How can I fix this slop?

[Jay C]

Guys, my Widgitmaster router is great except for some looseness in the cross carriage (I call it X axis on mine). The bronze bushings might be worn as there is visible movement in the (B axis) when I grab the Z stepper and torque it side to side.

What options do I have to fill in this gap?

for reference to B. And a photo of the router.

Jay

[Jay C]

Here is a closeup of the carriage and the bronze bushings. The Z bushings are nice and tight so no issues there.

[ViperTX]

Shoot Eric (Widgetmaster) a PM, I'm sure he is more then willing to help.

Paul

[Jay C]

Yep, sent him an email ... he is out on a family emergency so I wanted to tap the collective wisdom of the forum

[BillTodd]

I wonder if it would be possible to modify it to use Eric's bearing pre-load design?

[Jay C]

I had another suggestion of replacing the bronze bushings with http://www.vxb.com/page/bearings/PROD/Kit8063. Still playing with the CAD drawing, but looks like they will fit. My concern is that the issue is the fit between the shaft and the bearing will still be loose unless I replace the rods too. Precision drilling hardened rod ... not my cup of tea

I measured the existing Thomson rails at .4985" and the bore on the bushings at .4995" so .001" undersized.

Jay

[Jay C]

After a few hours in Autocad (I drew the whole X axis but am only focusing on the carriage) here is my plan.

Buy two of the Super Smart ball bushings and get a local machinist to bore out the .875 holes centered on the current bronze bushings.

Any words of caution?

Jay

[BobWarfield]

Just that I'd be sure to discuss with the local machinist exactly what you're trying to do. If he doesn't put the bores in the right place, things aren't going to fit and you'll wind up needing more machinework.

Should be straightforward to just bring him the machine though. He may have some other ideas too, so you might do that before ordering any parts.

Cheers,

BW

[cheetahcnc]

What is the actual dimension ID of the bushings? I have bored aluminum and then saw cut, or milled, a slot similar to that bushing/housing design. Due to added heat or stresses in the material the bores changed quite a bit. In your case the bushings don't have a whole lot of wrap around the shaft, and the housing thins out, which exaggerates the tolerances.

Jim

[Jay C]

Originally Posted by cheetahcnc What is the actual dimension ID of the bushings? I have bored aluminum and then saw cut, or milled, a slot similar to that bushing/housing design. Due to added heat or stresses in the material the bores changed quite a bit. In your case the bushings don't have a whole lot of wrap around the shaft, and the housing thins out, which exaggerates the tolerances. Jim

Are you asking for the ball bushings (.5000/.4995 per the datasheet), or the current bronze bushings (I measured the bore on the bushings at .4995" so .001" undersized). Eric, finish bored the bronze bushings after he milled the slot in them (see here). The issue may be wear I can't be sure.

[Jay C]

Question, are the SuperSmart linear ball bushings going to be "looser" (more slop) than the current hard bronze bushings? The local machinist is thinking that will be the case based on the tolerances of both the bearings and the rails.

I contacted Eric, but he has not replied so I'm looking for some advice please.

[MrWild]

Try this simple fix first. The rails are supported rails. If they are not doweled to the mail cross piece, you could loosen and then either spread, or tighten the distance between the raiis. This would preload the system and also give you adjustablility for future wear.