Getting Drill Press Belt Replacement K 31 Right: Fit, Tools, and Final Checks
The K31 is one of the most common little V-belts in the benchtop world, which is exactly why people get it wrong: they see “K31” on a dozen listings and assume any of them will drop in. A drill press belt replacement in K 31 size is easy to fit, but only once you understand what the K31 designation actually means and confirm it against your pulley grooves.
A K31 belt is a metric K-section V-belt, roughly 5/16 inch wide and 31 inches in effective length. It carries motor power to the spindle across the stepped pulleys, and the K-section profile is narrower than the wider A-section belts used on larger presses.
Short answer: confirm your press actually takes a narrow K-section belt (measure the groove width and the belt path), then fit a K31 belt, slacken the motor to install it, and re-tension to about half an inch of deflection.
Confirm the K31 is really your size
Two quick checks stop a mismatch:
- Groove width. K-section is about 5/16 inch. If your groove is wider (around 1/2 inch), you have an A-section press, not a K31.
- Length. K31 is about 31 inches effective. Measure your old belt or wrap a string along the pulley path to confirm.
Many Delta, Craftsman, Ryobi, and SKIL benchtop presses use exactly this belt, which is why it is so widely stocked.
The belt to fit
When your press genuinely takes a K31, a K31 drill press V-belt is the direct match, made from reinforced rubber that runs quieter and lasts longer than the thin urethane belts that crack. It fits the many benchtop presses built around this size.
The honest drawback: a molded K31 is a fixed length, so if your press sits between sizes you may need the next size up or down. Who should skip it: anyone whose press uses a wider A-section belt, since a K31 will ride too high in the groove and slip.
Fitting it, step by step
- Unplug the press.
- Open the pulley cover.
- Loosen the motor lock knobs and slide the motor toward the spindle to slacken the belt.
- Roll the old belt off and the K31 on, seating it in the pulley steps for your usual speed.
- Slide the motor back to set tension, then lock it.
- Spin the spindle by hand to confirm tracking, then close the cover.
Confirm the profile, then it drops right in
Drill press belt replacement in K 31 size is simple as long as you confirm the narrow K-section profile and the 31 inch length against your press. Match both, slacken the motor, and set tension by feel.
Three takeaways:
- K31 is a narrow K-section belt, about 5/16 inch wide and 31 inches long.
- Confirm your groove width; an A-section press needs a wider belt.
- Slacken the motor to install, then re-tension to about half an inch of give.
FAQ
What does K31 mean on a drill press belt? It is a metric K-section V-belt about 5/16 inch wide with a 31 inch effective length. The K identifies the narrow profile.
Which drill presses use a K31 belt? Many benchtop presses from Delta, Craftsman, Ryobi, and SKIL use this size. Confirm by measuring your groove width and belt length.
How do I know if my press uses K31 or A-section? Measure the pulley groove width. About 5/16 inch means K-section (K31); about 1/2 inch means A-section.
Will a K31 belt work if my press is between sizes? A molded belt is a fixed length, so you may need the next size up or down. Measure the belt path to confirm.
How tight should the belt be? About half an inch of deflection midway between the pulleys. Too tight strains the bearings; too loose slips.
Why does my new belt slip? Usually the wrong profile riding high in the groove, or too little tension. Confirm K-section and set tension.
References
- Delta Machinery, drill press manuals and parts information: https://www.deltamachinery.com
- Sears PartsDirect, Craftsman drill press belts and parts: https://www.searspartsdirect.com
