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Re: [taigtools] Practical minimum limits for parting off?

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  • C. A. Weagle
    ... I have to say that this...is a remarkable device. Are there any larger-scale versions implemented anywhere in industry, or in the commercial prototyping
    Message 1 of 14 , Feb 3, 2003
      > BTW, a twenty disc cast ceramic system with blade thickness around 2.5
      > thou.
      > and casing and shaft, bearings and injectors would way in at less than
      > an
      > ounce! The target is to produce somewhere around 2HP from all this!

      I have to say that this...is a remarkable device. Are there any larger-scale
      versions implemented anywhere in industry, or in the commercial prototyping
      stage? I'd love to see more.

      As for the discs, I have done a fair amount of lathe work for an R&D firm,
      occasionally with thin sections as you describe. It's pretty tricky, and we
      have a nice Hardinge to use! But your post really got me thinking "how wouuld I
      go about this, making very precise, repeatable, thin discs?" So I'm going to
      ramble on at some length here.

      If you're really going to head for 2.5 thou, my suggestion would be to find some
      sheet of the correct thickness & material (as another poster mentioned) and make
      an _oversized_ (10 thou radially) punch for the OD, with an undersized (but
      precise) hole for the ID. Perhaps 0.125 so that a 4-40 shoulder screw (the ones
      with the nice bearing surface on them) will slid right in.

      Then make up a 'consumable' aluminum backing block for the lathe. Something
      that has a peg to fit a larger collet, and a 1.5" diameter body, maybe like 1/2"
      long. Drill and tap a countersunk 4-40 hole for the shoulder screw. Put the
      disc, burr out, on that screw, then a larger fender-type washer or two to cover
      most of the disc.

      Basically, this jig will hold the part well enough to let you clean off the burr
      from the punching operation, without it vibrating all over the place. I've done
      this sort of thing on 10 thou thick 4" aluminum discs at >1500 RPM and had a
      clean cut.

      Were I doing all this, I would then go to a mill, and set up a collet-block (or
      some other means of holding the part, still on the backing block, face up). Use
      a center-finding dial indicator (like the Starret Last Word) and dial the part
      into the exact center. Maybe put some clamped blocks down so that this step
      happens only once.

      I'd then use either CNC or tables from the Machinist's handbook to lay out the
      bolt circle, and drill that _though the washer_. I'd tap three holes in the
      backing block _though the washer and disc_ and screw that down (this can be much
      less precise than the center screw hold-down, but there are a limited number of
      times it can be done before you run out of backing block and need to make
      another).

      Then take the center screw out and carefully (so as not to hurt the threads -
      maybe use a long-shouldered 4-40, like 3/4 or so) drill the center hold on the
      disc to size.

      All of this should be very repeatable and precise. I'm sorry about the length
      and perhaps excruciating detail here (for all I know you're machinist yourself),
      but I enjoy trying to figure out how to make a tricky fixturing operation work.
      I'm all about the fixtures - some of my co-workers have laughed when I've told
      them that I spend 6 hours making the fixture and setting it up, and 10 minutes
      making the cut - but it was a _good cut_!

      --
      Christian A. Weagle

      We pray for one last landing on the globe that gave us birth; let us
      rest our eyes on fleecy skies and the cool, green hills of Earth.
    • Tom Benedict
      ... AHA! I was wondering! Good to know I m not the only one messing around with that. ... Ouch. Yeah, I can understand. I was making mine to be run off of
      Message 2 of 14 , Feb 3, 2003
        On Mon, 3 Feb 2003, Patrick Head wrote:

        > First, thanks to everybody for the great ideas!
        >
        > The parts I am trying to make are "smooth disc turbine blades" (Tesla
        > turbine/turbo pump).

        AHA! I was wondering! Good to know I'm not the only one messing around
        with that.

