Stop Collar Set: How to Set Drill Depth Accurately Every Time
By Welcome to Kreg Tool | Published: 2026-11-01
Category: Tips & Care
Learn how to set consistent drilling depth with a stop collar set, including sizing, installation, and checks that prevent over- or under-drilling.
Quick answer
Slide the correct-size stop collar onto your drill bit, set it to your desired depth using a test hole or the bit’s exposed length, and tighten the hex screw firmly. Then drill a scrap test hole to confirm the depth before working on your project.
Why stop collars beat eyeballing depth
Eyeballing depth works until you need repeatability. A stop collar creates a physical limit on how far the bit can enter the material, so every hole in a row matches. That matters for pocket holes, shelf pins, and any joinery where a few millimeters of variation shows up as a loose or proud joint.
The trade-off is that a stop collar only controls depth along the bit. It does not correct a tilted drill, worn bit, or inconsistent pressure, so pair it with a steady stance and a sharp bit.
Match the collar to the bit shank, not the tip
Stop collars grip the smooth shank of the bit, so the size must match the shank diameter—not the cutting diameter. A 3/8-inch bit with a reduced shank may need a smaller collar than its tip suggests. Check the shank with calipers if you are unsure.
The Stop Collar Set covers five common shank sizes—1/4-inch, 5/16-inch, 3/8-inch, 7/16-inch, and 1/2-inch—which handles most standard bits. Specialty bits with unusual shanks may still need a dedicated collar.
Where a stop collar helps most—and where it doesn’t
A stop collar is most useful when you are drilling many holes to the same depth: pocket-hole pilot holes, shelf-pin holes, dowel joints, and counterbores. It is less useful for through-holes where you want to break through the far side, because the collar will stop the bit before it exits.
For pocket-hole bits, the collar must sit against the bit’s built-in stop shoulder or the jig’s guide. If the collar slides past that point, the bit will not seat correctly in the jig, so verify the setup before drilling.
How to set and use a stop collar step by step
- Measure the exposed bit length: Insert the bit into your drill and measure from the tip to the desired depth mark with a ruler. Subtract that from the total bit length to find where the collar should sit. Common mistake: measuring from the flutes instead of the tip, which leaves the hole shallow. Write the measurement down; you will reuse it for every hole in the batch.
- Slide on the correct-size collar: Choose the collar that fits the bit shank snugly and slide it to your measured position. It should slide freely but not wobble. If it rocks on the shank, you have the wrong size. A collar that wobbles will set at an angle and drill an inconsistent depth.
- Tighten the hex screw firmly: Use the supplied hex wrench to tighten the screw until the collar will not twist by hand. Do not overtighten to the point of stripping the screw. Checkpoint: try to rotate the collar—if it moves, tighten again. Recheck the screw after the first few holes; vibration can loosen it.
- Drill a test hole in scrap: Use the same bit, drill, and material as your project and drill one hole. Measure the depth with a ruler or the bit itself. Adjust the collar if the depth is off, then retighten and test again. Test on scrap of the same thickness; a different material can change how the bit enters.
- Drill your project holes with steady pressure: Keep the drill perpendicular to the surface and let the collar stop the bit. Do not force past the stop. Common mistake: angling the drill at the end, which lets the collar dig into the workpiece and throws off depth. If the collar contacts the workpiece, stop and check alignment before continuing.
- Remove and store the collar after the batch: Loosen the screw and slide the collar off the bit. Wipe off dust and store the set in a dry place. Checkpoint: if the collar is hard to remove, clean the bit shank before storing. Leaving a tightened collar on a bit can flatten the shank or make the collar seize.
Product facts
- Stop Collar Set: 5-piece set of Drill Bit Stop Collars with two hex wrenches. You get the five common sizes and the wrenches needed to tighten them, so you can set up multiple bits without hunting for tools.
Stop Collar Set - Stop Collar Set: Fits the most common drill bit sizes: 1/4", 5/16", 3/8", 7/16" and 1/2". Most standard twist, brad-point, and pocket-hole bits fall within these shank sizes, so one set covers typical workshop drilling.
- Stop Collar Set: Single piece design, zinc plated for rust resistance. A one-piece collar is less likely to shift or loosen than a multi-part design, and the plating helps it hold up in humid shops.
