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Some Ideas for Ease of Use

Discussion in 'CNC IN THE HOME SHOP' started by MontanaAardvark, Apr 25, 2017.

  1. MontanaAardvark

    MontanaAardvark United States H-M Supporter - Premium Content H-M Supporter-Premium

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    Thanks. I was just looking for a model at Grabcad to see if it had all the dimensions, but I haven't found one, yet. I'd probably need to hold one of the TTS holders in my hand to understand what I have to do.

    The tool holders all seem to have a taper on the end that goes into their TTS holder. If I can just take my 3/4" R8 taper EM holder and grind the face flat, that taper can't be an important dimension, right? It has to be there just to help the tool changer pick it up and get it started easier (human or automatic changer).
     
  2. MontanaAardvark

    MontanaAardvark United States H-M Supporter - Premium Content H-M Supporter-Premium

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    Back to the other topic, I "found" a piece of 1/2" aluminum plate in the shop (it was hidden under some stuff and I forgot I had it!) so it seems natural to cut it to make a tooling plate. It's 20x14.

    I don't know what size to make. If I make it wider than the table, I'm sure it doesn't buy me anything. My Y axis travel is a little low, like 6.65 instead of the factory 6.875, so if it's wider than that, I don't see the cutter can reach it. The X travel is normal. Other than supporting something unusually big, I don't see making the tooling plate bigger buys me anything.

    Making it smaller: the size of the middle part of the table makes a lot of sense. The area between the outer T-nut channels is 4-1/2 wide, and between the channels on the ends it's 24 3/4 wide. If I make it as long as I can and 4-1/2 wide, I can get clamps from the T slots all the way around the table. I could put tapped holes and holes for 1/8" dowel pins in lots of places. Since my Tee nuts and clamping set all use 3/8-16, that seems like the size to use. As bonus, the middle of the plate would be on the center T-slot, so I can put some short bolts (3/8-16 x 3/4") in a couple of places to help mount it to the table

    So it sounds to me like making it 20 long by 4-1/2 wide makes the most sense. Comments?


    Bob
     
  3. spumco

    spumco United States Active Member Active Member

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    The taper is just there to ease insertion as you surmised. Probably also to keep a sharp corner from nicking the inside of the R8 collet if the shank is hardened. Put a 30 degree chamfer on the shank and then round it a bit with a file and some sandpaper.

    As for your tooling plate... Something I've seen that might be useful to consider would be make it wider then your travels by a bit - maybe 1/2" or 3/4. Then when you're done with drilling/tapping it use an engraver or V-bit and engrave a shallow groove all the way around that helps you visually indicate the machine limits. You'll also need to drill & ream a hole in two corners for dowels that you might use to indicate the plate since the machine won't reach the outside. That, or some other feature(s) for squaring the plate to the X-Y axis if you have to remove it and then re-mount it.

    Also, if it's a bit wider than the table you can have threaded holes outside your limits for clamping bit stuff. The clamp holes don't need to be precision located - just a few for some strap clamps.

    Something else clever I've seen is to space it up off the table with 1/2" or 1" standoffs. If you use plenty of big diameter standoffs and mounting screws it won't flex that much and will make it WAY easier to clean the swarf out of the holes and the table slots. You won't need to use a million plastic screws to fill the unused threaded holes - just leave them empty and blow them out. The standoffs won't need to be super-precise in length because you'll bolt the plate down and use a fly cutter to deck the whole top a few 'thou with it's in place. That's why I suggested making it a bit bigger than the travels - but not bigger than a 2"-3" fly cutter can reach. Just plan on re-decking it every time you have to re-mount it.

    All of this assumes that you aren't using strap clamps to mount it. 1/2" is a little thin, but some 3/8-16 flat head screws countersunk straight in to the T-nuts would keep you from having to worry about clearance heights over clamps at the perimeter. Just counterbore the holes 0.075" before you countersink and that'd give you plenty of extra fat to deck the plate a few times without running in to the screw heads.

