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Flush-cutting a door jamb is a small job, but the wrong reciprocating saw blade can turn it into a damaged floor, chewed-up trim, or a blade that binds halfway through the cut. The best choice is usually a short, flexible demolition blade with fine-tooth or medium-tooth geometry—not the longest, most aggressive blade in the package.
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The best blade type for door jambs
For cutting a jamb so flooring can slide underneath, start with a 6-inch flexible wood reciprocating saw blade with roughly 6 to 10 teeth per inch (TPI). A blade in this range cuts through pine, fir, oak, and painted trim without removing material too aggressively.
A flexible blade matters because the blade needs to lie nearly flat against the floor. Its back can bend slightly as you work, allowing the teeth to cut the bottom of the jamb while the floor protects itself from the blade body. A stiff blade tends to lift the saw or force you to hold it at an awkward angle.
Use a shorter blade when possible. A 6-inch blade provides enough reach for most interior door casings and jamb legs, while leaving less exposed length to whip around. An 8-inch blade can work, but it is easier to bend, vibrate, and mark the wall or floor. Blades longer than 9 inches are generally unnecessary for this task.
Blade choices compared
| Blade type | Best use | Advantages | Drawbacks |
|---|---|---|---|
| Flexible wood blade, 6–10 TPI | Standard wood jambs and casing | Fast, controllable, conforms to the floor | Teeth dull quickly in nails |
| Bi-metal demolition blade, 6–10 TPI | Jambs containing nails or screws | More tolerant of embedded metal and abuse | Usually leaves a rougher cut and costs more |
| Fine-tooth wood blade, 10–14 TPI | Clean cuts in hardwood or finished trim | Less splintering and better control | Slower; clogs more easily in soft wood |
| General-purpose blade, 8–12 TPI | Occasional mixed-material work | Useful if you already own one | Not ideal at either fast cutting or finish quality |
If the jamb is ordinary painted softwood and you are installing carpet, laminate, or floating flooring, the cheaper wood blade is fine. There is little benefit in buying a premium blade for one or two cuts. Choose a bi-metal blade if you expect to hit nails, staples, metal corner reinforcement, or an unknown material.
Tooth count and blade construction
Tooth count changes both speed and cut quality. A 6-TPI blade removes wood quickly but can grab and splinter the jamb. A 10- or 12-TPI blade cuts more smoothly and is easier to control near finished surfaces. Very fine blades—around 14 TPI or higher—are not usually the best choice for a thick jamb leg because they cut slowly and can pack with sawdust.
Bi-metal construction is worthwhile when the jamb may contain fasteners. These blades combine a flexible spring-steel body with hardened teeth. They cost more than basic carbon-steel wood blades, but one hidden nail can destroy a cheap blade almost immediately. Do not assume a “wood” blade will tolerate nails just because it has a thick body.
Look for a blade with a narrow kerf and a pronounced, flexible body. A wide demolition blade is durable, but it removes more material and can make it harder to keep the cut tight to the floor. If you need a replacement set, compare bi-metal 6-inch reciprocating saw blades rather than buying a long mixed pack filled with sizes you will not use.
How to flush-cut the jamb
Remove the door and check for wiring, plumbing, or other obstructions on both sides of the wall. A normal interior jamb is not usually a utility hazard, but the wall cavity can be. Mark the height of the flooring or underlayment and add about 1/8 inch of clearance. The flooring should slide under the jamb without being forced.
Place a scrap of the actual flooring upside down next to the jamb. Rest the saw blade on the scrap and make a shallow starter cut. This automatically sets the correct height and protects the finished floor from the blade body. If underlayment will be installed, include its thickness in the spacer.
Hold the saw with both hands and use a low speed for the first few seconds. Let the blade’s teeth do the work; pressing hard causes the blade to flex, wander, and bind. Once the kerf is established, increase speed modestly and keep the shoe or lower portion of the saw supported against the spacer.
Cut from the visible face toward the back of the jamb. Stop before the blade reaches drywall or the opposite casing, then finish the last section carefully. A utility knife or sharp chisel can clean up a small uncut corner. Do not twist the saw to finish the cut—twisting is a common way to bend teeth or snap a blade.
Common failures and fixes
Blade binds: The cut may be closing on the blade, especially in a heavily painted jamb. Back out with the trigger released, clear the kerf, and restart with less pressure. A slightly shorter blade also reduces flex.
Floor gets scratched: The blade was likely held above the spacer or allowed to dip below it. Use a thicker scrap, tape the scrap to the floor, and keep the saw shoe supported throughout the cut.
Jamb splinters: Switch from a coarse 6-TPI blade to a 10- or 12-TPI wood blade, and score the cut line first with a sharp knife. This matters most with stained hardwood trim.
Blade hits metal: Stop immediately rather than forcing the cut. Change to a reciprocating saw blade rated for wood with nails. If the metal is a screw, removing it with pliers or a driver may be faster than cutting through it.
What to buy
For most flooring installations, buy a 6-inch flexible wood blade in the 8- to 10-TPI range. Select a fine-tooth version for hardwood or visible finished trim. Choose bi-metal construction when the jamb is old, repaired, or likely to contain fasteners. A two- or three-blade pack is enough for a single room; buying a large assortment only makes sense if you regularly cut lumber, nails, and demolition material.
The best blade is therefore the one that matches the jamb, not the most expensive blade on the shelf. Short length, moderate tooth count, and enough flexibility to ride on a flooring spacer will produce a cleaner, safer cut than brute-force demolition teeth.