Well I went back to lowes today cause my son thought that the all thread didn't need to be perfectly straight.

While I was there swapping the all thread out I looked to see if they had some bushings for the Z axis.
Sure enough they did!.

Heres some pics off the tolerances.
BTW all my linear rods/rails are 1/2 inch.

Hopefully this will save someone from having to order online and wait to finish their Gantry.

These things glide soooooo smooth yet tight. Remember I did use the great polishing the rails mod.
I also wet sanded the rails down with a foam sanding pad and then polished.

Eric

Also this is not a new MOD someone else posted this Mod all ready but more of letting you guys know lowes does carrying these.

 

Looks like a great mod and if the price is not that much different we might see it as standard item on the pp v2.

I bought drill rod to replace the Lowe's rods and I had the opportunity to get them slightly larger, 15/32 instead of the 7/16. They still fit in the Pex pipe and essentially they are pre-polished. They cost about the same but not everyone has access to an industrial metal supply. I figured they would also have less flex that the 7/16, which they do. But I suppose 1/2 would be even better.

I could not read the numbers on your second picture so I did a little photoshop magic and made it more readable.

Stelio

 

Hmmm, I haven't started my build yet. I did decide to change the 7/16 rods from cold rolled steel to precision ground O-1 from McMaster Carr. I'm going with the bronze bushings too. Lowes doesn't carry 7/16" bushings, at least the one I went to didn't. Do you see any flex that would suggest that 1/2" rod is necessary?
Dave

 

I have built other machines (hence why I already had the 1/2 rod) and they all flex.
Over a short time I have seen smaller than 1/2inch get a natural bow with out much hard plunging, cutting material simular to the hardness of 1/16" wood.

1/2 will bow as well if you begin to plung into very hard materal or crash the tool into the material to hard, to fast etc.

I purchased open linear bearing so that if I begin to see an issue I can weld support bars in.

Bottom line any rail not supported will bow sooner or later.

BTW I have the gantry completed and the bushings slide like glass of the polished rods.
There is no play once its all installed.

With the kits that are being made now I suggest using a step bit to make the holes larger for the Flange bushings and for the rods if your going to a large OD rod.
The step bit will allow you to center your drill in the pre cut 7/16 holes etc, and from there jump to the next size hole. I would try to find a step bit that had 1/4 depth steps but if you come across the more common 1/8" dont worry you'll just have to do the top side and flip the part and do that side.

Eric