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View the video to gain insight into the functionality of the Back Bolt Fixture Plate.

Transcript Back Bolt Fixture Plate Overview

Back Bolt Fixture Plate Overview

Are you tired of machining soft jaws or building dedicated fixtures for every new job? Managing and maintaining special fixtures can get overwhelming.

To solve this, we developed the McChine Back Bolt Fixture Plate for a standard machine vise. This system reduces setup time, eliminates part bowing from vise pressure, and lets you machine parts from billet material, from micro-sizes up to 5" x 11".

Hi, I’m Jay McFarlane, owner of McChine, and today we're showcasing the Back Bolt Fixture Plate.

Features and Capabilities

Machined from durable 6061-T6 aluminum, our fixture plate is currently available in two sizes: 4" x 8" and 6" x 12". Each plate features a precise 0.250" grid pattern with rows of 3/16" counterbored holes spaced every inch for accurate locating.

It's the perfect solution for machining non-ferrous materials like aluminum, brass, and plastic, especially for job runs of up to 100 parts. While a dedicated fixture might be better for larger production runs, our plate offers a unique advantage: the flexibility to start production immediately while you finalize a permanent fixture design. The number of parts you can machine at once depends on their size, from multiple small components to a single large part.

The Back Bolt Advantage

Our unique workholding design uses small 8-32 cap screws that pull your part down securely to the fixture plate. This offers several key advantages:

  • Low-Profile Clamping: When tightened, the cap screws protrude only 0.100" from the plate's surface. Since the bottom of your part sits 0.150" above the plate, you can fully machine the entire profile without crashing into a clamp or hold-down bolt.
  • Secure Holding Force: Each screw provides 490 lbs of holding force, ensuring your parts remain secure throughout the entire machining process. This eliminates common issues like part bowing and shifting.
  • Zero-Point System: Here’s the real time-saver. Once you've established the fixture plate offset, you can machine a wide variety of parts without touching your machine setup. Simply reposition the 8-32 cap screws to match the new part and you’re ready to go. This dramatically reduces setup time and maximizes productivity.

The Machining Workflow

Let's outline the typical strategy for machining a part using this system.

Setup 1: Creating the Picture Frame

In this setup, we'll load raw stock into a standard vise on parallels and machine the back side of the part.

  1. Drill & Tap: Create the 8-32 threaded holes for the hold-down screws.
  2. Machine the Nesting Surface: Mill the surface that will sit on the fixture plate, leaving two 3/16" diameter posts that are 0.050" tall around two of the tapped holes. These posts are for precise locating.
  3. Mill the Pocket: Machine a pocket 0.150" deep around the part profile. This pocket should be 0.010" larger than the part, except in 2-4 small areas where you will leave tabs.
  4. Machine Other Features: Finish any other pockets or holes accessible from this side.

Setup 2: Finishing the Part

Now, the part is loaded onto the Back Bolt Fixture Plate in the vise.

  1. Rough Material: Rough out the excess material from the entire part, leaving about 0.010" of stock around the profile.
  2. Finish Features: Finish machining all the remaining features of the part.
  3. Finish Profile: The final operation is to machine the part's profile and expose the tabs. This typically involves two finish passes:
    • Pass 1: Machine the profile 0.010" above the bottom of the part.
    • Pass 2: Lower the cutter to 0.010" below the bottom of the part to cut through, starting and ending this pass in the middle of a tab.
  4. Remove Part: Finally, remove the finished part from its "picture frame," and you're done!

If you're eager to learn more or ready to purchase your own Back Bolt Fixture Plate, please visit our website at mcchine.com. We're confident this innovative tool will revolutionize your machining process.

Transcript How to Load a Back Bolt Fixture Plate

How To Load A Back Bolt Fixture Plate

In this video, we'll demonstrate how to load a part onto the McChine Back Bolt Fixture Plate and then how to properly secure the fixture plate in your machine vise.

Part 1: Preparing the Fixture Plate

  1. Bring your fixture plate and 8-32 cap screws to your computer.
  2. Reference your CAM model to identify the correct hole locations for your part.
  3. Insert the cap screws into the plate from the top side. This keeps the row and column labels visible for easy reference.
  4. Flip the plate over to the back side. Using another cap screw, push each mounting screw out from the back, leaving the "pushing" screw in its place to hold the part during assembly.

