Dongguan Pinsi Machinery Co., Ltd. is a professional linear motion manufacturer & supplier since 2013, we specialized in Precise Linear Motion Products like Linear Guides, Ball Screws, Cross Roller Guides, Linear Module, Linear Motor and more for various industries. In addition, we provide one stop linear motion solution.Welcome to contac us.

A customer once sent me a message:

“I need a 1610 ball screw for my CNC router. 1000mm travel. Quote please.”

I asked what motor he was using. He said a NEMA 23 stepper, around 3 Nm, with a 36V supply. Then I asked how fast he wanted the machine to move.

He said, “As fast as possible.”

That’s when I knew the 10mm lead was probably a mistake for his setup. Not because 10mm is bad, but because his motor wouldn’t have enough torque to actually use the speed he was imagining. He had picked the larger lead because it looked faster on paper.

That conversation happens a lot. People see “10mm lead = double the speed” and stop the calculation there. But lead changes more than speed. It changes thrust, acceleration, motor RPM, and sometimes the whole feel of the machine.

So if you’re trying to choose between 5mm and 10mm, let me walk through how I actually think about it.

A guy emailed me last week asking for a price on a C5 ground ball screw for his CNC router. He was building a machine to cut wood and plastic, with a target tolerance of maybe plus or minus 0.1 mm. Nothing crazy.

I asked him why he specifically wanted C5.

He said, “Because C5 is better, right?”

That’s a very common way to think. And it’s not completely wrong. C5 does have tighter lead accuracy than C7. But on a wood router with a flexible frame, a handheld router spindle, and a workpiece that moves with humidity, that extra screw accuracy is probably going to disappear into the noise.

I’m not saying C5 is useless. I’m saying it’s only worth paying for when the rest of the machine can actually use it.

So if you’re trying to decide between C5 and C7 for a ball screw, here’s how I think about it—not from a catalog spec sheet, but from the machines I’ve worked on and the mistakes I’ve seen.

I keep seeing the same question on forums and in emails:

“Should I use SFU1605 or SFU2005 for my CNC?”

Usually the person asking already has a machine design in mind. They’ve read that the 20 mm screw is “stronger” or “more rigid,” so they’re leaning toward the bigger one just to be safe.

That instinct isn’t wrong. But it also isn’t the whole story.

SFU1605 and SFU2005 are both 5 mm lead ball screws. The only major difference is the screw diameter—16 mm versus 20 mm. That 4 mm changes how the screw behaves mechanically, but it doesn’t automatically make the bigger screw the right choice.

I’ve worked on small CNC routers, compact linear stages, and a few heavier gantry machines. In almost every case, the final decision came down to what the axis actually had to do, not just which screw looked more substantial on paper.

So instead of giving you a catalog-style comparison, let me walk through how I actually think about this choice.

What to Check Before Replacing an Original Linear Guide Block

When a CNC machine has a worn linear guide, the obvious solution is to order the same part again.

Sometimes that's the best choice.

But not always.

We've had replacement projects where the original guide was available only with a long lead time, or the cost didn't make sense for an older machine. In those cases, a compatible linear guide slider can be a practical alternative.

The problem starts when “compatible” is treated as meaning “same size.”

It isn't.

A guide block can fit the rail and still have different preload, running resistance, accuracy, or load behavior. In a precision machine, those differences can show up after installation rather than when the part is sitting on the workbench.

So if you're sourcing a THK or HIWIN compatible linear guide slider, here's what I would check before placing the order.