I need to buy an angle grinder to undercut the bricks on a raised fireplace hearth. There are better tools for this application but they are either too expensive to buy or not available to rent.
I plan on getting a 4 1/2″ grinder and using a diamond blade. How powerful a tool do I need? Brands?
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Replies
Whatever you get, wear goggles and a face mask.
Brick Cutting
I'm thinking a hazmat suit. I'm planning on enclosing the area with plastic drop cloth. I'm also thinking that I should skip the brick cutting and just framing the hearth with the hardwood flooring. I've been spending more time thinking than doing. My wife keeps asking how it's going.....I tell her I'm still in planning mode.
The $19 grinder sold at Harbor Freight seems perfect for your purposes.
Angle grinder -> virtually anything will work.
Power/brands: basically irrelevant. They're all basically the same tool.
As renosteinke suggested, the cheaper the better. And if this is your first outing with an angle grinder, remember that they're one of most dangerous tools ever invented, due to the lack of an emergency off function. Once you trip the ON switch at the base, it keeps running till hell freezes over or the power line is physically disconnected. So never, never try mounting a wood-cutting circ saw blade to an angle grinder (I dunno about your neck of the woods, but such blades are definitely sold here in Japan). A wood-cutting blade has too much chance of digging in and ripping the tool from your hands, then (since theswitch doesn't turn off automatically), it climbs its way across the floor and back, ripping across your torso and sending you to the hospital for major repairs--or worse.
They sell the chainsaw blades for angle grinders in the USA. I always thought those looked dangerous. I might have to try one out to see just how dangerous they are. I try to not lock the the switch on when using angle grinders. I was using an angle grinder with a wire brush cup on it and sat it down while it was still spinning and it caught my tee shirt and turned it into a tourniquet, which was kind of good to cut off the flow of blood from the road rash. Actually it wasn't too bad, but it was some bad.
Similar experience
Twenty years ago, just after moving into our new (not-yet-completed) house, I was making a bunch of bookcases for my study, and I saw my children showing interest in the angle grinder I had equipped with a sanding disk. I told them the grinder was extremely dangerous and warned them against touching it w/o permission. Not ten minutes later I accidently swiped the still moving disk against my left thumb and cut into part of the ligaments at the 2nd joint. Blood everywhere. No real permanent damage (a tiny bit of stiffness remains), but it made a graphic lesson in the danger of such tools.
Angle Grinder
I plan on using a segmented diamond wheel to cut the brick. From what I have read this is a Type 1 and requires a Type 1 cutting guard vs a Type 27 grinding guard. The Type 1 guard is listed as a stronger piece of equipment and will cover 180 degrees of the blade and will contain the blade if it breaks. After reading this I decided that I would be better off with a more substantial tool than what I could get for short $ at Harbor Freight. I'm looking at the Bosch 4 1/2" 8.5 amp angle grinder. It's on sale for $79. My thinking could be 100% wrong but if this an inherently dangerous tool then I want a good one. I remember somebody saying that nobody ever regretted buying a good tool. This may be a one time use for the tool but $50 is a cheap price to pay for peace of mind.
Quite often these grinders are offered in a 2 for the price of one deal. I bought 2 Bosches this way for my second and third grinders. Since I already had one I could wait for the sale. I've never heard of different guards. I buy some stuff at Harbor Freight, but not small power tools. I just don't like the feel of junk.
Angle Grinder
I was reading the Bosch owner's manual and it says to use a different guard type depending on the attachment,e.g. grinding, cutting, cup. I think I figured out what each type number refers to but I can't find anything on the Internet that lists the numbers and their exact meaning. A grinding disc came with the tool and it has Type 27 printed on it. A diamond cup for surface grinding is a Type 11. The tool comes with a Type 27 grinding guard but the manual says do not use it with a cutting wheel....use a Type 1 guard instead. I had to read it a couple of times before the light went on. I'm going to call Bosch on Monday to see if they can provide confirmation. It seems to be a matter of safety....using the 'correct' guard. Bosch has a Type 1 guard for use with a tuck pointing wheel which has a vacuumn port. I checked the HF grinders but didn't look at the owner manuals. This stuff seems to be pretty application specific.....live and learn.
Bosch Angle Grinder
I didn't see any deal like that at HD. I found one on sale at Lowe's for the same price as Amazon....model AG40-85P. Do you know anything about the Types, e.g. 1, 11, 27? I think I know what I need but would like as much info as possible. What type of blade to do garden tools....I've got lawn mower blades, loppers, and trimmers....would like to sharpen them myself.
Look here for information on the wheels, The 1A, 27, 29 wheels are different material and grits, etc
http://www.boschtools.com/Products/Accessories/Pages/BoschProductSubCategory.aspx?catid=1096
That's a good grinder, but I don't like paddle switches much, they're easier to turn on accidentally. I think all Bosch 4 1/2 inch grinders are paddle switches now. That wouldn't stop me from buying one.
I only use grinders to sharpen garden tools like shovels, hoes, mattocks etc. Grinders take off material aggressively. I use files for loppers, trimmers and that sort of things. I follow up sometimes with a stone designed for garden tools, and they are plenty sharp, with very tiny material loss.
A Norton 87938 stone or Lansky Lawn & Garden Multi Purpose Sharpener, are flat stones that work well. A Lansky Abrasive Sharpening Hone Multi Purpose Sharpener is another that I use which is oval in cross section and fast cutting (and wearing). I use both types of stones.
I use flap wheels on the grinder when working down welds on autobodies, they cut with much more controllability than grinding wheels.
I've used cutting wheels on occasion to cut stuck nuts off bolts. Cut off a broken padlock once. Cut iron pipe during a rehab. They are handy.