        > The end result of all this is to produce a very small scale turbine
        > driven/turbo pump for an amateur rocket engine. One of the problems
        > associated with small rocketry is the need for pressure tanks. These
        > are not a big deal on really small rockets, but when one starts scaling
        > up the design, the tanks become too heavy.
        >
        > I am just experimenting with some ideas right now. I may settle on a
        > pressurized tank system, but the turbo pumps have some real advantages.
        > One, the tankage on a smallish rocket can be very lightweight plastic
        > "bags". Two, the design scales well. Three, the propellant pressures
        > can be controlled across the entire rocket burn. Plus some others.
        >
        > The drawbacks are the weight of the turbo pump, the serious complexity
        > of the turbo pump design (for standard bladed ones).
        >
        > Well, I have been doing some pretty serious research/discovery of the
        > Tesla turbo pump idea. It uses thin smooth faced disks, and the latest
        > lab research indicates that very high efficiencies can be achieved.
        > This translates to MUCH easier design, construction, and lighter
        > weights. So off I go on this path ... :)
        >
        > I originally looked at turning the parts, then thought why not stamp
        > them. I may still try to stamp them. The issue here is that a center
        > hole with a notch for shaft alignment has to be punched, around that
        > hole imagine a concentric circle of larger diameter. Then, on that
        > circle, six holes are punched thru. Then at least one or two even
        > larger concentric circles have 9 dimples of fixed depth stamped into
        > them. Of course, the outer diameter of the disc needs to be cut as
        > well. Making such a punch/die seems somewhat complex, but then again,
        > it is probably a whole lot easier to build one such tool, and then
        > achieve highly repeatable disc dimensions, than to try to cut a whole
        > bunch of them on the lathe.
        >
        > In addition, spacers must also be produced that are kind of star shaped
        > and match the profile of the center of the turbine discs.
        >
        > I will need at least five such discs, but really up to 50 will be needed
        > for the complete turbo-pump design. It is really a turbine engine, with
        > two propellent pumps attached.
        >
        > The propellents are Hydrogen Peroxide and Ethanol. The H2O2 is used to
        > power the pump. When it decomposes, the products are super heated steam
        > and pure oxygen gas. Therefore, the only real material choice is
        > stainless. Aluminum could be used, but probably only for tests, as the
        > steam temps are in the melting range of Aluminum.

        Ouch. Yeah, I can understand. I was making mine to be run off of air, so
        my choice of materials was a lot wider.

        > The thinner the discs the better. Of course, as I near 40, my eyesight
        > also limits some of these dimensions! The power of the turbine is not
        > dictated by thickness but by diameter and number of blades. And to a
        > lesser, but still important degree, by the geometry/area ratio of the
        > center holes, and the nozzles for the engine part, and blade
        > spacing/diameter ratios. Many of these dimensions are best determined
        > by experimentation.
        >
        > One thing that IS important with these devices - face smoothness of the
        > discs. Case clearance is not overly critical, so outside diameter of
        > parts is not critical at all (within common sense).
        >
        > I have also thought of machining a very close tolerance mold and casting
        > the discs with incorporated spacers and dimples from some exotic high
        > temp ceramic reinforced with chopped carbon fiber. The material costs
        > for this are astounding, but the amount I need for such a small machine
        > are miniscule, so still affordable. The casing parts could also be cast
        > this way.
        >
        > My ideal thickness for blades and spacers would be around 0.001 inch,
        > but up to 0.005 in would be OK.
        >
        > BTW, a twenty disc cast ceramic system with blade thickness around 2.5
        > thou. and casing and shaft, bearings and injectors would way in at less
        > than an ounce! The target is to produce somewhere around 2HP from all
        > this!
        >
        > Anyway, any ideas would be greatly appreciated, and none-the-less it is
        > just fun to share some ideas.

        Yow! You're way ahead of anything I was doing. Some thoughts, though:

        1 - You might have the pieces laser cut. I know it takes it out of your
        shop and into someone else's, but the results should be quite good.

        2 - You can make a stamping die, but my guess is it'd get complicated in a
        hurry.

        3 - See how much time and effort would be required to make a fixture to
        hold them all and do the machining on them as a stack.

        #3 is how I'm approaching it. I'm using steel for mine. I got a bunch of
        roughly 2.5" diameter steel disks that were reasonably close to the same
        size. My plan was to make a fixture that would let me stack about 25
        disks at a time, and clamp them at the edges. The center hole, the ring
        of vent holes, and the bolt hole pattern could all be drilled through the
        entire stack. The keyway could then be broached in.

        I figured doing it in a stack like that would minimize the distortion to
        the metal, and any slight distortions I got could be removed with careful
        lapping after they were removed from the fixture.

        Again, though, mine is not designed to take high heat. I don't know if
        machining it that way would leave residual stresses in the metal.

        Man, best of luck! I've been interested in rocketry, Tesla turbines, and
        machining, so I have some idea what you're up against.

        You wouldn't happen to be launching out at Black Rock, would you?

