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Question or Advice:
Chisels and planes need to be very sharp in order to work properly. They are both sharpened in the same way; for a plane you'll need to turn the blade at an angle if it is wider than your oilstone so that the whole width is sharpened each pass.
The chisel blade's tooling end usually has two angles: a ground angle of 25-degree finished off with a honed angle of 30-degree at the very tip. If a blade has been abused and has chunks missing it will first have to be reground on a grinding wheel before any attempt is made to hone it. If you do not have your own grinder, take it a tool shop which has one. Another method is to use a small electric grinding machine, or a drill attachment, which can usually hone the blade by substituting the grinding stone for a honing one. (Some can also make a rough attempt to sharpen a limited range of twist drill bits.) It's easy to overheat the steel thus ruining the temper. Hence, it is very important to keep the blade cool.
Chisels should be re-honed before every job. Final honing is best done by hand, using a honing guide and a fine-grade oilstone (or water or diamond whetstone) before every job. Good honing guides are available and have wide wheels which do not damage the stone. Oil the oilstone. Insert the chisel into the guide, set for a 30-degree angle. Pull the blade over the stone several times until a burr is raised on the top side. Remove the chisel from the guide, turn it over and lay it flat on the stone. Rub it from side to side until the burr has gone. Protect yourself and your chisels by keeping them in a soft leather tool roll.
Diagnosis, Analysis, Solutions and other Feedback:
You may prefer silicon carbide wet and dry paper for sharpening chisels. Find something really flat, a 6" square of plate glass is ideal but an off-cut from a kitchen worktop works surprisingly well too. Clamp the chisel in the honing guide and start working it on fairly coarse (say 180 grit) paper. If there are bad chips or nicks in the edge -- which means you need take a lot of metal off -- consider starting with something even coarser. Work through finer and finer grades of abrasive until it is as sharp as you need (at least 600 grit). You may go as fine as 1200. The most important thing is to make sure that you lap (flatten) the back of the chisel with as much care as you hone the bevel (front edge). If the back is not flat and finely polished you won't get or keep a decent edge.
Perhaps you have the Stanley sharpening guide, which is used in conjunction with an oilstone to sharpen chisels and plane blades. Many find this relatively easy.
First you must restore the primary bevel which tends to be about 20 degrees. Use the coarse side of the stone and grind until you have a perfect bevel, then turn the chisel over and lightly remove the burr. Next, repeat the process with the fine side of the stone, just removing enough material to get a fine finish. Once the primary bevel is OK, grind a secondary edge at 30 degrees. Use only the fine side of the stone. Remove the burr.
This results in a chisel which is plenty sharp. Fanatics will insist that back and bevel need to be mirror polished but they obviously require sharper tools than most. [Note: we're is using a two-sided "combination" oilstone here].
Twist drills which are past their best are anathema to any good DIYer but it seems such a waste to just bin them. In reality, the smaller sizes are difficult to sharpen but they're cheap and so not really worth attempting by the beginner. But how do you sharpen the bigger ones?
Some manufacturers make electric grinding machines which will be fine to true up a chisel *before* final sharpening by hand, and will sharpen larger drills. Small ones [drill bits] are so cheap they're not worth bothering with. These are by no means professional tools, which is reflected in the price, but are suitable with a bit of practice for DIY.
You can buy attachments for portable drills to sharpen drills. They may not be much use below about 1/4" diameter though and you should consider how many new drills you could buy for the same price.
Or you could learn to do it by hand with a grinding wheel and save a packet. When you really need to follow a center-spot, you need to be able to sharpen your drills first. New drills quite often come with eccentric points.
Get a good trade-school metalwork, machine tools or Engineers textbook and learn about the required angles for cutting, clearing swarf etc. and the methodology used to sharpen metal cutting tools. We've seen some absolute abortions produced by otherwise quite intelligent people when they decide to "sharpen" a drill etc. Somehow it never seems to occur to them to look at a new drill before ending up with something like a needle point and wondering why it won't cut anymore.
All cutting blades need a backing-off (or clearance), lathes, drills, etc.
