Spin & Indexing

Evolution of the Hermann Schmidt Stainless Steel Rotary Index Fixture

SUB-X 1800 indexer with control

Historically, grinding applications in the manufacturing industry used a rotary device for hand grinding pins placed either in a v-block or 5C Collet which was designed into the unit.  This is a dry grinding operation with the fixture being spun by hand.  The indexes were set up on a sine plate, indicated in and stops set.

This grinding operation  evolved to a motorized option, eliminating the need to spin by hand.  The motor delivers steady speeds so the operator can concentrate on grinding.  This is also done dry.

Further innovation came by manufacturing the same fixture in stainless steel with ceramic bearings. The stainless steel construction allowed indexing functions in the wire EDM.  The ceramic bearings resulted in a tool that could be used in all EDM operations as the ceramic bearings isolated the bearing race from electrical discharge.

Further development to use this unit while submerged opened the potential to also spin and burn in the EDM environment.  These solutions were always considered an add-on option.  The results were often limited due to the challenges of successfully submerging a small, high torque, high rpm motor.  Usually at best 2 of the 3 above requirements were met.

Hermann Schmidt decided to redesign the product to meet today’s new demands for a device of this quality and flexibility while also addressing the changing workforce that the industry is experiencing.

We see a trend where manufacturers tend to have fewer toolmakers and more specialty operators in an area.  As a result, broad-base experience is diminished and many employers make this up with more sophisticated systems.

Stainless Steel Rotary Index Fixture in the Grinding Area

In the grinding area the SUB-X 1800 improves on all abilities of previous products as follows:

  • Compactness of design maintained.
    Face diameter of 5″ and maintaining thru hole capacity of 1″ allows customers to use previously developed face tooling.
  • Ceramic bearings allow a higher preload without generating heat.
    Previously as a unit was spinning the ball bearings would warm and expand.  As a result lower preloads needed to be used.  The end result is the tolerance on the spindle can be held tighter.
  • The programmable interface allows precise positioning, without indicating a position on a sine plate.
    This is significantly quicker than previous products.  This also allows a less skilled operator to set up the fixture to toolmaker tolerances.  Output can be in either decimal or degrees-minutes-seconds, eliminating the need for calculations.
  • The unit is submersible.
    If flood grinding is required, the internal motor option allows spinning. The applications for this are usually seen in high-pressure oil type grinding or when flood grinding chromed materials.

Stainless Steel Rotary Index Fixture in the EDM Area

In the EDM area, our SUB-X 1800 – along with optional high RPM internal motor – changes what has previously been available to the industry.  Many work pieces previously ground can now be EDM’d.  Tighter tolerances with smaller details can be manufactured with greater repetition of accuracy.

  • Compactness of the design allows flexibility of placement in EDM.
    Small size also allows easy movement from machine to machine.
  • Ceramic bearings isolate the unit from electrical discharge.
    This prevents any damage to the bearing race during EDM. The ceramic bearings also allow for a heavy preload, maintaining high precision with heavier work holding fixtures and work pieces installed on the spindle face.
  • The digital readout allows setting of the indexes while the unit is installed in the machine and squared to the machine travel.
    Previously the unit would need to be uninstalled, indexes set up and reinstalled.
  • The high-torque and high-rpm internal motor gives precise control up to 1800 RPM.
    This combination has not been available until now.  The high torque is required so proper face tooling options can be utilized at the high rpm required on smaller diameter work pieces.

Flexible, Expandable Options

The face tooling options can be purchased as required by the customer when their needs change.  None needs to be added to the spindle at the time of purchase.

Our face plate allows the ability to mount directly, any of our BTD style chucks up to a 2” capacity, a 4” magnetic chuck, or any type of system 3R, Hirschmann, or Erowa mount system.

Many customers in the mold, medical, and small part business area, have found great savings in time, and an increased level of quality in their parts by moving to a wire EDM machine equipped with a Hermann Schmidt SUB-X 1800 rotary indexer.

Evolution of the Hermann Schmidt Stainless Steel Rotary Index Fixture Read More »

Selecting the Right Spin & Index Fixture

Customers often ask us: “Which spin & index fixture do I buy?”

I have already discussed SquareTech, which is a specific solution for high accuracy 90° indexing.

We sell four other styles. Here is some information to help you decide the best solution for your application:

Flatspin – NBFS  NBFS

Mostly used for face grinding on a surface grinding or jig grinding ID/OD.

The unit also has 15° internal indexing stops. Manufactured from tool steel the spindle can be used in a wet environment with pressurization. This unit is sold motorized as a plain spindle without tooling. All face tooling options are available.

Flatspin Spin Indexer product info.

Grindit – NBG  NBG

A very all-purpose tool for spinning and indexing.

The unit has 15° internal indexing stops and adjustable stops for off angle locking and arc limiting. Adjustable stops are set by mounting on a sine plate and indicating the angle. Zero-null feature allows for adjustment of zero +- 8° off of index origin. Manufacture from tool steel the spindle can be used in a wet environment with pressurization. This unit is sold motorized with v-block and 5C collet capabilities. Other face tooling options are available.

