BT48 Table (X) Motor Mount

[yankeepapa]

Group-

My new BT48 (pre-assembled) has the table (x) motor mount "rotated". The mounting bracket isn't square with the table frame. However, there seems to be a stop/adjustment screw that has been set to make the exact amount of rotation desired and correct.

What is this for? Maybe the table has already been "adjusted" properly?

-David

[erik_f]

not really following you. The screw is an adjustment for how firmly the pinion seats in the rack. If the pinion is not seating in the rack squarely...then you should not run the machine until you solve the problem.

[dubliner]

Maybe thats my problem too! In looking at the bolt & how the motor is pivoted, the bolt will either push the motor down away from the rack, or if up all the way no pressure other than the spring mechanism, what should it be? Motor seems very tight against the rack with spring only.

[erik_f]

The threaded rod acts as a spring and the adjustment bolt will take off tension the more it is taken out. I set mine trying to find the loosest spot in the rack pinion connection. Then adjusting the threaded rod and adjustment bolt right until all the slop was out of the losest area in the rack and pinion. I also filed out some of the area where the motor bracket was getting close to run into the cross member that holds up the motor mount.

[dubliner]

Erik, it turns out some machines were shipped with the cam handle for the extendable table ( mine was ) Seems like when I close the cam it has springs on it that appear to set the rack & pinion just right. My motors are grinding a little in certain places or moves & I thought it might be too tight.Back to the drawing board.

[erik_f]

Isn't there some sort of adjustment for the spring tension? When you release the cam handle, does it allow you to pull the pinion out of the rack? If so...does the table move freely when not in gear? Also...is it possible that the cross member that holds the motor mount (the one that spans front to back on the table frame) is not aligned with the rack? If this were the case maybe your pinion is not entering the gear rack perfectly creating your binding. Maybe I'm wrong...but I think you're lucky to have the spring loading...the only trick is to find the right tension for the sping.

[gordon]

You're both on the right track. First, if the pinion is not seating squarely into the rack you must loosen the bolts on the ends that connect the motor bracket to the upper supports, seat the pinion properly and then retighten. This must be correct before proceeding onto the springs.

Now you can adjust the pressure on the pinion into the rack. The bolt in the bottom of the motor bracket is for adjusting how much engagement the pinion has with the rack and consequently the amount of pressure on it. By setting this you can minimize the amount of backlash in the X, as well as, the wear on the pinion by keeping it from being forced into the rack. So, how it works: Erik has the right method for his tool that has a threaded rod. For one with a CAM handle the method is even easier. First, make sure that the cam is down and the pinion is engaged in the rack. The turn the adjusting screw in/down to push the pinion away from the rack. While decreasing the pressure you'll know when you're close to the proper pressure when the pinion starts to become loose in the rack. You test this by pushing in/out on the X as you're turning the bolt. When it starts to clip you're too loose and should then back it out until the clicking stops. This is the idea pressure point for the pinion. Before you start cutting there is a locking nut on the adjuster that needs to be retighted to prevent the adjuster from vibrating loose.

The springs in the CAM assembly shouldn't need to be adjusted. They're set here at the factory. To make sure they look right: the larger spring that connects the CAM to the motor bracket is simply to aid in disengaging the pinion and can't be adjusted. The heavy die spring on the CAM connection to the motor plate should be almost fully compressed when the CAM is in the engaged position, there should be a very small gap between the coils. If you tighten this too much you won't be able to engaged the pinion easily and will but a great deal of strain on the adjuster. Hope this helps.

If you're still experiencing "binding" during movement of the table let us know so we can help you figure out where it is happening.

Gordon Bergfors
ShopBot Tools, Inc.
Development

[dubliner]

Dave I must apologize I hijacked your thread, but if you have problems with binding,do as Erik & Gordon suggest. That fixed my problems. I ran the file 3 times without fault at 3 ips. Neville