Take a drill bit, hold it at a fixed angle to the grindstone, and rotate it. It will produce a nice conical pointy bit, and a nice cutting edge.....BUT, at that instant the metal behind the cutting edge is parallel to it, there is no clearance. Try to use that drill and it will just rub and overheat. The backing-off behind the cutting edges has to be carefully put in as a separate grinding operation.
A fine backing-off (A is small) produces a drill that cuts clean holes, with minimum chatter, but with a tendency to overheat if pushed too hard. It needs patience to use.
A coarse backing-off gets a drill that cuts fast, but with a tendency to grab and chatter... oversize rough holes.
You have to judge what to do according to the material being drilled... for example, brass grabs and snags, so anything less than minimum backing-off is lethal. Indeed, it is even quite useful for brass to slightly blunt the cutting edge with a slipstone.
In the larger drill sizes it is quite handy to have a varying backing-off.... almost nil near the point, so that it remains steady, increasing near the edges.
More on "Backing off:
If you took a drill and held it at angle X to a rotating grindstone, and then keeping the angle the same turned the drill. You would have a lovely spear point on the drill but it would not cut anything ... it might burn through wood.
What you need is that the leading edge of the cutting face of the bit higher than the trailing edge, that way the leading edge cuts into the material, and the part of the drill immediately behind it is not in contact with the material, allowing swarf to come away and avoiding friction.
There are jigs that change the angle of the drill as you rotate them, which is the professional way to do it. Unfortunately not many people have these.
Most fitters will do this by eye, first rotate to get a smooth clean face all round at the correct angle, then one face at a time line up the cutting edge to just be touching the grindstone, then rotate, altering the angle of the drill to grind away a clearance. Only needs a degree or so on hand drill sizes.
As to the angle - like the drill point angle itself this depends on the material you are going through and the thickness of it. i.e. if you were to drill soft thin sheet, you need a flat drill bit angle with little clearance - otherwise it will corkscrew into the work when it breaks the other side. For thicker and harder material, points can be more acute and also more clearance.
More on "Backing off:
If you took a drill and held it at angle X to a rotating grindstone, and then keeping the angle the same turned the drill. You would have a lovely spear point on the drill but it would not cut anything ... it might burn through wood.
What you need is that the leading edge of the cutting face of the bit higher than the trailing edge, that way the leading edge cuts into the material, and the part of the drill immediately behind it is not in contact with the material, allowing swarf to come away and avoiding friction.
There are jigs that change the angle of the drill as you rotate them, which is the professional way to do it. Unfortunately not many people have these.
Most fitters will do this by eye, first rotate to get a smooth clean face all round at the correct angle, then one face at a time line up the cutting edge to just be touching the grindstone, then rotate, altering the angle of the drill to grind away a clearance. Only needs a degree or so on hand drill sizes.
As to the angle - like the drill point angle itself this depends on the material you are going through and the thickness of it. i.e. if you were to drill soft thin sheet, you need a flat drill bit angle with little clearance - otherwise it will corkscrew into the work when it breaks the other side. For thicker and harder material, points can be more acute and also more clearance.
More on "Backing off:
If you took a drill and held it at angle X to a rotating grindstone, and then keeping the angle the same turned the drill. You would have a lovely spear point on the drill but it would not cut anything ... it might burn through wood.
What you need is that the leading edge of the cutting face of the bit higher than the trailing edge, that way the leading edge cuts into the material, and the part of the drill immediately behind it is not in contact with the material, allowing swarf to come away and avoiding friction.
There are jigs that change the angle of the drill as you rotate them, which is the professional way to do it. Unfortunately not many people have these.
Most fitters will do this by eye, first rotate to get a smooth clean face all round at the correct angle, then one face at a time line up the cutting edge to just be touching the grindstone, then rotate, altering the angle of the drill to grind away a clearance. Only needs a degree or so on hand drill sizes.
As to the angle - like the drill point angle itself this depends on the material you are going through and the thickness of it. i.e. if you were to drill soft thin sheet, you need a flat drill bit angle with little clearance - otherwise it will corkscrew into the work when it breaks the other side. For thicker and harder material, points can be more acute and also more clearance.
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