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DW840 7" Angle Grinder

renosteinke's picture

I recently had to remove a cast-iron tub. I decided to cut the tub in place, and remove it in sections.

A trial cut using a 4" angle grinder proved the concept - but this job really called for a larger tool. So I chose the 7" DeWalt. My choice at the time was this DeWalt, or a similar Ryobi.

DeWalt calles this a 'medium body' grinder. They hve other 7" grinders that they call 'large body.' Mine has only two handle positions, and will accept only 7" blades; a 9" won't fit.

Good News: The grinder worked well. It was very comfortable; you didn't need to think about where the controls were, I actually held the tool by the handles. Cutting wheel was held securely. I don't remember any vibration.

Other notes:

1) Claiming to be a '13 amp'  tool, I did trip the 15-amp breaker a few times on starting;

2) The way the wheels attach can distort a cutting wheel, which might make it break;

3) The nose seems 'fat,' not letting the tool access tight places. In tight spaces you find yourself wishing there were more choices of handle placement;

4) The tool comes in a cardboard box, with no indication that there's a tool bag inside. There is, and it's a fairly decent bag. There's room for a few wheels and other accessories. I doubt there's room for a full-face shield, though.

5) The tool 'seems' to have a decent cord, but you'll need an extension cord to get anything done.

As for the job itself"

1) Safety glasses work, but goggles are probably a better idea. I keep a pair in the bag, with the tool.

2) The tool creates far more dust and grit than it appears while you're at work. A devent respirator is a must, the dust feels like little knives inside your sinuses, and you will have a headache that night. Again, keep the dust masks with the tool.

3) Other 'grit control' measures worth having are a Shop-vac air filter (made a big difference) and a vacuum. You also need to 'tent off' or close off the work area.

4) You won't be able to reach everywhere with the grinder - but a stick a thin pry bar in the kerf, give a slight twist, and the remaining iron will just fall apart.

Reno (post #207349, reply #1 of 8)

How long would you say it took to make that tub smaller?

Did you give any thought to the usual method of dealing with a cast tub?

A Great Place for Information, Comraderie, and a Sucker Punch.

Remodeling Contractor just outside the Glass City.


"usual method" (post #207349, reply #3 of 8)

I think an 8 pounder is about right for a geezer.

Safety goggles is about right for the rest of the equipment.


old (post #207349, reply #4 of 8)

I'd have to go out and get the sledge, weigh it and get back to you.

The head is one I got easily35 yrs ago, the handle..............not sure on that, but.

I know it's a whole hell of lot heavier now.

Goggles, a must.  A crappy cover of some sort doesn't hurt-drop, pcs of old carpet taped on the sides-maybe just the pad I used on one tearout.

Keeps the shards somewhat contained.


I didn't hear reno mention ear protection with the grinder..................

A Great Place for Information, Comraderie, and a Sucker Punch.

Remodeling Contractor just outside the Glass City.


I didn't hear reno mention (post #207349, reply #5 of 8)

I didn't hear reno mention ear protection with the grinder..................

Maybe that's because you've gone deaf.

Of all the preposterous assumptions of humanity over humanity, nothing exceeds most of the criticisms made on the habits of the poor by the well-housed, well-warmed, and well-fed.  --Herman Melville

Nope. No hearing protection. (post #207349, reply #6 of 8)

Nope. No hearing protection. Oh, I have it ... the noise of the grinding wasn't that loud. Nowhere near 85dB. No ear ringing or stunned eardrums, not even immediately afterwards. No problems with normal conversation or listening to the radio in the next room.

Whacking the tub with my 2-lb maul did make a painfully loud noise.

For everyone else ... I had heard of the sledge hammer approach, but discarded it. Confined space, fears of sharp shards flying everywhere, having to handle all the irregular bits again, and not having a sledge.

Time? Maybe 45 minutes of grind time. I wasn't counting. Took a lot longer to open the walls, remove the tiles, disconnect the plumbing, etc.

I'm sure the grinder will come in handy when I get to replacing the cement siding (ACB tiles off, Hardiplank on).

Side Note: It's amazing how much 'cold' entered the house the moment I opened up the tub. We don't think of cast iron as an insulator, but it was keeping a lot of heat in. Even after I closed the plumbing openings, there was quite a draft in the bathroom - a draft that didn't stop until I covered the subfloor with a piece of plywood.

Small wonder my heating bill is so high.

Whatever sort of tub I use in the future, there WILL be insulation under, around, and within it!

For large grinding tasks and (post #207349, reply #2 of 8)

For large grinding tasks and drywall sanding, I've actually come to love my full face respirator. Combining full eye protection along with air filtration is a great deal. I spent about $150 on my North mask... I normally wear it instead of paper masks and glasses/goggles. It's great for overhead work too.
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Pricing (post #207349, reply #7 of 8)

The DeWalt cost me about $130, plus tax.

I see that there is a 7" grinder available at Harbor Freight for $40. That's about normal; HF is usually 1/3 the price of a 'comparable' tool.

To be fair, there are other DeWalt models that go for more than $200. None of those were available to me at the local store.

Folks who have followed my tool threads might wonder why I didn't just go to Harbor Freight.

I'm an hour -or more- from any town with 'real' shopping. My choices here are 1) Lowes and 2) Wal-Mart. A trip to HF would kill three hours, and cost (using the IRS deductable) me at least $50. Suddenly HF isn't such a bargain. I had the money; I didn't want to spend the time.

So, I am not able to tell you how the HF tool performed.

My overall 'feel' of the Dewalt that I bought is that this is definitely a homeowner-level tool, and not to be seriously compared to what Bosch, Metabo, and Flex have to offer.

It's funny, but I like ther (post #207349, reply #8 of 8)

It's funny, but I like ther versatility of their "Homeowner" line of reciprical saws better than their hight end ones.

The lower end ones, which includes their new compact one, has a 4 position blade mount that really allows you to get close to the surface for flush cutting.

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