How do I do this?

[Wongster]

Hi guys,

I'm back. Been off machining for a while.

My dad passed me a worn piece of a bushing from another model of his drink dispenser to duplicate. This piece has kind of a "key" at one end of the through hole which I wonder how to go about duplicating that feature.

Pics attached:

The shaft which the bushing is inserted into has 2 flats at the end. When the shaft rotates, the bushing turns with it.


From the other end:


Regards,
Wong

[Bill Gruby]

The one you have there is probably cast. I gotta think about this for a while. It's a toughy.

"Billy G"

[TomG]

Hey Wong,

The obvious way would be to make the bushing, less the keyed hole in the end and then machine the key on the rotary table with a small end mill.

Another option that would result in a functionally equivalent part would be to make the bushing and machine the bore straight through. Then make a mandrel with the two flats, insert it in the bushing and squeeze the end of the bushing on the mandrel with the mill vise to generate the flats. You might then need to take a clean-up cut on the O.D. of the bushing to remove any raised areas where you upset the flats.

Option three would be to make the bushing less the keyed hole, lay out the key shape in the end and file it to shape.

Another option would be to cut the keyed hole using a custom ground slotting tool like I used to square up the corners of slots on my Steven's Favorite project.

Hopefully these suggestions will get you started in the right direction.

Tom

[Bill Gruby]

(08-20-2012, 12:49 PM)TomG Wrote: Hey Wong,

The obvious way would be to make the bushing, less the keyed hole in the end and then machine the key on the rotary table with a small end mill.

Another option that would result in a functionally equivalent part would be to make the bushing and machine the bore straight through. Then make a mandrel with the two flats, insert it in the bushing and squeeze the end of the bushing on the mandrel with the mill vise to generate the flats. You might then need to take a clean-up cut on the O.D. of the bushing to remove any raised areas where you upset the flats.

Option three would be to make the bushing less the keyed hole, lay out the key shape in the end and file it to shape.

Another option would be to cut the keyed hole using a custom ground slotting tool like I used to square up the corners of slots on my Steven's Favorite project.

Hopefully these suggestions will get you started in the right direction.

Tom

The first one would be my choice Wong. Tom is usually right there with the answer.

"Billy G"

[Wongster]

Thanks guys. I'll try using the rotary table and a small endmill to see if I can pull this off. Only 3 pieces needed this round.

Regards,
Wong

[PixMan]

You may need to finish the "corners" of the milled shape by hand with a file. The bigger the end mill you use, the more finishing you may need to do.

The original was either as-cast or broached. If you can make one out of bronze, brass or aluminum, it would be a piece of cake to make a HSS broach.

Another method, if you can use a soft steel, would be to make a shaped mandrel, then a thick-walled blank of the part. Slip the blank over the shaped mandrel and pound the blank bushing down around it until the shape is completely forged. Use center hole in the mandrel to finish turn the O.D.'s, press it out when done. That would give you the ultimate strength part.

[claudef]

You can also create the bore round and silver solder two small segments in bore to create the two flat sections,

[Mayhem]

Another option would be an "insurance job" to replace his whole machine but that is probably the last option you should consider

[Wongster]

Thanks for all the inputs.

Pixman, I was told that the bushing has to be 304 SS as it will be submerged in the drink dispenser during most of its life time. Will the broach idea still work? How do I go about making one?

Regards,
Wong

[PixMan]

You would have to make a slightly oversize "male" version of the shape out of a good tool steel, heat treat it, then grind it to a final size. Given the tough stainless steel (I'd go with 316), I'd suggest a half-shape broach. You could then mount it in the spindle of your mill, lock the spindle and incrementally feed out until the half shape is complete. Then rotate the broach 180º and finish the opposite side of the shape.