B&I Gem Maker making a bad sound

[mossagatemac]

SAE 841 Oilite Bronze  FF 1013

Crud.  I'm pretty sure I got the FF-1011-4.  The marker is a little worn off where they wrote it, but pretty sure. 
Is this going to be a big deal?  Here's the differences:

                      ID Max    ID Min        flange OD
FF-1011-4:     0.7505    0.7495       1-7/16
FF-1013   :      0.751    0.75             1-1/2


Everything else is the same.  Same OD, length, etc.  Just a smaller flange by 1/16th of an inch, and 0.0005 inch difference on ID. 

[Isotelus]

Yes, you need the full diameter bushing flange so the steel flange on you arbor does not wear unevenly. The rest of the specs are acceptable ID Max and Min.

That arbor flange also takes the brunt of the pressure from flat disc grinding which is something these machines are good at. You really don't want to mess up your arbor shaft there is no replacement for them part wise unless you have a machinist friend. That said they are not a real complicated arbor for a machinist.

The stock numbers are a pain with these-- so many variants.

I also have a few on order while my machine is down I am going to add a grease groove to mine to see if I can quit spoon feeding the top bearing grease

[dickb]

If you add or enlarge a grease groove, make sure it is in that spiral shape, otherwise the shaft will make the bore egg shaped. A Dremel with a ball bit should do it for you. Just work the spiral from both ends of the bushing. A quarter turn would work but a complete revolution would be best.

Dickb

[mossagatemac]

ok, got the bushings, cleaned everything out with mineral spirits, and put the new bushings in.  The shaft seems to fit pretty well so I'm excited about that. 

The problem I'm currently facing seems pretty basic compared to the rest.  I'm putting the pulley on, but the little screw that holds it on to the shaft won't screw in.  It seems like I'm cross threading it or something because i get just a little ways in and it stops.  I don't want to force it and am worried I already went too far.  What are my options? 

[dickb]

Those pulley's are notorious for cross threading. Take the setscrew out of the pulley.

Stick the allenwrench through the screw hole and slide the setsecrew into the bore of the pulley so you can engage the allen wrench in the setscrew and back the setscrew up into the pulley as the setscrew comes through the screw hole it will re-align the threads in the pulley casting, It's delicate work but if you put a little grease on a stick like a popsickle stick you can position the screw where you can get the wrench into the setscrew then lift up on the stick to start the screw into the threads, that may get you out of trouble.

Dickb

[mossagatemac]

Great idea dickb! I'll try it in the morning if i can get some time.

Next question -- as I'm reassembling this thing, how do I know if the belt tension is correct?  They way it was set up didn't allow me to change the belt tension so I'm going to rotate the motor 90 degrees which allows me to adjust the tension. 

[dickb]

Those bronze bushings don't stand a lot of side load so the tension only needs to be tight enough that the belt doesn't slip under load. You should be able to flex the belt up and down about 1/2" or more at the center between the pulleys. A flat lap should not have the cab pushed down hard enough to slow the lap. Let the grit cut the stone, not burn it off.

Dickb

[mossagatemac]

Well, that screw was way more of a problem than it should have been.  Long story short, it's where it should be now.

Everything is back together, and I rotated the motor 90 degrees so that the belt tension can be adjusted.  Also replaced the belt because there were a few hard spots on the original; so as long as I went through all of the trouble to replace the bushings i may as well do the belt too.

Just ran it for about 2 hours and things are sounding pretty good.  Not much heat coming off of the shaft and it is running pretty smoothly. 

Thanks for everybody's help! 

[dickb]

Glad I could help. Now go have fun!  yes16

Dickb

[phishisgroovin]

i have to replace these bushings in my grinder like this also, im just too lazy to go to my local hardware store and buy the new ones.
McLendons where i used to work has these in stock all the time.

[light house jack]

Memories... my dad ordered me that same machine from Sears and Roebuck over 60 years ago.  I have an agate in my showcase that I flat lapped way back when.

[slabbercabber]

I prefer Kroil as well.  It is available directly from the manufacturer or from McMaster.com