Compressor for jackhammer-quick answer ?

[bcarwell]

I'm in urgent need of an answer or educated guess for sizing a compressor for a pneumtic jackhammer on Craig' List.

All I can tell you about the jackhammer is it is 90 pounds, has a "rotary tip" function and uses "larger" hoses. The guy is calling back with the brand/model but in the meantime I thought maybe you could at least get me in the ballpark.

I need to know if I could get any use out of it with an obviously undersized 2HP running, 6HP max, 30 gallon, 8.6 cmf @40 psi, 6.4 cfm @ 90 psi compressor.

When I say "any" use, let me be clear. I am in Central Texas putting in about 15 fence posts on my property and go down 18 inches and occasionally hit limestone of varying size, thickness, such that my post hole digger doesn't go further. I am NOT concerned about being able to have a high duty cycle like professionals who break up highway concrete for a living. I just need it to pop the bottoms of these holes a few times and rest while the compressor builds back up and I clean out what it broke up, and then repeat, and hopefully allow the post hole digger bit to catch and get down another 6 - 12 inches. If it takes 1/2 hour per hole to get through this last 6 - 12 inches that's fine.

I don't think many other suggestions of alternates would be of much help as I've thought of/tried most. A Beltec hydraulic downpressure 3PH post hole digger is out of my price range- renting or buying. I've tried water to lube the hole which helps some, and a fishtale bit on my auger. I don't think weight on the PH digger would help either. There is an electric jackhammer for rent for about $100- half the price of this jackhammer which is 2 years old and priced at $200. The rented electric jackhammer is only 60 pounds and I bought and returned an electric jackhammer from Harbor Freight that was about the same weight because it didn't do much. I hired a guy to dig 20 or so holes in another location- too pricey and I doubt anybody'd even do 10 holes or so. I have a LOT of patience in digging these holes and just can't think of an alternative I haven't tried to a jackhammer (which people use around here use to put in sign posts- electric jackhammers but the signs are not intended for permanent installation unlike fence posts).

Bottom line is could I get even five or six useful pops from the jackhammer out of such an obviouly undersized compressor before it needed to recharge ? If so this pneumatic jackhammer would be useful, as I occasionally have the need for drilling only 5 or so post holes from time to time- not enough to justify renting or buying anything else. But it would be nice to have something around here permanently that could at least break this stuff up a little and to avoid the inconvenience and expense of repeatedly renting from time to time.

Sorry I don't have specs on the jackhammer yet. I just thought maybe somebody could guess what the absolute minimum compressor requirements for these boys, given the weight of 90 libs (which doesn't sound like a Godzilla type jack hammer).

Any info quickly would be much appreciated.

Bob

 

[MtnViewRanch]

Save your money, you would be waisting your time trying to use your compressor.

 

[Scooby074]

6.4 CFM?

Dont even think about it. Even the smallest Rotary would be well over 60CFM

A 60 pounder is pushing 120CFM

 

[bcarwell]

Okay, thanks guys. I was having trouble finding specs but finally found reference to 80-90 cfm @ 90 psi, so your answers are not surprising.

Now to the fallback... Would any of those 60 or 90 pound electrically driven jack hammers do what I'm after ? I'm thinking maybe the one from Harbor Fright was either defective or just the cheapo Chinese things that look but don't function like the real deal.

Maybe a real one, a rental like Bosch or Hilti or Thor or Hitachi... ? The local Home Depo rental guy says they have a 60 pounder that will do the trick but I was leary because of my Harbor Freight experience. Maybe I could ask him if I can get my money back if I return it within the hour after trying it on a hole or two...

Bob

 

[MtnViewRanch]

One of my brothers has had good luck with the HF jack hammers. He uses it for just what you want to use it for, post holes. Now he did wear his first one out after several years and had to buy his second one, but is still happy with it. Maybe you just got a bad one, my guess is that it is a 50/50 type of thing. Might be less $$$ to just rent a good one and get the job done.

Good luck

 

[Pops15]

80 or 90 CFM would be marginal. If you use a 90# hammer you should have a 135 cfm compressor. You should be able to rent a hammer and compressor for a couple hundred.

Those 60# electric hammers don't work well when what you're breaking is in a confined space. They sometimes work ok when you've got a clear area around what you're hammering.
I've used the electric Bosch, and Hitachi hammers. They don't hit hard enough or fast enough, and a 60# hammer just isn't heavy enough. They're barely better than using a sledge hammer.

Renting a big compressor and 90# hammer is probably your best bet. You could try a big roto-hammer like a Milwaukee Thunderbolt or US1 to drill a bunch of 3/4" holes in the rock then use a pry bar to break it apart and pry out the pieces.

 

[Scooby074]

ive used a bosch brute several times on concrete. they work well, plus are much more convenient then needing a large compressor. yourator would need a gene though

 

[dcyrilc]

80 or 90 CFM would be marginal. If you use a 90# hammer you should have a 135 cfm compressor. You should be able to rent a hammer and compressor for a couple hundred.

Those 60# electric hammers don't work well when what you're breaking is in a confined space. They sometimes work ok when you've got a clear area around what you're hammering.
I've used the electric Bosch, and Hitachi hammers. They don't hit hard enough or fast enough, and a 60# hammer just isn't heavy enough. They're barely better than using a sledge hammer.

Renting a big compressor and 90# hammer is probably your best bet. You could try a big roto-hammer like a Milwaukee Thunderbolt or US1 to drill a bunch of 3/4" holes in the rock then use a pry bar to break it apart and pry out the pieces.

We've run 90# hammers on a Grimmerschmidt 125CFM for years without problems. Now I use a borrowed 140# pile driving hammer for driving fence posts. No problem keeping up with the hammer. Now 6.4CFM?:laughing: :laughing: :laughing: :laughing: :laughing:

 

[EddieWalker]

Have you tried an SDS Max Rotary Hammer Drill? Mine is a Hitachi and it just about melts through concrete. My biggest bit is 1 1/2 inches, which I use for running 3/4 conduit through. It will also run Core Bits, which will drill a much larger hole. Five inch Core Bits are perferct for fence posts and used all the time for fences in existing concrete.

How big of a hole do you need? How far down do you need to go?

The best part about an SDS Max Hammer Drill is that it's a small, electric jackhammer. I use mine for moving drain lines in homes and busting up concrete into small pieces all the time. It's a very handy tool to own!!!!!!

I also have a Makita SDS Rotary Hammer that is just a smaller, lighter version of the SDS Max. Each has it's place, but for what you are doing, I'd sure give the SDS Max a try.

Good luck,
Eddie

 

[CurlyDave]

For concrete demolition I recently rented a Bosch Brute a few times ($100 per day) and then bought this HF hammer - Harbor Freight Tools - Quality Tools at the Lowest Prices. With discounts and coupons I paid about $300 and it is a much better deal than renting the Bosch. I actually think the HF hammer hits harder than the Bosch.

Don not confuse the big HF hammer with their small one, which has much less capability. - Harbor Freight Tools - Quality Tools at the Lowest Prices

OTOH I don't really think a jackhammer is going to produce a very good fence post hole. Not unless you are willing to backfill a very large hole with lots of concrete.

Digging a deep narrow hole in hard ground is very difficult.

I would be leaning toward T posts and a puff auger for your post hole digger.