    If you have a big enough drop or drops from the plate, you could make a tooling plate that fits in your vise. NYCCNC on youtube has a video about this that may give you some ideas.
     
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  4. spumco

    spumco United States Active Member Active Member

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    The idea is that any 3/4 shank tool can be modified to work with the TTS system. The trick is that you need a flange on the tool to bear against the spindle. The TTS shank is about 1-1/2" long, and the flanges are about 5/8" thick. Because the flange has to be locked to the shank, you need some mechanical device to keep the flange from sliding down the shank when the collet tries to pull the shank & flange up against the spindle nose.

    Method one is to use a tool with a shank larger than 3/4, and then turn the shank down. The flange then bears against the shoulder.

    Method two, which I plan to do, is start with 3/4" ground stock. I'll then turn a groove for a C-clip 2-1/8" from the end of the shank. The 5/8" flange is then pressed (or glued) on the shaft and the C-clip acts as a shoulder to keep the flange from sliding down the shank. The flange is then faced off (on the spindle side) so the flange-to-spindle mating surface is true and the holder isn't pulled to one side when the drawbar yanks it in. Keeps me from having to turn down a perfectly good 1" or 7/8" bar to 3/4" just so I can have a shoulder for the flange.
     
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  5. spumco

    spumco United States Active Member Active Member

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    In the interest of full disclosure, I've just started using the TTS system - having finished my drawbar a few weeks ago. I was having some problems setting up my 4th axis (also first 4th part) and noticed some runout on my edge finder when I was trying to touch off the side of the part. Getting the DTI out I measured +/- 0.003" at the end of the wiggler. 0.006" runout is way, way wrong.

    Long story short - the Chinese TTS holders, Tormach collet, and my spindle taper are fine - all within 0.0001" or so. I measured "only" about 0.0015" of Z change on the face of the spindle nose, but figured maybe skimming the nose be the ticket. I've seen videos of people taking a light cut on their spindle nose with a lathe tool held in the vise, and Tormach's TTS user manual even describes doing this.

    Turns out it was, and that when the TTS tool holder flange gets pulled up against the spindle nose any issues get magnified in to angular misalignment and resulting tool runout. Taking 0.005" off the nose in two passes and stoning the nose until the DTI read 0.00005" fixed everything. I now have 0.00015" (or better) 3" from the spindle nose regardless of tool holder orientation.

    Moral of the story - plan on skimming your spindle nose if you switch to TTS. Carbide inset lathe tool run at 250RPM and manually jogged across the face at around 4IPM gave a good cut and 30 seconds with a very fine stone got the last few microns down and averaged the surface nicely.

    -S
     
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  6. MontanaAardvark

    MontanaAardvark United States H-M Supporter - Premium Content H-M Supporter-Premium

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    Very interesting. For some reason, yesterday I was thinking about doing just that.

    I got the Mach3 2010.set going yesterday, and need to wire in the contact system. The hardest part will be getting my control box out of it's corner and onto a workbench so I can get to the BOB. Shouldn't take too long.

    I'm going to get the tooling plate done before I work on tool holding, but these suggestions are really helping me. I sure hope they're useful to the HM community.

    The TTS system has a lot going for it. I was thinking that I've got a tool box drawer full of cutters, and I just had to order a new size EM Friday. Most of my cutters are 3/8 shank from my Sherline, but they're still different cutters, some 1/8 shank, one 1/2, plus a few larger ones. The odd one is I have one of these sets which are all a different diameter - they will be harder to live with. If I figure I need 10 holders, as long as there's one dedicated tool holder with a tool assigned to it, even with buying everything from Tormach/LMS, it's not that bad. Even cheaper if I get some of those China.com holders to work.
     
  7. spumco

    spumco United States Active Member Active Member

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    Just for reference, I set up my 'starter kit' as follows:
    10/ea ER16 Chinese TTS collet chucks
    5/ea ER32 same source

    1/ea 1/2" drill chuck + TTS arbor from LMS
    2/ea 3/8 drill chuck +TTS arbor
    2/ea 1/4" drill chuck + TTS arbor (the cheap package deal they offer)

    Plus 1/ea 3/8" set screw holder I bought from Tormach a while ago as a guinea pig while I was building the drawbar. Now the wiggler lives in it.