Grindit Spin Indexer product info.

Indexer – NBI  NBI

Has all the attributes of the Grindit, but does not need a sine plate to set the adjustable stops.

Patented interlocking Vernier plates allow you to set the adjustable stops to 1 arc second accuracy quickly. The indexer can be left setup in the machine environment and adjustable stops can be moved in location. This model should be purchased if you are using non 15° stops on a weekly basis or less.

Indexer Spin Fixture product info.

Stainless Steel Rotary Index Fixture – RIF-S  RIFS

This is the next generation in small spin and index fixtures.

Manufactured from stainless steel, containing ceramic bearings in a fully submersible package allows the unit to be used in most manufacturing environments, Wire EDM – Sinker EDM – Grinding.

An internal rotary encoder allows you to set up to 45 adjustable stops within 15 arc seconds accuracy. This eliminates the need for setting up using a sine plate and re-verifies your index position every time. Output is switchable between degrees decimal and degrees, minutes, seconds.

This unit is sold as a plain spindle. Motor drive options are the external motor usually used for dry grinding or the internal motor. The internal motor is integral to the RIF-S body allowing for fully submerged operations. The direct drive motor allows for full control 5-1800 RPM and reversing. Indexing accuracy improves to 6 arc seconds.

Options available are:

  • EDM grounding system for ensuring continuity in the EDM environment.
  • Leveling head to add or remove taper from a workpiece.
  • Adapter to rotate spindle to vertical orientation.
  • All face tooling options

Stainless Steel Rotary Index Fixture product info.

Selecting the Right Spin & Index Fixture Read More »

SquareTech: Presetting Workpiece on Center

The workpiece should be delivered to the machine tool in a pre-centered orientation.

Workpiece Center PresetterThis presetter features reversible gage arms to allow workpieces up to 11” x 11” to be centered. It is compatible with System 3R: Macro, Macromagnum and Matrix systems.

The system is applicable to the following workholding solutions:

  • Magnetics
  • Direct to Reference System
  • Vises

The basic procedure is as follows:

  1. Measure workpiece with height gauge.
  2. Set up planar gauges to proper dimensions by using height gauge.
  3. Place planar gauges between workpiece and presetter arms.
  4. Align workpiece.
  5. Activate workholding mechanism.

This system allows for the centering and squaring of the workpiece within 0.002” quickly and efficiently.

Download PDF of this SquareTech article.

SquareTech: Presetting Workpiece on Center Read More »

SquareTech: Mounting of Workpieces

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

High Precision ViseTwo styles of manual vises apply themselves well to SquareTech

  • Self Centering
  • Precision toolmaker

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

Mounting Worpieces DiagramWhile 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.
  • Electro-permanent.

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.

Download PDF of this SquareTech article.

Please contact us with your specific application. The options in work holding are continuously improving. Applications which were impossible only a couple of years age are now common.

SquareTech: Mounting of Workpieces Read More »

SquareTech High Precision 90° Indexer: Real-World Test

SquareTech Precision IndexerWe make great claims of the quality and accuracy of our SQUARETech High Precision 90° Indexer:

Accuracy: Total indexing error is less than 2 arc seconds, creating a true 90 deg index. As an example grinding four sides of an 8” by 8” block will result in a block which is Square & Parallel less than 0.0001” TIR.

Repeatibility: Ensured by use of System 3R reference.

So how does the SquareTech Indexer actually measure up in the real world?
We tested it. Here are our results.

Results of SquareTech Precision Test

The SquareTech system was used to surface grind 80 pieces of fully annealed 1018, initially rough milled square within 0.001”. The workpiece size was 8”x8”x1 ¼”.

The goal was to be able to have a resultant accuracy of 0.0001” square and parallel. The surface grinder we used was a two year-old Okamoto ACC1224EXB. Measurement results are considered accurate within +- 0.000010” (ten millionths).

All four sides of the blocks were ground on the fixture. These measurements are total squareness and parallelism of all four sides. Results are summarized as follows.

Maximum Value 0.000060”
Average Value 0.000030”
Median Value 0.000025”

The average is ½ of the maximum value, with the mean value falling below the average, which shows that the majority of the measurements were toward the lower values.

Another way of looking at this is as follows:

85% of the parts were within 0.000050”
35% of the parts were within 0.000025”

This shows the accuracy of the system in a production environment. Remember we are measuring processed parts, so we are also dealing with the errors in grinding; we are not just indexing and measuring.

The above errors result in a total indexing accuracy below 2 arc-seconds.

An easier way to look at it is linear error based on part size.


Conclusion: High Precision Confirmed

Our tests show that our our SQUARETech High Precision 90° Indexer has a total indexing accuracy below 2 arc-seconds in a production environment.

Download PDF of this SquareTech article.

The following video is a presentation of fully automated SquareTech grinding cell.

Next post in this series: SquareTech: Mounting of Workpieces


SquareTech High Precision 90° Indexer: Real-World Test Read More »

SquareTech Precision Indexer