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Chassis Build

Discussion in 'CNC IN THE HOME SHOP' started by jbolt, Aug 21, 2016.

  1. vertcnc

    vertcnc United States Active Member Active Member

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    Looks great, nice work.
     
  2. Sendit

    Sendit United States Active Member Active Member

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    Jbolt, sorry i was in a bit of a hurry when I typed my message. How did you go about modeling the pocket in the chassis for the receiver to sit in? How did you correct the rear tang area since it was off the first time? I'm trying to get a accurate model of a Remington 700 but I do not have the correct tooling just yet to be confident in my measurements
     
  3. jbolt

    jbolt United States Active User H-M Supporter-Premium

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    The inlay is straight forward with the receiver being round. The size of pockets for the trigger, safety & bolt release were done by measuring the receiver/trigger and also one of the Bell Carlson stocks I have. Since I am using a box magazine I just used the magazine dimensions with some clearance for fit and measured its location on how it fits against the receiver.

    For the tang area the error was in my favor so material removal was necessary. The rear tang is not flat but has a slight radius to match a typical hunting style stock. I didn't bother with that since it is not important for this build.

    I have not fully modeled the receiver. Because I am not trying to make a receiver all I need is the relevant dimensions to do the inlay.
     
  4. jbolt

    jbolt United States Active User H-M Supporter-Premium

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    I couldn't find a check valve locally that would work and it was a week lead time to order one so I rolled my own. Works great!. I posted a quick build thread on that if anyone is interested.

    With the coolant system operational I was able to finish the last op on the barrel guard mount. The 2-1/2" flute 3/8" end mill chatters like crazy no matter what I try. Maybe solid carbide would be better but since this project is getting painted I can live with it. It just adds some handwork. The slots will be done on the 4th axis. The last photo is the fixture parts.

    BarrelGuardMount08.png BarrelGuardMount09.png BarrelGuardMountFixture.png
     
  5. vertcnc

    vertcnc United States Active Member Active Member

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    For those deep cuts I have used a reduced shank carbide end mill. Various sizes are available. I have used the 3/8" with the flute length of 5/8" and the shank is something like .370. It takes a few steps down for deep pockets or in your case, outside profile. Then a finish pass of .005 pretty much removes all tooling marks. Also make sure you only have the tool sticking out of the holder the min. required. I purchased these from Maritool in Woodale, IL (they have an online store.)
     
  6. jbolt

    jbolt United States Active User H-M Supporter-Premium

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    Thanks vertcnc. I figured there was something like that. I'm familiar with Maritool. Of course now I have done all the deep stuff on this project. :confused:
     
  7. Silverbullet

    Silverbullet Active Member Active Member

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    Watching for more very nice build. What's your finish weight target. About seven pounds I'm guessing.
     
  8. jbolt

    jbolt United States Active User H-M Supporter-Premium

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    The stock or the whole rifle?
     
  9. jbolt

    jbolt United States Active User H-M Supporter-Premium

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    A little more work completed. I got the 4th axis completed and running but the first motor I used was too long. I had to put a sorter stepper motor and coupler so it would clear the new enclosure so I could use the flood coolant. It also took a while to get the Mach3 post modified correctly for the 4th axis.

    This is the vent slots on the barrel guard mount. To index in HSMWorks I had to create an individual tool path for each slot. That's just a matter of duplicating the first tool path and editing it for the correct orientation and contour of the next slot.

    BGM07.png

    I decided error on the side of caution and run a test part before committing the actual part to the last operation on the 4th axis which I am still getting used to. I turned a piece of stock the same diameter as the finished part and set the offsets for the actual part so if it was successful then the actual part can be ran with no other setup needed other than orientating the part in the 3-jaw.

    Success! (and no the chuck key was not in during the machining)

    BGM01.png

    Here is the actual part mounted in the fixture in the 3-jaw ready to machine.

    BGM02.png

    Machining completed!

    BGM03.png

    That was the last operation for this part so it is now completed.

    BGM04.png BGM05.png BGM06.png
     
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  10. TomS

    TomS Active User H-M Supporter-Premium

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    Beautiful piece of machining!

    Tom S.
     
  11. jbolt

    jbolt United States Active User H-M Supporter-Premium

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    Thanks Tom. There is definitely room for improvement. I'm still discovering the appropriate tools for certain jobs.

