Newbie- Choosing drive related parts

[aggrav8d]

Can someone please explain to me how to choose the appropriate size of lead nut and thread? Obviously they have to match and the thread count affects the speed parts can move at. I don't get the difference between, say, a 1/4" thread and a 1/2".

Also, I've been looking at parts (like @dumpstercnc.com) and I see lead nuts but I don't see how they're supposed to be properly attached to each sled. I keep expecting to see some kind of flange with screw holes in it.

What am I missing?

Please and thank you.

[ger21]

They do have a flange with holes.
dumpsterCNC - 1/2"-M12 Flange options

[CarveOne]

If you do not specify a particular mounting option from their list you will get a plain round flange with no mounting holes. It will be up to you to modify the flange shape and drill holes to suit your own design needs. The flange cuts easily with a band saw and is easy to drill.

CNCRouterParts has a different style that has two holes and is intended to mount to a flat surface that is parallel to the lead screw.

CarveOne

[ger21]

Can someone please explain to me how to choose the appropriate size of lead nut and thread? Obviously they have to match and the thread count affects the speed parts can move at. I don't get the difference between, say, a 1/4" thread and a 1/2".

A 1/4" screw is 1/4" diameter, and a 1/2" is 1/2" diameter.

Choosing the correct screw depends on how long it needs to be, how fast you need to move, and how much weight your moving. For most homebuilt machines with screws 4 ft long or less, 1/2" tends to work pretty well.

But which 1/2" you choose depends on how fast you want to go, and what motors and drives you're using.

[aggrav8d]

NEMA23s. I'm planning to use SparkFun EasyDrivers with PC cooling fans attached, and I have no idea how slow/fast I should be going. I'd like to cut aluminum, woods.

I hear 2-start is better than 1-start and I don't much care about turns per inch.

What do you advise?

[johnmac]

Screw diameter and turns per inch are important. A small diameter screw can sag, causing it to whip when spinning fast. Turns per inch will determine the speed range. Stepper motors produce more power when running slow than when running fast, so you don't want to have to "rev it up" to get desired speed.

A 1/2" screw with 8 or 10 TPI and 2 starts is a popular choice if you plan to directly couple the motor (no "gearing").

John