Over the last 80 years that grinding has become a very documented and researched manufacturing method, it has grown quite popularly with ID or Boring Grinding. Using a relationship between spindle speed, tool diameter, and crystal size/chip depth. Typical jog grinding happens with a spindle speed around 10,000-50,000 RPM; however, with technology advancements, we are seeing spindle speeds capable of 120,000+ RPMs. This has allowed jig grinding to gain some ground, being able to run your tools at much higher spindle rpms and SFPM, allows for higher in-feed rates, reducing overall cycle time for the operation.
When running a DPM Mandrel, we recommend a SFPM of around 7,500, with in-feeds around 3-8″ Per Minute. Depth of cut, somewhere in the 0.100″ range depending on the P-Line or Surface contact on the tool. We recommend per 0.25″ of contact, reduce infeed by 0.010″ This is due to tool pressure and deflection. If the user has a very stiff shank and large crystal sizes, they can run in-feed and depth outside this range. Our Jig Grinding mandrels are capable of sizes from .0080” to 20.000”. Our mandrel size is limited by our tanks. We do have partners that can plate over a 20″ piece.
Now, these speeds and feeds that were listed above are general in-feeds for HSS with a 40-60 Grit Mesh. Running Diamond on Carbide or PCD is a different story. We recommend running the same Surface Foot Per Minute, but reduce your in-feed rates by about 40%, this will help the crystal load and heat build up from the Carbide or PCD. They tend to make a better or easier chip to deal with, but also require quite a bit of force to cut resulting in high temperatures.
Lets talk oscillation, we recommend a cross-feed or oscillation rate of 0.010″ Per 0.50″ or P-line contact. This will help keep your hole more concentric and hold a tighter tolerance to your desired blueprints than running a straight bore or wipe/drag feed method.
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After years of exposure in the grinding industry, we found that broach grinding was a very demanded industry. Due to the size of the work piece, as well as, the complex geometry, has left only a few players in the broach grinding industry. With this demanding market with a starved supply from diversified supplies has left the broach grinding industry thirsty for a quality product that can compete. With our success in Jig and ID Grinding, we found that broach grinding wasn’t far off, we only needed some small tweaks to our formulations to handle the types of stresses that broach grinding places on a grinding wheel.
The results of us using a hardened steel or carbide shank, with specialized superabrasive crystal, mixed with our superior bonding technology has provided a “free-cutting” long tool life. These diamond plated wheels want to remove material, they hold up to fast in-feeds and hold form and finish throughout the cut. We produce anything from small diameter and small radius to large radius, large diameter wheels. Our max diameter is 1200mm or 45.27″ this is due to the limits on our CMM machine. Most broach grinding wheels are in the 4-8″ dia. with radius from 0.010 – 0.50″. Due to the small radius and our proprietary bonding methods produce a product that holds throughout the cut and minimizes the need to be dresses. When grinding slabs for a broach, large amount of material removal means that the wheel being used needs to remain open and crystal exposure needs to be optimal. Any time a wheel starts closing down and your feeding large stock removal, you can run into a loading or smug issue. This is typically cleared up by dressing the wheel to help remove that gummy material and provide crystal exposure. You can also try running the wheel at a high SFPM or spindle RPM allowing the wheel to act harder and minimize the chip load on the crystal. Sometimes your in-feed can cause some issues with loading, if you are taking too light of a cut, causing a plasma state chip to load into the structural porosity of the wheel. Keep in mind that crystal exposure and structural porosity are similar, but not quite the same. When refering to crystal exposure, remember this is exposure of a cutting edge within a chip depth cut from the outer dia. Where as structural porosity is the space and depth or peak and valley of the crystal and the bond.