Bench grinder cutoff notcher conversion : Blacksmithing How-to on anvilfire iForge

Cut-Off Machine

By Hugh Mcdonald
Gooseberry Hill, Western Australia

Presented by Jock Dempsey
January 15, 2003 (Updated May 28, 2011)

JOCK D -		Hugh McDonald is best known as the inventer of the McDonald Rolling Mill. Hugh also has a great imagination and manages to come up with an original twist on all his work. Huge sent these to us almost a year ago. Many apologies for the delay

HUGH M		While I always seem to be making tools or gadgets to help speed or simplify jobs in my workshop I have seldom made anything as useful or versatile as the cut off machine shown in the photo.

HUGH M		For docking (blanking) bar stock, the popular drop cut off machine (chop-saw) has no equal but for many applications such as cutting and grinding between the ears or horns of some of the animal heads I make or cutting them free from the bar, it is not possible to clamp them in the vice provided. Feeding the work by hand into the cut off disc over the slotted table is quick and easy and safer than using the same cutting disc in an angle grinder

		Figure 2 Click for Detail	Apart from the adjustable slotted work support the machine is a standard 200mm (8") bench grinder. Discs are standard 203mm x 2.5mm x 16mm (8" x 1/8" x 5/8"). A 20mm (3/4") thick spacer the same diameter as the grinder collars is needed on the grinder shaft. Always use appropriate eye, ear, hand and body protection. Hugh McDonald. 19 April 02.

JOCK D		Questions, Comments?

PAW-PAW		Is that a special guard? I looks like you could make one out of a brake drum.

JOCK D		No, the guard is the original since this was a large diameter grinder to start. If you used a 6" ginder you would need to check the rated wheel speed and fabricate a larger guard for the 8" wheel.

NTECH		What is the chance of the wheel breaking?

JOCK D		Much less than in a hand held grinder, which people do, but I do not recommned. This design could also use a regular heavy angle grinder wheel for rough grinding - something you SHOULD NOT do with small vitreous wheels. They are designed for tool sharpening NOT clean-up of torch work. . .

HUGH McD		I have never broken or even chipped a disc using the machine. The original guards are much safer than running the disc in an angle grinder plus the neat slot in the table gives sideways support. It will notch a 1" x 1/4" mild steel bar in about four of five seconds so it can be easily snapped by hand. I can't find my hacksaw in that time.

JOCK D		MORE ON SAFETY: I've known two people severely injured while notching with hand held grinders. One had removed guards, both had the grinder kick back and strike them in the face with the rotating wheel. Both had life threatening injuries. One lost several teeth, had nerve damage losing feeling and control in his face, the other lost one eye and injured the other. These incidents were with hand held grinders that were nothing like this machine. The table on this machine reduces the likelihood of hangup and acts as a shatter guard. The machine cannot jump up and strike the user. While no grinder is perfectly safe this one is much safer for notching and doing small cutoff work than using a hand grinder. While using grinders it is best to wear both side shield saftey glasses and a face shield. The clear guards mounted on a grinder DO NOT substitute for personal protection.

Links:	Grinder Safety Guards and wheel mounting. Motor Buffer Polisher Another DIY machine WHEELS: Buffing and Grinding Recomendations and facts.

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