303 and 416 are both totally reasonable to machine; 303 is identical
in machinability to 1018 and 416 is better, per
http://www.carbidedepot.com/formulas-machinability.htm . It does take
more power than aluminum, so really cheap belt drive or plastic gear
benchtop lathes may have problems.
304 or 316 are worse but still can be done, having the speeds and
feeds right with the correct tool makes a lot of difference. They're
not free machining, but they weld a lot better, and in larger sizes of
nozzle making it becomes cheaper to make it with a mix of welded and
lathed parts.
On Sat, Mar 30, 2019 at 4:19 PM Rick Maschek
<dmarc-noreply@xxxxxxxxxxxxx> wrote:
Here's my two cents...I used a variety of steels but they all corrode if not
cleaned, dried, and perhaps a bit of oil to prevent rusting. A former friend
told me years ago that you can't machine stainless steel, that it took
special expensive equipment to do so and I always wondered about that. Then I
got my own lathe and was able to pick up some 303 stainless as a remnant
(when metal stores get to the end of bar stock and can no longer cut things
from it because of it's length or they have pieces that were cut wrong for an
order. I paid/pay $2,89 a pound for it at the metal shop I use.
I like turning it more than I do 6061-T6. I love the look of it and I can
fire a motor and if I don't get around to cleaning it up right away, no big
deal. To clean I simply drop the nozzle into a bucket of water and rinse off.
I don't even have to dry or oil it as it does not rust. I have one 3" nozzle
with over 25 firings (static tests and flights) that includes 3 CATOs and it
looks great.
Rick
On Friday, March 29, 2019 05:35:43 PM PDT, Steve Peterson
<dmarc-noreply@xxxxxxxxxxxxx> wrote:
OOps! Typo. 1080 should be "1018". Sorry....
--Steve
On 3/29/19 5:32 PM, Steve Peterson (Redacted sender steve_peterson for DMARC)
wrote:
1080 (aka "CRS" -- cold rolled steel). But if you actually *like* machining
stainless, go ahead :-)
A slightly more machinable alloy is "12L14" also known as "ledloy" which has
a tiny amount of lead added to the steel to make it more machinable. I've
used both and seen no difference in erosion or other wear.
--Steve
On 3/29/19 4:54 PM, William Schmiedlin wrote:
This is great news!
What alloy are people using? 300 series stainless steel?
Regards,
William Schmiedlin
On Wed, Mar 27, 2019, 10:45 AM Rick Maschek <dmarc-noreply@xxxxxxxxxxxxx>
wrote:
Somehow I thought this had been announced here. Some of you may already be
aware.
This is a post by Steve Shannon, TRA President on the TRA forum from last
month:
"At LDRS 36 in 2017, Rick Maschek requested the Board to consider amending
the Tripoli Research Safety Code to allow steel nozzles for use with sugar
motors used at Tripoli Research Launches. At the time we requested that he
provide data to our Tripoli Research Committee Chair, Dr. Terry McCreary, to
demonstrate that the use of sugar motors would not increase risk. The concern
as I understand it is that the additional density of steel would lead to
increased momentum and thus greater range in the event of a nozzle being
spit. The counter to that is that nozzles in properly flying rockets are spit
downward rather than horizontally. For static tests it's possible to require
that they be held vertically so the direction of a spit nozzle would be
vertical and thus have limited horizontal range. NFPA does not prohibit steel
nozzles.
Since that time Rick and Terry and I have discussed this electronically
several times, but we never did really receive data.
Honestly, most of us don't feel that steel nozzles necessarily increase risk
when used for sugar motors as long as all other rules are followed.
So, rather than leaving this unresolved, Terry proposed that we provisionally
allow the use of steel nozzles with sugar motors for both static burns and
flights as long as the static burns are vertical. The board voted on his
proposal last week and it passed easily.
The motion was for steel nozzle usage to be allowed for this calendar year
(2019). During that time we want Prefects and users to come to this thread
and relate any first hand accounts about their use of steel nozzles, both
good and bad, and especially observations about spit nozzles. Of course for
flights, an angled blast deflector could redirect a spit nozzle, so
observations about that should also be made. At the end of 2019 Terry and the
board will review the data and make a determination whether to incorporate
that change permanently in the Tripoli Research Safety Code. If we do
nothing, this provisional permission to use steel nozzles will expire at the
end of 2019.
I should also point out that this is not mandatory. Local Prefects have the
latitude to ban the use of steel nozzles at their home fields. Local Prefects
always have the authority to adopt policies that exceed NFPA and the Tripoli
Safety Codes."
Rick
