Friday, November 18, 2016

Jigs

I started talking about jigs a couple days ago because I was planning to make one to help me get the tube that I need to have parallel slots to help me get the first slot vertical once the tube is turned 180 degrees so the next slot is also vertical.  Then I thought of the work involved and decided to go back to a longer 1/2" end mill so that I can cut both slots in one operation (probably at 0.5 in/min at first as an experiment).  I found one with the flat spot on the shaft and 1 1/4" cutting length for $5.40.

There's still one issue: I need to drill two .2010" holes (for 1/4"-20 tapping) at right angles to the slots and a 1/4" hole aligned with the slots.  Rotating the part without a rotary table is going to be approximate at best.  The solution I think is to drill the pilot hole for the 1/4" hole at the same time as the slots.  As long as I don't loosen the clamp, I can remove the endmill and put the drill chuck in with a center drill and mark the location,  Then put in the drill press and complete the hole through.  Next, I put a 1/4" rod through the hole, and rest the tube on a .5" high support to keep it level for drilling the .2010" pilot hole.  The rod will rest on the jaws of the clamp, forcing a 90 degree angle for drilling the pilot hole.  I use the pilot hole on the drill pressto cut through both sides.  All I need now is a 3" long, .5" high, .75" wide piece of acetal as the support for the tube.  I will mill a .2" slot by .2" deep slot down the middle so the tube rests instead of rolling.

1 comment:

Jim Dunmyer said...

My mental picture of your job is a tube, maybe 1" diameter, with slots on opposing sides. Also, 2, 1/4-20 holes on opposing sides, 90 degrees from the slots. If that's correct, my procedure would be to make the slots, then insert [something a few inches long] that fits snugly in the slots and use it to index the tube. In certain setups, you can eyeball it off the table/vise/whatever, or you can measure each end to the table/vise/whatever.

Pictures help. (hint, hint)