        Tom
      • Tom Benedict
        ... There are. I can t remember the name of the company, but there s a company that makese pumps using this approach. It s pretty neat since the more viscous
        Message 3 of 14 , Feb 3, 2003
          On Mon, 3 Feb 2003, C. A. Weagle wrote:

          > > BTW, a twenty disc cast ceramic system with blade thickness around 2.5
          > > thou.
          > > and casing and shaft, bearings and injectors would way in at less than
          > > an
          > > ounce! The target is to produce somewhere around 2HP from all this!
          >
          > I have to say that this...is a remarkable device. Are there any
          > larger-scale versions implemented anywhere in industry, or in the
          > commercial prototyping stage? I'd love to see more.

          There are. I can't remember the name of the company, but there's a
          company that makese pumps using this approach. It's pretty neat since the
          more viscous the fluid, the better these pumps work. Even with very large
          plate spacing, the principle still holds, and they still pump. The
          company whose site I was on made a big point of saying their pumps were
          perfect for pumping stuff like solid/liquid bodily waste. This is
          apparently an application where standard pump designs tend to fail. I...
          I took their word for it. It's not something I'd ever really thought
          about.

          Tom
        • Patrick Head
          Tom, I am planning on using the Rocket Research Society s Mojave Test Area for engine tests and launching. That is if they ever approve my membership
          Message 4 of 14 , Feb 3, 2003
            Tom, I am planning on using the Rocket Research Society's Mojave Test Area for engine tests and launching. That is if they ever approve my membership application. I am hoping it is just a holiday delay thing.There is a great Tesla Turbine site at Tesla Engine Builder's AssociationIt is very informative, contains anecdotes of other experimenters, and has a book, or plans that can be purchased.Christian, this site also contains links to a couple commercial applications of Tesla Pumps. It also has a lot of history about Tesla and his pumps. The reason these pumps aren't very popular is because of Tesla's general temperment. He tried to sell the idea to exactly one firm in Wisconsin. He bypassed the engineers, made them mad, and was attacked in a sales meeting. He got fed up with trying to explain it all, and just gave up. He was evidently quite a character.I truly thank both of you for your super ideas for making these parts. I like the idea of using a punch to get the basic disk, then machining the rest in some fashion. Stacking them seems a very fast way of achieving good results.I would still have to come up with a way to form the dimples, I suppose the stamp could do that. It would even allow for registration of the parts while stacked.The dimples are to maintain proper spacing and limit flexing. They may be superfluous on parts this small. That would make the production MUCH easier.What do you think of this idea?I stamp cut the discs, using a circular die/punch of the correct dimensions. This die/punch would also punch thru the center hole.Then I mount the whole stack on an arbor much like Tom suggested. The arbor would be designed to fit in my 4 jaw chuck, so I could do offset drilling of the remaining holes. The arbor "clamping end" would just be of the same diameter as the disks, with guide holes drilled in the correct places. Another alignment tool is made with close tolerances that just fit the guide holes. The alignment tool is chucked up just like the drill bit would be. When the aligment is correct, I replace the alignment tool with the drill bit and go to it. I repeat this process for the remaining five concentric holes.What do you think? Would this be reasonably achievable by a mere mortal, and by the way rank amateur machinist?If anyone is interested, my rocket design is to design an engine system using the linear aerospike configuration, but four sided, so each side can be throttled for complete directional control. Then once I am satisfied with this, I'll try flying the thing on a conventional rocket, then move on to a singe stage lifting body design that would allow low throttle flight to high altitude, then when aerodynamic forces are sufficiently low, to into full throttle ballistic mode. This should achieve remarkable altitudes. One of the launches at MTA has achieve over 150,000 ft! I think a design like mine go do significantly better.My goal is low earth orbit with possible recoverable reentry. Of course, with this weekend's happenings, keeping things from burning up on reentry is obviously very tricky.Thanks again!Patrick

            Patrick T. Head
            4309 1/2 Temecula St.
            San Diego, CA 92107
            (619) 269-6316


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          • Patrick Head
            I apologize for the formatting of this message, I was trying to HTML tags to include the web site address, and either yahoo or the groups thing mucked it all
            Message 5 of 14 , Feb 3, 2003
              I apologize for the formatting of this message, I was trying to HTML tags to
              include the web site address, and either yahoo or the groups thing mucked it
              all up.

              The tesla web site is at http://my.execpc.com/~teba/main.html

              Sorry.