    I desperately need to fix the backlash in the system that has creeped in over the last two years. Not so bad for one off parts but it really shows with the multi faced assemblies. The double ball nuts seem to be the way to go.
     
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  12. jbolt

    jbolt United States Active User H-M Supporter-Premium

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    Well it was bound to happen sometime. I scrapped my first part. I started on the barrel guard and I think I was a little too optimistic about my setup.

    Here is the CAD.

    HG_07.png

    Here is the guard modeled in the fixture.

    HG_08.png

    Here is the turned guard blank ready for machining.

    HG_01.png

    The guard is mounted between a plate that is attached to the rotary axis and a plug that rides on the tail stock taper. A threaded rod is between the plate and plug to hold the guard under compression. The guard at the plate end is tapered and is very thin. There was not enough surface area to properly grab the face of the plate.

    HG_04.png

    In addition my lead in speed was too fast, the lead length and lead radius were too small.

    The end result.

    HG_03.png

    I remade the plug that is pressed into the plate with a larger OD that is a press fit into the guard. On the tail stock end I drilled out the center of the plug and made a Chicago bolt to go through the plug. The bolt head is counter-bored for the tail stock. This gives me greater clamping pressure.

    HG_06.png

    I also decided to not turn the OD and taper yet to leave a greater clamping surface.

    Here is the revised fixture.

    HG_05.png

    Ready to try again as soon as I tweak some of the g-code.

    HG_09.png
     
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  13. jbolt

    jbolt United States Active User H-M Supporter-Premium

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    Things went pretty well today. I learned a few things but overall I'm happy with the result.

    First op was to cut the flats on eight sides. I'm glad I modeled the fixture in solidworks. I caught a cut interference with the button head cap screws that hold the fixture to the rotary axis. I was able to change the lead out to avoid it.

    HG_10.png

    Next was drilling the holes.

    HG_11.png

    Next is milling the slots.

    HG_12.png HG_13.png HG_14.png HG_15.png

    Next is the chamfer on the slots. I was getting some chatter out at the tail-stock end. At first I thought it might be because as the slots were being cut the torsional rigidity was being compromised allowing that end to twist a little. Turned out the tail-stock was not tight. Oversight on my part.

    HG_16.png HG_17.png HG_18.png

    Final op on the 4th axis is the front contour. I couldn't figure out how to do this tool path in HSMWorks so I used Aspire for the CAM. I added some additional screws to keep the end plug from rotating in the part during cutting.

    HG_20.png

    Off to the lathe to turn the final OD and rear taper.

    HG_23.png HG_24.png

    Completed part ready for final deburing.

    HG_25.png HG_26.png HG_27.png
     
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  14. TomS

    TomS Active User H-M Supporter-Premium

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    Very Nice!

    Tom S.
     
  15. Boswell

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

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    Awesome work Jay. You make this look easy.
     
  16. jbolt

    jbolt United States Active User H-M Supporter-Premium

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    Thanks Boswell.

    It doesn't feel easy sometimes. It has been a lot of fun though and I'm learning a lot.
     
  17. jbolt

    jbolt United States Active User H-M Supporter-Premium

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    Here is the picatinny rail.

    My original 3D model of the receiver was not correct so I had to spend some time drawing one with enough correct details to finish the picatinny rail model. I searched the interweb for dimensions of the radius of the rear bridge where the rear scope mount sits. It also sits lower than the front. Everyone I found was different and varied a lot so I figured out a way to measure it using a TDI in my drill press and a machine vise on a X Y table.

    By zeroing the TDI on the center-line of the receiver and moving a measured amount right and left I could plot the radius. Height gauge was used to measure the offset.

    Measure01.png Measure02.png

    Here is the old (left) and new (right) 3D model.

    Receiver_OLD.png Receiver_NEW.png

    Machining of the picatinny rail. It was machined from 1" x 2" stock. The CAM was done with the model inserted into a model of the stock to set the coordinate origins for the top & bottom operations. The full rail is 22.2" long which exceeds my table travel so it was made in two pieces. The main piece shown here is 16.2" long

    Tool paths.

    PR-CAM01.png PR-CAM02.png

    The bottom was done first. For the top operations the part can be held by the machined sides under the bevel and still have room for the cutting tools.

