Equipment Care & Repair

Undercut and Jamb Saw Blade Changes

Changing blades on Crain and Roberts undercut, jamb and toe-kick saws: unplugging, spindle locks, blade direction, height and depth settings, and brushes.

Updated · 4 min read

Undercut and jamb saws are simple to service: unplug, lock the spindle, swap the blade with the teeth facing the right way, and reset height and depth. The blade screw loosens counter-clockwise and tightens clockwise; every Crain and Roberts manual we checked uses a standard thread.[1][5]

Safety

Switch off and unplug the saw, and wait for the blade to stop, before any adjustment, blade change or repair.[1] Cutting masonry or tile creates silica dust; use dust control and respiratory protection.[4] OSHA Table 1 has no row for undercut saws, so the employer must assess and limit exposure under the silica standard.[7]

Choose the right blade

Use the blade the saw maker lists for the material.

Crain

Saw Blade Cuts Notes
No. 835 No. 836 carbide, 40 teeth Wood Wood doors, jambs, base and drywall only[8]
No. 835 No. 822 diamond Masonry, ceramic tile, stone Never on metal or wood[9]
No. 835 No. 805 abrasive Brick only, not tile or stone Good for roughly 7 to 10 ft of undercutting[10]
No. 575 No. 556 carbide Wood [2]
No. 777 toe-kick No. 787 carbide Wood Use only Crain No. 787 or No. 789 blades[3]
No. 777 toe-kick No. 789 diamond Masonry, tile Cut no more than 6 ft, then let it cool[11]

Roberts

Saw Blade Cuts Notes
10-56, 10-46 10-47-2 carbide, 36 teeth Wood Recessed arbor for flush cuts[12]
10-56, 10-46 10-47-6 carbide Wood [5]
10-56, 10-46 10-55-24 masonry Masonry The 10-56 needs the masonry blade adaptor[5]

Changing the blade

Unplug first, every time. The steps differ by maker.

Crain

For the Crain No. 835:[1]

  1. Unplug the saw and let the blade stop.
  2. Retract the height adjuster flush with the housing for wrench clearance.
  3. Push the spindle lock and turn the hex wrench until the lock engages.
  4. Turn the wrench counter-clockwise to loosen. If it's very tight, hold the blade with locking pliers and add an extension to the wrench.
  5. For the No. 836: seat the blade driver on the spindle, then the blade with the driver nubs through its holes. For masonry and diamond blades, use the spacer and blade clamp instead.
  6. Reinstall and tighten the blade screw firmly with the spindle lock pressed.

On the No. 777 toe-kick saw, never use the spindle lock as a motor brake.[3]

Roberts

For the Roberts 10-56:[5]

  1. Unplug the saw.
  2. Fit the blade with the teeth facing the direction of rotation, which is counterclockwise viewed from the bottom.
  3. For a masonry blade, insert the masonry blade adaptor first.
  4. Press the arbor lock and turn the blade screw clockwise until tight. The 10-46 uses a retainer nut the same way.[6]

Set height and depth

Reset both after every blade change. Full technique is in Undercutting door jambs and Toe-kick saws.

Crain

  • Height (No. 835): set the saw on a piece of the new flooring and bring the adjuster down to the floor. For a snug fit, lower it one reference line; each line is 3/32", one blade thickness. Turn both knobs together to keep the blade parallel.[1]
  • Depth: no more than 1/2", so you don't hit studs or nails, and only as deep as the wood base. Cutting drywall makes dust that damages the saw.[1]

Roberts

  • Height (10-56): align the top of the blade with the scribe mark on the jamb, check that the body is parallel to the index lines, and keep the blade off the floor and substrate.[5]
  • Depth: set it just deep enough to clear the jamb or base molding.[5]

Feed direction

Both makers are specific about direction, and both feed left to right.

Crain

  • Always push the No. 835 against the blade rotation, moving left to right. Never pull it toward you or cut in reverse.[1]
  • The saw plunge-starts: plunge slowly before pushing forward.[1]
  • A dull blade loads the saw heavily and raises the risk of kickback.[1]

Roberts

  • Always feed the 10-56 to your right so the teeth advance into the wood.[5]

Other maintenance

Neither maker gives sharpening instructions. Both say to replace dull or damaged blades and run sharp blades at all times.[1][5]

Crain

  • Dust behind the blade guard, especially drywall dust, can jam it open or shut. Check the guard before each use.[1]
  • The No. 777 clutch handles about 500 disengagements before it needs factory service.[3]

Roberts

  • Replace both brushes once either wears to about 1/3" long. Other repairs go to an authorized service center.[5]

Common mistakes

These damage blades and saws.

  • Blade on backwards. Check tooth direction against rotation.
  • Using the spindle lock to stop the blade.
  • Cutting into drywall or plaster. The dust wears the saw.
  • Wood blades on tile. Use the diamond blade.
  • Pulling the saw backward. It can kick back.

Saws and blades we carry

These are the saws, blades and parts we stock.

References

  1. Crain No. 835 manual
  2. Crain No. 575 manual
  3. Crain No. 777 manual
  4. Crain No. 837 dust cover manual
  5. Roberts 10-56 manual
  6. Roberts 10-46 manual
  7. OSHA 1926.1153, Silica
  8. Crain No. 836 carbide-tipped blade (product page)
  9. Crain No. 822 diamond undercut blade (product page)
  10. Crain No. 805 masonry blade (product page)
  11. Crain No. 789 toe-kick diamond blade (product page)
  12. Roberts 10-47-2 blade product data sheet

Linked PDF documents are archived copies saved by PreFloor Tools so they stay available if the publisher moves or removes them. Check the publisher's website for the latest revision.

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