Part 2: Mounting the Part

  1. Take your part stock from Setup 1 and carefully inspect the nesting surfaces for any burrs.
  2. Turn the fixture plate on its side and align the clocking mark on your part with the corresponding mark on the side of the fixture.
  3. Move the part into position over the screws. It's easiest to start by lining up the two Ø0.186" locating posts that have tapped holes.
  4. Carefully start threading the screws to pull the part onto the fixture.

Troubleshooting Fit Issues

Stop immediately if the part does not slide easily onto the Ø0.1875" locating holes in the fixture plate. Forcing it can damage both the plate and your part.

If the part doesn't fit, here are three things to check:

  1. Clocking Marks: Confirm the marks on the part and fixture are properly aligned.
  2. Post Diameter: Use calipers to verify the diameter of the Ø0.186" posts on your part.
  3. Bolt Pattern: Double-check that the screw placement on the plate matches your CAM model.

Part 3: Securing the Part

  • Secure all screws until snug. A good rule of thumb is to tighten them by feel, about a quarter-turn past hand-tight.
  • If you use a torque wrench, tighten to 14 in-lbs.
  • NOTE FOR PLASTIC: When threading into plastic parts, tighten just enough to pull the nesting surface down. Over-tightening will strip the threads.

Part 4: Loading the Fixture into the Vise

  1. Place two clean parallels into your machine vise.
  2. For a quick visual check, ensure the clocking mark on the fixture is on the left-hand side.
  3. Set the fixture plate on the parallels with the side locating pin facing the solid vise jaw.
  4. Slide the fixture plate until the pin makes firm contact with the solid jaw.
  5. Tighten the vise and use a dead blow hammer to seat the plate firmly on the parallels.
  6. Finally, check that the parallels are secure by trying to push or pull them. They should not move.

Learn More

We have now demonstrated the process of loading the part onto the Back Bolt Fixture Plate and loading the fixture plate into the machine vise.

For more information on the Back Bolt Fixture Plate system, to purchase one, or to see more guides, please visit mcchine.com.

Like and subscribe for more videos!

Watch this video to learn how to remove the finished part from the picture frame.

Transcript Picture Frame Removal

How to Remove Your Part from a Picture Frame

In this guide, we'll discuss two methods for removing a finished part from its picture frame after machining:

  • Standard Method: Breaking the tabs on a rigid part that is not prone to distortion.
  • Foil Tab Method: A gentler technique for fragile parts where "foil tab breaks" were machined into the frame.

Method 1: Standard Removal (For Rigid Parts)

This method should only be used on parts that will not easily distort or bend. This can be done with a machine vise or a pair of 1-2-3 blocks.

  1. Position the Part: Open the vise jaws just enough so the part fits loosely between them, with the picture frame resting on top of the jaws.
  2. Break the First Tab: Take a piece of soft aluminum bar and place it against one of the tabs. (Note: It's important to use aluminum on aluminum parts to avoid damage.) Lightly strike the bar with a hammer to break the tab.
  3. Remove the Frame: Once the part is loose and held only by the other tab, simply push the picture frame back and forth to wiggle it free.

Method 2: Foil Tab Removal (For Fragile Parts)

This is the recommended technique for delicate parts prone to bending, as it reduces stress and prevents distortion.

  1. Remove Island Stock: If your part has any internal scrap material ("island stock"), you can remove it first by pushing it back and forth until it falls out.
  2. Cut the Tabs: Use a pair of tin snips to carefully cut each foil tab in half. Be careful not to scratch your finished part with the snips.
  3. Break Away the Frame: Gently bend the frame material back and forth at each tab location to remove it from the part.

Final Deburring

After the frame is removed, you will be left with a few small tabs that are 0.005" to 0.010" tall.

  1. Place a sheet of 320-grit sandpaper on a flat surface.
  2. Gently sand the edge of the part until the tabs are gone, leaving a clean, finished edge.

And that's how you remove a part from a picture frame!

For more information on the McChine Back Bolt Fixture Plate, to purchase one, or to see more guides, please visit mcchine.com.

Like and subscribe for more videos!