Over the past few years, I’ve used a Bosch SDS-Plus Bulldog Xtreme (11255VSR) rotary hammer to bore a thousand 3/16-inch to 1-inch holes in everything from 30-day to 30-year concrete. I’ve tossed the tool around in my truck and on site and exposed it to endless Pacific Northwest rains. Although it isn’t the fastest model on the market, it has been a steady workhorse.
Last January Bosch introduced the SDS-Plus Bulldog Xtreme Max (RH228VC) rotary hammer, which is billed as a step up from the Xtreme. I recently poured a foundation that involved pinning some of the footings to bedrock with rebar dowels and drilling holes for anchoring the mudsills. The job gave me a chance to test-drive the Xtreme Max and compare it head-to-head with my older model. My first impression? The new tool works great.
My Xtreme and the new Xtreme Max share many features. They’re both D-handle models, which are longer than pistol-grip and L-shape models and well-balanced for the downward drilling I commonly do as a framer. By using the longest bits available, I can often start my rotary hammer at waist height and bend over slightly as the bit works its way to the desired depth. This makes the job easier on my back.
Both models have rotary-hammer, rotary-only, and hammer-only modes; an internal clutch that slips when a bit binds or the tool overloads; and a rotating brush plate that delivers equal power in forward and reverse. Both also have a pivoting strain relief on the power cord for improved durability, and a comfortable side handle with a removable depth stop that you can adjust quickly by pushing a release button. And finally, both have a fold-out hook on the handle so you can hang the tool off a ladder, scaffolding, or sawhorses — a feature I really like. Neither model has a trigger lock-on button, which would be handy if you do a lot of chipping.
But the real story is the hammering mechanism inside the Xtreme Max. Like the Xtreme, the new tool uses a piston to launch a free-floating striker, which in turn hammers an impact bolt against the bit. An air space between the piston and the striker compresses and drives the striker forward as the piston advances, then vacuums it back as the piston retreats. The air space also acts as a shock absorber. The Xtreme Max has a longer piston, impact bolt, and air space than the Xtreme, which increases its power and drilling speed while reducing vibration. Whereas my Xtreme can handle spiral-fluted bits up to an inch in diameter in concrete with an optimal drilling range of 3/16 to 5/8 inch, the Xtreme Max can power 11/8-inch bits, with an optimal range of 3/16 to 3/4 inch.
Bosch also gave the new tool an internal counterbalance (to further offset vibration) and a metal gear cover.
I rode the Xtreme Max hard for several hours on my foundation job, using various SDS-plus Bulldog bits to bore anchor holes from 3/16 to 5/8 inch in diameter. To better compare the speed and handling of the old and new models, I poured an extra unreinforced pad with the leftover 25-MPa (3,626 psi) concrete and let it cure for 28 days. Then, using new Bulldog bits, I timed how long it took each tool to bore five 5/8-inch and 3/4-inch holes to a depth of 2 inches. The Xtreme averaged 12 seconds for the 5/8-inch holes and 19 seconds for the 3/4-inch holes. The Xtreme Max averaged 10 seconds for the 5/8-inch holes and 18 seconds for the 3/4-inch ones. Although the new model wasn’t radically faster than the old one, the results were consistent. As for vibration control, the Xtreme Max was way easier on my body than the Xtreme.
The Bottom Line
There’s nothing wrong with the Bosch Bulldog Xtreme rotary hammer I’ve been using. It’s reliable and has no problem drilling common anchor holes in concrete and bedrock, though it’s a bit of a rough ride when drilling the larger holes. But with the risk of cumulative trauma disorders just around the corner, I look for any excuse to give my wrists and hands a break. The new Bulldog Xtreme Max is faster than my Xtreme while neutralizing much of the vibration. If I were in the market for an SDS-plus rotary hammer right now, I’d buy the Xtreme Max.
—Kyle Dunkley is a carpenter based in Shawnigan Lake, British Columbia. This article first appeared in JLC.