This Narrow Wheel Dresser is designed to dress the sides of grinding wheels quickly to a very thin width. This method directs the pressure up into the wheel, not to the side.
The rate of stock removal and the width to be dressed are determined by the wheel structure, hardness, density, and grit size. The narrow wheel dresserwill dress the sides of any width wheel to a specific size quickly and accurately.
This narrow wheel dresserhas successfully dressed wheels down to .010″ with minimum wheel failure.
Set the narrow wheel dresserat 25-degrees to true up the back of the wheel.
Rotate the crank in counterclockwise direction and feed the wheel down.
Next, set the dresser at 20-degrees and rough-dress the front side down to 0.40″. Stock removal failure depends on wheel structure.
Dresser will easily remove 3/16-inch on one pass on most wheels.
To dress wheels below .040″, set dresser at 45-degrees.
Magnetic chuck design has evolved to maximizing work holding power while taking into account the application. The strongest magnetic chuck is not necessarily the best. Here are some considerations when selecting a magnetic chuck.
Permanent Magnet Fine Pole Maintains a low magnetic penetration to the work piece. This allows for superior holding on thinner pieces. No negative effects on Sinker EDM operations near the surface.
Permanent Magnet Standard Pole Maintains a deep penetrating magnetic circuit and is used to maximize holding power as the work piece is usually unsupported.
Wire EDM The single pole design eliminates the potential for removed material to affect the cutting zone.
Permanent Hard Milling Concentration of the magnet forces allows holding of smaller hardened pieces. Superior magnetic flux control allow rough and finish mill operations without buildup of chips in the cutting zone.
Electric Magnet Most commonly found on surface grinder. Fairly inexpensive to manufacture while giving good holding power and variable settings.
Electro-Permanent Magnet Incorporates the highest strength for the broadest range of work pieces. The use of top tooling creates 5 sided access and thru hole machining. The design allows palletization. No thermal growth allows for higher accuracy applications. The control allows variable power settings and demagnetization cycle.
A high-quality surface grinder is, of course, critical to successfully grinding parts flat. However several basic areas should be addressed before effectively evaluating the quality of the surface grinder. Correct and precise set up procedures are necessary to achieve the best results of the grinding tool.
Grind the machine table flat. Grind deep enough to remove all rust.
Grind the bottom of the magnetic chuck. Grind so there is approximately .0002” of dish per 6” of chuck length.
Mount the chuck with a light coating of oil between the surfaces. Tighten the right hand bolts first and then just snug the left side bolts.
Important: The ground-in dish and just snugging the bolts on one side allows the chuck to move due to thermal changes – while minimizing changes in flatness.
Grind the top surface of the chuck
Set the chuck magnet to “on.” With a properly built chuck this does not matter, it should not matter if the magnet is “on” or “off.” However, to be safe, grind with chuck magnet “on.”
Always grind with flood coolant (if available) and use an open-structure wheel, in order to minimize heat buildup in the grinding area.
Use small down feed increments with frequent dressing to minimize distortion.
These steps are done yearly in our shop as rust builds up between the chuck and machine bed.
Grinding Wheel Selection and Balancing
Select a wheel that will not introduce stress or heat into the work piece. Your wheel supplier should be able to assist you in selecting the proper wheel.
Wheel balancing is an important part of flat grinding. An unbalanced wheel will produce a poor surface finish and shorten the life of you spindle bearings.
Wheel balance should be checked during the life of the wheel as it will change as the diameter is reduced.
Diamond Selection and Set Up
As a rule of thumb, the minimum size diamond should be ½ carat per inch of wheel face.
Large diamonds dissipate heat better, last longer and dress faster due to more contact with the wheel.
The diamond should be set approximately 10° in the direction of the wheel location.
Minimize the shank length and mount as rigid as possible.
Dressing feed depth should be a maximum of .001” per pass. Use flood coolant if possible.
Rotate the diamond to a sharp surface whenever possible.
Improve the Return on Your Investment
Careful installation of your surface grinding setup is vital to get the precise results that the grinder and the workholding tools are designed to deliver. Following these steps will not only improve your flat grinding, your grinding tools will continue to perform as expected for a longer time.
The return on your investment in Hermann Schmidt tools to support your precision grinding operations will be far greater with careful set up and ongoing maintenance.
Using a magnetic squaring block (magnetic squaring chuck) is the most accurate and quickest way to square parts on a surface grinder. The magnet will hold the workpiece without distortion that will be caused by mechanical clamping, while release/clamp time is significantly reduced.
To get the finest results from a squaring block, correct setup is vital. Here are key steps in the process.
Check that the magnetic chuck on the surface grinder is flat and nick free.
Grind the first side of your workpiece flat.
Mount the magnetic squaring block (MSB) with the on/off switch on the right side and hardened rail on the left.
Place a support block near the lower left corner of the MSB.
We like to use a block with a button head screw in the top so the part rests on the top of the screw. The screw allows you to adjust workpiece height to extend beyond the top of the MSB.
Turn on the magnetic chuck on the surface grinder
To mount your workpiece, place ground side on against MSB. Slide the workpiece against the rail and down to the support block.
Turn on the MSB.
Grind the first side.
Turn off the MSB.
Clean both the workpiece and MSB.
We do not use the air hose here, we wipe the contact surface with our bare hand
Follow previous steps, placing the last ground surface against the rail.
This will accurately square up the two sides you ground to the third side you located from. When removing the MSB from the surface grinder, care should be taken to not slide the MSB.
