Operation Recommendations for Diamond-Impreg Mills, Shoes, and Reamers

Our MX mills, XDS and SXDS shoes and SXR reamers contain Diamond Grit sized from 25 to 100 mesh that is impregnated into a retaining matrix of Tungsten, Tungsten Carbide,  and other components that hold the grit and is slowly worn away as the individual diamonds are dulled from impact or abrasion (heat build up) and are then sloughed out of the retaining matrix which wears away to expose fresh grit. This cutting action is done on a very small scale and is much like grinding  which creates very small cuttings (dust particle size). There are hundreds of small diamonds in contact with the target at any given time which is about 20 to 30% by volume of the total contact area. We have seen from experience that between 100 and 400 psi (X the contact area) is the optimum WOB for cutting most extreme targets that include mild steel, HT Carbon steel, case hard wickers & slips, carbide (loose and solid), 13 chrome, Incoloy and Inconel, Titanium, and other materials.

The most common reason for these tools not working is the application of too much WOB. The retaining matrix is not intended to support high compressive loads and can actually overheat and "move" when stressed beyond its limits.  

Our mpreg mills and shoes have been run at RPM's from 60 to 600 and like most grinding applications they tend to work best at a linear cutter speed of about 100 to 300 ft per min (2 1/2" diameter = 450 RPM and 17 1/2" diameter = 65 RPM).

Circulation rate should be matched to the area of the mill or shoe. An 8 1/2" x 7" shoe has an area of 18.2 sq. in. which is about the area of a 4 3/4" bit, so it is obvious we would not run the GPM for an 8 1/2" bit through it, so this shoe size should have about 3-4 barrels per min instead of 9-10.

Point loading of the target contact area can accellerate wear. If the 8 1/2" x 7" shoe is only in contact on the ID with an area of 4 sq. in. it is easy to see that WOB transfer through 18 sq. in. for a 300 psi force (5,460 lbs) would quickly overload the same WOB through the smaller area (1365 PSI).

Pushing without rotation can result in forces that impreg cutting structures are not intended for. An example