Part 5- The Main Axle
UNIVERSAL TOOL AND CUTTER GRINDER
In retrospect there is one thing I would do differently. Instead of spending a lot of time trying to straighten the Main Axle, it would be much easier to buy a quality steel rod, maybe even chrome plated and turn a new axle from scratch.
I am starting with the Main Axle (MA) because I made several modifications to the axle and there must be a clear understanding of how it works. You must be able to take it apart and re-assembling it. Next to the Index Head that positions your part this is one of the most important parts of the machine.
Main Axle (MA)
- Allows precision feeding a part (X Axis) into the face of the grindstone.
- Allows the Index Head to swing across the grinder face (Y Axis) in a controlled range of movement using an adjustable Driver.
MA Micrometer Assembly has six parts. The feed knob, micrometer adjustable ring, the ring spring, the collar, the outer sleeve and the inner sleeve. The micrometer adjustable ring has 100 division marks and will rotate independent of the feed knob with a mild resistance to allow a zero setting for the knob.
Your first look at the micrometer knob marks may lead you to “assume” that each mark on the dial is .005” however, if you take a close look you will see that the .005” indication on the collar and the marks on the knob are not the same spacing. Each mark on the spindle is metric and moves the IH .000395”. I think the intention was to round the marks up to .0005”.
The Pull Spring's purpose is to keep the Main Axle seated tightly in the threads of the Micrometer Knob.
REMOVAL, INSPECTION AND REPAIR OF THE MAIN AXE
(Photo #005) Remove the MA Adjusting Knob by backing off the two MM 6-1.0 set screws. The Micrometer Ring and spring will come off with the knob. (Only remove the ring from the knob if it is not working properly).
- Remove the three MM 4-0.7 screws that hold on the MA Collar, and slide the collar off the shaft.
- Under the knob and at the end of the shaft are the two Jam Nuts that adjust the play in the shaft. Using a punch, tap the outside nut ccw, till it loosens, then remove both. The inside nut may be removed and replaced using needle nose pliers. (Photo #005).
· Loosen the Micrometer sleeve Key-way Screw (Photo #006).
Now you may pull out the Micrometer collar (Photo #007).
Loosen the Indexing Head lock lever (Photo #001-d)
Roll the Grinder on its back and remove the bottom cover.
· Back out the MA Rotational Limit Set Screw(#001-c)
· Loosen the Index Head Lock (#001-e).
· Swing the driver towards the front of the machine to expose the Driver Set Screw and back it out.
Pull out the MA from the casting to the right, away from the grinding wheel. Rock the IH to move it to the left as you pull out the MA to the right. The MA shaft is .9788” (24.8615 mm) in diameter. The threaded end is M10-1.0 with 24 mm (.945”) of thread length.
After cleaning, I did a test assembly on the axle without the IH or driver.
Checking the MA for Straight-ness:
The first thing to check for is if the Main Axle is straight. This can easily be done by rolling the part on a surface plate or any known
flat surface. If the axle only has a slight bow, you can most likely use a press to straighten. I place a Dial Indicator under the part as
I apply pressure and take it very slowly until it goes past zero, then with the pressure off relaxes back to zero. Re check it on the
Surface Plate. It does not have to be dead-on to work properly.
If the axle has multiple bends you may have to chuck it in the mill and run the Dial Indicator over the top to see where the problems
are. This may require several secession's with the press to get it straight. (I will repeat this- "It may be easier to purchase a ground
rod that is already straight" and machine the ends).
My axle had a .010” bow (photo #012) that I straightened using V-blocks a hydraulic press.
The threaded end of my MA was out .027”.
This was straightened using the lathe, then the vice and pipe (Photo #013 & #14).
The Micrometer Collar:
I found that with the MA in place, the collar did not line up with the 3 screw holes in the casting. This is a problem that will place side pressure on the axle restricting or preventing smooth dial movement.
I had to make a decision to re-drill and tap new holes or mill the collar to widen the screw holes. Since the casting holes were within .050” and the side of the collar does not show I machined the collar. There needs to be ‘wiggle room’ in these holes to properly center the axle in the collar.
Attach the collar with the most accurate hole. Using a drill bit in another hole, measure how much
and what direction needs to be machined.
Center the holes using a fitted dowel.
Move the table to the new location and widen the hole.
The finished collar shows the completed holes with Allen Head Cap Screws replacing the poor quality Philips Screws.
The next six Modifications are optional. I made them in my effort to get as much flexibility from the machine as possible. Read it over and decide or maybe do it later as I did when I needed it.
To get the maximum travel of the Axle I did two things. Move the detent hole that locks the Driver to the Axle .300” towards the threads, to line up the edge of the driver with the shoulder of the Axle. (Photo #019)
Install the Driver on the MA and check if the Driver Face is parallel to the MA. I had to take off .045” to make the face true (Not shown). Failure to do this step will result in the IH twisting as you adjust the MA in and out along the Driver Face.
The Sleeve Threads:
I wanted the Micrometer Dial to read in Thousands instead of Metrics. I made a complete new Inside and Outside Sleeve with10 TPI. If I did it over, I don’t feel it was worth the effort, the new thread is course and the dial is harder to move. If you decide to do this, go with 20 TPI. When using the machine most often I just reach over and give the knob an arbitrary twist.
The End Cap:
While researching all the shop made machines I found they all had push springs to keep the tension on the MA. This is necessary to insure no lost motion or play as the MA is advanced or retracted. The Deckel/ Asian Grinders use a pull spring. Measuring the tool motion I found the spring did not keep the axle tight. I did make the push spring however, you may not find this to not be necessary. I now think when you swing the Index Head that will very likely seat the axle properly with the pull spring.(untested)
Remove the plastic dust cover and spring by pulling the cover out just enough to expose the spring and hook. Grab the spring’s hook with needle nose pliers and unhook it from the cover. Drive out the roll pin to remove the MA spring.
(Photos #020, #021 and #022)
The New Main Axle Spring Cap:
New Axle Swing Limit Knob:
The Bolt (Axle Swing Knob) is a loose fitted, poorly threaded part. Also the threads are only as long as the casting thickness and needs it longer threads the keep the bolt from wobbling.
I drilled out the hole oversized, made a new, longer insert and made a new bolt and knob. For the threads I used Grade 8 Threaded Rod (1/2- 20).
The Axle Swing Knob turned out to be too small so I made a larger one.
The Wheel Cover: (Easy Removal)
The plastic cover has 3 AHCS holding it in place. After taking the cover off and on dozens of times it occurred to me that I could make this much better. Photo #031 shows that I took the two 5-.08 mm AHCS and replaced them with long set screws. I turned off the threads of the screw that stick out of the body so the cover can slide on and off.
I made a new 8-1.25 mm screw knob to allow the
cover to be removed with a few turns of the knob.
The nuts in the inside cover (#032) are to prevent over-tightening the cover.
The Body Casting:
This next modification was for me the most difficult. My grinder had excessive play in the outer bearing (right side). I felt this was going to be a problem holding close tolerances. I choose to press in a bronze bearing. There are many ways to do this; I have a right angle head for my Bridgeport so that is what I went with this method.
This is not shown but start with shimming and clamping the casting and dialing in the Main Axle parallel and level to your table.
This is my most current version of the Main Axle Feed Knob.
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).