Finish have a 9” disc grinder made from a thread mill motor. Seems to work pretty good so far. Hope is that it cuts down on the hours of hand sanding. https://imgur.com/gallery/vbeoppK
Nice @Bluefish! Is the variable speed the main want for a disc grinder? I am asking because it seems the big difference money wise, like everything else with a VFD, as a normal woodmakers 12" disc grinder comes in at $350 roughly and these 'knife makers' disc grinders are all double or triple that!
Griff, I don't think variable speed as a big deal on a disc grinder. Perhaps depending on what you are doing with it, but I have found that I run mine pretty much wide open all the time. If you want variable speed, move the piece you're working on from near the center to the edge of the disc. The surface speed at the outer parts of the disc can be very fast. Speed at outer edge of disc 9" (1800 RPM x pi x 9)/12 = 4240 SFM. Speed at half way between centre and edge of disc 9" (1800 RPM x pi x 4.5)/12 = 2210 SFM. Double these for a two pole (3600 RPM) motor. I think it's way more important to be able to reverse the motor, which is a feature I don't see on a lot of generic imported 12" models. Having open access to both sides of the disc is important for right-side left-side work. On a budget I would buy a good, balanced disc, find a used reversible single phase motor around 1 hp and wire in the reversing switch. Should be able to do that for $350. Expect half the cost to be the disc itself. Dan
Thanks @dancom! I see TruGrit has two 9" billet discs available, 5/8 Arbor, and one of those with a 1 degree bevel.
Yes this is variable speed and reversible, I turned the disc myself, added a 1 degree bevel. It’s run off of a treadmill motor. Cheap and easy. Cost of materials was basically nothing. $20 maybe and a bit of time. Pretty much paid itself already, nice to come out of heat treat, 5 mins on the disc then jump to 600 grit hand sand.
@Griff Looking good in blue anodized. I bought the 1° bevel disc from USAKnifemaker. $83 US plus all the gory shipping and details. It is also a 5/8" keyed bore. It runs very true.
@Bluefish I was wondering how you attached the wheel to the treadmill motor. Damn those are hard things to work with.
Had to dr the key as only had standard brooches, 5/8 x 3/16 worked then ground the key to fit... handmade step key.
Nice grinder! I have to say, i think i like making tools and machines as much as making knives. I know i'm better at it. Not to say i'm that great at either but my grinders grind and my knives cut. There's just something really satisfying about engineering and building a machine with your own two hands that can be used to create so many other things. Very satisfying. I'm sort of satisfied for you and it's not even my grinder : )
Yes i’m The same, love the machine builds. I think my machine build list is as long as my knife build list. Heat treat oven, molten salt pot, hydraulic press, better 2x72.... and that’s just the short list.
It's a slippery slope man. Next thing you will be looking at making your own lathe and Junk Yard power hammer.
