I am researching making patterns to cast al flywheels. I found a drawing from Elmer Verbergs info at the Jon-Tom website. How do I machine the tapered spokes, shown in the drawing below, on a rotary table? I can understand the setup for drilling the corner holes for the cutouts, but how do I offset for the taper of the spokes?
Chuck
no drawing but you will probably have to off set your tailstock
sorry found drawing someplace else, you can do it on the rotary table you will just have to get things aligned or take out as much as you can then file to the line
Or make them as separate parts and put the pattern together as an assembly, ring spokes and hub.
bit tough to explain in writting . but you need to center your r/t then off set it from center the correct amout on one axis then turn the table so you are on one edge of a spoke say left edge then with your other axis cut every left edge , then return r/t to center and then offest for the right edge and machine all the right edges of the spokes . there ya go clear as mud.
i could show you but i cant put it in writting very well .
johno
(10-25-2014, 07:43 PM)texx Wrote: [ -> ]bit tough to explain in writting . but you need to center your r/t then off set it from center the correct amout on one axis then turn the table so you are on one edge of a spoke say left edge then with your other axis cut every left edge , then return r/t to center and then offest for the right edge and machine all the right edges of the spokes . there ya go clear as mud.
i could show you but i cant put it in writting very well .
johno
Got it, Johno. Thanks.
Chuck
What about a tapered end mill?
(11-06-2014, 10:21 PM)Dr Stan Wrote: [ -> ]What about a tapered end mill?
Actually, DR Stan, I have a tapered endmill somewhere... Good idea.
Chuck
Another point in pattern making. Most of the time I've tried to make a match plate, in other words half of the pattern on one side and half on the other making sure the draft is correct. This way you'll have half of the casting in the cope and the other half in the drag. One can even include the gating system, except for the sprue and riser, in the match plates. The main advantage in this is having the same amount of sand above and below the casting making cooling fairly symmetrical.
Match plates will also improve efficiency and reduce time, if, and that's a big if, you make enough of the castings. Depending on the complexity of the pattern I usually will not make a match plate unless there is at least a dozen pours. Since a flywheel is fairly simple I would seriously consider a match plate if there are as few as six pours planned.