              --- Patrick Head <patrick_head46035@...> wrote:
              > Tom, I am planning on using the Rocket Research Society's Mojave Test Area
              > for engine tests and launching. That is if they ever approve my membership
              > application. I am hoping it is just a holiday delay thing.There is a great
              > Tesla Turbine site at Tesla Engine Builder's AssociationIt is very
              > informative, contains anecdotes of other experimenters, and has a book, or
              > plans that can be purchased.Christian, this site also contains links to a
              > couple commercial applications of Tesla Pumps. It also has a lot of history
              > about Tesla and his pumps. The reason these pumps aren't very popular is
              > because of Tesla's general temperment. He tried to sell the idea to exactly
              > one firm in Wisconsin. He bypassed the engineers, made them mad, and was
              > attacked in a sales meeting. He got fed up with trying to explain it all,
              > and just gave up. He was evidently quite a character.I truly thank both of
              > you for your super ideas for making these parts. I like the idea of using a
              > punch to get the basic disk, then machining the rest in some fashion.
              > Stacking them seems a very fast way of achieving good results.I would still
              > have to come up with a way to form the dimples, I suppose the stamp could do
              > that. It would even allow for registration of the parts while stacked.The
              > dimples are to maintain proper spacing and limit flexing. They may be
              > superfluous on parts this small. That would make the production MUCH
              > easier.What do you think of this idea?I stamp cut the discs, using a circular
              > die/punch of the correct dimensions. This die/punch would also punch thru
              > the center hole.Then I mount the whole stack on an arbor much like Tom
              > suggested. The arbor would be designed to fit in my 4 jaw chuck, so I could
              > do offset drilling of the remaining holes. The arbor "clamping end" would
              > just be of the same diameter as the disks, with guide holes drilled in the
              > correct places. Another alignment tool is made with close tolerances that
              > just fit the guide holes. The alignment tool is chucked up just like the
              > drill bit would be. When the aligment is correct, I replace the alignment
              > tool with the drill bit and go to it. I repeat this process for the
              > remaining five concentric holes.What do you think? Would this be reasonably
              > achievable by a mere mortal, and by the way rank amateur machinist?If anyone
              > is interested, my rocket design is to design an engine system using the
              > linear aerospike configuration, but four sided, so each side can be throttled
              > for complete directional control. Then once I am satisfied with this, I'll
              > try flying the thing on a conventional rocket, then move on to a singe stage
              > lifting body design that would allow low throttle flight to high altitude,
              > then when aerodynamic forces are sufficiently low, to into full throttle
              > ballistic mode. This should achieve remarkable altitudes. One of the
              > launches at MTA has achieve over 150,000 ft! I think a design like mine go
              > do significantly better.My goal is low earth orbit with possible recoverable
              > reentry. Of course, with this weekend's happenings, keeping things from
              > burning up on reentry is obviously very tricky.Thanks again!Patrick
              >
              > Patrick T. Head
              > 4309 1/2 Temecula St.
              > San Diego, CA 92107
              > (619) 269-6316
              >
              >
              > ---------------------------------
              > Do you Yahoo!?
              > Yahoo! Mail Plus - Powerful. Affordable. Sign up now
              >
              > [Non-text portions of this message have been removed]
              >
              >


              =====
              Patrick T. Head
              4309 1/2 Temecula St.
              San Diego, CA 92107
              (619) 269-6316

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            • J Hamilton <james7799@yahoo.com>
              This is so facinatingly off topic and wonderful that I looked around for a picture somewhere to see for myself. Link below to a list of pumps (available on
              Message 6 of 14 , Feb 3, 2003
                This is so facinatingly off topic and wonderful that I looked around
                for a picture somewhere to see for myself. Link below to a list of
                pumps (available on CD?) to see it. Tesla was quite a mind!

