Yes, manganese bronze valve guides can be reamed. However, it's important to note that manganese bronze is a much harder and tougher material compared to other types of bronze, which makes the reaming process slightly more challenging. Here's how to approach reaming manganese bronze valve guides:
Considerations for Reaming Manganese Bronze:
- Tool Selection: Use a high-quality, sharp reamer made from high-speed steel (HSS), carbide-tipped or solid carbide as these materials can handle the hardness of manganese bronze.
- Lubrication: Use a good cutting fluid or lubricant specifically designed for tough metals. This will help reduce friction and heat, preventing tool wear and ensuring a smoother finish.
- Machine Reaming Preferred: Machine reaming provides more consistent pressure and speed, which is beneficial when working with harder materials like manganese bronze. Driving the reamer with a handheld drill is not recommended.
- Speeds and Feeds: Use a lower RPM compared to softer materials to prevent overheating and tool wear. A general rule of thumb is to reduce the cutting speed by about 20-30% compared to standard bronzes. Maintain a steady and appropriate feed rate. Too slow can cause rubbing, while too fast can damage the tool or create a poor finish.
- Avoid Excessive Force: Applying too much force can lead to tool breakage or a poor-quality hole. Let the tool do the work with consistent pressure.
- Check Alignment: Ensure the reamer is perfectly aligned with the valve guide. Misalignment in hard materials can cause significant issues.
- RECOMMENDED: A rigid type standard or diamond abrasive hone (not a flex-hone) is highly recommended for finish sizing manganese and high nickel bronze alloys. Honing the last .001 inch with a rigid hone will ensure proper finish size and finish.
Steps to Ream Manganese Bronze:
- Prepare the Workpiece: Securely clamp the cylinder head in a sturdy fixture or on a machine table to prevent any movement during reaming.
- Ream the Valve Guide: If using a machine, set it to the recommended speed and feed rate for manganese bronze. Ensure the reamer is aligned, and begin reaming with steady, even pressure.
- Check the Result: After reaming, check the hole for size and finish. If necessary, repeat the process with a slightly larger reamer to achieve the desired dimensions. It is highly recommended to finish hone with a rigid valve guide hone using traditional or diamond abrasives.
- Clean and Store: Clean the valve guide and the work area, and properly store the reamer to avoid damage.
Tips:
- Inspect the Reamer Regularly: Manganese bronze can wear down tools more quickly, so check the reamer for sharpness and condition before and after use.
- Consider Cooling: Depending on the depth and length of the ream, additional cooling methods (like air blowers or coolant systems) can be beneficial.
Reaming manganese bronze requires a bit more care and the right equipment, but with the right approach, it can be done effectively.