This is a derivative or alternate construction method of the Thing O Matic Z stage mod by barrychuck http://www.thingiverse.com/thing:6184 . [If you can tell me how to do a linked derivative I will make it so]The hole enlargement for the 21/32" tubing can be problematic to do accurately. I found a way to do it in my shop using more commonly available drill sizes and tools. Accurately.Basically, if the pieces of 21/32" tubing are sleeved, with 21/32" tubing then they fit perfectly inside 11/16" standard drill hole.I will otherwise confess that I found this out accidentally by thinking the 11/16" would be perfect (slipped the tubing in a Forester bit cap and thought it fit good) but didn't do a test hole. Accidental or not - it works great.Please remember - this is just a construction alternative derivative for http://www.thingiverse.com/thing:6184 and only helps construction - so that thing itself is best for discussion and commentary on the mod itself. Discussion on this page should be on this construction method.Please read all instructions thoroughly all the way through. Then proceed.Checking your bits:You'll need a 5/8 and a 11/16" drill bit. Preferably Forester as illustrated. As we use the 5/8" to index the 11/16" it needs to be perfectly on center. Surprisingly - many aren't.If you don't check your bits, and particularly the 5/8" we use to index, then your quill will be off center and thence your 11/16" bore. If your 11/16" isn't perfect then you'll just get a bigger hole. Not great, but not off center.One simple enough way to check your bit is to spin it (by hand) after indexing it in the steps below. There should be zero runout / wangle on your board as you rotate the bit in the hole. Your second hole will also show perfect concentricity with the original hole if everything is good.Preparing the Wood:We counter bore a larger hole on exactly the same center. To do this accurately requires a drill press or a mill. Preferentially also use Forster bits.First step is indexing. Chuck a 5/8" Forster bit and lower it into the hole. It should fit perfectly. Now clamp this wood down while still with the bit inside. Preferentially with a backing board (which I didn't use due to my vise). This indexes the drill and importantly the quill.Here's a good point to check that 5/8" bit for concentricity. If you turn the chuck nothing should bind or move and the bit should rotate perfectly within the hole.Second step is drilling. Check a 11/16" Forster bit and start a cut. Just a hair. Check that the outer edge is perfectly concentric with the hole. It should be - but maybe you bumped it? the drill is bent? Check it as stated above. After checking this complete drilling the hole through.Repeat this for the 2nd bearing hole set.You may need to clean up the bottom side of your piece depending on use of backing board, drill speed, etc. I do this with roughish sandpaper at a 45 across the edge to just cut off any slivers and flash.Preparing the tubing:Cut your 21/32" tubing to your desired lengths per the original Z stage mod. I used 3" and 5.25" as my metric ruler wasn't handy.Cut two additional pieces of that tubing for the outer sleeves. They don't need to be full length - just to span the height of the Z state assembly plus a little. I used 2.25" and cut two pieces.Cut a slot the entire length. I marked mine with a straight edge - but it's not critical to be perfectly straight - though it does count for style points! I braced the tubing in a clamp with soft jaws as shown to make the holding and slotting easier.Use some sand paper to clean the flash off the edge. backside of a No 11 may work too. You want both sides of the edge inside and out smooth and free of burrs.Slide your sleeves on - they should fit perfectly. If not - adjust them.Now bond your sleeve to your tube. I used my propane torch and soldered them, but for this low-strength application you could as well use super glue or ThreadLock Green to wick in. Just be sure it's all clean and scuffed. Trim up your edges if anything walked while you did this.Test fit these into your holes. They should go in smoothly but with a small amount of friction. Tighter is better - but we'll pin these so as long as it's centered and not wobbling it's OK. (shouldn't be if drilled in a press)Now with fitment checked you can insert the bushings. I found I didn't need any rolled edges. The bushings went most of the way in. To make sure they stayed put I again used ThreadLock Green. Super Glue would work. Apply a bead and firmly set it into place. Be very careful not to get it inside!Let this dry. When thoroughly dry (which isn't just when you think it is dry - RTM) you should use your 3/8" rod and pop the inner bushing free and move it about. Then set them so the rod slides through as this alignment (or close) is necessary when installing in the MakerBot.Install in the Z Stage:Now you can install your sleeved tubes in the Z-stage. This follows the original build.Myself I utilized about 1/8" overhang on the top to make it easier to apply a setting bead of glue later and keep it out of my bearing. To do this easily just invert the Z-stage assembly and level it. Then install the bushing tubes until they hit bottom. Now they're spaced perfectly out at the same height as the M-3 bolts nearby. Apply a drop or two of super glue to the bottom of each tube. Only that now.You're done and now have perfectly aligned tubes for your BarryChuck Z stage mod.After all normal fttment into the chassis then you should apply beads of superglue around the tubing to lock it in. Again - nothing new here. Just reminding you to not fully set the tubes until after chassis fitment.