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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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Finishing Output Gears

Our customer works mainly in the Automotive and Manufacturing industries. We want to share with you a custom precision solution for output gears we created for them.

Custom Quick Change Jaws - Northfield Sliding Air Chuck
Northfield 650 Sliding Air Chuck – Custom Quick Change Jaws

I discussed this our senior applications engineer Mitchell to get his insights on the project. First of all Mitch please tell us about the brief from the customer?

Brief:

Our customer manufactures output gears and needs to grip the inner diameter of a family of transmission input/output gears for finish turning.

That sounds like an interesting project and not an easy one to solve. What are the main challenges with this brief?

Challenge:

The first main challenge is working with a variety of part sizes. The loading process also needs to take place quickly without swapping the complete chuck during the process. The additional challenge is including enough clearance from the chuck for cutting the parts internally to the required depth.

That’s a lot to work with, how did you solve this and what did you deliver to the customer?

Solution:

The idea behind our design is a “quick-change” style. To handle the different sized parts, subjaws are permanently mounted to the chuck’s master jaws. The Quick-Change top jaws are held in place with a single bolt. It passes through a keyhole slot in each jaw pad. Each jaw segment only has one fastening bolt, meaning no locating pins.

A 3-legged universal Axial Locator is also mounted to the face of the chuck. All parts fit to this without changeover, saving time and reducing errors when switching between parts.

Thank you for that great wrap-up Mitch. How can our readers contact you for any challenging workholding projects they may have?

Sure, You can simply head to the Contact Northfield page on our website or give us a call (516) 431-1112.

The team is always happy to help.

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No need to regrind - Long Lasting Custom Jaws

Our customer is a precision manufacturer of engine and fuel injection systems. 

The Challenge 

is to solve the problem of extreme wear on the grip area on the jaws. Northfield Chucks can be customized with a variety of top tooling options. Here is one of our standard 4” sliding-jaw chucks (Northfield Model 450). Especially modified for our customer.  

Custom Carbide Chuck Jaws
Custom Carbide Chuck Jaws

Solution

To solve this, we developed a custom set of jaws containing brazed carbide for the grip lands of the jaws. The result, the jaws last approximately 3 times as long, before requiring a regrind.  

Could this kind of modification to a standard work holding chuck help you solve a problem?  

Then get in touch with the team.  

Contact Northfield – Northfield 

Or call: (516) 431-1112