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+-- Thread: Demo Hammer Bit As Turning Tool? (/showthread.php?tid=7366157)
Demo Hammer Bit As Turning Tool? - crokett™ - 11-22-2021
I broke part of the shank off an SDS demo hammer bit last week so can no longer use it in that tool. It's a 3/4" wide flat chisel. I'm wondering about grinding it and turning it into a turning tool. I figure since it was designed for busting masonry it's probably a good hard steel.
RE: Demo Hammer Bit As Turning Tool? - AHill - 11-22-2021
How long is the shaft? Are you wanting to use it as a skew chisel or some other tool? Generally speaking, the shafts of turning tools need to extend at least 4-6" into the handle to ensure a catch doesn't cause the business end to break off the handle and impale or cut you. One other thing to consider is the type of steel in the bit. I doubt it's M4 or some other exotic tool steel found in turning tools. You may end up sharpening the bit more often than a typical HSS tool steel used for turning tools.
EDIT: MM's advice on length of the tang is better information than what I provided above. The key is using a decent metal ferrule that can prevent the wood retaining the ferrule from splitting.
RE: Demo Hammer Bit As Turning Tool? - MichaelMouse - 11-22-2021
(11-22-2021, 09:23 AM)crokett™ Wrote: I broke part of the shank off an SDS demo hammer bit last week so can no longer use it in that tool. It's a 3/4" wide flat chisel. I'm wondering about grinding it and turning it into a turning tool. I figure since it was designed for busting masonry it's probably a good hard steel.
2 1/2" tangs on my old "came with" carbon steel tools. After forty years, that's about as long as the tool itself on the most-used. I would say 4-6" would be abundantly cautious. If you keep your toolrest close, which you should ALWAYS do, a hit half inch on one side of the fulcrum won't translate into much at the handle. Hardwood and a driven ferrule should do you.
Then there's that other advice that says keep air over your tool and you won't "catch" much. Means cut above center on outside, and below center on inside cuts.
If you slice wood, carbon steel is more than hard enough. Exotic alloy stuff in my arsenal requires diamond hones, while carbon needs only an India gouge stone to tune the edge. Grinding needs to be done with care so as not to overheat and make the edge brittle.
Don't skew the business end. Leave it straight across and use it like a chisel. My straight chisels plane wonderfully, with me doing any skew to the travel by moving the handle.
RE: Demo Hammer Bit As Turning Tool? - crokett™ - 11-23-2021
The tang is about 2" long, but I could grind something longer if needed. I might make it a smaller skew. I was thinking more along the lines of a bedan tool or similar.
I have a straight chisel. It's an old tool I got that I reground. I think it was originally a scraper but it was too wide and not thick enough to be effective at that. I use it like a skew where the cutting edge is presented at angle to the rotation but I might be doing it wrong.
RE: Demo Hammer Bit As Turning Tool? - SceneryMaker - 11-24-2021
(11-23-2021, 08:56 AM)crokett™ Wrote: .... but I might be doing it wrong.
Does it make nice curly chips instead of just sawdust? Does it make a smooth surface with little to no tearout? If so, then you're not doing it wrong.
RE: Demo Hammer Bit As Turning Tool? - crokett™ - 11-24-2021
(11-24-2021, 08:25 AM)SceneryMaker Wrote: Does it make nice curly chips instead of just sawdust? Does it make a smooth surface with little to no tearout? If so, then you're not doing it wrong.
Long grain, yes. End grain, not so much. I had some walnut cutoffs that were cross cuts. I decided to try to turn one as a spindle - so I was effectively turning end grain. I had a fair bit of tearout with both a straight and skew chisel.
RE: Demo Hammer Bit As Turning Tool? - SceneryMaker - 11-24-2021
(11-24-2021, 09:25 AM)crokett™ Wrote: Long grain, yes. End grain, not so much. I had some walnut cutoffs that were cross cuts. I decided to try to turn one as a spindle - so I was effectively turning end grain. I had a fair bit of tearout with both a straight and skew chisel.
I've found that a fresh sharpening on the chisel makes good cuts on end grain but it soon starts producing dust and tearout again. Really sharp seems to be really important on end grain.
RE: Demo Hammer Bit As Turning Tool? - crokett™ - 11-25-2021
(11-24-2021, 05:26 PM)SceneryMaker Wrote: I've found that a fresh sharpening on the chisel makes good cuts on end grain but it soon starts producing dust and tearout again. Really sharp seems to be really important on end grain.
Yes. I also did some experimenting and I was likely trying to take too big of a bite. I should have done the roughing with a roughing gouge
RE: Demo Hammer Bit As Turning Tool? - MichaelMouse - 11-25-2021
(11-25-2021, 09:28 AM)crokett™ Wrote: Yes. I also did some experimenting and I was likely trying to take too big of a bite. I should have done the roughing with a roughing gouge
Or any of the true "spindle" (Continental) gouges with broad sweep, like these. Forged HSS Gouges - Lee Valley Tools
Very handy in finishing inside bowls as well.