Part 7- Index Drum
UNIVERSAL TOOL AND CUTTER GRINDER
To start, and I wish that I had done this early on, make a Main Axle Fixture (arbor) with a rectangular end. This will save hours of time not having to get out the Main Axle every time you make an adjustment to one of the Index Head Parts. It is easy to dial in and hold in your mill vice.
Friendly reminder- you probably already know- as you remove the parts put keep them together. I like the magnetic dishes that Harbor Freight sells. As careful as I am I lost the cone shaped springs from the levers 3 different times. I did eventually locate them, but they would be a lot of work to make new ones……..JL
You will need the Index Head Base off of the grinder for the most of the rest of the Index Head repairs. Remove the IH and the Index Head Base from the Grinder (detailed in Part 5, The Main Axle).
- Remove the Cross Slide Drum from the Index Drum:
- Remove the CSD lock bolt.
- Remove the CSD Axle Jam Nuts by gently tapping on the tooth of the outer nut until loose, then remove both. You may use needle nose pliers if needed.
The CSD should now slide out of the ID without much resistance. The axle on my CSD had a burr caused by the CSD Lock so I had to gently rotate the two until they could be separated.
You can see in the photo below that the Stop Guide AHCS (Allen Head Cap Screw) have been replaced with Set Screws.
Prior to making the MA Axle Arbor, I clamped the ID to a 123 Block to measure how flat the Platter was. As you can see with Ø = zero, the opposite side is out .0025”. I am fortunate to have a surface grinder but the Milling Machine will, with a good sharp cutter clean this surface up very nicely.
This is at this point in the project I made the Axle Mandrel (photo #003).
The Axle Pivot hole in these castings are very poor and oversized. For me, putting in the bronze bushings is not an option. If you want your tool to make parts that are close tolerance, you must correct these imperfections. All the Bronze Bearings came off the shelf at Ace Hardware.
Clamp the Index Drum in your mill vice squarely against the rear jaw, this is assuming that your vice jaws are flat and square to each other. Because I took the part from the Surface Grinder to the Mill I used a 123 Block and a clamp to hold the parts together.
Run the Dial Test Indicator around the Platter to insure it is parallel to the table, recheck the tightness of the vice then recheck the DTI.
Find the center of the Axle Pivot Hole and bore out the hole to the size of your new Bronze Bearing. If you cannot find a Bearing long enough, use one Bearing in each end.
It should be a light press fit to install the Bearings. If you mess up and they are too loose, use loctite to glue them in.
Note: Keep the DTI (Dial Test Indicator) on the part to make sure it does not move during the boring operation.
There are two Rotation Stops. One is fixed and one will retract. Both stops are zero adjustable.The fixed stop limits the Clockwise travel of the Cross Slide Drum (CSD).
Photo #013b demonstrates how the Counter Clock Wise Stop is adjusted to +90°. Loosen the CCW lock screw and the stop can be rotated using a 10mm wrench. Moving the Cross Slide Index Ring, the CSD will rotate zero to +90°. It is the same rotation but changes the readout.
The Clockwise Rotation Stop is a fixed stop and should be set to stop the CSD rotation at -90°. Fine calibration adjustment can be made by loosening the CW Set Screw (photo #006) and rotated with a Hex wrench. Retighten so the CSD stops at -90°.
The Clockwise Rotation Stop has two settings. Pull it out and rotate the knob slightly. It will stay in the extended (out) position. Rotate it again until the tiny pin drops a hole. Now the Stop is positioned (in) to stop the CSD in the zero position. To fine adjust the pin to stop on zero, loosen the CCW Set Screw (photo #006) and rotate the pin till it stops on zero.
With the CCW Stop in the up (in) position, the CSD should swing from zero to -90°. Adjust until both stop precisely at their correct positions.
With the CCW Stop in the down (out) position, the CSD will swing past zero, only stopping at -90°. With this setting, the tool will swing to about +240°.
Increase Degree Rotation of the Index Drum:
Using the grinder I found that I needed to increase in the ID rotation. To gain more rotation I made this modification to the Hex Head of the CSD Rotation Bolt. This modification puts the shoulder of the lever almost touching the casting (see #022).
· Drill the threaded hole about .300” deeper using a #20 drill for the 5mm-.8 thread.
· Re-tap the hole adding additional threads to the bottom of the bolt.
· Turn off .250” off the end of the hex end of bolt, chamfer and re-install handle, yours may differ so make sure not to take off too much.
This modification only gave me 2° more rotation, really not worth the extra effort.
More Degree Rotation of the Index Drum:
For a grinding job I needed more rotation of the ID. I replaced, only for this job, the lever with a 8-1.25mm, 30 mm long Set Screw. After this job I replaced the lever and saved the Set screw for future use.
Using the Set screw allows the Index Drum to use the full 40° rotation.
I found to CCW stop to be poorly made and the tiny pin was loose enough to fall out. I made two new Stops when
I discovered that I needed to rotate the tool past the zero setting to sharpen Boring Tools.
This is what mine looks like today
As I used the grinder I found that when regrinding a tool previously ground, the new grind would be very slightly off from the previous grind. I surmised that I was not getting the Index Rings **Fiducial readings exactly aligned to the *Reticle of my previous setup.
I made new Fiducial’s from Brass with .020” slots, that is the same width as the reticle lines on the Index Ring and allows me to obtain better/repeatable setups. It is also possible to accurately line up the Fiducial’s between the Reticle lines.
On a suggestion from my colleague @ CSULB, Martin Brenner, who is an expert in this style of very precise measuring on Balloon Theodolites (http://web.csulb.edu/~mbrenner/balloon.htm), I added a second Fiducial to the Index Drum at the 3:00 position (the original Fiducial being 12:00). This allows me to re-position the Cross Slide Index ring and read it from the right side of the Index Drum. This is very useful when it is difficult to get a clear view of the front (12:00) Fiducial
Later in my articles I will post set-ups for different tooling. For example the standard Right Hand Lathe Cutter or sharpening a Boring Bar. This is the reason that the Cross Slide Drum Fiducial is identified as F-A and F-B. ID-A is the original Fiducial.
Increase Degree Rotation of the CSD:
Using the grinder I found that I needed to increase in the CSD rotation. To gain more rotation for the CSD I made this modification to the Hex Head of the CSD Rotation Bolt (see Photo #022). This modification puts the shoulder of the lever almost touching the casting.
Drill the threaded hole about .300” deeper using a #20 drill for the 5mm-.8 thread.
Re-tap the hole adding additional threads to the bottom of the bolt.
Turn off .250” off the end of the hex end of bolt, chamfer and re-install handle, yours may differ so
make sure not to take off too much.
To get the maximum CCW rotation of the Index Drum, use a Set Screw with no stick-out.
*A reticle, or reticule (from Latin reticulum, meaning "net"), also known as a graticule (from Latin craticula, meaning "gridiron"), is a net of fine lines or fibers of a sighting device.
**A fiducial marker or fiducial is an object placed in the field of view of an imaging system which appears in the image produced, for use as a point of reference or a measure. It may be either something placed into or on the imaging subject, or a mark or set of marks.
Terminology of parts Disclaimer:
Several names of the parts have been taken from the Deckel Catalog; to insure you the reader, will always know what part I am referring to. I have applied the identification of parts from other machines, catalogs and some I created for a clear description of the parts function, (eg. Top Slide Tool Holder).