Bench Grinders

ToolInfoBox Bench Grinder
Synonyms:	bench top grinder, grinding wheel; DE: Doppelschleifer, "Schleifmaschine"
Type:	power tool
Material:	metal
Access Requirements:	upon introduction
Tutors:	Lukas
Similar (More or Less):	disc grinder, files, sandpaper

This "Brüder Mannesmann" bench grinder from 1996 is used but still in decent condition; the wheels run true and quietly. The grinder is equipped with two different stone wheels with different grits (35 & 60); one for heavy-duty and quick material removal, one for a finer and more precise material removal that will also leave a way nicer surface finish.

Safety

As the bench grinder is not only a power tool but one with openly accessible spinning parts, precautions need to be made. Have a tutor show the machine to you before touching it!

• clamp the grinder down tightly as it will vibrate quite a bit
• never wear gloves and/or scarves, roll up long sleeves and tie back long hair so nothing gets caught
• always wear personal protection, especially safety goggles and if necessary some ear defenders and dust masks

Usage

• after plugging the grinder in, turn it on and wait until it reaches its final speed
• if you hear any rattling or other funny noises turn it off immediately and check whether something is loose or whether tiny parts are inside of the casing
• grind whatever you want to grind by holding it against the stone wheel; make sure the piece is supported either by the little table in front of the wheel or some other structure
• do not force your workpiece onto the wheel as that will produce a lot of heat; cooling your piece from time to time is always a good idea

Sharpening

• approach the spinning wheel slowly so your workpiece doesn't catch on it!
• when sharpening hardened steel make sure to keep the blade cool, otherwise previous hardening may be undone
• it's a good idea to press the blade firmly against the upper support (check the image) to keep a consistent blade alignment
• check the squareness of the blade often to be able to make corrections
• keep in mind that the grinder itself is only for roughing out the blade geometry, for a truly sharp blade you definitely need to work with some wetstones afterwards

Maintenance

The wheels need to be "dressed" from time to time in order to produce nice straight edges and maintain stability. Apparently, it's possible to do that with nothing more than a few spring washers on a piece of threaded rod!^[1] We should try this before spending time and money on a more sophisticated tool.

Upgrade Ideas

For really sharp knives, we could turn an MDF wheel on this grinder and use it as the final "grit".