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  • Hey everyone, looking for some info on my drill bits.

    I made a Sgain Dubh out of some Damascus but I think somewhere along the way it hardened before I was wanting it too as for the life of me I could drill this steel.

    I bought cobalt bits and finally carbide tipped bits that with a lot of patience, ground their way through.

    Anyway, today I was working on a knife, out of bog standard 01, and none of the expensive bits were biting. Just sort of dishing it out.

    In my despair I grabbed a cheap HSS 3mm bit out of my driver case that hasn't been used on metal before and it cut like butter!

    So my question, through use is it possible to roll the edge of a bit so it doesn't cut any more, and if so is it worth trying to sharpen them or should I just stump for some new ones?

    Thanks everyone.

  • You can dull the edge of a bit fairly easily. Get a drill gauge and practice sharpening them. It isn't hard. You can also play with the rake and edge flats to improve the cutting. Brass actually prefers dull bits since it's a bit grabby.

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  • SharpestEdge use a bench grinder and keep tip cool by plunging in water.

    It's hard to explain how to but lots of info on youtube

    Most of all keep practising:thumbup:

    Great explanation, even thinning the web. I don't think you need to plunge into water when you're grinding a big diameter drill like that, especially when you're holding it in your fingers so you feel the heat, and you're taking it off the wheel to check it so often.

    One thing he doesn't mention, though he talks about point geometry, is the angle for drilling very thin stock.

  • SharpestEdge belt grinder might work if you are gentle and don't push too hard.

    Keith_Beef to be honest I haven't watched video it was the first that came up. When working in engineering and drilling thin sheet it was always advisable to place a piece of wood under work piece and clamp together to stop drill from snatching.

    When drilling brass,plastic etc it is normal to back the cutting edge off as mentioned by Iron Hoarder

  • When mentioning thin stock, I was also thinking of brass liners. As well as backing with a piece of wood, it's good to have a more oblique point angle so the outer edge of the hole is cut soon after the point breaks through.

    For drilling brass, Camm's little booklet (undated, but seems from online sources to be 1951) on drills suggests 15° of lip angle and 160° of point angle instead of the standard 12° and 118°. I'd have to dig out my SKF & Dormer book to look for more up to date info.

  • The older info is usually better. I have a first edition of Machinery's Handbook and some of the information there is nearly lost for ding things by hand.

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  • most people get carried away with geometry and so forth, iv have drilled thousands of holes in my years as a machinist and have only ever used one grind shown above in the video, 118deg ish, bit of clearance in the web and have found above all, especially in stainless,titantium and anything hard that having a sharp correct ground drill, flood coolant to prevent any localised heat buildup and slow speed high feed works every time.

    Hope this helps

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  • I agree with the video but a final check should be carried out if accurate diameter holes are needed.

    The corners of the sharpened edge must be at exactly the same height.

    Get a vertical plate put black marker on it,

    Place the base of the drill in a hole in front of the board and scribe a line (Curve) with each corner.

    These lines should be at the same height.

    If not then the one side will cut more than the other creating a larger hole that desired.

    This will show up as more swarf in one of the grooves than the other one when drilling.

    There should be an equal amount of swarf in each groove.

    The actual angle used is not critical the points being at the same height are !

  • Agreed, especially with no pilot hole, if a large enough pilot has already been used, unequal lengths give or take a little will still drill size, due to the centre of the two points having no material to offcentre the drill giving the greater diameter.

    Only Worry About What You Can Control----Don't Stand Where Thar Can Sit, Don't Sit When Thee Can Lay

  • Ditto.

    I've sharpened from 30mm down to 0.8mm using this method of point measuring and it works well.

    With the smaller sizes , less than 1.5mm , its easier to eyeball it and drill a test hole , then check for tolerance with a plug of the required size.