How Do You Get The Glue Off A Hardwood Floor That Someone Has Applied To Stick Down A Carpet?

I went through the same with my house where I removed the vinyl flooring to expose the wooden floors.  It took me weeks to complete one room, I tried all sorts of things, the only ways are to replace the wooden floors with new boards, replace the carpet with new carpet or to scrape the glue off using a scraper, or use a drill with a wire brush wheel that you can attach to the end, however, with the wire brush answer this can damage the floor boards and I wore the motor out on my drill in about two days!.  never use any kind of removal liquid like acetone as this takes the top layer of glue off the boards but leaves a bottom layer like a residue that is harder to get off than scraping all of it.

Also NEVER use a belt sander directly on the glue as the belt sander gets hot and the glue then melts directly onto the sand belt.  If you do go for scraping of the glue, then you will leave small pieces of it that have worked their way into the grooves of the floor.  This will be removed by the belt sander, however, this will eventually clog the sand belt with the glue and it will not come out.

Having completes one room, I could not go through the same pain with my second room, so I have removed the Vinyl flooring and replaced with carpet.

Hope this may help.