[slp_prlzys]

hello All,

I've been browsing here for a couple of weeks now. I became very much interested on this hobby CNC thing and
suddenly felt the urge to build a hobby CNC router myself. , There's so much information to read and digest but I'm learning a lot, atleast I know more, than 3 weeks ago.

I don't have any background in the field but know a little bit of electronics, so please bear with me.

Initially I wanted to build a small one about 12" x 12",
I started collecting parts from scrap printers.
I've been reading about leadscrews,acme rods, and ballscrews and now know the difference between them, the problem is where to find them without buying online, I live in Montreal and I'm trying to look for a place to buy and yesterday me and my friend went to a flea market outside Montreal searching for pressure switch that we're going to use for his homemade airbrush compressor from a fridge compressor, We stumble to a
mechanical junk store and found this:
Linear

I got this for $200 CAD, I'm not sure if I got jiffed cause I don't really know how much this actually cost, and the guy that sold it keeps giving me the price for each component of the thing while I'm trying to bargain with him, and I figure it's already been built,
and I don't want to miss the opportunity so I grab it not knowing the exact specification of the ballscrew, and it's condition. I sprayed it last night with WD40 and cleaned some dirt build up and some rust on the end where the bearings don't reach. As far as I can tell it's still in good condition though I think I'm hearing like there's a sand inside the pillow block maybe it's just dirt, because it's still slide from end to end with no problem.

It's about 44"x 21" with a travel of 36" because of the stopper on each end, now the ballscrew thread pitch is a bit tricky to measure
I just refer to this site on how to measure ROTON
If I'm not mistaken I got 6 TPI and 5/8" in major diameter, the shafts are 3/4".

Now to my questions:

What resolution can I expect on this one?
Since I still dont' have the leadscrew/ballscrew for the other axis,
Do I need to have the same specification for those in terms of TPI etc.?

Can anyone please make comments/suggestions with the draft layout I have on my link, I wanted it to have 24" travel on the X-axis that's why I extend it. I'm going to built this using MDF and will most likely use stepper for the drives. My use for this is not very specific as I wanted to build a pcb drill before I got this, I think I will use it to route woods and/or cutting computer cases for modifications along with pcb drill.

Any suggestion for the motor sizes?

I guess this is all I can ask for now, while I wait for response.
and I'm sure there will be, because this is a really great site.

Thanks.

[ger21]

Since I still dont' have the leadscrew/ballscrew for the other axis,

You can use different pitch screws for the different axis'.

Du you plan on laying that thing on it's side? What size diameter are those shafts? You may have a problem with them sagging.

[slp_prlzys]

ger21

Thanks

the shafts are 3/4" in diameter.

no, I'm not going to lay it sideways I'm going to make a
table for it.

I'm a little concern with the ballscrew placement most of
the design I've seen here has it centered.

[whiteriver]

Good find.
If those pillow blocks are open on the bottom then you could make a support for under the rail with baltic birch ply. Just cut a V in the side and set the rod down in it..
As for acme rod close to home. Hmmm your in a big city just look in the phone book for fastners or nut and bolts. Find a store that just does that. Not a Home Depot type store. The store owner may have or can order you some acme rod.
You can go to your local steel store and get chromoly rod for more slides for the other axis. Buy Pillow blocks or use one of the roller skate bearing setups you'll find info about here.
Good luck and keep posting your questions.

Donny

[JOE65]

If your able give up a closeup of the bearings/bushings that ride on the shaft.

[slp_prlzys]

whiteriver:

thanks for the tip, there's no open side on the pillowblocks,
just the alluminum block with the bearings inside. I have small bearings that I got from a scrap xerox machine 11 of them. I wanted to use them as triangle style setup that would run on a 3/4" drill rod, but there are groove on the bearings close to the edge, the groove was used for the retaining ring.


Joe65:
Here's a closeup of the pillowblock

[whiteriver]

Uggghh. Bummer On the Blocks. Well try and make a light gantry with a light spindle and maybe you won't get to much flex. Or scrap the blocks for that axis and use them on your Z. Then use the triangle bearing idea for x and y with the plywood or AL supports under the rails..
Just a idea. Always trying to save money.

Donny