how do you properly hone a tool bit?

mickri

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Give me a hone and a tool bit that needs final sharpening and I will make it duller faster than you can blink. I am honing challenged. I see lots of references to using a hone to put the finishing touches on a tool bit. But I have yet to find anything on how you go about doing that. In my feeble attempts all I seem to do is make the tool bit duller. Help me out please.
 
I could also use instruction on this. Thank you for bringing it up mickri.
 
That's a tough one. You need to feel the flat of the surface wanting to be honed and if anything fall away from the edge to not roll it over. Sometimes I hold the stone in my hand and sometimes I hold the tool in my hand with the stone on the bench. Try to alternate directions so yo can read off the old scratches what adjustment you might need in your angle. Take a sharpie cover you tool then work up to the edge without taking the sharpie off leave that till the last strokes. Lots of light and magnifiers usually.
 
I have seldom felt the need to hone a tool bit; if they are properly sharpened on a grinding wheel of fine grit after having been roughed out on a coarse wheel, they are sufficiently keen edged for most any job. I save the diamond grit on a slab of plastic for sharpening knives, for that, they are wonderful! For woodworking edge tools, I use a 3 stone set like the butchers use, finishing with an India stone, got hard Arkansas, but rarly use it.
 
Do you stroke towards the edge or away from it.
 
For me time is cheep so I usually give my lathe tools a quick hone on a medium stone, but they probably don't need it. I wet the stone with kerosine to keep it clean. If you grind your tools on a grinding wheel the hollow shape left by the radius of the wheel makes honing quick. Hold the cutter so that the ground face is flat on the stone. A few swipes back and forth will show the honed edges at the top and bottom of the grind. Repeat on the other faces. Form tools such as threading tools that have a flat top just require a rub with the face flat on the stone.

Greg
 
I've been honing tools for a little while now so I'll give this a shot. The decision to hone or not is up to you. Many experienced machinists don't bother. I do it because the tool cuts easier, more accurately, finishes finer with fewer surface defects from an unground edge and they last longer. I don't usually regrind a tool beyond the initial grind. I hone them until my rake angles are no longer effective and I throw them in a bucket; this can take 10-15 years to occur. Until then, a honed tool cuts like new.

It is important to grind a good tool. This means your tool has a geometry that you feel will work for you and that the faces of the tool are not full of facets or grind marks. If you have these defects it will take you a long time to get rid of them so grind the tool well.

It is also important to understand that you are not honing to produce an edge. You are honing the three faces of the tool so that they are dead flat, or at least the upper and lower edges are flat and co-planar to each other on a tool ground on a wheel. The edges are precise intersections between these flats and by flattening each face, the edges take care of themselves. When all three faces are flat, the edges will be very sharp and will not reflect light. If you see light reflecting off an edge then that means one of the tool faces is not flat.

You can use water or oil or diamond stones to hone. Sand paper does not live long enough to be an effective medium for initial honing, although you can use it for touch ups. I usually prefer diamond stones for most sharpening/honing but for fine finishing tools or gravers, I go from my extra-fine diamond to a fine India stone and then to a Translucent Arkansas stone. This puts a mirror finish on the tool and it cuts like a razor.

For honing lathe tools, I use a steel backed diamond stone. I prefer a 6-8" bench stone for initial honing and the credit card sized ones for honing between uses. A few seconds of attention to each flat before the tool is put away keeps my tools sharp and ready to go whenever I am. I stay away from plastic-backed diamond sharpeners for lathe tools; they flex under pressure.

I also use water with a bit of Dawn soap or a wetting agent in it to lubricate. This helps flush debris away and keeps the stone cutting well.

Again, the goal is to produce a very flat surface on each face. I usually start with the side cutting face. My personal technique is to hold the stone in my left hand (I am right handed) and the tool in my right hand. I get the face flat in both the vertical and horizontal directions, lock my wrists and apply moderate pressure on the pull stroke only. A diamond stone cuts best under light to moderate pressure; high pressure only wears the stone and doesn't cut any faster. Let the stone cut. I hone over a container with water/wetting agent or soap in it and dip the stone after a few passes. The goal, again, is to flatten the face and I check it often to make sure I am doing exactly that.

I start with a coarse diamond stone, then go to a fine stone, then an extra-fine stone. The goal is to produce a homogeneous surface across the entire face. Once you get that, move to the next grade and do it again, and again for each face.

Once I get the side flat, I move to the end and then the top. The process is the same - get the face you're honing set dead flat on the stone, make sure your wrists are locked (locked, not rigid) so your tool angles don't change and hone on the pull stroke with moderate pressure. I find that applying pressure on the push stroke works too but the tendency to roll the tool and grind down an edge happens too easily so I avoid doing that.

For me, the hardest face is the end face. The surface area is very small and it is difficult to feel when the tool is flat on the stone. It helps to color the face with a Sharpie so you know when your wrist angles are right and then try to maintain it. It takes a bit of practice to do this so stick with it.

Once I have all three faces dead flat, I create the nose radius with a extra-fine diamond stone and then take a final pass on the top face of the tool to eliminate any burrs that may have formed. Then I check each edge under light to be sure there is no reflection. Then I know the tool is sharp and ready to go to work. My freshly honed tools will cut curlicues in newsprint and they will definitely cut flesh so be careful with them.

That's basically it - hone for the flats.

Hope this helps.
 
Mikey, That helps a bunch and exactly what I was looking for. Thanks for the very instructive description on how you hone a tool bit. I will start practicing.
 
I have seldom felt the need to hone a tool bit; if they are properly sharpened on a grinding wheel of fine grit after having been roughed out on a coarse wheel, they are sufficiently keen edged for most any job. I save the diamond grit on a slab of plastic for sharpening knives, for that, they are wonderful! For woodworking edge tools, I use a 3 stone set like the butchers use, finishing with an India stone, got hard Arkansas, but rarly use it.

My bench grinders are a little on the economic side , I find that grinding the tool and then finishing by hand with stones is best for me, I do lust after a real nice grinder with nice rests and no vibration , mmmmm.

:)

Stu
 
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