What is the best way to undercut a hearth that is situated at a corner of a room? The difficulty with corner hearths is the fact that the inside corners are impossible to reach using a Crain undercut saw. Would a reciprocating saw with a 9" diamond masonry blade do a clean job? There's a DeWalt model that actually lets you adjust the blade such that you can make flush cuts. However, I have not tried it. All ideas/experiences are welcome. Thanks.

crain undercut for the meat of the job then a angle grinder to finish up where the crain wont go. the sawzall is rough to keep flat.

Thanks for your reply, Kevin. Unfortunately, a 4.5" angle grinder is still too bulky for this tight area. If your think the reciprocating saw blade would be too unstable, what if I used a long masonry drill bit?

If you have a FEIN Multi-master or Super cut, they have blades to do that. I have used it to cut 22 foot long wall of brick. Took some time but gotter done and neatly too with not much dust

The Fein tools are the bees knees if you do this for a living. If your just a diehard dyi its probbally too much tool for your needs. You can pick up knock offs all over the place bosch,dremmel,rockler,harbor freight all make one now from 40 to 100 bucks but the fein will still run you 4bills.

Thanks for your reply. I bought the one at Harbor Freight, but I'm not sure which attachment I actually need. I would be cutting mortar only, not stone. Can a circular diamond blade attachment that Harbor Freight advertise to cut grout, do the job?

Good news! I bought a pseudo-"multimaster" from Harbor Freight ($40) and bought a diamond blade grout cutting attachment. It reached into the corners with ease. Thanks for the tip.

Glad it worked for you. Since FEIN lost the patent for that tool there is lots of competition in the market. But unfortunately, they have not met the price challenge and sales have dropped dramatically.

Dennis that must have took awhile to undercut 22ft w/ the Fein, holy smokes. I started out in the corner doing a 12ft undercut with the Fein but quickly switched to a grinder w/ a diamond dry blade, it was taking me forever. As you said though the dust comparison between the two was a huge difference even with a shop vac hooked up.

Ya it took a while all right, but the alternative was a 3 hour round trip to the shop to re-equip. And since it was a cottage we were doing, I went out to the dock for a bit of impromtu fishing while the grunt actually did the work. lol

I knew there had to be a good reason