After demagnetizing the surface grinder magnet, apply force at the top of the MSB to break any residual magnetism and surface tension
Lift the MSB straight up
Clean and oil the MSB
Get the Most from Your Hermann Schmidt Precision Tools
At Hermann Schmidt, we offer two models of magnetic squaring blocks. For most high-precision squaring operations, Our standard pole 6-inch Magnetic Squaring Block delivers a quick and extremely accurate method of grinding blocks square. Our 4-inch Fine Pole Magnetic Squaring Block is a fine pole, low profile magnetic chuck designed for fast and precise squaring up of smaller parts.
Following our guide to using magnetic squaring blocks will help you get the most out of your tools.
UPDATE: Question was asked to see some setups. The following is a couple of pictures of a work piece set up on the 6″ squaring block. The top of the stop in the 123 block has a radius on it so the work piece is sitting on a point.
When comparing Fine Pole Magnets to Hard Milling Magnets in work-holding applications, it is important to consider these three key factors:
Specific application / manufacturing environment
Let’s look into how these two magnetic solutions compare.
Fine Pole Magnet (FPH*)
The FPH magnetic circuit is designed specifically for the sinker electrical discharge machining (EDM) environment. It is also used in the grinding environment as it meets the performance requirements there.
The FPH allows for the EDM process to continue into the surface of the magnet if necessary without any re-burn due to materials staying in suspension. This is an area where the strongest magnet is not the “best” magnet.
Hard Milling Magnet (HSM*)
The HSM magnet is designed specifically for the hard milling area. It has the highest strength of any permanent magnetic circuit. The HSM magnet generates a primary and secondary field which allows it to provide a strong holding force while not magnetically penetrating deep into the part, hence minimizing chip contamination in the cutting zone.
While this circuit does not penetrate deep, it does create a situation where use in the sinker edm should be avoided. If an electrode tip is within approximately .25” of the magnetic surface and you are in a situation where the length /depth ratio of the area is greater than 5, you can get reburn. As the electrode cycles the coolant is evacuated from the hole and some solids can stay in magnetic suspension. When the electrode returns to the hole, we can get depth & finish problems.
Note that while we recommend the FPH magnetic circuit for sinker EDM for the reason described above, Hermann Schmidt does have customers that successfully use HSM magnets just fine in the EDM environment.
Cost is always a consideration, especially when automated cells can easily exceed 20 palletized magnets.
The HSM magnets cost 30% more to build and it is reflected in the price. Many customers want just one type of magnet to do all the work. We believe that is usually not reasonable. At Hermann Schmidt, we build magnets for the manufacturing environment and do not recommend trying to make a magnet design work where it does not belong.
Choose the Right Magnetic Tools for the Environment
Between selecting between fine pole magnets and hard milling magnets, consider the manufacturing process and the performance requirements first. Once that is established, the cost can be factored in – with cost going well beyond the initial purchase price.
* Throughout this post we used our FPH and HSM abbreviations to match our corresponding product lines. When selecting the correct magnetic tool for your specific application from Hermann Schmidt, look for models with the matching designation. If you have any questions about using the right tool for your application, please give us a call at 860.289.3347.
The final component of the SquareTech system is the holding of the workpiece.
The 90° indexing fixture accepts the Matrix pallet and drawbar from System 3R. The pallets can be either manually loaded and indexed or integrated to a fully automated manufacturing cell.
The following options are available for mounting of the workpiece
Directly to Matrix pallet.
To a reference system.
To a manual vise.
To a magnetic chuck.
Mounting directly to Matrix Pallet
The workpiece can be mounted directly to the Matrix pallet (approx 5” diameter) utilizing a series of predrilled holes. The pallet is also available in a 6” automation ready version which allows for custom hole layouts for specific applications.
Larger sub-plates are easily implemented for custom mounting, jigs, etc.
Mounting to a Reference System
Many facilities are already using System 3R, Erowa or Hirschmann referencing systems. Already-mounted components can be used by mounting the preferred referencing system manual chuck to the face of the Matrix pallet. The Matrix pallet is still used for the indexing function.
When the squaring procedure is finished, the pre-mounted components can be moved to the next process.
Mounting to a Manual Vise
Two styles of manual vises apply themselves well to SquareTech
The self-centering style of vise has many jaw options available to satisfy various part geometries. The repeatability of location of these vises is 0.002” on center. Most applications will use a sacrificial portion of the workpiece for workholding then remove that section when the process is finished.
The precision toolmaker style of vise requires a workpiece with parallel sides, in order to function properly. This vise also only allows for centering in one direction. The benefit is that workpiece location will repeat exactly and squareness to the indexing feature is predetermined.
Mounting to a Magnetic Chuck
While selecting a magnet chuck, careful consideration must be given to the size, shape, type of material and process to be applied to the workpiece.
Two styles of magnetic chucks apply themselves well to SquareTech:
Permanent magnetic chucks are a cost effective solution for use in this application.
The benefit here is that only one workpiece surface is utilized for part holding. Many sizes and shapes are available with varying holding performance. In general the limiting factor most situations is that the part is smaller than the magnetic chuck contact surface. This limits the access to the workpiece.
The ultimate solution when magnetically holding a workpiece is the use of an electro-permanent magnetic chuck, which has be specifically designed for workpieces mounted on its centerline.
This magnet concept was originally applied to conventional milling applications only. Its unique characteristics allow the use of top tooling. Top tooling is a consumable plate which allows the transfer of magnetism to the workpiece. The top tooling can be machined away until a pedestal of material is remaining which is undersize of the workpiece, giving full access for machining.
Top tooling is removable and can be reused on repeat jobs or refashioned to fit new workpieces. Recent advancements in surface coating applications to top tooling have resulted in holding performance doubling.
This is an application driven area. These magnets have successfully completed jobs with part sizes below 1 sq. in to over 100 sq. in.