Home-Made Slow-Speed Grinder

[Dr.Al]

This is my home-made slow-speed grinder. It's based on an idea from Stefan Gotteswinter, although everything in my version was designed from scratch. It uses 150 mm diameter diamond grinding discs, which are cheap (the ones I bought were about £5 each) and have the advantage (compared to conventional grinding wheels) of being flat so surfaces prepared on the grinding disc can then be easily honed on a whetstone or waterstone.



Mostly made from aluminium flat bar (15 × 100 mm and 8 × 200 mm), with a 0.8 mm mild steel cover, shafts made from EN1A steel and gears made from steel and acetal.



It can also be placed on its back (and in fact this is how I most often use it) for grinding steeper angles; the table can be placed in two positions - the one shown in these photos for normal operation or in a higher position for grinding wider tools.



The table and fence keep the tool to be sharpened square to the disc, so it's really useful for reshaping second-hand tools that have been sharpened a long way off square. The low running speed (up to 400 rpm) keeps the tool from getting too hot.



The reference surface is parallel and coplanar with the disc so can be used with a honing guide as an alternative to using the table. This is particularly useful as the edge can be shaped on the grinder and then the honing guide can be transferred to a fine grit waterstone for final sharpening.

There are lots more photos (including internal ones and higher-resolution copies of the ones above) and details on my website: https://www.cgtk.co.uk/metalwork/gri...owspeedgrinder