Tapered screw threads

My dad has an old "Barkbuster" wood splitter, it takes a PTO from a
tractor and drives a cone, about a foot long which has a 1 or 2 tpi
square cross section (maybe 1/4" square) thread along its length. The
idea is the cone screws itself into the wood, splitting it. It works
really well, but over the years the tip has worn to the point where it
won't bite. He got it back working after a fashion by building up the
tip with an arc-welder and regrinding the point and first turn or two
of thread- but its a temporary fix.
Since about 4" of the tip of the cone is theoretically replacable
(assuming the rusted solid pins can be removed, etc), he was wondering
if a new tip might be turned on his SB 9".
He thinks the angle of the cone is about 10 degrees off the
centerline. The length is about 4". The thread cross-section doesn't
really need to be square, but it does have to be pretty deep and it is
1 to 2 tpi. He thinks the 2 problems are be getting his SB geared for
the threading and managing the taper (he doesn't have a taper
attachment), and was wondering what others might think of the problem.
Reply to
Greg Menke
Loading thread data ...
Some things are cheap enough to buy. I have seen several of that type splitter still in production. It may be worthwhile to look into that.
Personally, I would probably look at freehand cutting the thread on the cone with an angle grinder, or building a unit similar to a spindle lathe as sold for use with a router, except set up to hold the angle grinder on edge.
Thread cutting at that kind of angle will be problematic.
Cheers Trevor Jones
Reply to
Trevor Jones
Making the part is possible. But there is a reason these have faded away. They are damned dangerous! More than one death has occured with these types splitters.
Ron Thompson Was On the Beautiful Mississippi Gulf Coast, Now On the Beautiful Florida Space Coast, right beside the Kennedy Space Center, USA
formatting link

The ultimate result of shielding men from the effects of folly is to fill the world with fools. --Herbert Spencer, English Philosopher (1820-1903)
Reply to
Ron Thompson
I nearly died of frustration using one!! When we lost all our elms through Dutch Elm Disease back in the 70's I tried to split some elm blocks using one of these on a 23hp(?) Diesel Kubota Minitractor. Had to drill pilot holes to get the bloody thing to work at all & it regularly stalled the whole tractor, jammed into the endgrain, requiring a surgeon's hand on the chainsaw to cut them off the screw without touching it with the chain! Ended up chainsawing the whole lot (2 of the trees were 19 feet in circumference) which took literally years - in fact over a decade before it was all used up. Come to think of it, the saw would have probably cut that screw easier than the elm ----------------------------------------------------------------------------------------------------- snipped-for-privacy@boltblue.com John Lloyd - Cymru/Wales
Reply to
This is no surprise! I saw these things in Mother Earth News back in the 70's, and couldn't believe the design. This was the Scroozler, or something like that, that you attached to a driving wheel hub on your car. So, you can't set the parking brake (on a RWD car or pickup), you have to have one wheel on the ground, and you shove the log onto the point! If the log manages to bind up in the wheel well, the car takes off across the field. Get wrapped up in your work? If working alone, it might just keep whapping you round and round until the car runs out of gas. I was a lot crazier when I was young, but there was no way I'd even WATCH somebody use one! A little blood doesn't scare me, but I'd rather not see dismemberments live!
I find it EXTREMELY hard to believe these things are still sold new, and I'm sure anyone who has one would be VERY glad to find somebody to unload it on!
Reply to
Jon Elson
I believe I've seen these mounted on a two-wheel Gravely tractor, and have been thinking about making one. Slow speed, with a heavy frame and stop bar to keep the log from spinning, and a slip clutch on the gearbox should make it fairly safe. I don't think I'd want to use it on a car with one wheel jacked up. Although I did do something very close to that when I jacked up one wheel of my Landrover so the tire was maybe an inch off the ground, and threw under it green walnuts that I was trying to hull. Didn't do too bad a job of it, although some did come out with a bit of speed. If you've ever hulled American black walnuts, you'll know why I was "driven" try this.
But John, you shouldn't have been surprised by your frustration. After all, you said the magic word. ELM. It just plain doesn't split, which is why they used to make hubs for wagon wheels from it. As someone who started splitting with sledge and wedges, and thought that a 6 pound splitting maul was one of the greatest inventions of all, I became intimately aware of the splitting (and non-splitting) properties of many different woods. Of the common woods, elm is about as bad as it gets.
My saving grace was the line from the old poem:
"elm wood burns like churchyard mould, e'en the very flames are cold"
That line, and the fact that we didn't have much elm on the property, could usually convince my father that those logs really didn't need to be split for the firewood pile.
Try anything else.
John Martin
Reply to
They're not that bad- the cone doesn't spin all that quickly and if you're careful, they work just fine. Show me what wood-splitting equipment that doesn't come with such a proviso.
We had great luck using it to split the stringy pin-oaks that the hydraulic splitters we borrowed couldn't hack. Logs with super tangled up grain would stall the tractor, but most anything else would split right away. The tricky logs were those that held long enough for the cone to dig a good ways in, then they'd go all at once. You feed the wood with it set against the "steady rest" so it won't get away from you- and you go easy so if the wood shifts and spins as the cone bites, your body parts are already out of the way.
Your average rush hour is a greater risk to life and limb. I've nearly been killed twice by people who simply HAD to be talking on their damn cellphones- never got more than the odd little bruise with the barkbuster.
Reply to
Greg Menke
Aarr! 'Tis a wonderful thing, experience. I know that now!
----------------------------------------------------------------------------------------------------- snipped-for-privacy@boltblue.com John Lloyd - Cymru/Wales
Reply to
I've never had occasion to do this myself, but one of my old textbooks describes cutting threads on a taper. First choice, taper attachment, second choice between centers, and finally, 'if the work must be held in a chuck, a fairly good job can be done by slowly feeding the tool toward the operator as the work turns.'
Since you are not making a thread that will screw into a mating part, I should think doing an adequate job should not be that hard.
Reply to
Mickey Feldman

PolyTech Forum website is not affiliated with any of the manufacturers or service providers discussed here. All logos and trade names are the property of their respective owners.