Anyone else using a CNC mill to make bows, &c?

[William F. Adams]

I've got an upraded hobby-level mill running (a ShapeOko), and have begun drawing up bows to cut them out using the mill.

Unfortunately, I'm limited by a 1 meter Y-axis (1.2m rails weren't available when I upgraded, and I don't have the room for 2m), so I need to come up w/ a handle splice I can use when cutting out the profile (or I guess I could commit to doing a takedown) --- suggestions?

Currently considering a scarf joint w/ a butterfly key....

[TroutGuide]

Sounds cool. I would focus on risers if it were me. Limbs are more dynamic than just a cnc formula, IMO.

[Eric Krewson]

Not a CNC machine but the late and infamous Jimmy Taylor had one or more milling machines he fed his glued up bow blanks into to shape the limb profile.  After one pass through his milling machines he would string the bow and complete tillering on a balloon sander. Total time lapsed from blank to finished bow, about 15 minutes.

[Dan Bonner]

A number of high end custom bowyers use CNC. You may want to give Bob Morrison a PM. He is a nice guy and will likely help you out.

Bonner

[LittleBen]

I think what everyone has said pretty much sums up my view. I think risers are more conducive to CNC than limbs due to the need to tiller.

regarding the splice, I think you could do a slightly modified Z splice. The only thing you'd need to do in order to accomidate the limitations of the endmill is the following:

Imagine each side of the splice having an outer projection [that will sit to the outside of the riser] and a center projection [the one which extends into the slot in the opposite splice]

Each side of the splice also having a center slot for accepting the center projection.

Use a small diameter endmill ... say <1/4", at least for the final cutting.

Make the end of each projection rounded to the same diameter as the endmill, then make the bottom of each slot rounded to the diameter of the endmill to accept the rounded tip of the projection.

I hope that made sense. I will try to get a diagram drawn up. But I think that should work.

Or you could make a sleeved takedown like Big Jim uses.

That would be very rapid and very accurate on a CNC mill. If your bay is 1m long I assume it's probably .5m wide or so ... meaning you can lay both halves side by side and cut them both. The only issue you're going to have is only being able to mill the left or right side or the riser then you'll have to flip the blanks over to finish the cutting.

I think you can address this issue by first drilling two small holes through the portion of each blank which forms the sleeved portion of the riser [do this with the mill so it's very accurate]. Then you can use these holes to define an axis and a zero point for the CNC so that both sides of the riser are cut in precise alignment.

You should be able to 'teach' the machine the location of the holes by first attaching the blanks to the bed of the CNC, then using a v-bit endmill, you can direct manually the endmill to the hole [without the endmill running] and move it downward until the tip of the v-bit is in the hole, do the same for the second hole and you have two reference points, and by definition also a reference axis. I've never done this but mathemiatically it's sound, just a matter of whether you have the software capability to do it.

Lastly, if the machine is programmed for a process like this, you can probably also have the machine automatically detec the precise positon of the hole by first putting the endmill in roughly the correct place as described above, and by running an automated script where the machine moves in x and y very slightly in a radial pattern, and testing the z direction for contact with the material. The point where contact occurs at the lowest z position is your x, y center.

[William F. Adams]

Not expecting a finished bow, just planning on roughing out to floor tiller or a bit better and resolving the joint --- I simulated it, and believe the keyed scarf joint will work out.