Several years ago I made an index wheel for my G0602. At the time I was building a modified Brooks cutter/grinder and had a number of calibrated dials and knobs to make. I never wrote up the index wheel project. However, the index wheel has appeared in many photos that were incorporated into other posts that I made and as a result of seeing these photos I have received a large number of requests for more information on the project via private messages.
I recently received another such request and in the process of exchanging emails with the requester it was pointed out that the math I used to calculate the spacing of the inner row of holes for the vernier plate was wrong. It was an obvious error and I am surprised it was not identified earlier. In any event to correct the record (with apologies to those whom possess the incorrect data) and to provide information for those that may desire to add this feature to their G0602 I submit the following post.
How to make an index wheel for the G0602.
The gear on the bar on the right side of the spindle housing is a reverse idler which has been detailed in a separate post.
One point to be aware of is the room on the spindle shaft to mount the index wheel resulted from removing two sheaves of the drive pulley. Since I had previously installed a variable speed motor and rarely changed the belt position removing two unused sheaves was not a problem
The index wheel that I made for my lathe has two rows of holes used for indexing. The outer row has 36 holes and is used in conjunction with the vernier plate to resolve angles to one degree or multiples of one degree. The inner row has 20 holes and is used in conjunction with the vernier plate which has 5 holes to resolve angles in 3.6 degree increments. This allows you to locate in multiples that correspond with 0-100 or sub multiples of 100.
I surfaced the disc in the mill (it was an old piece of rusty iron). Using the center hole I located the disc on my rotary table making sure that the center of the disc was exactly aligned with the center of the rotary table and then I secured it to ensure no movement during the drilling process. To help locate the wheel on the table I made a center hub to mount the plate on and a tapered mandrel to fit in the Morse taper located in the center of the table. You can see this arrangement in the following photo #3.
I made three discs before I got it right. I use the index wheel for making calibrated dials and quickly found out that any small error in the disc will be quickly visible on the dial you are making. Here is an example of some the dials I made.
Doing the math. Here is a better view of the wheel after the drilling operation.
The outer row of holes is spaced 10 degrees apart, the outer vernier holes are spaced 11 degrees apart (11, 22, 33, etc). The first vernier hole is “0”, the next is 1 and then 2 up until you reach 9. Using a position of “0” as your reference, if you wished to move to “1” then you would insert the pin into the number “1” hole, if you wanted to move to “11” degrees then you would insert the pin into the number “1” hole and move the wheel to the next outer wheel hole which is ten degrees from your reference point. When making dials depending upon which direction is increasing in value you would reverse the process so that the vernier hole for “9” becomes “0”, etc.
The inner row of holes is 18 degrees apart and the vernier holes are as follows:
The first hole is at “0” degrees.
The second hole is at 18 degrees plus 3.6degrees or 21.6 degrees total.
The third hole is at 21.6 degrees plus 21.6 degrees or 43.2 degrees.
Using the inner row to locate sub multiples of 100 is the same as above.
Drilling the holes. This is the tricky part and you need to allocate some uninterrupted time for this part of the process because it a very repetitious process this must be done exactly the same for all 56 holes. Any variation will lead to trouble. Always use a spotting drill to locate the hole, no exceptions. Make sure your drill bits are sharp and ground evenly, an off center grind on the bit will result in oversize holes. I would advise a new “machine screw drill bit” just for this project. I always use machine screw bits when possible since they are shorter and provide better centering. Always run the rotary table in the same direction and use something to hold the table so backlash is not introduced into the process. Always clamp the table before drilling. When you are done chamfer the holes slightly using a hand drill.
The vernier. This is also a tricky operation and requires careful thought on how to perform the machining steps. I have a DRO on my mill so this was used to locate the radius of both the wheel and the vernier, it is apparent that they must be exactly the same. The shape of the vernier plate will depend upon how you mount it to your lathe. You can see from the first photo how mine was mounted. The most difficult part was figuring how to locate the mounting holes so that everything aligned properly.
I hope this provides enough detail for you to proceed. I have found this addition to the lathe is most handy since I frequently make calibrated dials and plates. As always if you have any questions or comments please do not hesitate to contact me.