Here's the question.
I'm working on a little suspension project where I want the tightest tolerances I can achieve with my meager tools. I have a small table top drill press and an assortment of drill bits, including a 7/8" uni-bit.
I need to make two identical parts by drilling a 3/4" and 1/2" holes in two 2.5' long sticks of 1 1/4" x 1 1/4" x .130" aluminum square tube.
I need them centered on the long axis.
I'm looking for specific steps to prevent the bits from walking, the hole going egg shaped, etc. and making both parts identical to each other. How would you go about doing this?
Here are my normal procedure:
1. Use adjustable square to mark center of each axis for each hole.
2. Punch center with spring loaded punch.
3. Adjust drill press to allow proper drill depth.
4. Drill pilot hole with small drill bit (usually 3/16") [Here might be the start of problems I've had as this bit walk or bend]
5. Move up to 1/4" then up to 3/8 then 1/2" After that I have to go to the Uni-bit. [What is the correct size increments to move up each time?]
I guess this question falls under "what are the proper machining techniques" category, if that makes sense?
Thanks!
Erich