The Diablo Rebar Demon 7/8-inch bit with a 16-inch working length is a long, large-diameter carbide hammer bit for deep anchor holes in concrete that may contain rebar. Bits of that size in the Rebar Demon line are SDS-Max, not SDS-Plus. Confirm the shank on the Amazon page and make sure your rotary hammer takes SDS-Max. The Diablo Rebar Demon 7/8 x 21 in SDS-Max bit handles larger holes in rebar-filled concrete.
Diablo Rebar Demon 7/8-inch bit specs
| Spec | Detail (per Diablo and retailer listings) |
|---|---|
| Diameter | 7/8 inch |
| Working length | 16 inches per the listing |
| Overall length | 21 inches on retailer listings for the 7/8 x 16 in. size (model DMAMX1180) |
| Shank | SDS-Max |
| Head | 4-cutter full-carbide head with Dura-Carbide |
| Joining method | Tri-Metal Fusion Welding between carbide head and steel body |
| Tip and flutes | Precision tip and optimized flute design for dust removal |
| Heat claim | Carbide withstands up to 1800 F, versus 800 F for standard bits (manufacturer claim) |
| Weight and warranty | Not listed on the retailer pages checked |
What the Rebar Demon design is meant to do
A standard masonry bit can overheat and chip when it strikes rebar. The Rebar Demon uses a full-carbide head with four cutters, which Diablo says take smaller bites of rebar and reduce vibration. The head is joined with Tri-Metal Fusion Welding, which Diablo and retailers say gives a bond up to 3 times stronger than standard bits, and Diablo also claims up to 7 times longer life. These are manufacturer claims and were not tested here.
The optimized flutes move dust out of the hole, which helps keep the bit cooler. Some listings also mention an integrated wear mark that shows when the bit is worn.
Best uses for a 7/8-inch, 16-inch-working-length bit
- Large anchor holes in structural concrete, where the anchor spec calls for 7/8 inch.
- Deeper holes that shorter bits cannot reach.
- Retrofit work where rebar contact is likely.
If you need a shorter 7/8-inch bit, the DMAMX1170 review covers the 13-inch, 8-inch-working-length version. For other sizes, see the 3/4 x 21-inch DMAMX1140, 3/4 x 13-inch and 5/8-inch DMAMX1090 reviews.
Safety and setup
- Use only an SDS-Max rotary hammer with the correct mode and side handle. A large bit can bind and twist the tool, so keep both hands on it.
- Wear eye, hearing and respiratory protection. Concrete dust contains crystalline silica, which is a health hazard when inhaled; use dust control.
- Scan for rebar, conduit and pipes first, and follow engineer or inspector guidance in structural members.
- Mark depth, drill steadily and pull back regularly to clear dust.
Pros and limitations
Pros
- Long working length for deep holes.
- Full-carbide 4-cutter head built for rebar contact.
- Dust-clearing flutes and a precision tip.
Limitations
- Needs an SDS-Max rotary hammer.
- Heavy and long, so it is harder to control in tight spaces.
- Overkill for light masonry work.
- Weight, warranty and the exact model for this ASIN were not confirmed.
- Not hands-on tested for this article.
Frequently Asked Questions
Is the Diablo Rebar Demon 7/8-inch bit SDS-Plus?
No. Bits of this size in the Rebar Demon line are SDS-Max. Check the listing and your hammer manual before buying.
How long is the working length?
The listing describes a 16-inch working length. Retailer listings for the 7/8 x 16 in. size give 21 inches overall.
Can it drill through rebar?
It is built for reinforced concrete and takes small bites of rebar, but avoid cutting rebar where you can, and move the hole or use a rebar cutter when you hit steel.
Can I use it with a cordless rotary hammer?
Retailer listings say the line works with corded or cordless rotary hammers, provided the tool has an SDS-Max chuck.
What warranty does it have?
Warranty was not listed on the retailer pages checked. Check the Amazon listing and Diablo’s support information.
Bottom line
The Diablo Rebar Demon 7/8-inch, 16-inch-working-length bit is for deep, large anchor holes with an SDS-Max rotary hammer. Check the shank, diameter and length on the Amazon listing before you order.
