Hello All,
As some of you know, I recently received A
Harbor Freight 4" Rotary Table from Bob - ESS Systems AKA - Carbide Bob. Just another quick ""Thanks to Bob""
I did a fair amount of reading about this Rotary Table and most of it was bad such as, there was no way to adjust or eliminate the slop from the poor fitting and or quality of the worm gear setup. Well if you know me, I just didn't think that something could not be done about fixing this problem, after all ... its just a dang Rotary Table.
Well to my surprise, it was a very easy fix!
For those of you that have this little diamond in the rough, you will have a big surprise when you see what it took to make this Rotary Table have ZERO, Zip, Nada ... No Slop!!!!!!!!
I will list the problems and the fixes below.
Here were the symptoms:
1). 1.5* slop on the gear train.
2). Binding of the gears every 180* when rotating.
3). Table was not level to base.
First I took the whole thing apart, every piece except the bearing and gave it a 1 hour soaking in acetone. This loosened up all the packing grease. I was a little concerned at first about the bearing soaking in the acetone because I could not remove it to repack it and I didn't have another one to replace it in case I screwed it up in the removal process. I tried to remove it only to realize, I better leave it right were it is considering it is a sealed bearing. I know ... some acetone might have gotten inside the bearing but after the soaking, it felt as smooth as it did before the soaking so I am confident its fine.
Now I started tracking down the problems;
Problem #1 Slop:
I found that when they cut the relief for the bearing, the edge of the bearing was sticking up and was interfering with the worm drive by almost .093 as shown in the first picture below.
Solution:
I used a grinding stone on a dremel and removed the bearing shoulder until it was flush with the casting surface and that is shown in the second picture.
Problem #2 Binding:
I measured the worm gear that is cut into the crank handle shaft and fount it to be .017 out of round on the outside diameter. The bottom of the threads were fine.
Solution:
I just chucked it up on the lathe and trued the outside diameter until it was round. Now for the removal of the backlash you need to do a balancing act when reassembling it back together. There is a set screw that pushes against the handle mount (worm gear) inside the base into the main gear. You need to adjust that at the same time as the 4 screws that mount the handle assembly and you will find that you can completely remove any and all the slop between the gears.
Problem #3 Table not level:
I measured the tables levelness to the bottom of the base and it was .009 off.
Solution:
Well I guess I got lucky on that one. When I assembled the Rotary Table back together, It was level. I am guessing here... I think when it was assembled at the factory, The bearing was not seated all the way in and upon reassembly I must have seated bearing all the way in.
Well there you have it. If you have one of these Rotary tables from Harbor freight, make the checks I have outlined here and you might have a winner.
Sorry the first two pictures were done with a cell phone.
Good Luck
Bill