[AR] Re: My Cavitating Venturi
- From: Peter Fairbrother <peter@xxxxxxxxxx>
- To: arocket@xxxxxxxxxxxxx
- Date: Sun, 26 Jul 2020 09:53:27 +0100
On 25/07/2020 18:45, Terry McCreary wrote:
14 degree (full angle) carbide burrs are a standard item and
inexpensive. Long shank tools are available, as well as those with
wider flutes for cutting aluminum. >
Best -- Terry
On 7/25/2020 11:24 AM, Daniel Dyck wrote:
Thanks Theo. Machining was definitely complicated. For a college team
w/ limited resources I would highly suggest going AN, aluminum, and
designing it to slide into the flare, w/ no curves (like my waterflow
demo venturi). Additionally if your diffuser half angle is 7 deg, you
can buy 7 deg tapered end mills.
For other angles and shapes, if you have a lathe you can make and use a
D bit.
Turn the exact inside shape you want on the lathe in tool steel,
harden/temper/polish (or grind a bit of broken HSS tool to shape). Then
grind just less than half of it away so the remainder is a thou or two
greater than half diameter and has a D profile.
The end and the corners of the D form the cutting edge(s). Should be
used in the biggest lathe you can find rather than in a drill, if at all
possible. Use drill bits to rough out the shape before using the D bit.
Can get very accurate holes.
Works well in aluminium, stainless less so but in a bigger lathe with
coolant it is possible. Can even be done in copper for eg chamber
throats, but then the straight part of the D should be noticeably more
concave - this takes practice to get right, and should be done before
you turn the outside of the chamber.
It is of course possible to buy teeny boring bars and braze/solder/hold
them in the end of some suitable stock.
Peter Fairbrother
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