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  1. #21
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    mbelfer,

    The depth of the 60 degree side is .140". But a straight edge across the roller perimeter to the bit tip will be as accurate as the setting tool. That would match the frame angle. Then; more = sharper tip angle; less = less tip angle. And, as you 'grind' the tip, the less the angle becomes.

    Keep the land of the bit on the axis of the rollers and tool, and as you sharpen and check the tip you will see a lagging angle of the land. The keeness of the very tip of the bit is dependent on the setting of the bit lands. Be careful of sharpening a bit backwards...or with the lead of the land receding from the straight land edge. That is a common mistake even with professional sharpeners such as Darex with a slipped cam and is easily overlooked. Drilling stainless with one of these will bring out the carbide to correct!

    Also, a tiny amount of lapping oil or grinding oil will make the job go much faster and keep the stone from clogging with Chinese steel (if those bits have such a pedigree). There are diamond 'stones' of various grits that will sharpen a bit (carbide included) very quickly.

    Yes, a double ended or multi set tool would be very handy. Keep in mind that the collet chuck does not need to be very tight at all. You will not need much pressure when honing the tip and only tight enough to prevent slipping down into the collet is all that is necessary, and it is much easier to reset the bit as it is ground. The beauty is that both sides will be at the exact same angle and making them equal is the only concern. You'll see as you sharpen a few - it's so simply easy and such a very efficient little tool.

    Bill C



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    Hi Mike, at a pinch you could also measure the "stick out" length by comparing it with a ruler, but I'm not too sure where the fixed point you would measure from on an original "wishbone" sharpener.

    At any rate, even if a new design is made, the principle is the same, whether you rub from side to side or across the stone.

    Many years ago I made a facetting tool for a chap in our local lapidary club, and the wishbone type sharpener is of the same principle, except the tool and stone being facetted are stationary while the lap revolves, which leads on to having a revolving copper lap charged with diamond dust and applying the wishbone sharpener and drill the same way.

    Having a power driven revolving lap would make sharpening small carbide drills so much easier, when there is no hand movement to control.
    Ian.



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    Thanks Bill and Ian. The ruler parallel to the fixture edge method was how John Wilding (Model Engineer, December 2000 & Jan 2001) set up for using his adaptation of the Wishbone.....strikes me as a method more susceptible to error with a broken or (previously) badly sharpened drill, however.

    Meanwhile, since it seems I have all of the Wishbone except the setting jig, I think I will shut up a while till I get a chance to try all this out; when successful, maybe work out the geometry of a setting jig with steps at, (at a SWAG estimate) maybe .175 and .115 as well as the .140, aiming at somewhere near 138deg and 108 deg points. But that's a ways into the future (under a pile of tuits.....circular ones)
    Thanks again., Michael.



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    In case anyone is interested in making one of the drill sharpeners, here's a few pics to show the tool and a couple of dimensions to make one.
    Ian.

    Attached Thumbnails Attached Thumbnails Sharpening Small Bits-dscf0702-jpg   Sharpening Small Bits-dscf0707-jpg   Sharpening Small Bits-dscf0717-jpg   Sharpening Small Bits-dscf0719-jpg  

    Sharpening Small Bits-dscf0720-jpg   Sharpening Small Bits-dscf0722-jpg   Sharpening Small Bits-drill-sharpener-jig-8-jpg  


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    A broken bit would need to be reset once or twice with either sharpener in both axis, and length to achieve a tip angle required for the work. A light sharpen of the cutting edge would usually only require one setting.

    A Quorn or other cutter grinder works well too but tedious begins to have meaning with a cutter grinder and a .004" (.1mm) bit! Build Ian's or a wishbone, you'll be happy you did. They seem crude but are actually the cutting edge in small bit sharpeners since the tip angle with these tiny bits is very forgiving anyhow...

    Bill C



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    Default Home endmills.

    I have been grinding down the end of broken 1/8" shank 0.5mm carbide drills (1mm long is all that's left) to 0.3mm diameter using dremell drill holder and a CBN wheel in the lathe.
    Needs a magnifying glass to approach wheel, then just go by the dials. When it sparks out, I grind the end flush and square.

    Doing some nice engraving with them on stainless steel.
    The flexing of the 1mm x 5mm long original support piece seems to let the cutter get it's clearance. I only break them when I get tired, and it takes 5 minutes to make a new one.

    Once one is working I can run it for 6 or 8 hours without a problem (until I get tired).
    Going down to 0.2mm works OK but I have to halve the feed rate !
    You start to appreciate run-out in the collets too.

    Getting the black powder coating in the grooves is a challenge.
    Those are 1mm spaced lines. 15mm / minute at 3600RPM. Wish I had more speed.

    Attached Thumbnails Attached Thumbnails Sharpening Small Bits-engraving-jpg  
    Super X3. 3600rpm. Sheridan 6"x24" Lathe + more. THREE ways to fix things: The RIGHT way, the OTHER way, and maybe YOUR way, which is possibly a FASTER WRONG WAY!


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    Neil,

    Try blackening those engraved grooves or etched grooves, then polish the brass with a firm felt wheel and some rouge. Or use a syringe to place some black in the grooves. We make a brass plaque now and then and use these methods....Miratic Acid to clean then Birchwood Casey Brass Black.

    Saved a hand full of 1/8" carbide shanks and use them as you describe. Some have ridiculous hours on them being used for engraving. More useful than when they were factory made tooling.

    Making a miniature end mill is too tedious for me.

    Bill C



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    Cool on the engraving, Neil.

    As for the Wishbone thing. I just got a Work Sharp. I bet I could use the Wishbone on it with very fine grits (sounds like time for breakfast).

