specifications on the Lead Screw?

Hi all,
I can’t seem to find the specifications on the Lead Screw that is included in the 2010 KOP. The number is BZ8M16x15, and I’ve looked on the website of it’s supplier, Kerk, but this number doesn’t seem to be there.

Does anyone know the specs or where I can find them for this piece?

Thanks much
Mike :slight_smile:

Wow, that’s a pretty tough one.

Looking at the KOP picture, it looks like a much longer pitch than previous years. if it’s actually 15" long, then the lead looks to be just under 3", so I’m guessing it’s 75mm lead.

I don’t have one to measure, but can you get the OD? that will help dig around the site. I checked the 1/2" and 5/8" pages, but nothing had more than a 50.8mm lead.

The part number builder is no help at all.

I’ll keep digging.

Edit: I’m not looking at a high enough resolution picture. The lead I saw was a side effect of the pixels. If you can provide a good picture, or the overall length, diameter, and number of turns, we can probably nail it down pretty quickly.

I don’t have any new info at the moment. I even downloaded their catalog and just browsed through it to no avail.
I will be able to measure it tonight and get a better look at it, Thanks for looking.


Below dimensions are approximate(measured with tape measure):
Overall Length - 15-1/8"
Diameter - .5"
6 turns of screw - 3-3/4" movement of nut.

Screw has 6 starts

Nut is 1-15/16" long

Thanks for measuring that. Now to convert it to which model of theirs it is. That way I can find out how much force we can push with it.


Based on our measurements (which match well with those posted above) and the part number, I believe it is the 16mm lead part listed in this table:


That would put the efficiency at 80%, giving you all the values you need to calculate linear force from torque.

F = 2piT*E/L

F = Linear force
T= Torque
E = Efficiency
L = Lead

You can do this calculation with any units, but be careful that your units all match. For example a lead in inches should be used with a torque in in-lbs to get a force in lbs.

The nut most resembles the BFW series with triangular flange:

The table on that page puts the max dynamic load at 150 lbs for a 1/2" lead screw.

Thanks for the info.
I’m disappointed in the load capability, I was hoping for double that for an arm to de-turtle us as it were. lol

I’ll have to revisit the design to see what we can do.

Say, check my math if you wouldn’t mind.

If I want to move the nut such that it travels 12 inches in 5 sec or less, that converts to 3.2 revs/sec (with a lead of .625) which is 38.4 rpm.

If one looks at the FP motor torque curve at .2Nm (max power) the speed is about 700 rad/sec which is about 6700 rpm. Thus I would need to reduce that by about 174:1. This would give a perfect world torque of about 305 Lb-inches

I (based on wanting to lift 300 lbs, and yes, I know Ill have to change that) need 300/(.625*6.28)=about 76 Lb-in
Throw in about 80% for the lead screw and about 75% for the reducer and we get a 183Lb-in available to drive a 76 Lb in load.

Some how it just doesn’t seem like I’d have that much extra oomph out of a FP motor.

The big question is how am I going to get a 30 inch arm up with only 15 inches of travel and be able to flip our 150 lb robot. Hmmmmm

Thanks for your thoughts everyone.