Multi-Start ACME rod

[Stern]

In my quest for info before building my CNC PCB router, I have come across some info someone gave me regarding the ACME drive screws. Seems many use multi start rod as its supposedly more efficient than standard single start (seems 10TPI isnt as good as 5TPI 2 start). I have used ACME rods before but really wasnt aware of multi start rods except some references in machine lead screws.
Now another problem pops up, are there rods as common and easy to get as standard single start ones, AND I also assume you cant use a normal nut tap for a multi-start rod (meaning I would need a special multi-start tap to make the matching nuts.).

Anyone have any info or used multi-start ACME ? any info would be a great help.

[Duffy]

Multi-start Acme rod

I would think that, in small diameters, multi-start would have advantages like low thread profile for high advance rate.
As far as obtaining it, I would try Keystone Threaded Products. I know that they have real people on the phone, and seem to be very helpful. I got 7/16-LH rod from them- from stock would you believe! For nuts, you may be forced to make Evanuts, especially after you get a quote from Victor for a custom tap.
IF Keystone has multi-start rod, they probably also have matching nuts.

[dalee100]

Hi,

I've used multi-start threads for adjustable back gauges on shears of different types. They can be nice in some applications, but aren't really needed.

They provide the speed of movement of a course thread with the fine adjustment of finer thread pitches. And could be a nice upgrade to your router. They can have a number of different starts, double or triple starts being the most common. I try to buy them, but I have single pointed a couple of triple starts over the years, mostly a pain in the backside.

You will need a matching nut, and they do cost noticeably more than a standard acmes. If your funds allow, I would go for one here. But if the egg money runs a bit short, you can get by fine with a standard thread.

dalee

[Stern]

Thanks for the info Did some digging and seems thay can be found (rod) in 2, 3 and even 5, but you do need to buy the matching tap (yea, thought the two normal ACME taps were pricey, the multi's are really expensive.) May just end up using a normal rod, but still have a lot of digging to do, and if the rod suppliers have matching nuts them I may go that route.

[Highpower]

This place is local to me and have some very friendly and helpful folks working there. The products might not be cheap, but the willingness to share their knowledge and experience with me has been priceless.

[elf]

My CNC router uses 3/8x12 two start acme lead screws from McMaster-Carr. If you don't want to make your own nuts, then get anti-backlash nuts from DumpsterCNC. They aren't that expensive, but EvaNuts only cost a dollar or two to make.