3 * RM1610 ballscrews, 780mm & 660mm

[Swarfing]

ha! ha! ha!

Think he is hoping for a fortune then?

[Jonathan]

Sold, now to get some more.

[JAZZCNC]

Sold, now to get some more.

Jonathan my screws have just arrived from Chai.!!!. . . . .WRONG. . . . sent 5mm pitch not 10mm so may become available depending on what he intends to do about it.?

Knowing Chai we'll come to some deal, I need 10mm pitch so they will be available or going back thats for sure! . . .. . I'll let you know what happens.!!!

[Jonathan]

7 days from ordering - not bad at all.
I'll be interested in at least a couple of the 5mm you end up keeping them.

[JAZZCNC]

7 days from ordering - not bad at all.

Not if the bastards are wrong.!!!!!!!!!!!

[JAZZCNC]

Jonathan the screws are correct and I owe a big apology to Chai. . . . Just spotted it's twin start thread.
In my defence it's the first time he's sent me twin startscrew. . . . Better send him an email quick. .:whistling:

[Jonathan]

Jazz did you hear anything from Chai?
With 6 plastic inserts they must have 6 rows of balls, as each insert is a ball return tube. Additionally they're not going to use 3, or any odd number, rows of balls as that would result in uneven wear and all sorts due to having more balls running in one track...
I wonder if they're preloaded. A twin start screw with offset tracks in the nut is one way to apply preload - that would make them worthwhile.

As a general rule of thumb don't go below a 15T pulley with 5M HTD belts, and if you need much above 3:1 use double reduction. Use one of the many on-line calculators to find the number of teeth in mesh on the smallest pulley. They will give a warning if it is below 5...

http://www.sdp-si.com/cd/default.htm

[Karl]

Just out of curiosity, is there a rule-of-thumb for whether and when to use 5mm or 10mm pitch ballscrew when constructing an XYZ table (for routing mainly hardwoods)?

[Jonathan]

Just out of curiosity, is there a rule-of-thumb for whether and when to use 5mm or 10mm pitch ballscrew when constructing an XYZ table (for routing mainly hardwoods)?

It depends on numerous factors. 10mm pitch gets you much better speed and acceleration, but unless you use pulleys (which you really should...) you clearly have half the resolution of a 5mm pitch screw. If the axis is quite long you'll certainly want a 10mm pitch screw, since because the screw pitch is greater the rpm for a given feedrate is less so the screw will not whip until twice the feedrate it would with 5mm pitch. For a short axis, like Z, whipping isn't a problem so 5mm is fine. In most cases on a 'reasonable size' router 10mm pitch with pulleys is the way to go for X and Y and choose the pulley ratio depending on what your're cutting (to favour resolution for speed).

However clearly there will always be exceptions and each case is different, so you need to read up on it, decide and calculate for yourself.

[Karl]

... but unless you use pulleys (which you really should...) ...

So what's the rationale for using pulleys to drive a ballscrew rather than connecting the stepper motor directly inline via a flexible coupling?