    I will probably wind up with about 5-10 home made set screw holders for frequently used, lower-speed tools like 1/4-20 taps and such.
     
  8. spumco

    spumco United States Active Member Active Member

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    TTS update 2:

    My new outboard spider chuck just came out of the mill. The TTS system was stupid fast to change 5 tools (drill-mill to spot, Q drill, #7 drill, drill-mill for chamfer, 3/8-24 tap, 1/4-20 tap), and there was no wobble, run-out, misalignment or other issues with the tool holders.

    Running that 3/8 tap almost an inch deep would, I think, have revealed any slip or tool holder problems. I'm sold.

    Watching the 4th axis dance during the chamfer op was pretty magical. I'd post a video but it's too big and needs some editing.

    IMG_3415.JPG
     
  9. MontanaAardvark

    MontanaAardvark United States H-M Supporter - Premium Content H-M Supporter-Premium

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    BTW, do you have a G0704 or something else? I've never tapped holes under power on the mill, but allowed my lathe to pull the tap in under power.

    A spider chuck is on my list of things to make for some possible gunsmithing projects.
     
  10. spumco

    spumco United States Active Member Active Member

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    I have a Mikini 1610L mill. It's an orphan mill, company is out of business since about 2012. Superb mechanical parts, ferociously crap electronics. SumDood in California set up a company around 2006-7 to import the mill frames and he designed (or paid for design) & sourced all the electronics from backyard Chinese sweatshops rather than proven COTS components. The result was utterly unreliable spindle operation and some incredibly cheap, failure-prone components. The axis motors & drives he bought open-market; oddly enough those work fine and I've kept them.

    Bought it last year knowing the reputation and I've spent the past 8 months gutting it and re-doing every eletrical component on the mill. New computer, BOB, spindle motor, VFD, etc. Price was right due to the known electrical issues, and it cut down on the time/effort of a manual to CNC conversion.

    It's about the same size as a Tormach 1100, but has linear rails instead of turcite-coated dovetail ways. So mine is probably a touch less rigid, but much, much faster rapids and no gibs to adjust. The basic mill mechanicals are still being manufactured and sold under the brand SkyFireCNC, but with a few updates and far superior electronics.

    As to tapping, I bought a big (too big, frankly) spindle motor with an encoder on the shaft and rigged up an index trigger on the spindle. The controller software I'm using is UCCNC and it has the capability of rigid tapping out of the box. Because everything is working well and the software isn't as (potentially) glitchy as Mach3, I can actually peck tap and not wipe out the threads.

    Spindle speed goes up to 7400rpm, and I've set the rapids to 200IPM, but it can go a bit faster. Cutting speeds up to 100IPM without losing steps (with low-pressure tool paths). If I ever make some money with it I'll probably switch over to 750W servos just to bump the rapids and cut down on the irritating stepper noise. It's plenty accurate now, but I fantasize about UCCNC upgrading their motion controller & software so I can use servo encoder output to close the loop back to the controller.

    And yes, the spider chuck is for my G4016 14x40 lathe for exactly the same reason you want one.
    IMG_3354.JPG


    The lathe mess. I'm a slob. Tablet is a home-made DRO.
    IMG_3416.JPG


    The new spider chuck. 0.001" runout after tweaking the screws. Woo!
    IMG_3417.JPG
     
  11. jbolt

    jbolt United States Active User H-M Supporter-Premium

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    Tools are for using not displaying. I call that getting work done!
     
  12. MontanaAardvark

    MontanaAardvark United States H-M Supporter - Premium Content H-M Supporter-Premium

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    Nice shop.

    The reason I asked was comparing spindles. At the speed mine will dial down to, it says 50 RPM on the dial, I figured I could tap a full 3/8-16 hole in about 20 seconds. I could stop it if the spindle started making odd sounds, but my experience with taps is that the first odd sound I hear is "snap!" I think I felt something odd the last time one broke on me. I know there are such things as tapping heads to attach to tools, they're just out of my price class.