Angle Grinder
Thank You for all the info. The paddle has a lock-off switch which you have to push before the paddle can be depressed to turn the tool on. Hopefully the tools designers got it right. I've got some other Bosch tools and really like them. Until now the most distasteful part of this project was the thought of a brick and concrete dust storm but after reading all the posts about how dangerous an angle grinder can be the dust might be the least of my worries. As I mentioned I intend to buy the recommended blade guards for the project and brace the tool during the cut.
A grinder is not really that dangerous if you're careful. They can be a bit squirrely sometimes when using wire brushes and metal cutting disks. I forgot to mention I cut the entire floor and firewal, frame parts etc out of a 65 mustang my son and I are working on. Actually he did most of the cutting. It's not anywhere near done, but it is drivable again. We used about 28lbs of MIG welding wire, untold cutting disks, and a bunch of flap wheels to do the job. Now on to the exterior rust....
Angle Grinder
Have you got pictures?
No, but I could take some of the nearly finished floor. It was quite a job, and I learned to weld on this job. I have a Hobart MIG, but used flux core on the flooring due to working outside. Will be MIG welding on the body panels to keep warping and burn through to a minimum. Flux core is tough on thin sheetmetal. The car is still a little rough on the exterior, but the running gear is OK, (new carburetor, clutch, shocks, brake lines, brake linings, wheel cylinders, hardware etc, new gas tank, new fuel pump, new fuel line, new rear frame rails, new trunk flooring, new torque boxes, new metal under the hood on passenger side, new splash shields, new rubber weatherstripping, new windshield, new heater core, radiator is original but repaired-radiator shop said it's much better than a new one, new spring shackles, I don't know what else. He has new seat covers, carpet and headliner to go in. Needs a lot of work on the exterior first. It's been a good father son project, but I'm getting tired of it. My son has progressed a lot on restoration work, and became a ASEE certified mechanic for a rental car company during the project.
And I used a lot of Harbor freight tools on the job, but no HF angle grinder for me. I did buy a small metal cutting tool like an angle grinder that uses something like 2" disks, it trips out the built in breaker a lot, but cuts pretty good. Wish I had a plasma cutter instead, but I figgured that I can't have everything I want. Not enough space or money.
To grind steel you want a metal grinding wheel. This is the ticket for sharpening the lawn mower or the bush hog blades. Sanding discs [requiring a backing pad] can be useful for sharpening an axe.
Getting either of these tools on your loppers or shears is inviting disaster. Here you need a file or coarser hands held whetstones.
You can cut masonry pretty fast with a diamond blade or masonry grinding wheel. But I'd try to figure out a better way for running wood flooring up to brick.
As far as the danger factor my chief concern is my wrists if things go bad. Most of the other risks will involve survival.
Angle Grinder
I've pretty much explored all the options for installing the hardwood flooring around the brick. I plan on using the angle grinder with a segmentd diamond blade and a tuckpointing guard.. I just have to find out if I can get the grinder close enough to the bottom of the brick with this type of guard attached. If not I'll get the Type 1 cutting wheel guide, rest the grinder guard on the sub-floor or board and work my way along the brick hearth. I won't be freehanding this cut. I appreciate your warning....can you be more specific as to where the danger is in my plan. The only other tool available (rental) is the Roberts Long Neck undercut/jamb saw which has a masonry blade.....couldn't find the company website or info on putting a diamond blade on it.
Focus and no worries
I don't see your brick cutting as being very scary at all. I think I'd rather be tangled up with a diamond blade than most of the other wheel options. Anyway as long as you focus on the work it will be no problemas. For what it's worth if the diamond blade is an issue for kerf width the masonry abrasive wheels have a much wider kerf.
It's the whole idea of undercutting to make the flooring work that I am bothered by. Seems a long way around the horn and where is your expansion room unless you cut a deep kerf? But, hey it's your job and I don't see it as a threat to national security or even the price of cheese in the long run. Enjoy.
Angle Grinder
I've weighed all the options and the pros and cons of doing each vs what the finished floor will look like. I need 1 /2" to 3/4" for expansion which I figure I should be able to cut no problem. To just frame the raised hearth I'd need to add molding which I don't like the look of. Another problem is the fact that the concrete pad that the brick hearth sits on extends out 3 1/2" from the front face of the brick and is 1/8" proud of the plywood subfloor. The sides of the brick hearth sit right on the plywood subfloor. Easier to rabbet the bottom of the floor boards where they will sit on the proud concrete and let them run into the undercut brick. I also wanted to grind down the proud concrete but I don't think I could adequately seal a diamond cup grinder dust shroud due to it's width vs the width of the proud concrete pad.
If you decide to just cope the flooring instead of cutting the brick, you can get coarse sanding disks like 80 or less grit to fit the grinder and use that to cope the flooring. That would be my preferred method. I think it would be faster.
COPE
I'm installing 3/4" solid wood flooring so I'll need expansion gaps.....can't cope the boards that are parallel to the brick. An undercut in the brick will provide the expansion gap and give a clean look similar to the way flooring runs under baseboards. This is the room we and visitors spend most of our time in so I want it to look good. Plus I'm kind of looking forward to a new tool and a new project. I've completed installing hardwood floors in all the other rooms in the house and installing hardwood stairs...... this is the last room to be done.
Well, how about putting a baseboard on the brick?
or a custom piece...
Anybody not onsite [me for one] is speculating uninformed but one thought is a little thin piece, say 1/4" x1" laid flat over the flooring which would need a tiny [at most] grooving of the brick and still cover the expansion joint. Easy work with a table saw and outer or even hand sanding an eased edge.