[AR] Re: Thrust Chamber Manufacture
- From: 1bcjolly <1bcjolly@xxxxxxxxxxxxx>
- To: arocket@xxxxxxxxxxxxx
- Date: Fri, 14 Aug 2020 20:43:06 -0400
Both thumbs up! Sent from my Sprint Tablet.
-------- Original message --------From: Peter Fairbrother <peter@xxxxxxxxxx>
Date: 8/14/20 20:32 (GMT-05:00) To: arocket@xxxxxxxxxxxxx Subject: [AR] Re:
Thrust Chamber Manufacture On 14/08/2020 22:03, 1bcjolly wrote:> Don't know if
my experience is proper as I am a self taught machinist. > Use the smallest
center drill you have. Mine have a tip about 1/32 of > an inch. Spin the part
under power in the lathe chuck. Using the > tailstock, advance the center
drill point until it just touches the > surface of the part. Depending on how
much runout you have in your > chuck and how much "slop" is in your tailstock
the point of the center > drill will find the center of rotation of the part.
Once this is done, > go ahead and drill a small spot on the part. Change out
the center > drill for one of the appropriate size for your hole. Spot the
stock > again and you should be fairly close to centering your hole. One word
of caution, do not go too deep with that small center drill especially > if
it's in aluminum. Those small points will gum up and break. Then you > have to
dig the point out and ruin all the work you just did. Hope this > is
helpful.You can also use center drills in a mill/drill. If the attack angle is
90 degrees, ie the hole is to be perpendicular to the surface of the workpiece,
you can also use a spotting drill.If the hole is at an angle then a center
drill works better than a spotting drill, and using a milling cutter to make an
overlarge circular indentation with a flat bottom at right angles to the hole,
followed by a center drill, works better still - a carbide sleeve probably
works best of all, but it isn't easy to hold in place.Another simple thing, to
avoid exit burrs: get a thick piece of the same material you are making the
injector face out of and clamp it to the injector blank. Then drill through the
blank and through the join with the waste piece. Simple, and no exit
burrs.Peter Fairbrother> Barryll> > > > Sent from my Sprint Tablet.> > >
-------- Original message --------> From: Norman Yarvin <yarvin@xxxxxxxxxxxx>>
Date: 8/14/20 15:59 (GMT-05:00)> To: arocket@xxxxxxxxxxxxx> Subject: [AR] Re:
Thrust Chamber Manufacture> > On Fri, Aug 14, 2020 at 11:20:17AM -0700, roxanna
Mason wrote:> > the drill> >just digs in wherever it happens to hit, with no
self-centering,> >> >Hasn't anyone heard of,let alone used, a center drill?
And/or spot face> >with an end mill tool?> >Apparently not. You wanna-be
machinist need to take a Machinist 101 (no> >pun) in your local community
college.> >I learned these fundamental techniques in high school, 1&2nd
years.> > Of course I've used a center drill; in fact, that's what I was using>
when I discovered how to do this right. If you jam it in hard and> fast, even
a center drill digs in where it hit with no self-centering> action. Being
smaller and stubbier, a center drill's tip tends to be> better aligned in the
first place, but that wasn't the topic at hand,> which was where the
"self-centering" action comes from -- an action> your old-time machinists
mention a lot but never really explain.>
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