    I'm not familiar with that brand of mill, though.

    My big lathe is the LMS 3540, which is sold as an 8.5 x 20, so "almost" a 9x20.
    LMS_Lathe.JPG
    There's enough room to stand comfortably between the mill enclosure and the lathe.

    Turning to the left and backing up a little to get everything to fit.
    Grizzly.JPG
    The G0704, controller box (lower middle - an orange plexiglass top) and the computer that runs it all. You can't see the Ethernet Smooth Stepper that allows me to run three different CNC machines. It's behind the PC on the left. If you look on the right end of the table, you see rough cut Rev.1 of a tooling plate. I need to pull the vise and work on that.

    Turn to the left a little more, and see the Sherlines.
    Sherlines.JPG

    The mill is really a Sherline/A2ZCNC combo. To its left are a fully manual Sherline 4400 lathe and a CNC-driven Sherline lathe. I need to work on that; I'm going to replace the original wiring I made for it with an ethernet cable for the better flexibility. Actually, the mill needs some maintenance, too.



    Bob
     
  13. spumco

    spumco United States Active Member Active Member

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    Bob,

    Likewise on the nice shop.

    As to tapping, you have a couple of options short of spending quite a bit of time and money on a closed-loop spindle system with different control software.

    1. Tension-compression tap holder. These apparently work quite well. Tormach sells them for use on their 1100/700 mills, and they don't have an encoder or even an index signal. Tapping a blind hole is dodgy unless you have plenty of over-run room, but it can be done. Through-holes are a breeze. You just can't peck-tap because the controller has no idea where in the rotation the spindle is and because of the fact that the compression feature means the thread doesn't start in exactly the same place every hole.

    Shars sells a 3/4" shank ER20 floating tap holder for about $100. There are a few from China on ebay for about $80. Press a flange on it, grind the shank to length with a taper on the end, and you now have a TTS-compatible floating tap holder. Or, for $135 you can buy a genuine Tormach TTS floating tap holder.

    2. Thread-mill. You've got a CNC mill, why not stretch it's legs? Threadmills aren't cheap, but you could grab an old tap and grind off all the teeth except for one just to fool around with it. Just be sure to grind the tip off so your new single-point thread mill has a full profile. I believe there's a youtube video or two about using a homemade threadmill - have a look.

    There are plenty of resources online to help with the code, but basically the thread mill goes down to the bottom of the hole, moves in to the hole side wall to cutting depth, and then does a helical interpolation up at the thread pitch. Repeat at increasing depth of cut until the thread fit is to your preference. You helix up so that you're climb milling rather than conventional, BTW.

    Zero spindle feedback needed, and the spindle speeds are probably in a range more suited to your G0704 than 50RPM. If you like thread milling then you can go buy a swanky carbide one and you'll be able to cut a wide range of threads with one tool. Another nice thing is that if you snap one, the shank and cutter are smaller than the hole so getting a broken one out isn't a big deal.

    Down side is that the single-point thread mills are slower than a regular tap, and kind of pricey ($25-50 for a 1/4-20 to 56TPI). Big deal, right?
     
  14. MontanaAardvark

    MontanaAardvark United States H-M Supporter - Premium Content H-M Supporter-Premium

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    Thanks for the info on that. I essentially just know what thread milling is, but haven't looked at doing it. Since the majority of things I thread are fairly small holes, I was just concerned with tapping by hand. Right now, I have four holes to tap in 4-40 and two to tap 10-32in my tooling plate. I thought all of those are too small for a thread mill. The G0704 being limited to about 2300 RPM is a detriment, too.

    I had a rude surprise, yesterday. I pulled my vise off the mill so I can set up to trim my Rev 1 tooling plate to size. The bottom of the vise and the mill table were both rusty. I think I've used my Fogbuster for only a few hours. For sure, I'm still on the first quart and the whole system has only been working since Mid-April.