                http://www.animatedsoftware.com/pumpglos/pumpglos.htm

                Cheers,
                Jim



                --- In taigtools@yahoogroups.com, Tom Benedict <benedict@h...> wrote:
                > On Mon, 3 Feb 2003, C. A. Weagle wrote:
                >
                > > > BTW, a twenty disc cast ceramic system with blade thickness
                around 2.5
                > > > thou.
                > > > and casing and shaft, bearings and injectors would way in at
                less than
                > > > an
                > > > ounce! The target is to produce somewhere around 2HP from all
                this!
                > >
                > > I have to say that this...is a remarkable device. Are there any
                > > larger-scale versions implemented anywhere in industry, or in the
                > > commercial prototyping stage? I'd love to see more.
                >
                > There are. I can't remember the name of the company, but there's a
                > company that makese pumps using this approach. It's pretty neat
                since the
                > more viscous the fluid, the better these pumps work. Even with
                very large
                > plate spacing, the principle still holds, and they still pump. The
                > company whose site I was on made a big point of saying their pumps
                were
                > perfect for pumping stuff like solid/liquid bodily waste. This is
                > apparently an application where standard pump designs tend to
                fail. I...
                > I took their word for it. It's not something I'd ever really
                thought
                > about.
                >
                > Tom
              • Tom Benedict
                ... The folks at RRS are a pretty good bunch, and definitely encourage non-standard approaches. A friend of mine launches steam rockets out there. ... I ve
                Message 7 of 14 , Feb 4, 2003
                  On Mon, 3 Feb 2003, Patrick Head wrote:

                  > --- Patrick Head <patrick_head46035@...> wrote:
                  > > Tom, I am planning on using the Rocket Research Society's Mojave Test
                  > > Area for engine tests and launching. That is if they ever approve my
                  > > membership application. I am hoping it is just a holiday delay thing.

                  The folks at RRS are a pretty good bunch, and definitely encourage
                  non-standard approaches. A friend of mine launches steam rockets out
                  there.

                  > > There is a great Tesla Turbine site at Tesla Engine Builder's
                  > > AssociationIt is very informative, contains anecdotes of other
                  > > experimenters, and has a book, or plans that can be purchased.
                  > > Christian, this site also contains links to a couple commercial
                  > > applications of Tesla Pumps. It also has a lot of history about Tesla
                  > > and his pumps.

                  I've read it. Man, Tesla was a CHARACTER! It's kind of a shame, in a
                  way. The electrification of the household is typically attributed to
                  Thomas A. Edison, but to be honest it's Tesla's designs that are in use.
                  Edison couldn't stand the idea of using AC power, and Tesla couldn't stand
                  the fact that his boss (Edison, at the time) wouldn't sit down and do the
                  basic math to see the line losses were unacceptably high with DC power. I
                  can only imagine what would've been possible if those two could've worked
                  together.

                  > > The reason these pumps aren't very popular is because of Tesla's
                  > > general temperment. He tried to sell the idea to exactly one firm in
                  > > Wisconsin. He bypassed the engineers, made them mad, and was attacked
                  > > in a sales meeting. He got fed up with trying to explain it all, and
                  > > just gave up. He was evidently quite a character.

                  Man, no kidding.

                  > > I truly thank both of you for your super ideas for making these parts.
                  > > I like the idea of using a punch to get the basic disk, then machining
                  > > the rest in some fashion. Stacking them seems a very fast way of
                  > > achieving good results.I would still have to come up with a way to
                  > > form the dimples, I suppose the stamp could do that. It would even
                  > > allow for registration of the parts while stacked. The dimples are to
                  > > maintain proper spacing and limit flexing. They may be superfluous on
                  > > parts this small. That would make the production MUCH easier.

                  I'm kinda hoping they're superfluous, but I make no gurantees. Tesla's
                  original design used the star washers and rivets. I was thinking of
                  drilling through the disks and using screws that thread into the far end
                  plate. Still, as you said it would simplify life a lot if they're not
                  required.

                  > > What do you think of this idea? I stamp cut the discs, using a
                  > > circular die/punch of the correct dimensions. This die/punch would
                  > > also punch thru the center hole. Then I mount the whole stack on an
                  > > arbor much like Tom suggested. The arbor would be designed to fit in
                  > > my 4 jaw chuck, so I could do offset drilling of the remaining holes.
                  > > The arbor "clamping end" would just be of the same diameter as the
                  > > disks, with guide holes drilled in the correct places. Another
                  > > alignment tool is made with close tolerances that just fit the guide
                  > > holes. The alignment tool is chucked up just like the drill bit would
                  > > be. When the aligment is correct, I replace the alignment tool with
                  > > the drill bit and go to it. I repeat this process for the remaining
                  > > five concentric holes. What do you think? Would this be reasonably
                  > > achievable by a mere mortal, and by the way rank amateur machinist?

                  I think it's a good start. My guess is there will be hidden gotchas we're
                  not thinking of at the moment. I'd offer more advice, but mine is still
                  just a set of CAD drawings. I haven't started cutting metal yet.

