Kapex KS 120 fine “gritty/sandy” sound when sliding head on rails

E

emmakun

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Joined
Jul 10, 2024
Messages
3
Hi everyone,

I recently bought a lightly used Kapex with manufacturing date 2024/07. Motor sounds great and the saw cuts fine. The only concern is a kind of loud (at least louder than my old WEN saw) “gritty/sandy” sound when I slide the head along the rails. No binding, travel is smooth end-to-end, and there are no scoring/wear marks visible on the tubes.

I recorded two short clips:
  • Video 1 – Kapex rail sound:

  • Video 2 – Old saw (WEN mm1011T) as reference (sound is there but the Kapex is louder and less "smooth"):


What I’ve already done
  • Cleaned both tubes with odorless mineral spirits until the blue shop towel came out clean.
  • Lubrication: used 3-in-1 (aerosol), sprayed a little on a blue shop towel and wiped a thin film onto each tube (did not spray directly on the saw).
  • Cycled the head many times full stroke, then wiped off any visible excess.
  • Slide lock fully released; miter/bevel locked at 0°.
  • Travel feels uniform with no stick–slip; the “gritty” sound is consistent across the stroke.
What I have NOT done
  • No grease, no wax, no PTFE/silicone “dry lube”.
  • Haven’t opened the carriages (assuming they’re sealed/wipered).
  • No solvents other than odorless mineral spirits for the tubes.
Questions for the group
  1. Is a fine granular/whisper sound normal on Kapex recirculating-ball rails, even on newer units, or should the slide be almost silent?
  2. If not normal, what would be your next field-safe step beyond clean + thin oil film (e.g., repeat wipe-and-cycle, different oil weight, specific product)?
  3. Could this indicate internal contamination in the carriages/wipers, and if so is that service-only?
  4. What is the lube best practice you prefer on these rails?
  5. Any recent production changes (2023–2025) that make newer Kapex units sound different vs older ones?

Thanks in advance! I just want to confirm whether this sound is within the normal range or if I should plan for a service visit. Happy to upload more clips (slow/close-up) if that helps.

-- Emmanuel
 
Sounds like the bearings in mine. Use a dry lube for the rails, my favorite PG2000, or in a smaller bottle one of fancy bicycle chain lubes. If you think it slides smoothly now, just wait for the after lube.

Peter
 
Thank you all! The rails work, they are not hard or anything like that. I guess I'm just surprised that it sounds louder and grittier than my previous, really inexpensive saw. I'm also not super impressed with the stock 60T saw. I cleaned it up, but it rattles when it's cutting. I guess it may be out of balance, or maybe I just didn't tighten the nut enough? The inexpensive Oshlun 80T blade cuts much better so far, will keep it in the saw as my main blade for now, but I'm still in the look for something that cuts as smoothly as my old Freud LU79R010 thin kerf ultimate melamine & plywood blade.
 
The stock blade is pretty high quality, shouldn't wobble unless it wasn't seated correctly. Festool would likely provide a new one if it was defective right out of the box.
 
My Craftsman radial arm saw slid as smooth and slick as could be when it was delivered. That was because the bearings were excessively loose and it would allow the very dangerous “stock climb”. I adjusted the bearings so that there was no up/down movement, and it felt slightly gritty.

Sliding miter saws cut on the push and not on the pull, so stock climb is not nearly as dangerous. If your saw is smooth-as-glass, grasp the saw head and check for up/down movement. There should be no noticeable movement.

My guess is that the gritty feel is the result of a tightly adjusted linear bearing. Check for up/down movement, and I would guess that there is very little or none (a good thing).

Compare that up/down movement with a saw that moves “smooth-as-glass”.

In any case, if the saw does not fight you sliding fore and aft, than it is probably OK.
 
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