    Rust.JPG

    I'm using the Kool-Mist brand fluid. One of the reasons I bought it was they say it's non-corrosive and a few reviewers on MSC said that they didn't have any rust with it. One reviewer said he adds a little alcohol to the mix to prevent growth of slime that encourages rust.

    I sprayed the vise bottom with WD-40 and rubbed it lightly with wet/dry sandpaper. 400 grit, I think. Did the same to the table. It seems deeper than pure surface stain.
     
  15. jbolt

    jbolt United States Active User H-M Supporter-Premium

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    I have no experience with the Kool-mist fliuid. I have used a formula from Tormach, Rustlick 5050 and KoolRite 2290. Of the three the KoolRite 2290 is by far the best I have used for being operator friendly and machine friendly. The Tormach fluid had a strong odor and irritated my skin, the Rustlick 5050 has a mild odor and was easy on my skin but stained every thing, had some light rust issues and was an excellent paint & adhesive remover. With the KoolRite 2290 I have had no rust issues, has a mild odor and does not remove paint or bother my skin.
     
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  16. MontanaAardvark

    MontanaAardvark United States H-M Supporter - Premium Content H-M Supporter-Premium

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    I noticed a spot on my powder coated hardware yesterday, thought it was a drip of loctite and promptly pulled up a strip of paint when I rubbed it with a fingernail. I didn't think it might be related to the Kool Mist spray.

    I hadn't put 2+2 together about that.

    Thanks as always, Jay.
     
  17. jbolt

    jbolt United States Active User H-M Supporter-Premium

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    The Rustlick 5050 attacked the paint and the body filler under it. It was quite amazing where that coolant would get into. On a machine with flood coolant I'm not too concerned how it looks as long as it functions properly. Rust isn't cool. Staining or darkening is okay but not pitting.

    I also wonder how the chemical makeup of the city water affects different coolants. I'm sure there are papers on this.
     
  18. spumco

    spumco United States Active Member Active Member

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    I find that wiping everything down with FluidFilm before installing a vise or whatever seems to help. I have wicked condensation problems in my garage from time to time, and have spent 2-3 weekends with greenie-weenies getting all my lathe chucks and collets un-funked.

    I'm using flood coolant at a pretty high concentration in the mill so I haven't seen any rust inside since I started using fluid film once in a while.

    You can get threadmills down to #2; they look like expensive little needles with an itty-bitty head. Frankly, I'd rather trust a threadmill that small than a tap. http://www.lakeshorecarbide.com/singleprofileuncoatedthreadmills.aspx

    -S
     
  19. Boswell

    Boswell United States Hobby Machinist since 2010 H-M Supporter-Premium

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    I have used at CoolMist formula for at least a year (now in fog buster setup) but have not had ANY rust or discoloration. I use rainwater to mix the concentrate with a neutral PH.
     
  20. TomS

    TomS Active User H-M Supporter-Premium

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    Jay - you raise a good point about the chemical differences of tap water. I use Rustlick 5050 mixed at 30:1 and haven't experienced any issues with rust. Removed my vise earlier this week that has been on the table for three or four months. No rust and only minor discolorization on the table. Must be the northern Cal water!

    I use Kool-Mist in my Fog Buster and rust is a problem. Removing the vise and wiping down the table with oil is what I do. A real pain.

    Tom S.
     
  21. jbolt

    jbolt United States Active User H-M Supporter-Premium

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    Our water comes from various sources so you never now what the makeup is. I ran the Rustlick as high as 5:1 and still had problems. Also left the machine sticky.

    The Koolrite 2290 is mixed at 7.5:1 per manufacturer. They give no ranges just 7.5:1 for everything. Drys super fast with little residue.

    Why not use the Rustlick in the fog Buster?
     
  22. MontanaAardvark

    MontanaAardvark United States H-M Supporter - Premium Content H-M Supporter-Premium

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    I'm a boater - in saltwater - so I have some corrosion sprays and things around the house, I just didn't use any because I didn't think I needed it. I thought the coolant had anti-corrosion additives in it.

