dern
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| posted on 4/3/05 at 09:32 AM |
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Sharpening drill bits
How do you sharpen drill bits on a bench grinder? I did one and it worked a treat and then did another and it was completely blunt so I guess the
first one was a fluke.
Any tips for doing it by hand?
Thanks,
Mark
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ReMan
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| posted on 4/3/05 at 09:45 AM |
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Try this?
http://www.locostbuilders.co.uk/viewthread.php?tid=22181
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timf
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| posted on 4/3/05 at 09:46 AM |
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Have a bench grinder?
Scribe a 59 degree line (should look like the hour hand at 1 o'clock) on the tool rest.
Clamp a small peice of steel stock on the line. That serves as your fence.
Turn the grinder on.
Using the fence as your guide slowly feed the bit towards the wheel and turn the bit clockwise.
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dern
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| posted on 4/3/05 at 09:57 AM |
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Cool, thanks 
I'll give that a go later.
Regards,
Mark
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Mix
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| posted on 4/3/05 at 10:36 AM |
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Sorry timf but it's not quite that simple 
Your method will give no lip clearance and thus no cutting edge. This means excessive pressure will have to be used to 'induce' the bit to
cut. You need to grind back from the cutting edge a 9-12 degree clearance.
Mick
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clbarclay
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| posted on 4/3/05 at 12:02 PM |
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To get the rough way of measuring both sides of an drill bit, take 2 sufficiently big nuts and weld them together side by side like in diagram
below.
This gives and angle of 120 degrees, only 2 degrees of ideal angle. 120 as oposed to 118 is still plenty acurtate enough for good drilling.
 
Rescued attachment drill bit angle.JPG
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DarrenW
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| posted on 4/3/05 at 02:44 PM |
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I learnt how to do them by hand as part of my toolmaking apprenticeship. Even after a few years of not having to do them ive always managed them first
try when doing the build. Its a skill that you just dont forget after plenty of practice. I cannot however even start to think how to describe in
writing how to do them.
Why not try;
1. Take a perfectly good (eg 10mm) bit and try to copy it. Look at the land across the flank and offer it up to the wheel to learn how to hold them. I
use my left hand as the jig and control the bit movement with right hand. Try getting the angles without switching the grinder on at first. I gring
the cutting edge first then pivot the bit vertically upwards to get the clearance. Keeping angle constant (dont move left hand, just rotate the bit
off the wheel) repeat on second side. Using a good bit as a guide will teach you what the geometry should be.
trust me, once youve sussed its not hard and you will be wondering what the fuss is about.
The biggest mistake people make is by rotating the bit while grinding it - you cant get the chisel tip right doing that. I touch on at correct angle
then pivot the bit that is resting on fourth finger of left hand verticall upwards in a straight line - no rotation.
2. Get a plasplugs bit grinder or similar and make it easy for yourself.
Its annoying me this as i could show someone in 3minutes how to do and after 30 mins with an old box of bits you could be doing a good job.
Tips - dont get them too hot. Have a cup of water handy (i assume you wont have coolant) to keep them cool.
When sharpening dull bits just touch them onto the wheel - dont try and take too much off. Once youve mastered that then go for re-grinding chipped of
damaged bits.
Both cutting faces need to be same length.
Ive tried to find web link but no success - they all refer to jigs and tools.
[Edited on 4/3/05 by DarrenW]
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Mix
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| posted on 4/3/05 at 04:53 PM |
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See here for info on drill sharpoening
http://www.machine-tools.org.uk/guide.html
Mick
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Jon Ison
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| posted on 4/3/05 at 05:12 PM |
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I would find it impossible to explain in words how too sharpen a drill bit, like stated above could show you in a matter if mins.
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clbarclay
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| posted on 4/3/05 at 08:24 PM |
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Does any body know how tools like the Bosch S 41 drill bit sharpener work and whether they are any good?
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Mark Allanson
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| posted on 4/3/05 at 08:53 PM |
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Non of the 'magic' drill sharpeners work - it is all down to practice. I learnt by working on large broken drills chucked at me by old men
in manilla dust coats. Once you have the feel for it, you can sharpen even the smallest of drills in seconds
If you can keep you head, whilst all others around you are losing theirs, you are not fully aware of the situation
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clbarclay
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| posted on 4/3/05 at 09:28 PM |
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Just like sharpening knifes then, I've tried the pattent knife sharpeners (usuall when at a friends house and they don't have a steel),
Theres a lot to be said time, effort and a good basic tool.
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Simon
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| posted on 5/3/05 at 01:26 AM |
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Angle grinder.
Sharpen a twist bit in about 15 secs
ATB
Simon
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the JoKeR
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| posted on 12/3/05 at 06:00 PM |
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Not sure if these are sold outside of North America, but I'm VERY happy with the Drill Doctor.
It takes care of just about all the bits I'll use, up to 3/4". It does standard bits, split-points, and masonary bits. Yes, it can be
done by hand by people with the right touch, but that's not me! It sharpened the following bit so well that the following spirals were made
with a regular hand held drill going through 1/4" steel. It's not cheap, but it saves me a LOT of time and I always have sharp bits
on-hand.
__________________________
Jeff
http://www.midwestwelding.com
http://www.locostusa.com/forums/
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