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Flush-trim bits and pattern bits both guide a router along a template, but they are named from opposite directions. A flush-trim bit usually has its bearing at the tip, below the cutters. A pattern bit usually has the bearing at the shank end, above the cutters. That small difference decides whether the template sits above or below the workpiece—and which layers the bit can cut.
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The practical difference
With a tip-bearing flush-trim bit, the bearing follows a template placed beneath the workpiece. With a shank-bearing pattern bit, the bearing follows a template placed on top. Both can make accurate copies when the bearing and cutter are the same diameter, but they suit different stack-ups and access needs.
| Feature | Flush-trim bit | Pattern bit |
|---|---|---|
| Typical bearing position | Tip end, below cutter | Shank end, above cutter |
| Typical template position | Under the workpiece | On top of the workpiece |
| Best fit | Trimming an overhanging layer or copying from a bottom template | Routing with a top-mounted template or jig |
| Main clearance check | Room below the work for the bearing and bit | Room above the work for the bearing and shank |
| Common risk | Bearing loses contact if the template ends before the cut does | Cutter may cut into the template if it is too thin or poorly positioned |
Choose by template position
Start with the template, not the bit label. If the template can be clamped to the top of the work and kept clear of the cutter, a shank-bearing bit is usually the straightforward choice. The bearing runs against the template while the cutter trims the material below it. This arrangement makes it easy to see the cut and is useful for routing parts that sit on a bench.
A tip-bearing bit makes sense when the template needs to sit underneath, such as when a thin workpiece is fastened to a thicker pattern or when the top face must stay unobstructed. The bearing tracks the lower template while the cutters trim the upper piece. Check that the router base, workpiece, and template leave enough space for the bearing to reach the guide surface.
For common template work, compare pattern router bits and flush-trim router bits by bearing location, cutting length, shank size, and cutter diameter—not just by the name on the package.
Match cutting length to the stack
The cutter must cover the full thickness you intend to trim, but extra cutting length is not automatically better. For example, if a 1/2-inch template is fastened beneath a 3/4-inch workpiece, a bit with roughly 3/4 inch of usable cutting length can trim the workpiece while its lower bearing rides the template. If you want to trim several laminated layers at once, add their total thickness and allow a little margin so the cutting edges fully clear the stack.
Do not let the cutters reach a template you need to preserve. A shank-bearing bit can cut the top template if the cutter extends too high or the template is too thin. Use a durable template material, check the cutter’s position against the bearing, and test the setup on scrap. Likewise, a tip-bearing bit can damage a bottom template if the cutter extends down past the workpiece.
When the work is thicker than the bit can safely reach in one pass, use a longer bit only if the router, collet, and setup are rated for it. A safer alternative is to remove material in stages or use a template and bearing arrangement that keeps the cutter engaged at a controlled depth. Never extend a bit farther out of the collet than necessary.
Check bearing and cutter diameter
For a true copy, the bearing’s outside diameter should match the cutter diameter. If the bearing is smaller, it may follow a tighter path than the cutter and leave the part oversized or undersized, depending on the setup. A larger bearing can prevent the cutter from reaching the template’s full outline. Some specialty bits intentionally use different diameters for offset routing, but that requires calculating the offset rather than expecting an exact copy.
Also inspect the bearing before use. It should turn smoothly without wobble or grit. A seized bearing can rub or burn the template, then pull the router off the intended path. Replace a rough bearing and stop immediately if it binds; pushing harder is not a fix.
Control heat, tear-out, and kick
Template routing is often a long cut with the bit continuously engaged, so heat builds quickly. Make several shallow passes when the cut is deep or the material is dense. Keep the router moving steadily; pausing in one spot can scorch the edge or the template. Take particular care in hardwood, plywood edges, and abrasive materials such as some composites, which can dull cutters faster than softwood.
Feed direction matters. With a handheld router, the normal cut is counterclockwise around an outside edge when viewed from above. Climb-cutting can grab the work and pull the router forward. It may help with a tiny finishing pass in expert hands, but it is not a good default for template routing. Clamp the work and template securely, keep both hands on the router, and make sure the bearing stays in contact through curves and corners.
Which one should you buy?
Buy a pattern bit if most of your templates will sit on top of the work. Choose a flush-trim bit if you commonly place patterns underneath or need the top face clear. If you route both ways, having one of each is useful; you do not need a large set to get started. A good-quality bit in the correct shank size for your router is a better purchase than a cheap assortment with mismatched bearings or more cutting length than your jobs require.
The cheaper option is fine for occasional work in softwood or plywood when the bearing runs smoothly, the carbide is sharp, and the bit matches the job. Replace or upgrade it if it chatters, burns despite a steady feed, leaves a rough edge, or has a bearing that loosens. Before buying, measure the template and workpiece stack, confirm which side the template can occupy, and verify that the bearing can touch it without the cutters reaching a surface you want to keep.