    The FluidFilm says it's lanolin-based, so compared to something like WD-40, I'd guess it's a thicker, waxy film. That's like LPS3, but I just checked and don't see any. I know I used to have a can, so I must have used it up. I have some CRC Marine 6-26, which is more like WD-40 but a bit thicker and won't destroy electrical insulators. (I had WD-40 eat through spark plug wires on an outboard years ago). CRC 6-26 is really popular for boats, trailers, RVs and such, but I've never thought of trying it for this.

    Lanolin? I could rub the vise with a Chap Stick.
     
  23. TomS

    TomS Active User H-M Supporter-Premium

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    My fog buster is on the manual mill and I use it very little. Just haven't got around to changing it out.

    Tom S.
     
  24. spumco

    spumco United States Active Member Active Member

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    Fluid film is more like soupy sour cream in viscosity. It doesn't dry like a wax. Just wipe/brush or spray some on and smear it around. Smells like sheep, which might be a bonus for some folks. It wets out nicely and the capillary action is pretty helpful around screw heads and similar crevices. Set your slimy rag aside when you're done and use it again from time to time to wipe everything down. I suspect it may be like like other oils and if you have a pile of them then keep them in a fireproof steel rag bin if they're really juicy.

    Crevice corrosion is the killer on these machines. Anywhere you get oxygen exclusion you'll get a corrosion cell forming - especially if there's a helpful electrolyte like water or coolant.

    Same thing for galvanic corrosion - that's why I mentioned using stand-offs on the aluminum fixture plate you were talking about earlier. If you don't paint or anodize it and just bolt it to the iron table, you'll be very, very sorry if you leave it there for a while if you're using a water-based coolant or mister. Fluid film and other barrier films/oils aren't as effective as an actual electrical insulator (aluminum oxide) against galvanic corrosion when the two materials are very far apart on the galvanic chart.

    And unlike the zincs anodes in your boat, the iron will become the anode and your table will pit badly.
     
  25. MontanaAardvark

    MontanaAardvark United States H-M Supporter - Premium Content H-M Supporter-Premium

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    Thanks for that. I have the aluminum plate mounted to the table now, and overnight. The fog was never on, so it should be safe. I was getting ready to make a test cut on aluminum with a different hold down method, but after working on setting up to do it yesterday, I'm having second thoughts now.

    I'm making a GB-22, a single shot 22 pistol that Mark Serbu posted to YouTube several months ago. The frame is a 3/16" steel plate, and I'm going to hold the work down on the tooling plate with the two 10-32 screws in the grip. I'm not sure if this is going to work, so I'm going to take a practice cut in a piece of aluminum. It's only a 1/16" aluminum plate, so I can't really emulate cutting the whole thing and I'm having misgivings about trying it already. Much of the cut is right near those two screws, but there's a cutout up where the 1/16 piece sticks over the end of the tooling plate. I can visualize the 1/16" piece bending down with nothing to support it. I'm afraid this cut might end up meaning nothing.

    If I make that cut, the Fogbuster will be on, so I'll take the big aluminum plate off the mill after that.

    Test-cut-GB22.JPG

    Bob
     
  26. MontanaAardvark

    MontanaAardvark United States H-M Supporter - Premium Content H-M Supporter-Premium

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    The test cut was uneventful. At some point, I told myself, "this is a test piece - it doesn't matter if you add some more holes". So I put in two new holes and used 1/8" spring pins to hold everything together, along with the three other screws that were already there.

    FrameTestCut.JPG

    I think it's time to move on to the real, steel work piece. I'm not sure if I'm going to use the same tool plate, but I took it off the mill and wiped everything down with some oil.
     
  27. Groundhog

    Groundhog United States H-M Supporter - Premium Content H-M Supporter-Premium

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    I've used Trim C-350 coolant/lube in my cnc mill for years. When I lived in Idaho I just mixed it with tap water and did not have rust problems. Moved to Kansas and had immediate rust with tap water. Switch to distilled water (@ $1 a gallon) to mix with my C-350 and no more rust problems.
     
