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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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Lathe Finish Turning

Our customer is an OEM manufacturer of welding equipment.

Brief

The work holding requirement is for a lathe. Our customer needs a chuck that expands to grip the inner diameter of welding shield caps so they can finish-turn its rough outer shape.

Northfield Solution

A Highly-Specialized, 4.500” Diameter Northfield Collet Chuck
A Highly-Specialized, 4.500” Diameter Northfield Collet Chuck

Shown here is a highly-specialized, 4.500” diameter, Northfield Collet Chuck with custom top tooling mounted.

As the chuck’s internal diameter collet expands, it also acts to pull the part down and onto its outer banking surface shown in the photo at the right. This insures repeatable location onto the datum surface, saving time and reducing error.

This is just one of many examples of our work across a variety of industries and machining situations. Do you have a project that requires a custom solution? Then get in touch with our team and chat with a Northfield engineer to see how we can help solve your problem. Contact Northfield – Northfield or call – Phone: (516) 431-1112.