Carbide tools

[Mike6453]

I'm have carbide tools and am new to turning.
How do you know when you need to turn the carbide insert to a sharper spot?
Do you have any ballpark as to how long one spot on the insert lasts before it dulls (maybe as in number of pens)?
Do you try to sharpen the insert or just toss it and replace it when all sides are dull?
Thanks!


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[mecompco]

Basically when it stops cutting as well as you'd like, you go to a new surface. With a new cutter, you can turn quite a few pens. How many will depend on many variables (type of material, etc.) You can sharpen them on a diamond card (I have the set of 3 and use the fine and very fine cards) with a little cutting fluid. They don't get "quite" as sharp as new, and don't last as long before they need sharpening again. Luckily, it only takes a few minutes.

 

[jttheclockman]

Hello Mike

I hope this does not sound harsh or crude in any way. Have you ever worked with cutting tools of any kind such as saws, routers, knives, hedge trimmers, lawn mowers or any other tool that cuts?? I ask this in a informative way. If you have answered yes to any of the above I am sure you noticed that the device used does not cut the same as when it was brand new with time and uses. I would assume you then sharpen the blade. Well the same thing applies to carbide tools. The blades are meant to last longer but they dull just as well as any HSS tool does. You should feel the drag on the blade and the more effort it takes to do the same thing it use to take less time to do. The safety aspect of this is the sharper the tool the safer it is. That is because you are not forcing the tool to do the work. It should glide over the material and slice it.

There is no formula for changing carbide blades or positions because every person uses their tools differently. The material you are cutting, the amount of pressure you apply when cutting, how sharp was the tool to start with, the quality of the carbide used. My point is if the blade feels it takes too much effort to cut with then rotate it or change out the blade. And yes they can be sharpened with a good diamond card. I like to use the Trend system

 

[magpens]

Sharpening ....

After you have rotated the cutter through 360 degrees, or as you see fit, take it off the handle, turn it upside down on a fine or extra fine diamond card, apply a little fluid, and swirl it around about a dozen times. . This gives you almost a "new" edge, and you can do this virtually forever. . Do not try to sharpened the tapered edge, just the flat top.

 

[penicillin]

Here are the signs that tell me that that the carbide tip is not sharp enough and needs to be turned, sharpened, or replaced:

* The carbide tip doesn't cut as well as it did.
* The carbide tip doesn't cut as cleanly.
* The surface of the wood is rougher.
* The carbide tip vibrates and chatters more.
* The carbide tip makes a different, louder sound.
Most important:
* As soon as you turn the carbide tip, you notice the difference immediately. Everything cuts better, smoother, nicer, ...

The problem with carbide tips is that they spend most of their useable life in the "sharp enough to use, but not as sharp as I really want" zone.

You can always rotate the tip and then try the new edge for a few cuts to see if it makes a big difference. After that, decide whether you want to turn it back and squeeze some more cuts out of the old edge, or continue using the fresh one. If you compare edges like that a few times, you will teach yourself the difference between a sharp carbide edge, a sharp-enough carbide edge, and a carbide edge that needs to be turned.

I use both carbide and high speed steel (HSS) for pens and other turning. When I want the sharpest possible turning tools, I rely on the HSS tools. When I was turning bog oak blanks a few days ago, I found that they snagged and chipped out more with carbide. The HSS tools left smooth, clean surfaces. The challenge with HSS turning tools is always keeping them sharp for when you need them. It is so easy to reach for the carbide tools when you want to turn a pen and your HSS tools need sharpening. ;-)

 

[TonyL]

When I find I need to apply pressure - when the weight of the tool is not enough to make cuts as cleanly as when the edge was new.

I have not had much success sharpening cutters. I have used trend diamond cards and CBN "stones" with oil. The edges improve, but I can't get the achieve a "like new" edge.

I am sure it is possible I just haven't been able to get it right.

 

[penicillin]

Yesterday evening, I resharpened my square radius and round carbide tips. I put them on a DMT DuoSharp HC Fine/Extra Fine stone. I did 100 passes on each side of the diamond stone. After that, I did 100 passes on each side of the 1000/6000 grit water stone. The carbide tips cut like new. Sweet!

Terminology (my own, not from any reference): A carbide tip has a flat "back", which faces up when you use the tool. It has a sharp beveled edge around the side. I call the part that faces down and rests on your turning tool the "base." Here is what I do:

Your goal is to remove a small amount of carbide evenly across the entire back. If you do it well, you will peel off the topmost layer of carbide. That includes the outermost edges, which have micro- nicks and micro- rounding that make them dull, poor turning tools. In peeling off that topmost layer of the back, you will expose fresh new edges with the same bevel angle.

* Gently place the back side (largest side) of the carbide tip down on the fine diamond stone.
* Use your finger to press lightly on the center of the base of the carbide tip. Your goal is to apply even pressure across the back surface and edges of the carbide tip.
* Square Radius: Move the tip side-to-side for 50 back-and-forth passes, then rotate the tip 90 degrees and do 50 more passes, and finally 10 "swirls" clockwise and 10 swirls counterclockwise (anti-clockwise).
* Round: Use a swirl pattern, but lift your finger and turn the carbide tip every 10 passes. Alternate between clockwise and counterclockwise every 10 passes as well. Reminder: The goal is even pressure and even wear across the entire back.
* Use the full surface of the stone, not just a small area. If you are doing it correctly, you should see a small buildup of black "swarf" - the carbide material that was removed.
* Repeat for each subsequent stone: I use a fine diamond stone (600), an extra fine diamond stone (1200), a 1000 grit waterstone, and a 6000 grit waterstone in that order. I am not sure whether the 1000 grit waterstone helps or hinders, but I think it helps.

The etched markings on the back will disappear, if you didn't lose them in a previous sharpening. When I am done, I use a Sharpie marker to mark each tip with a dot. I always rotate tips clockwise. When the dot has come full circle, it is time to sharpen again.

Done correctly, you should be able to squeeze a long life from your carbide tips. Nonetheless, I keep a new tip of each shape ready for when I may need it.

P.S. I keep a thin layer of water on the diamond stones to lubricate them and help float away the swarf (but I store them clean and dry). I soak the waterstones in water for 30 minutes before using them.
P.P.S. Your waterstones must be very flat before you start. I flatten waterstones with an extra extra course diamond stone.