CNC3 3018 PRO threaded rod

Recently acquired a CNC3 3018 Pro and wish to enlarge the carving area from 300mm x 180mm to 400mm x 400mm. I can see the various linear guide rods required but unsure of the screw (threaded rod) to order. My parts list shows a T8-4 screw but need clarification what this means - is it 8mm diameter by 4mm lead with 2mm pitch?

I think the T is for Trapazoid. and I think the 4 may be the number of leads.

Cheers for that, I just wasn’t sure. Do you know if it matters if lead is 8 instead of 4?

I’m pretty sure the 8 is 8mm diameter. Yes, the leads of the rod must match the leads of the nut.

Leads (or sometimes called starts) are the number of places where the thread begins. If you look at a canning jar, there is one thread that winds all the way down. If you look at a modern jelly jar in your fridge, you’ll see that it has many thread starts. That’s so machines can easily attach the lids with just a small rotation.

Threaded rod is the same. with more leads one turn will advance the nut farther.

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Thank you.