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I am installing floating floors in a 1970s condo where the door frames are metal. Side jambs are right against the concrete subfloor with no gaps.

I tried an oscillating tool with Bosch carbide-tipped blades and after a full minute, it looked like a fingernail scratch. My current tool is a cheap B&D - would it be worth borrowing a friend's tool to see if it makes a difference?

Another option was grabbing the right blade and getting down with an angle grinder. I have no experience using them and it honestly looks pretty frightening. However if there are no alternatives then I will just have to do my research and be careful.

The last option was renting an electric jamb saw tool and buying metal-specific blades. This path would be over $100 and some effort to find one as they are all rented out nearby.

Hoping anyone has better ideas for how I can undercut the metal! Maybe there's some secret multitool technique that I'm missing? Thanks all

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https://i.imgur.com/fk4QpEX.jpg

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  • Pics or it didn't happen! If blades don't cut it well, it may be a particularly hard material, your tool may not be strong enough, or there may be something wrong with your technique for particularly hard or resilient metals, an abrasive usually works better. Be advised that metal door frames are often concrete filled, so even with a grinder you may need to remove as much metal as possible with ordinary abrasive discs before switching to diamond discs to cut into the stone. With safety goggles, a grinder is not particularly scary to use, although precautions are necessary to protect surfaces.
    – K H
    May 13, 2021 at 1:35
  • Diamond discs will cut metal or plastics, but heat can ruin the diamonds and plastic and some metals tend to stick to the disc, necessitating frequent cleaning or lubricant. You can cut some regular stuff in normal body positions to build up your confidence and figure out how you need to brace the grinder before you attempt an awkward cut.
    – K H
    May 13, 2021 at 1:38
  • Add pictures though as between the people here we've seen a ridiculous number of tools and there may be one that is particularly suited to your application. Note that it's not uncommon to cut the flooring instead. If the flooring installation method prevents an adequate finish, transition molding gives your another option.
    – K H
    May 13, 2021 at 1:42
  • thanks for the detailed response! that will save me a lot of time on finding the right discs since I will be borrowing it from a friend if I need to.
    – Nate
    May 13, 2021 at 2:37
  • I edited the original post to include some pictures of the site and tool - imgur.com/a/GhDXELB
    – Nate
    May 13, 2021 at 2:38

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Use an angle grinder. I recommend practicing though I find angle grinders one of the easiest tools to control (no crazy binding like drills). Really you should buy one they are $15 USD at harbor freight. If you are going to use it more than once splurge and get the $30 one. Any metal cutting disc will cut that quick. Just get a thin kerf (3/32") blade, wear eye and ear protection and keep any plastic out of the way of the hot metal particles. Won't hurt to have an extinguisher near by.

I've used oscillating tools on metal - the blades dull really quick. A reciprocating saw can work but you have limited clearance. Even then the reciprocating blades can dull quick quickly on metal as well. I can't imagine using a jamb saw on that.

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    Would add to keep all flammable materials away or protected/covered. Sawdust, dust/dirt, cloth/carpet can all smoulder for some time before flames are seen. Sparks from a angle grinder can go a few feet easily.
    – crip659
    May 13, 2021 at 19:34

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