A 1.5 HP motor running on 110VAC would theoretically draw 10.15 amps. But you should refer to the motor documentation to confirm their ratings for maximum current draw. Start-up currents can be much higher.
^^ I think this is a typo... a typical 1.5hp motor running on 110v draws around 16 amps. The newest Baldor high efficiency 1.5hp motors draw about 13 amps at 110v. Some older 1.5hp motors draw more like 19amps at 110v. I have never seen a 1.5hp motor rated for only 10 amps. Actually, I have many 1hp motors (Leeson, GE, Baldor) that draw more than that (most are 12-13 amps at 110v).
As you noted, all of the above will draw up to 5x the rated nameplate amperage during startup. So this is why you need a switch that is rated to 1.5hp @ 110v (motor-rated switches are specifically designed for the startup current inrush). Use one with overload protection (heaters) if your motor does not already have this (even if it does, double protection is nice on a grinder where the motor will be worked hard).
If your motor already has overload protection and you do not want extra protection in the switch, then look for a
NEMA size 1 switch also known as a manual starter (NEMA 1 is the standard size rated for up to 2hp @ 110v). Arrow Hart, Furnas, and Allen Bradley make many of these and they are readily available on online auction sites (search "Furnas Motor Switch" or "Furnas Manual Starter" or "Furnas on off switch" for example -- unfortunately, people who sell them call them all sorts of different things). Something like a Furnas 13BA21B would be fine, for example -- several of my machine tools use this switch (again, no overload protection on it, so make sure your motor says "thermally protected" on the info tag before you use a switch without it!).
If you need motor protection, then look for a NEMA 1 starter. Allen Bradley 609 or 709 are arguably the best, but many manufacturers make them. You can buy them with on/off buttons built in, or wire them to a separate on/off button (the starter monitors the button and does the work of switching on/off the power when the button is pushed). In this case, you'll need to buy 'heaters' sized for your motor -- these are sortof like fuses...they go in the starter and shut off power when too much amperage is drawn.
The best, fanciest solution (and the one you would use if you had this in a OSHA-approved shop with employees) is to use a mag starter with heaters for overload protection. Mag starters keep the machine turned off if there is a break in power. So if power in your shop shuts off for a minute and then comes back on, the machine will not spring back to life after you've put your fingers in it to try to figure out what went wrong. Therefore, a NEMA 1 mag starter would be a great solution. Expect to pay a bit more for this than you would for a Furnas motor-rated snap switch like the 13ba21b, though.
Whatever you do, please do NOT use a lightswitch -- if you've seen others doing it, then they are definitely NOT professionals and, frankly, have no idea what they're doing. They may get away with it for a while, but it is a serious fire hazard and will certainly also burn out the switch contacts and stop working in relatively few on/off cycles.
