# Reparing the HF Electric Roatry Hammer

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#### BrownOut

##### Banned
Since there is no other forum for this sort of thing, I'm putting it here. Recently, I've been rebuilding the outside decks on my house. After demolishing the old decks, I had a requirement to drill many, many large (1/2") holes through the exterior brick siding to allow me to screw the new ledger boards into the house's floor joists. I quickly learned my hammer drill, which easily drills cement, is completely insufficient for driling brick. In my first attempt, I drilled for about 20 minutes and didn't get through a single brick. So, after some research, I learned what I needed is called a rotary hammer. These electric monstrosities are quite expensive. So I shopped for a local tool rental where I could get one for a day. I was set up to pick up my tool on Saturday after Thanksgiving, but when I arrived at the store, they had decided to close for the rest of the week.

And then I remembered that I had a couple HF rotary hammers in a pile of power tools I bought at auction back in the Spring. Neither of them worked. But I took one apart and after fooling around for awhile, I realized that the "hammer" part was the problem. It was basically an air cylinder in which the front end of the hammer would slide back into the rear end and compress air that's trapped between the two ends. This scheme softened the "blow" a little using the compressed air as a sort of spring so the tool doesn't tear itself apart. The air had lone ago escaped and the hammer was simply collasped upon itself. Examination of the other unit revieled that it has the same problem. I realized the solution was to insert a spring into the hammer component so that it can recover on the upstroke and draw air back into it from an existing bleeder hole on the hammer. I found a nice spring at Home Depot that was nice and stiff and fit nicely in the hammer component. The unit now works perfectly and cuts through the brick easily. I was able to get both units working.

These tools have alot of problems, but sometimes, the problems can be easily corrected.

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##### Banned
Nice that it's working for ya. A little surprised the springs worked as well as a pneumatic cylinder.

#### shortbus=

##### Well-Known Member
Not knowing anything about the HF hammer insides, but I have a ancient Skill hammer similar to it. On the Skill, where the pneumatic cylinder is, it is filled with oil. Being old it leaks the oil out between uses.

When there is no oil it stops working. There a no piston rings in the pump or anvil pistons of the cylinder. It just relies on the oil film to seal them. Check to see if the HF uses a oil bath on it. May just be too dry to seal.

Cary

#### BrownOut

##### Banned
Thanks guys. I didn't know about the oil, but I'm pretty sure mine just uses air. It actually has a very small bleeder hole To allow a tiny bit of air escape on the down stroke. But there seemed to be no mechinism to allow the escaped air back in on the upstroke. That's what the spring does now, expands the cylinder to draw air back in. Otherwise, the tools is very sturdy with heavy duty gears and actuators. And even though the motor is build cheaply, using the tool's pastic housing to hold the brushes in place, it has good torque. I just finished drilling 14 holes, each 1/2" in diameter and 3 1/2" in length in brick, and it took about an hour. Since I never did this before, I don't know if that's good or not. But it's certainly much, much, much faster than my hammer drill was working.

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#### Diver300

##### Well-Known Member
I've got a drill a bit like this:-

When it hadn't been used for a few months, the relatively poor grease that was in it when it was new had gone hard, and the heavy hammer piston didn't move at all, as it was only pushed by the air. The motor driven piston that was driven by the motor and a conrod moved fine, but no hammer action happened.

It just needed a clean out and new grease.

#### BrownOut

##### Banned
Should last you at least another 5 or 15 though right?

#### BrownOut

##### Banned
And he didn't have to fix the hammer design.

BTW, has anyone ever used one of these as a hammer? Is there an attachment that will allow me to drive a nail in a tight space and doesn't allow me to swing a hand hammer?

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##### Banned
Attach a small socket to it that's smooth. I think the hammer function is typically controlled by a cam action from the rotary part so you can't separate the rotation.

But I digress... If you can get a hammer drill into the spot you wanna hammer and you can't figure out how to use a hammer at the same spot... You have screws lose not problems with nails =)

#### BrownOut

##### Banned
I don't even know what that last comment was supposed to mean. It's OK though; I don't want to know. But I can select hammer only and not have the bit rotate.

##### Banned
The hammer force might not be right, the attachment has nothing to do with the function of a short range hammer like that that, it's all about the energy. Put a small socket it on it, stick a nail in it, put it on hammer and see if it goes into the board. If not it won't work.

Clarify things at all?

#### BrownOut

##### Banned
Not really. What I want to know is if there exists an attachment with the SDS slots that I can use is the chuck which had a blunt end which may be used to hammer a nail in a right space in which I can't use a conventional hammer. There isn't really a way to attach a socket. The reason I asked is because I saw an electric hammer at Home Depot tonight when I was there and I was thinking I might already have that, if there is such an attachment. Guess I'll try google, but I'd like to hear from anyone who has used one of these tools in this manner.

#### tcmtech

##### Banned
I've got an old Bosch thats hammer only that has a bad trigger so I cant control the speed on it. I will have to dig it out and see what I can come up with as for using it for a power hammer.
I think it should work rather well. I have used my little pneumatic air chisels before like that just using a rod stuck in the end of the head. They have no problems driving 4 inch nails into harder woods!

#### BrownOut

##### Banned
I was thinking about that last night, if my air chisel would work. That would be even better for tight spaces. I think it would be interesting to try both tools out. After all, it's called a rotary "HAMMER"

Oh BTW, I was searching around on the web and came across all kinds of attachments, including one that has a shovel head. You make make a power shovel out of these things. I might be interested once I began digging the footers for my new deck.

#### HiTech

##### Well-Known Member
Well BrownOut if you hang in the Tool Crib forums then I'm sure you've read about a good many of HF tools being labeled as gems in the rough. Even the woodshop forums claim the same. A little ingenuity, some parts, and some elbow grease often turns the tools into formidable performers.... that is if they have a good basic design to start with.

#### shortbus=

##### Well-Known Member
And he didn't have to fix the hammer design.

BTW, has anyone ever used one of these as a hammer? Is there an attachment that will allow me to drive a nail in a tight space and doesn't allow me to swing a hand hammer?

Take a look at this; - Harbor Freight Tools - Quality Tools at the Lowest Prices

If you have a air compressor these will drive nails any where you can get your hand in. I have one and it works great.

#### BrownOut

##### Banned
Well, my pride swelled chest got deflated. The tool broke apart yesterday while I was finishing up some work. The brekage might be related to the stiffness of the spring I used. So I broke down and bought an expenseive Bosh unit. (Bulldog Extreem) The new Bosh cuts 4 -5 times faster than the HFT one, maybe because the Bosh delivers 4 -5 hammers per rotation, while the HFT was 1:1. I'm much happier with the Bosh, though lighter in the wallet.

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