    The rail has a built in 25 MOA slope when installed so all the bottom finishing operations were 3D tool paths.

    After 3D adaptive roughing with a 0.5" 4 flute roughing end mill.

    PR01.png

    After the 3D horizontal profiling wth a 0.5" 2 flute ball end mill. Step over on the radius-ed areas that contact the receiver were done with a 0.012" step over. The balance was done with a 0.04" step over just because I like the look. When installed it is mostly hidden. The sides and bevel were done with a 0.375: drill mill.

    PR02.png

    Test fit on the receiver. Perfect! Unfortunately there is a shadow at the base so it does not show well in the picture.

    PR03.png

    Now the top.

    PR04.png

    Finished rail.

    PR05.png PR06.png
     

    Attached Files:

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  18. jbolt

    jbolt United States Active User H-M Supporter-Premium

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    Before I can drill the mounting screw holes in the picatinny rail I need to assemble the hand guard and double check the measurement from the receiver mount holes to the drilled holes in the guard just in case of error creep.

    The guard is pressed onto the guard mount and they need to be indexed to each other. To do this I made a jig to hold the guard mount so that the flat on the guard could be used for indexing.

    The jig.

    Jig03.png Jig01.png Jig02.png

    Here is the stock partially assembled to do final measurements for the scope rail.

    JT7-01.png
     
  19. firestopper

    firestopper H-M Supporter - Premium Content H-M Supporter-Premium

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    You do very nice work Jay, your extra effort in detailing and posting is inspirational. Keep it coming!
     
  20. TomS

    TomS Active User H-M Supporter-Premium

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    All I can say is, WOW!

    Tom S.
     
  21. Livnpaintball

    Livnpaintball United States Iron Registered Member

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    Top notch!
     
  22. Livnpaintball

    Livnpaintball United States Iron Registered Member

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    That's the stuff!
     
  23. MontanaAardvark

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

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    Good stuff, Jay!

    Just found this thread, and need to add it to the ones I follow.
     
  24. countryguy

    countryguy United States Active User Active Member

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    Man oh man that is Sweet! My Son is going to flip when I show him this post! Two quick q's... What do you use for coolant flood? I'm ready to start that now also. In the pic below, you have two vises being used to hold a long part. I've been looking for something exactly like that. Not too small, Not to big. You happen to know who made those ? Again... AMAZING work. incredible patience!

    ...again, AMAZING post. 2vise.jpg
     
  25. jbolt

    jbolt United States Active User H-M Supporter-Premium

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    I'm currently using Koolrite 2290 coolant. So far this is the best I have found for being machine and user friendly. No rust issues and almost no odor.

    The vises are 4" CNC style from Shars. They are great for the price but with a couple of drawbacks. The vises are not matched so one is a few though taller than the other and they only open 3.8". Other than that no complaints.
     
  26. jbolt

    jbolt United States Active User H-M Supporter-Premium

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    Now that life is settling down a bit this project is moving back toward the front of the line. Unfortunately I found and issue with the receiver block where I had modified a feature in the CAD model that had a relationship to the magazine well position. I didn't catch that and the result is the mag well is out of position by 0.1" which is too much to fix. Now that I have to remake that part I decided to change from a single stack magazine to a double stack ACIS compatible style. I'm also going to try some reduced shank end mills for the deep milling of the mag well and trigger well to see if I can improve the surface finish and avoid the chatter of the long flute end mills. I have some reduced shank end mills on order from Mari Tool so hopefully they will be here soon and I can get this project going again.
     
  27. spumco

    spumco United States Active Member Active Member

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    Jbolt,

    Superb. I bought a chassis for a Savage in my pre-CNC days, and your's looks every bit as nice.

    FYI - American Gunsmith Tools is an off-shoot of Lakeshore Carbide, and they have some very nice long-reach reduced shank 3/8" end mills specifically designed for deep pocketing the magwell and FCP on AR10/15's. I have used mine and it's quite nice - so if the Maritool isn't to your taste I can recommend the AGT carbide stuff. I suspect anything you get from Maritool will be awesome, but I figured I'd just throw it out there as an alternate.
     
  28. jbolt

    jbolt United States Active User H-M Supporter-Premium

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    Thanks for the heads up on AGT. I will keep them in mind. I had better like the Maritool cutters for the cost. LOL
     

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