Frustrated ? Discouraged ? what a difference a day makes !

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peterl95124

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Yesterday I needed a counterbore for a socket-head-cap-screw,
so decided to make a "D-bit" for this size that I didn't have on hand,
selected some O-1 rod for it,
and then thought, this is steel, I'm using it on aluminum, probably doesn't need heat treatment
Ooops !!!, that didn't work as expected !!!,

its a day later, and I'm over the discouragement, and ready to properly heat treat the tool and re-grind it

and the part I was counter boring, I need 5, started with enough bar stock for 6,
because, you know !!!, and only botch-counterbored the first 1,

what a difference a day makes !!!
 
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I have a collection of square ground twist drills.

As an apprentice, the first time I had to counterbore a largish hole for which we had no cutter, my artisan gave me a drill and told me to pre-drill all the holes - then to grind the drill square and follow up to counterbore depth and then re-sharpen the bit back to standard.

Seemed to me a lot of effort - so I have always kept all suitable broken or worn down stubbys which I keep for just this.

Sometimes I grind an existing drill and simply replace the drill.

The trick is to predrill the counterbore to just beyond depth (that will leave a small chamfer on the inside edge).

Counterbore.jpg


Preferably do it all without changing the position, swop drills and engage square ground drill into the prior drilled hole before starting the spindle - otherwise it might snag and wander. You only want to remove the prior drill point.

Similarly you can't start a square ground drill on a flat surface.

Regards, Ken I
 
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How does a square drill look? Similar to a 2 flute endmill? Possibly does not matter how the "middle" looks, when pre drilled.
Trying to make one now!
K1600_P1010064.JPG


I am shocked :) this thing works even without predrill, just like that. (yes just by coincidence, just 3 holes, than it began to wander about).

6 mm drill with a flat tip. Now I have my first flat bottom drill.
 
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They are usually started with the same size regular drill bit. Now and then We win one.;)
Yes, but my picky friend already complained. He needs one that drills the through hole and the flat at the same time. Possibly even the champfer.
I had to pass on this one for now. :) I guess the experienced Quorn Wizzards can do!
 
My father re-ground a drill - 3/8* I think? - to 1/4" for about an inch, with a flat for the larger countersink, just leaving a small corner radius. I never worked out what it was for, but I have since bought proprietary similar multi - diameter drills for pre-drilling holes for wood screws, with clearance and countersink parts. The first point of contact though is always a point or very narrow flat with 120-ish degree tapers.
K2
 
My father re-ground a drill - 3/8* I think? - to 1/4" for about an inch, with a flat for the larger countersink, just leaving a small corner radius. I never worked out what it was for, but I have since bought proprietary similar multi - diameter drills for pre-drilling holes for wood screws, with clearance and countersink parts. The first point of contact though is always a point or very narrow flat with 120-ish degree tapers.
K2
Kind of like these?

IMG_6217_Radiant_Photo.jpeg
 
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