  28. MontanaAardvark

    MontanaAardvark United States H-M Supporter - Premium Content H-M Supporter-Premium

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    That's a cheap experiment, which is my favorite kind. I'll try that. I'm still on my first quart, so I think a gallon will last a while.
     
  29. spumco

    spumco United States Active Member Active Member

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    When I wrote that you might get galvanic corrosion, I didn't mean overnight. I meant leaving it on for weeks or months without any sort of insulator or barrier.

    If the steel is less friendly than the aluminum, maybe a really sharp HSS endmill would be better than carbide. Lower tool pressure would be a good thing here. Something else could be to add some back-up blocks to the sides opposite the cuts. Run the profile in two operations and remove the blocks when they're in the way. Some mitee-bite clamps (or similar) would be pretty cool here to act as a stop if the screws start to flex from tool pressure.

    Another thing... once you have the steel main receiver/grip OD profiled, you could cut a matching profile in the aluminum plate about .125 deep and recess the frame in it to keep it from moving around. I foresee some chatter when you cut that long trigger spring section if the trigger/spring isn't held down with a little top clamp or something. It'll vibrate like a tuning fork. If it's not already in the $12 instructions, I'd suggest cutting the trigger free from the frame (at the front) as the very last operation. Same thing for the frame cut-out for the barrel assembly.

    Finally, is there some reason you can't up-size the 10-32 screws? they don't ride on anything and it looks like you've got room for some 1/4-28's or even 5/16" screws to hold the slide sections together. You could even use shoulder screws and ream the holes to get rid of any slop while you're holding them to the fixture plate. If it were me, I'd make them out of thicker stock, hold them in the vise on tall parallels for the profile and top features, and then flip & face and do the back side spring groove. No fixture plate needed for the slide sections.

    If you're going to make more than one, mill some soft jaws for the slide sections and bang out 5 or 10 of each component in no time - no having to re-indicate between each section.

    As for the GB-22... this looks like an open bolt action. For a single shot, won't the bolt sliding forward bugger the accuracy? And what is the barrel/liner?

    Please tell me you're going to thread the barrel and put a can on it. That'd be a sweet little rat gun.
     
  30. MontanaAardvark

    MontanaAardvark United States H-M Supporter - Premium Content H-M Supporter-Premium

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    I understand the galvanic corrosion. I've had a couple of aluminum boats and had to learn about that (some of it the hard way).

    There's a lot in your comments. The barrel is a rifled barrel that I got from an eBay seller, but not threaded for a can. I've never gone down that road, and don't think I will here. My plan is to finish this prototype and then build a nice looking one for my wife. The GB-22's designer came up with a closed bolt version that's cooler - there's a video on YouTube. Everyone is hoping he updates the plans, or offers them. I'm on the mailing list and haven't heard anything. If those plans come out sometime soon, I'm thinking I may end up building two of those, if I can't just modify the first two.
    G2210000REVA_1024x1024.jpg
    I've always planned to cut that slot (3/32) between the trigger and rest of the frame last. I have another large chunk of the aluminum (tooling plate) that is wider than my table and will allow me to put 1/8" pins in all four of the holes where the barrel goes. I think that will keep that area from moving. Those spring pins had to be hammered in and pulled out with Vise Grips, a fulcrum, and the same hammer. Making the holes for the grip screws bigger seems possible, and with no penalty. I need to look at what hardware I have.

    Right now, I have three CAM files: a rough cut that you can see the results of above. That's just one pass, because the Al plate is thinner than the steel is. I have a fine cut file that uses a 1/4" EM and cuts the main shapes to size. And I figured I'd follow that with the trigger cut file, using a 1/8" EM. It cuts around the trigger and that long slot to the left. The last operation is to cut the 3/32 channel between the trigger and the rest of the frame. Perhaps I should cut the 1/8" EM file first, since everything will be completely supported in that area while cutting.


    Bob
     

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