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High Precision Bores and Finish Grinding

Working for an international OEM supplier of the world’s most accurate precision rifle barrels. 

Brief: 

  1. Outer diameter clamping to grind bores in high precision bolt carriers for modern sport rifles.  
  2. Inner diameter clamping for finish grinding the outer diameter. 

Challenge: 

The two challenges are:

  1. Accommodating the extended part length
  2. Completing a second finish grinding step without damaging the first
Sport Rifle Bolt Carrier Grinding Group
Sport Rifle Bolt Carrier Grinding Group

Northfield Solution: 

The first operation involves grinding a bore to finish size. This bore houses the critical components that allow the firearm to function properly. 

We built a Northfield Model 620 Sliding Jaw Chuck with an extended air cylinder housing. This accommodates the long part length. The hardened and ground top jaws clamp on the rough outer diameter of the customer’s part.  

Custom Northfield 620 Air Chuck
Custom Northfield 620 Air Chuck

During loading, the part is set down on a hardened and ground axial locator, ensuring an accurate datum location each time.  

Secondly, this customer also requires work holding for finish grinding the outer diameter of the part. that they clamped on using the model 620 sliding jaw chuck in the first step.  

Custom Northfield Collet Chuck
Custom Northfield Collet Chuck

We achieved this with a custom internal grip collet chuck with a collet diameter of .5232in. This chuck clamps on the finished inner diameter while the other end is supported with a center. The operation grinds the whole outer diameter of the part, producing an accurate O.D. dimension. This ground diameter is one of the most critical dimensions required for the firearm to function reliably.  

 

Do you have a multi-step machining process that requires high precision work holding? Then get in touch.  

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Custom 4th Axis Tooling Package

Brief: 

The brief of this job is to create a custom tooling package for mounting on a 4th axis rotary table. Holding a raw aluminium extruded blank, for finish milling in a single operation. 

Challenge: 

As our work holding must not get in the way of their tooling paths. Therefore, the challenge is incorporating milling clearances within the axial locator and jaws.

Custom Northfield Model 670 set-up
Custom Northfield Model 670 set-up
Custom Northfield Model 670 0
Close-up Northfield Model 670

 

Solution: 

Our solution is a Northfield model 670, 2 Jaw Chuck with a custom set of internal grip jaws. Additionally, a custom axial locator that is finish ground and Electro Discharge Machined (EDM) allows for the required customer tooling clearances.  

The design also incorporates a timing block. This ensures correct loading of the parts each time, and that they do not spin or change orientation during the milling operations. 

Finally, the chuck is mounted to a 4th axis rotary table with a custom Northfield backported adapter plate. This allows air passageways to run though the rotary table into the rear side of our chuck for normal clamp and unclamp operations.  

Do you have a current 4th or 5th axis project? Get in touch to see how we can help – TOLL FREE: (800) 810-2482

Contact Northfield – Northfield

 

Custom Northfield Model 670 0
Close-up Northfield Model 670
Custom Northfield Model 670 set-up
Custom Northfield Model 670 set-up

 

Custom Air Collet 1
Custom Air Driven Northfield Collet Set-up
Custom Air Collet
Northfield 16c Collet Chuck
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Custom Collets – Air vs. Hydraulic

 

Collaborating with the finest in machine tool productivity innovation.  

Brief: 

The task is tooling up a standard dual head rotary table to accommodate the bolt carrier.

Challenge:

The challenge of this job is to provide a work holding solution, allowing actuation of the work holding on the customers table.  

Custom Air Collet 1
Custom Air Driven Northfield Collet Chucks
Custom Air Collet
Northfield 16C Collet Chuck

Northfield Solution: 

The Northfield 16C collet chucks are air driven units as standard. Pairing these with an adapter plate and air tube allows actuation on the customers rotary table. Additionally, these chucks allow the usage of standard 16C collets. 

Air vs Hydraulic: 

These chucks are also available in a hydraulic format. This same setup has been supplied to other manufacturers with a hydraulic configuration. Providing a greater grip force than our air driven units. This is useful when heavy milling or turning operations require a higher grip force capacity and the material being held supports such a setup.  

Sound useful? Then reach out – TOLL FREE: (800) 810-2482

Contact Northfield – Northfield

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5-Axis Machining in Two Steps

AR-15 Charging Handle Components

Firearms manufactures are hard at work designing new unique components and parts for the AR-15 platform. Northfield has the task of holding these parts for many aspects of machining operations.

This project is for AR-15 upper receiver components, with a unique contour and light design. For this, we developed a custom solution for multiple automated machine cells. 

Custom Air Chucks 5 Axis
Custom Northfield Model 470W Sliding-Jaw Air Chuck

Initial Brief:

High precision custom work holding, finishing all part machining operations in only two setups. Reducing error and saving time. 

Our Customer is a well-established high precision machine and automation provider. They required a custom solution to complete all machining operation in two steps.  

  1. Work holding on a rotary table within a 5-axis machine.  
  2. A chuck with custom hardened jaws to grip the finished side of the work piece from the first step. 

 

Northfield Precision Model 450W Sliding-Jaw Air Chuck (0.0001” TIR) with special top tooling attached
Northfield Precision Model 450W Sliding-Jaw Air Chuck (0.0001” TIR) with custom top tooling attached

The first stage chuck

is based on the 450W Sliding-Jaw Air Chuck, for mounting to a rotary table in a 5-axis machining environment. This handles the first side of the final product. 

To ensure a good grip on the customers rough turned blank, the custom top jaws are hardened and ground to size before coating with 150. Grit diamond.

Northfield work holding solutions include air detect axial locators. This case has, 3 air ports on the 3-part banking surface. These ensure positive part-seat confirmation before the machining process begins. 

 

The Second Stage Brief:

The process involves gripping the complete side of the part from the first step without damaging it, to finish machine the second side.  

To accomplish this, we added custom hardened and ground sub jaws to a Model 470W Sliding-Jaw Air Chuck. These hold specially Electro Discharge Machined (EDM) inserts, that grip the finished side of the part produced in the first machining operation.

Additional machine clearance was required at this stage, so the chucks are also mounted to custom Vertical base plate risers. This accommodates for the machine clearances. 

Additionally, this chuck also includes a special air detect axial locator, with 1 air port on the part banking surface, for positive part seat confirmation.  

Model 470W Sliding-Jaw Air Chuck with custom Vertical base plate risers.
Model 470W Sliding-Jaw Air Chuck with custom Vertical base plate risers.

 

Are you looking for a custom work holding solution that includes a collaborative design process? Then get in touch today and discuss your projects with the Northfield engineering team.