I need to cut 9/32 "scallops" into a 50-55 RHC Shaft
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    Default I need to cut 9/32 "scallops" into a 50-55 RHC Shaft

    It's for a personal project, but I need to cut these into a pretty hard hydraulic cylinder shaft. What's the best way of doing so? Cungsten Tarblide, obviously, but any special flavors?


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    I can't suggest any particular grade of carbide to use, but I would suggest tipping the head 1 or 2 degrees so that your not cutting on the center of the ball cutter.

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    I would use an interpolated path on a cnc mill because it is practically impossible to take a wide chip with the full radius of the tool in material that hard. Using a much smaller tool permits you to nibble away at the material with about a .005" depth of cut, and therefore, not a very wide chip per pass. Trying to do this on a manual mill would be quite tedious, and you'd have to assume you're going to dull quite a few cutters, because every instant that you dwell in the cut 'hones off' the cutting edge.

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    ram-type edm ?

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    Do the ends of the slots need to have the same radius as the sides? If not, grinding would be the way to go.

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    Quote Originally Posted by rimcanyon View Post
    Do the ends of the slots need to have the same radius as the sides? If not, grinding would be the way to go.
    not necessarily, they're breathing ports past a gland

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    Quote Originally Posted by APynckel View Post
    not necessarily, they're breathing ports past a gland
    In that case, it would be kind of you to keep the radius shallow (i.e. not perpendicular to the rod) at the ends. Your seal will be much more comfortable with such an arrangement if it's dynamic.

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    Quote Originally Posted by BoxcarPete View Post
    In that case, it would be kind of you to keep the radius shallow (i.e. not perpendicular to the rod) at the ends. Your seal will be much more comfortable with such an arrangement if it's dynamic.
    That's a good point, the less it moves the less likely to embrittle and fail.

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    Quote Originally Posted by APynckel View Post
    That's a good point, the less it moves the less likely to embrittle and fail.
    The seal moving won't cause it to "embrittle," that will be the result of temperature and medium exposure. Material selection is the way to combat that failure mode. Movement is fine, but the shallower the entry, the less likely the rubber will get shaved off and nibbled away every time it crosses the threshold.

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    If the gland must seal on the unscalloped part then I'd rethink that profile to remove any sharp edges. Any edge that touches the gland should be radiused and polished. If not, the MTBF will be measure is single or double digits of cycles I think, depending on gland design.

    As a wild ass idea, you could drill several radial holes, with radiused and polished edges, where the scallops end on the current design. Then drill a small axial hole down the center of the shaft, and add a seal plug. If you make the gland surface bigger (longer along the shaft axis) than the holes, you might get better life. The center of the shaft doesn't do much, so drilling axially shouldn't weaken it much.

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    Quote Originally Posted by bosleyjr View Post
    If the gland must seal on the unscalloped part then I'd rethink that profile to remove any sharp edges. Any edge that touches the gland should be radiused and polished. If not, the MTBF will be measure is single or double digits of cycles I think, depending on gland design.

    As a wild ass idea, you could drill several radial holes, with radiused and polished edges, where the scallops end on the current design. Then drill a small axial hole down the center of the shaft, and add a seal plug. If you make the gland surface bigger (longer along the shaft axis) than the holes, you might get better life. The center of the shaft doesn't do much, so drilling axially shouldn't weaken it much.

    Considering doing an electro control system with a solenoid triggering off crank timing, this is complex and is likely going to cause issues later with the seal.

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    Quote Originally Posted by APynckel View Post
    Considering doing an electro control system with a solenoid triggering off crank timing, this is complex and is likely going to cause issues later with the seal.
    Two things. First, a guy can blue sky. Sorry if this didn't meet your needs. So if I understand your point, the exact position of the slots ties into the function. Even if so, the design suggested might work with less wear on the seals.

    Second, I see boxcar Pete had the same idea but expressed it earlier. Pete, I salute you! And agree: slots going through a gland should be very carefully made else the gland won't like it.

    To the OP, good luck. What would life be without complex challenges?

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    Quote Originally Posted by APynckel View Post
    It's for a personal project, but I need to cut these into a pretty hard hydraulic cylinder shaft. What's the best way of doing so? Cungsten Tarblide, obviously, but any special flavors?


    I have good results in hard shafting material using MA ford tooling.


    156 Series - M.A. Ford

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    Is the idea to break sealing along a certain interval (is the length of the slots important)? There might be another way to achieve what you're trying to accomplish.

    One of our customers uses an interface much like the opposite of what you're doing, several different length slits cut into the bore that the seal will unblock one at a time to control flow as a function of position. The part validated to 3M cycles IIRC. Don't get discouraged about the possibility of this design working. It just needs to be approached carefully to protect seal life. Pressure will also be a factor.

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    Internal bypass for a shock absorber?

    Sent via CNC 88HS

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    Seems to me that using an abrasive wheel would solve two problems. First, it will cut a hardened shaft. And second, with a wheel diameter that is several times the diameter/width of the groove, the ends would have a smaller angle and would not harm the seals.

    Cleaning up and polishing those edges would still be advisable.


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