ACME / Trapezoidal leadscrews

[John S]

basic rule of thumb is Acme is usually imperial, trapezoid is usually metric so you get 1/2" acme versus 12mm trapezoid, also often know as power screw over here.

Acme is usually a cut thread and trapezoid is usually a rolled thread.

Another thing to bear in mind is that 10 tpi two start is worked out as 5 tpi, the greater the tpi the more torque you need to move a carriage.

Good website here.

http://www.kingston-engineering.co.uk/exstock.htm

John S.

[ZeroCount]

Thanks John, had a look at that web site, and it didn't clear the fog from my brain :confused:, but then I found http://www.automationcomponents.co.uk/ things are making sense now :).

As I understand it (using Marchant Dice codes as an example) a TR16-8P4 screw is 16mm in diameter, would move 8mm per revolution, and has 4 starts. Anyone able to confirm this for me?

Also MD don't seem to sell multistart nuts at all?! seems a bit strange.

[ZeroCount]

Another thing to bear in mind is that 10 tpi two start is worked out as 5 tpi, the greater the tpi the more torque you need to move a carriage.

Don't you mean the lower the tpi the more torque? I don't need help with being confused ;). Ignoring efficency issues 5 turns per inch of travel has to take more torque than 10 turns per inch.

[John S]

Just testing to see if you are awake...............:D

John S.