Getting Better Results from a Drill Press T-Slot Clamp
You only have to watch a workpiece spin out of a poorly clamped drill press table once to understand why hold-down clamps matter. A drill bit binds in the hole, the workpiece breaks free, and now you have a spinning chunk of wood or metal swinging on the bit while your hands are nearby. T-slot clamps are the straightforward fix.
Understanding Your Drill Press Table Slots
Before anything else, grab a set of calipers and measure the slot on your table. You want three numbers:
- Slot width at the top (the opening) - Most common is 5/8 inch.
- T-slot width at the bottom (the wide part) - Where the T-bolt head or nut seats.
- Slot depth - How deep the slot is from table surface to the bottom of the T undercut.
Standard 5/8-inch T-slots accept 5/16-inch-18 T-bolts almost universally.
The Two Main Clamp Types
T-Track Hold-Down Clamps (Standard)
A flat arm with a slot rides on a T-bolt, and a knob on top bears down through the arm onto the workpiece. Adjust fore and aft along the slot. Main advantage: simplicity. Main limitation: tightening applies slight rotational force - always tighten while holding the workpiece firmly against your fence.
Cam Lever Clamps (Quick-Release)
Replace the tightening knob with a lever that locks with roughly 90 degrees of rotation. Once set, you can lock and release the clamp repeatedly without touching a knob. Extremely useful for production drilling. The tradeoff: cam clamps hold less firmly than a fully tightened hold-down.
The Clamps Worth Buying
POWERTEC 71168 T-Track Hold Down Clamps, 2-Pack
Five-and-a-half inches long and 1-1/8 inches wide. Each clamp ships with a 5/16-inch-18 T-bolt, washer, and five-star knob. Two in the pack - the minimum useful quantity. The arm has a centered slot that accepts the T-bolt anywhere along its length, so you can accommodate different workpiece heights.
Pros: Solid fit in standard 5/16-inch-18 slots, adjustable clamping point along the arm, hardware included, practical two-pack. Cons: Plastic body limits maximum clamping torque.
POWERTEC 71501 Cam Lever Clamp Set, 4-Pack, 1/4-20
Four cam levers, four 3-inch T-bolts, four steel washers, and four rubber washers. 1/4-20 threading - fits tables with 1/4-inch T-slots. Verify your table thread before ordering this set. For the machines it fits, this is the fastest workholding solution available for production drilling. The rubber washer between the clamp arm and workpiece prevents marring on finished wood.
Pros: Fast cam-locking action, rubber washers protect finished surfaces, four-pack. Cons: 1/4-20 thread - not universal for all drill press tables, lower maximum clamping force than a full hold-down.
POWERTEC 71082 Mini T-Track Hold-Down Clamp
Small format at 3-5/8 inches long. Ships with a single 5/16-inch-18 T-bolt, washer, and five-star knob. Less leverage than longer clamp arms. Ideal for small pieces of wood, thin aluminum plate, and plastic panel when a larger clamp would physically block spindle travel.
Pros: Compact, good for small workpieces near the spindle, standard hardware. Cons: Single unit - buy multiple for full workholding, less leverage, not for heavy stock.
Clamp Comparison
| Clamp | Style | Thread | Length | Pack Size | Best For |
|---|---|---|---|---|---|
| POWERTEC 71168 | Hold-down | 5/16-18 | 5-1/2 in | 2 | General drill press use |
| POWERTEC 71501 | Cam lever | 1/4-20 | 3 in bolt | 4 | Repetitive production drilling |
| POWERTEC 71082 | Mini hold-down | 5/16-18 | 3-5/8 in | 1 | Small parts, tight tables |
Setup Tips That Actually Make a Difference
Locate the clamp arm correctly. The T-bolt should be roughly centered between the table slot and the workpiece edge. If the bolt is directly over the workpiece, the arm tips and loses contact.
Use a backing board. When drilling thin stock, place a scrap piece of the same thickness alongside the workpiece to give the clamp arm a level platform.
Check for chip clearance. Hot chips and swarf accumulate around the fasteners and can lift the workpiece slightly.
Never clamp directly over the hole. The clamp arm should be behind the hole or to the side.
Tighten firmly, but do not strip. Five-star knobs are designed for hand tightening. If you need pliers, you are using the wrong clamp for the application.
The Verdict
Buy the POWERTEC 71168 two-pack as your first purchase. It covers most general drilling setups and works on any standard 5/16-18 table. Add the 71501 cam lever set if you run the same operation repeatedly - just verify your table thread first. Pick up the 71082 mini clamp when you regularly hold small stock close to the spindle.
FAQ
What is the difference between a T-slot clamp and a hold-down clamp? Hold-down clamp is the broader category. T-slot clamps are hold-down clamps specifically designed to insert into a T-slot track, which is the most common type used on drill press tables.
Can I use router table T-track clamps on my drill press? Yes, as long as the T-slot dimensions match. The 5/16-18 standard is common to both drill press tables and router tables.
How many clamps do I need? Two is the minimum - one on each side of the workpiece to prevent rotation. For irregular shapes or long stock, three or four is practical.
Are T-slot clamps safe for metal drilling? Yes, but use full hold-down clamps rather than cam lever clamps for heavy metal drilling.
References
- POWERTEC product pages: powertecproducts.com
- WEN DPA2513 drill press table specifications: wenproducts.com
