Sharpening Drill Bits

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  #1  
Old 11-27-01, 02:37 PM
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Sharpening Drill Bits

I know many people here are used to doing drill bits by hand. Let me explain a better and more efficient way of sharpening your drill bits. Chuck the drill into your drill motor and precede with caution. Set yourself up a piece of wood on the side of the electric grinder, to steady your drill motor so your drill hits about 1/2 way or less on the grinding stone. You sharpen bits on the side of the grinding wheel, keep bit cooled with water or oil, and don't apply hardly any pressure while using high RPM on drill motor. The whole operation should be done in about 30-45 seconds.

The advantages here is the drill motor turns your drill clockwise. It also insures that both cutting lips of the drill are cut equal, so they both cut evenly. Also, if your chuck is wobbly for whatever reason it cuts the drill lips so it will drill straight.

Try to make the same cut on the drill lips as it previously was, about a 30 degree angle (I think it is). Use high RPM as you sharpen. I think they make a plastic guage for checking this.
 
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Old 11-28-01, 05:14 AM
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can i get a photograph of the fixture described
 
  #3  
Old 12-07-01, 02:02 PM
zalyx1
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Although the purpose of this method is well meant , it is also very dangerous as well as not capable of giving your drill the correct geometry for maximum performance. Prince, please don't think I'm knocking your idea, God knows I've tried hundreds of different shortCUTS (fingers included !) I happen to be a Toolmaker of 18 years and have seen many people get injured doing stuff like this.
First of all , if you circle grind your drill without a cam built into your fixture you won't get the correct releif behind the land (cutting edge) for proper chip evacuation. The area behind the cutting edge needs to be lower than the edge itself. It may look like it when you circle grind, but it's not.Although the drill may cut wood, the edge won't last half as long , especially if you cut harder materials. Hence the drill may keep cutting , but your pressure on the drill by hand will become greatly increased ( pain in the butt) and as you keep cutting the heat will increase because you have increased the surface contact of the drill by not releiving it. This will ultimately breakdown the molecular structure of the highspeed steel . Also because you have no space behind the cutting edge you will inevitably recut many of the chips which also leads to dulling as well as possibly seizing the drill in the hole. I know we've all done that ! Unfortunately this happens before the spiral flute can remove the chips. Good idea to remove the drill to releive the chips as you drill ( pecking motion with drill)
Your best bet is to get a fixture that mounts on your bench grinder, or an all inclusive bench mounted grinder. Darex is a decent brand name.It will give you the proper geom. , including the angle which is normally 31 degrees per side ( 118 deg. included angle ). As well as the proper releif and possibly the option of splitting the tip which help cut down tool pressure and gives the drill a self centering capability. There are many different drills and geometries but this is just basics for your average drill.
If you don't want to buy one , grab a box of dull ones and practice on your bench grinder. You can sharpen one in 30 seconds , no problem. Also, they do make a steel drill gauge ,which i recommend, as Prince mentioned. If you buy one , make sure it's double ended . Usually, one side is for 118(31) degrees and the other is for 135(22.5) degrees for harder materials at slower speeds. Coolant is good idea too, but if you keep drills sharp at the correct geom., you usually just have to kiss the cutting edge a little on the grinder to bring it's edge back which doesn't usually require coolant unless it's a larger drill over 1"
Be SAFE, the cost of a sharpener or proper fixture is well worth the price of your fingers ! Hope this helps !
 
  #4  
Old 12-08-01, 04:33 AM
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Sharpening Drill Bits

Hello 1Prince and Welcome to the Do It Yourself Web Site and my Sharpening forum.

The most useful general purpose sharpening shop machines are the belt sander and the wet stone for just about any household, shop or garden cutting tools the average do-it-yourself person can have.

I prefer the belt sander myself...you may not. However, after you have done some sharpening work, your precision and accuracy will improve and speed will become vital.

At this point is were the belt sander shines. Check the archives within this forum for sharpening other tools. Libraries have some books on the subject of sharpening also.

Drill Bit Sharpening:

With a good eye and a steady hand, almost any steel drill bit can be sharpened on a belt sander or grinding wheel. Keep in mind that practice does make perfect.

The first step is to view the bit closely from several angles prior to any grinding. Look at the center point with the bit facing upwards towards you. Then hold the bit vertical, at eye level and notice the cutting edges. Rotate the bit while at eye level. Notice the back side has a sloping angle.

That sloping back angle from the center point and from the cutting edge backside is called the "relief angle" and must be closely maintained. So must the center point which is called a "Web."

TIP: Failure to maintain the web centered and the bit will wonder when first coming into contact with the item being drilled. Failure to not maintain the relief angle and the bit not cut well.

Once your aware of these angles, you can best sharpen any drill bit. Once your ready to start sharpening, follow the existing angle on the bit. You'll have to also rotate the bit in your hand while sharpening.

Sharpening can be done more accurately using the side of the grinding wheel then using the front face. The side of the grinding wheel has a flatter and truer surface and is less likely to have been used prior. It also makes viewing the drill bit easier, which will help to create a more accurate cutter edge and relief angle.

I suggest using a fine grit belt or grinding wheel. Have a pot of cool water near by to cool the warmed bit. Do one side partially then the other but never any side completely at once. Continue sharpening each side until the bit is completely sharpened on both cutting edges.

Disclaimer:
The sharpening method described above is not the professionals method. However, for the Do-It-Yourself person, the method above will provide satisfactory results with some practice.

Another suggestion is to make the task easier and just purchase any brand table top drill bit sharpening machine. They work fine for non commerical purposes. They'll sharpen any steel drill bit used for casual useages just fine...

Regards and Good Luck
Tom_Bart....Company Enterprises.....TCB4U2B2B
Accurate Power Equipment Company.

Complete Saw and Tool Sharpening Service.
Reminder: "Work Shop Safety Is No Accident."
 
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