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Thread: Using worn out drills

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    olderdan's Avatar
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    Using worn out drills

    Drills can obviously be sharpened but what makes then useless is worn out lands causing them to jamb.
    There is a way of still using them for start holes for boring where size is not an issue, it is quite simply to sharpen them by hand deliberately slightly off centre, by hand this is easy.
    They will cut an oversize hole and will not bind in use, you will see only one swarf coil emerging, this only works for the larger size MT drills where an element of stiffness exists, which are also the most expensive to replace.
    I can not claim credit for this tip as our toolmakers did this and some of the drills were many years old, seems wrong and crude but it works and helps with a tight budget.
    I can see any comments on this may be interesting.

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    Paul Jones's Avatar
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    Great tip and will put it to use. It probably also depends on strongly built tailstock, or better yet a MT adapter in the QCTP for power driving the drilling operation. I also like using the OCTP with either a grooved extra deep tool holder (e.g., BXA 250-XL) or a MT tool holder to do power drilling for deeper holes.

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    Olderdan is correct. Offcenter will allow drill to operate. Two different point angles won't centered or not, will cause wander and breakage.
    I 'll bet old shop has MT 4's and 5's as old as me. Must be 3-400lbs languishing in a crate. All the shanks look good as far digging down revealed. Some mis-ground, more worn from excess rpm right at corner adjacent point and lands, fully rounded off. No radial drill, and hardly any hole work in the lathe. Gonna make an offer on total scrap weight...
    Time for making a drill sharpening fixture attached to 10" or 12" pedestal grinder, or larger disc sander. Far less expensive abrasives, that's for sure. Noticed many get better results on a disc, including myself. Belts have too little a definite platen supporting the belt.
    The common fixture is a long Vee block that swings to produce the wrist action like hand grinding. A stop at far end positions lengthwise, a register locates cutting edge/ web relative to centerline axially and radially. Needs a compound angle to generate 118*-135* point angle and clearance behind cutting edge. A wheel delivers that easily as you swing away from periphery while hand grinding.


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    Last edited by Toolmaker51; 02-12-2017 at 12:52 PM.
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