not thought about the fact that when the eccentric is adjusted the drive shaft changes relative position. After thinking about this for a while, I now realize that adjusting the eccentric can change the relative location ofthe drive shaft (used by the jointer) almost 3/16".

This almost necessitates that the SPT eccentrics be adjusted.

Thanks JPG.

This is also the reason the vent plate screw holes(in the belt cover) and the spring nut(flat tinnerman) are so large. Their size allows centering the plate over the varying location of the shaft.

I 'discovered' this 'feature' almost 50 yrs ago! My jointer still has STRAIGHT posts.
Offset ones are on my (ss)shopping list[too expensive on ebay!]. Since I am on the verge of possibly mounting it on two different(maybe three) machines, the straight ones are no longer viable!
This does not include the possibility of power station mounting, which has enough slop to get good enough alignment(probably not likely since the top speed is too slow).

The 1960's vintage setup instructions call for loosening the mounting screws of the cutter head so as to provide lateral adjustment!:eek: Vertical adjustment was accomplished by vertical positioning of the tubes in the jointer base. FYI, the straight tubes have a snap ring/groove that provides the vertical 'stop'.