    Rance



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    Default Re: Sharpening Small Bits

    Hi all, Have not posted much since 2009 and not sure if this is the best place for this question but: Considering making a sharpening jig but first, can anyone recommend an ideal geometry for .7mm drill bits used for drilling 12mm long holes, with the grain, in exotic hardwoods? The problem is that they often tend to follow the grain and get off center. Obviously I need advice on feed rate and spindle speed as well. Also, in a gang tool type setup, would a live tool help with the drilling of small diameter holes in wood? Many thanks in advance.



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    Default Re: Sharpening Small Bits

    15:1 length to diameter. A challenge.
    Wire twist drills, VERY sharp.
    The wishbone sharpener is a must, (IMHO)
    http://www.cnczone.com/forums/toolgr...tml#post500997
    8000-1000 RPM (a guess)
    Peck drilling 1mm steps
    Feed.. Quite slow.
    Some air cooling would help and let you run faster.

    Super X3. 3600rpm. Sheridan 6"x24" Lathe + more. THREE ways to fix things: The RIGHT way, the OTHER way, and maybe YOUR way, which is possibly a FASTER WRONG WAY!


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    Default Re: Sharpening Small Bits

    Quote Originally Posted by C&Me View Post
    Hi all, Have not posted much since 2009 and not sure if this is the best place for this question but: Considering making a sharpening jig but first, can anyone recommend an ideal geometry for .7mm drill bits used for drilling 12mm long holes, with the grain, in exotic hardwoods? The problem is that they often tend to follow the grain and get off center. Obviously I need advice on feed rate and spindle speed as well. Also, in a gang tool type setup, would a live tool help with the drilling of small diameter holes in wood? Many thanks in advance.
    A wood bit is somewhat different than what was being discussed here because the tip is ground completely different. The tip is ground to a needle point but the flutes are left long on each side but shorter than the needle point and sharpened on their leading edge to cut like an auger. The needle point guides the bit into the wood while the flutes do the cutting. You can use a conventional drill bit sharpened the usual 118° but you must run the drill as fast as possible and 'peck' the hole by feeding in .010" - .020" and draw the bit back out of the hole making sure that the flutes are clear of any swarf. That should get a deep accurate hole but small holes in hardwood are tricky. Pecking is best done on a CNC machine because of the accuracy needed on each peck - taking the bit in too far can cause it to begin to lead off - then you're done with accuracy with that hole. You need a CO2 laser to drill those holes....# 70 drill bits will be tough to grind for wood.

    Bill C Haven't been here for a while either.



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    Default Re: Sharpening Small Bits

    Thanks Bill and Neil, what do you think about a 60 deg angle, as is used for plastic/plexiglass drills? Yes, brad point would be great but the smallest I can seem to find them is 2mm. Pecking has worked very well for me for manual work, especially in plastics. I use a taig lathe with lever tailstock, but there is usually some substantial deviation with woods. Hoping to start some cnc production at some point and wondering how to manage this issue in that context. I also have a foredom type rotary hand piece set up in a drill press type arrangement, that works quite well at around 20,000 rpms and a moderate feed rate, but it is basically vaporizing the material and the bits burn quickly.



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    Default Re: Sharpening Small Bits

    And now for a completely heretical solution.......you could burn the holes in grainy wood by heating the "drill" bit, which is just plain wire, and as long as the wire is not too hot the hole does not get too big in diam.
    Ian.



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    Default Re: Sharpening Small Bits

    Quote Originally Posted by C&Me View Post
    Thanks Bill and Neil, what do you think about a 60 deg angle, as is used for plastic/plexiglass drills? Yes, brad point would be great but the smallest I can seem to find them is 2mm. Pecking has worked very well for me for manual work, especially in plastics. I use a taig lathe with lever tailstock, but there is usually some substantial deviation with woods. Hoping to start some cnc production at some point and wondering how to manage this issue in that context. I also have a foredom type rotary hand piece set up in a drill press type arrangement, that works quite well at around 20,000 rpms and a moderate feed rate, but it is basically vaporizing the material and the bits burn quickly.
    Have you tried making/using a spade bit for this? A Ø 0.028" (#70) piece of hardened drill rod or carbide (special wheels for carbide as you probably know - green) - grind the sides away equally (cutter grinder would be great for this but you could off-hand it too) to form a basic tapered spade bit. Give the sides about .100" length at about .010" thick at the start. Spin it up, peck and relieve it often. Carbide - spin as fast as you can but feed slow. High speed - spin maybe 6 - 10K and relieve more often with moderate feed.

    Spade bits are too dumb to lead off if they are not pushed and fairly accurately made. 60° is strictly for keeping plastic from heating and sticking to the drill bit - and still not so effective even then.
    BC



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    Default Re: Sharpening Small Bits

    Thanks Bill, I have tried making a spade bit but never managed to get the geometry right. That is probably due to lack of a jig. I have been playing around with a simplified design, based on jigs I have used for sharpening gravers for hand engraving. The lip angle is set by the protrusion of the bit from the pin vise and the difference of the levels of the sharpening stone and the surface the jig rides on, while the clearance angle ( 12 deg) is determined by the angle cut in the bottom of the jig. Attached some mock ups below. Thanks for the burning idea Ian, some of the woods smell quite nice when they burn! Would the CO2 laser really work?

    Hope you guys can advise me on this thread I just posted: http://www.cnczone.com/forums/vertic...26360-cnc.html

    Many thanks

    Attached Thumbnails Attached Thumbnails Sharpening Small Bits-screen-shot-2017-01-09-9-00-a   Sharpening Small Bits-screen-shot-2017-01-09-9-00-a  


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