Since there are at least three step motors on the CNC router, a template will save time and provide a higher degree of drilling accuracy. Here is how I made mine.
- 1/16" aluminum sheet cut to 3" by 3". 3/32" or 1/8" will work
- Draw a line between two adjacent corners
- Using the other corners draw a short line crossing the first. Using center punch, dimple this center point.
- Set an adjustable divider to 1 5/16" using machinist ruler.
- Scribe a 2 5/8" diameter circle using center point.
- Using long crossed line, dimple places where the line crosses circle.
- Use these points and a little geometry to determine a line 90 degrees to first.
- Dimple points where this line crosses circle.
- Drill the four points on the circle with 3/16" bit. Use center drill to start hole.
- Drill center with1/4" bit.
- Check on step motor for accuracy. Motor shaft is 1/4".
- Enlarge center hole to 5/8" with step drill.
Tools:
- Carbide scribe: HF #97336,
- Divider: Alvin Basic
- Awl or hand center punch, small hammer
- Hand Punch (optional): Amazon, Roper Whitney, Grizzly H7862
- Drill Press with center drill, 3/16" drill bit and Step Drill
1) If you are involved in sheet metal work, particularly electronics, you will find this small hand punch is very useful, especially with the optional bench base. I purchased a RW No.XX with a base several years ago. There now seems to be many Chinese knock-offs, and except for the Grizzly, none have bases. Many individual punch and dies can be purchased for the RW; however, they don't fit the knock-offs..
2) A compass can be used for the divider, but steel points must be used on both legs.
3) To make it easier to see the scribe lines, the metal can first be coated with layout fluid, such as, Dykem Blue DX-110. This product comes in a bottle with a brush and can be found at machine supplies like McMaster Carr.
4) Another useful tool is a tap guide which can be used to find the hole center on a drill press and hold a tap vertical during thread tapping.
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