                  > > If anyone is interested, my rocket design is to design an engine
                  > > system using the linear aerospike configuration, but four sided, so
                  > > each side can be throttled for complete directional control. Then
                  > > once I am satisfied with this, I'll try flying the thing on a
                  > > conventional rocket, then move on to a singe stage lifting body design
                  > > that would allow low throttle flight to high altitude, then when
                  > > aerodynamic forces are sufficiently low, to into full throttle
                  > > ballistic mode. This should achieve remarkable altitudes. One of the
                  > > launches at MTA has achieve over 150,000 ft! I think a design like
                  > > mine go do significantly better. My goal is low earth orbit with
                  > > possible recoverable reentry. Of course, with this weekend's
                  > > happenings, keeping things from burning up on reentry is obviously
                  > > very tricky. Thanks again!Patrick

                  Heckuva plan! Defintely talk to the people at RRS. A couple of groups
                  have done high altitude launches, so there's lots of expertise to draw on.

                  Can't wait to see how it works out!

                  Tom
                • Robin S. <lasernerd@hotmail.com>
                  Just a thought in regards to a die for producing those disks. The cutting clearence between the punch and the die are typically between 2% and 5% of the
                  Message 8 of 14 , Feb 6, 2003
                    Just a thought in regards to a die for producing those disks. The
                    cutting clearence between the punch and the die are typically
                    between 2% and 5% of the thickness of the material.

                    You can buy punches and die buttons ground to your specifications,
                    but you have to mount them yourself and that could get pretty hairy
                    when you're talking down to half a tenth of an inch (more precise
                    than most precision slide fits).

                    In fact, the more I think about it, the precision required to punch
                    out disks that aren't horribly deformed boggles my mind.

                    Also, the shallow draws you were refering to (*dimples* I believe)
                    would also be reasonably difficult to achieve due to the thin nature
                    of the material. I don't remember seeing how deep these must be, but
                    when you figure a ratio between the thickness of the material and
                    the depth of the draw, you may actually be *deep drawing* which
                    could require several progressive draws with possible annealing
                    inbetween.

                    I don't mean to sound like a nay-sayer, but one must consider these
                    factors when thinking about designing a tool. I'd be willing to do
                    some research into the design of a die such as discussed here, if
                    there is interest (I have some texts on the subject and am taking
                    tool and die making in college).

                    Regards,

                    Robin
                  • Tom Benedict
                    Something else to look at is your expected production run. If you re building a single rocket, your total number of disks is going to be considerably under a
                    Message 9 of 14 , Feb 6, 2003
                      Something else to look at is your expected production run. If you're
                      building a single rocket, your total number of disks is going to be
                      considerably under a hundred, I'd be willing to guess. Even without the
                      issues Robin raised, my guess is it'd be faster just to bore them out.
                      Less efficient in the long run if you're looking at making thousands of
                      units, but for the number you're making my guess is conventional machining
                      isn't a bad way to go.

                      Tom

                      On Fri, 7 Feb 2003, Robin S. <lasernerd@...> wrote:

                      > Just a thought in regards to a die for producing those disks. The
                      > cutting clearence between the punch and the die are typically
                      > between 2% and 5% of the thickness of the material.
                      >
                      > You can buy punches and die buttons ground to your specifications,
                      > but you have to mount them yourself and that could get pretty hairy
                      > when you're talking down to half a tenth of an inch (more precise
                      > than most precision slide fits).
                      >
                      > In fact, the more I think about it, the precision required to punch
                      > out disks that aren't horribly deformed boggles my mind.
                      >
                      > Also, the shallow draws you were refering to (*dimples* I believe)
                      > would also be reasonably difficult to achieve due to the thin nature
                      > of the material. I don't remember seeing how deep these must be, but
                      > when you figure a ratio between the thickness of the material and
                      > the depth of the draw, you may actually be *deep drawing* which
                      > could require several progressive draws with possible annealing
                      > inbetween.
                      >
                      > I don't mean to sound like a nay-sayer, but one must consider these
                      > factors when thinking about designing a tool. I'd be willing to do
                      > some research into the design of a die such as discussed here, if
                      > there is interest (I have some texts on the subject and am taking
                      > tool and die making in college).
                      >
                      > Regards,
                      >
                      > Robin
                      >
                      >
                      >
                      > To Post a message, send it to: taigtools@...
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                      >
                      >
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