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January 26, 2014 at 5:57 pm #48837chris mabbottParticipant
I watch quite a few videos on staff turning and most seem to use HSS gravers for the job, I often wondered why when toughness wise, carbide is better suited for the job and should, I suppose, provide a better finish.
The thought naturally led me to ask the question…
What do you guys prefer for your cutting tools when making staffs, HSS or Carbide and please state your reasons for choosing either.
ChrisJanuary 26, 2014 at 8:09 pm #55548
I watched a Perplxr video of a guy making a bushing with a graver. I think the narrator said “see, it’s only been four minutes and he almost has the diameter finished”. My thought was had the cut been done with a properly sharpened tool bit in a cross slide, it should have been finished in two passes, a rough cut and a finish cut. That shoulder at most should have been finished in 20 seconds. When watch and clock making first started, cross slides, dial indicators, and the concept of cutting to numbers had not been invented yet. The crossslide not only fixtures the cutter in a more stable way but it allows you to apply more force to the workpiece. Modern equipment allows you to form a mathematical model of the part you wish to make and allow you to transfer that model to the part being machined. With a graver the operator can look at the part and think that it is getting close but if it is a bad guess, the part is dead. This is why you always see someone who uses a graver constantly pulling out a micrometer and measuring the part during the machining process.
Needles to say, I personally do not have much use for them. Should you get the carbide or steel gravers? Get both. They are not particulary expensive and the best way to learn is to jump in and try it. The only problem with carbide is having a system to sharpen them. The only thing that can cut carbide is diamond. The good news is diamond wheels are now reasonably priced. Harbor Freight sells sets of small dremel size diamond cutting wheels that could fit in a lathe collet. These cutters should also be available on your side of the world at a good price.
davidJanuary 26, 2014 at 8:47 pm #55549willofiamModerator
Hey Chris, not that I have cut many balance staffs, but in practicing I have found a hss graver works just as good as a carbide, maybe better as I am able to put on and maintain a nice cutting edge on them, I have many gravers that have been made into different shapes and angles for certain cuts. I also have carbide and thru improper use? I have chipped the points in short order and as David has said they require a bit more work to get back into shape. What I am learning is that at the right speed and sharpness of hss graver you can get a pretty nice finish, using stones for finalizing some dimensions, polishing and burnishing. I have toyed around with using the cross slide to get certain dimensions then use the hand gravers to get the undercuts, tappers, coves or radius’s or whatever that would require alot of time setting up for with the cross slide. I am still pretty new at turning balance staffs, but I think whatever technique someone uses practice, practice practice and it will be your own best way, goal being a proper functioning part. Have fun, WilliamJanuary 26, 2014 at 9:46 pm #55550
What equipment and tools do you use to sharpen your gravers, especially the carbide gravers.
davidJanuary 27, 2014 at 4:48 am #55551aruthaParticipant
Chris, the carbide is great for cutting steel with hard bits or where you have accidentally burnished it with a blunt hss graver. I prefer hss but there are times when you need something harder.January 27, 2014 at 7:27 am #55552Bob TascioneModerator
I always choose HSS over carbide for making staffs. Although the carbide edge will last longer the HSS edge can be ground and honed sharper providing a better finish. For me when doing one off non-production work using HSS applies whether using hand gravers or a cutting tool in a tool post. It’s also easier to grind HSS into whatever geometry you may want. For production work then Carbide or Ceramic inserts always win. Also as Paul mentioned carbide is excellent for machining wear hardened metal.
I purchase M2 blanks for making both hand gravers and tool post gravers.
When making staffs I normally use W1 (or W2 when I can find it in small enough sizes). HSS will easily cut this tool steel after heat treating and tempering. W2 is the same as W1 except it has a higher percentage of Vanadium than W1 which helps maintain a finer grain structure during and after the heat treating process which I think not only helps give a better surface finish when machining but a better finish after burnishing or polishing.
BobJanuary 27, 2014 at 10:07 am #55553
When carbide chips, the damage to the tip has a distance that must be ground back to bring it to a sharp condition. I actually do have some gravers both steel and carbide I just don’t use them very often. My WALLER set came with a lapping wheel and some small tins of diamond lapping paste. This system is great for the final sharpening and polishing of the cutting edge but grinding out a damaged tip is time consuming. A diamond wheel has the diamond impregnated into a bonding resin and can cut carbide fairly quickly but a lap and paste method is a slow way to go. I have a single lip cutter grinder that can do this very quickly but it is heavy industrial machine and it was expensive. One idea that might work if you decide to go with carbide is to buy a diamond wheel and put it on a regular bench grinder. If you go this route make sure you do not sharpen steel on a rotating diamond wheel; only carbide. The heat generated by the grinding will cause a chemical reaction between the steel and diamond and the wheel will be ruined.
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