What size Chisel Bit - Concrete

[mobiledynamics]

I hava a 45lb Makita 1 /18 demo hammer....need to order a bit to break up a generator pad.
I don't know sch#### about demo bits. Comes in 1 1/8, 2" and 3"
Anyone can shed some insight - is narrow better or just get the 3"

 

[rlitman]

I have a Makita HM1301; their original 45lb demolition hammer that's been oh so copied by the Chinese. Today's models are pretty much the same thing, with slightly different bells and whistles.

If you want to break up a pad (I'm imagining something like a sidewalk, say 4" thick with some wire mesh), you want a pointed bit called a moil or bull point. Don't use a chisel. You'll lose too much impact energy. The point will easily allow you to break it up into manageable chunks.


The 3" chisels for these are intended for cutting a line into asphalt. They make a terribly messy cut, and you're usually better off with a diamond saw, but I have used my chisels to detach chunks of mortar from a slab.

Be aware that the tools that fit the Makita (or at least mine) are a slightly smaller hex size (28.6mm = 1-1/8") than what fits the Harbor Freight knockoffs (30mm), and Bosch uses an external ring collar retention system (like most pneumatic breakers) with a fully hexagonal head, while Makita uses a notch and has a round top, so there isn't much cross compatibility in tooling you can take advantage of.

 

[mobiledynamics]

Duh. Impulse purchase. Just opened it up. It comes with a bull point bit as such. Thx for the wiki regardless

 

[rlitman]

LOL, if you want a new impulse buy, I use the ground tamper attachment on my hammer way more than any chisel.

https://www.amazon.com/Makita-31485-Rammer-30-200-Multi-Colour/dp/B00AFZEZEC?tag=atomicindus08-20

 

[mobiledynamics]

was that a serious post RL. What use case would you use for that.....
Heh, the pad removal has been on my honey to do list for quite some time......just never got around to cross it off my bucket list.
I priced it out...with some guys who was working on the block on some neighbors house. It was about 1/2 the cost of the tool but then again, it also did not involve me doing any heavy lifting....

 

[RTM]

Something breaking, I agree on the point tool. I use my chisels for tile removal, or breaking off chunks of over pour to get sorta straight edges

 

[KnurledNut]

Depends on the concrete and reinforcement.
Bull points tend to drive in and get stuck. If it was a 65lb breaker, I’d go straight to a narrow chisel. On a 45lb I’d start with the same and switch to a bull if it was fighting me.
Best to start at the corners and work in.

 

[Hakeem]

Depends on the concrete and reinforcement.
Bull points tend to drive in and get stuck. If it was a 90lb breaker, I’d go straight to a narrow chisel. On a 45lb I’d start with the same and switch to a bull if it was fighting me.
Best to start at the corners and work in.

Agreed. Bull point for stubborn pieces only. I use the chisel to “cut” the concrete into chunks and pry them loose. I try to get it into as big of a piece as i can still handle, around football size ... bigger pieces mean less time using the hammer and a faster clean up.

For a generator pad that’s around sidewalk thickness I’d go with the 2” chisel, cover more ground that way.

 

[rlitman]

Depends on the concrete and reinforcement.
Bull points tend to drive in and get stuck. If it was a 90lb breaker, I’d go straight to a narrow chisel. On a 45lb I’d start with the same and switch to a bull if it was fighting me.
Best to start at the corners and work in.

Except it's not a 90lb breaker, and it doesn't have anywhere near the power of a pneumatic hammer. But yes, if you let it (especially in the middle), the bull point will still drill it's way in even with this smaller machine. Starting at the corners (exactly as you say), lets you break off good chunks, and at least on mine, the narrow chisel (1-1/8") tends to just slow me down, where it might work better on a bigger machine. YMMV, and the chisel just might be better on an overly thin slab.

 

[dutchgray]

Whatever chisel or bull point you use, you want another to use when you get the first one stuck.

If you ever hire a concrete breaker (In the UK where I am) it will always be supplied with two bull points for this reason.

 

[KnurledNut]

@rlitman
I misspoke. Corrected my post. Meant 65lb. electric.
I’ve ran Hitachi (H65?) demo hammers similar to the OP’s. Those things were beasts for their size.
We demo’ed an Alcoa factory floor that I was told was 7000psi iirc. Heavily reinforced and around 10” thick where machinery sat. It laughed at a 90lb pneumatic breaker. Ended up with a skid-steer for that job.

 

[OccupantRJ]

For what it is worth, in the past I rented a demo hammer to break up some brick steps. A few years ago I had another set of steps to do. This time, since it was within range of my air hose, I used my air chisel. It put the demo hammer to shame and was a hell of a lot lighter to use. Next time I have to break up concrete I will be trying it again.

 

[Leaflessshadetree]

How big and thick is the pad? Many can be easily broken with a sledge hammer, especially if you can lift an end so it is unsupported.

 

[mike93lx]

Depends on the concrete and reinforcement.
Bull points tend to drive in and get stuck. If it was a 65lb breaker, I’d go straight to a narrow chisel. On a 45lb I’d start with the same and switch to a bull if it was fighting me.
Best to start at the corners and work in.

I prefer a chisel for the same reason. Getting a 40+ lb hammer stuck *****

Just tonight I broke up a bunch of cmu and brick and used the chisel for all of it