Tapered Holes

[wojocad]

I'm thinking of buying a Shopbot. One of the parts I plan to make has a series of tapered holes with 22.5 degree beveled sides. I can buy a special bit for about $150, or I suppose I can use a series of tools in a parallel milling process, or will Shopbot do a series of narrowing and deepening circular cuts? What's the best way?

[beacon14]

how thick are your parts, and in what material?

[wojocad]

1/2" thick... either MDF or Expanded PVC (Sintra or Celtec brand names)

[billp]

Steven,
If I understand what you are looking for couldn't you simply use a 45 degree V bit to get the 22.5 degree angle? If that would work you'd just have to figure the cutting length you'd need to get that depth...
You could certainly buy V bits much cheaper than $150. I checked Pricecutter.com and found a 45 degree bit there for 17 bucks..
http://www.pricecutter.com/product.asp_Q_pn_E_P13-2113

[wojocad]

I checked and found a 22.5 degree bevel bit there. (The sides of the cone are 67.5 degrees not 45.)

Thanks for the lead on the bit. I'll just drill out the smallest diameter of the truncated cone shape with a standard drill bit and then use the bevel router bit like a drill to widen the sides of the hole. Thanks!

[mikejohn]

Steven
Why drill out the hole first?
1/2"(12.5mm) isnt that thick. If you cut a circle at full depth with the 22.5º bit you will get the hole you want.
You can 'drill' down the full depth with the bit first, then cut the circle.
I am assumimg a pointed end bit, not a flat bottomed bit.
...........Mike