I certainly agree with those who suggest using the quill of a mill to stroke the slot, once roughed. The amount of material to be removed isn't significant, but warrants grinding a small tool instead of filing, if for no other reason, to produce uniformity. The time spent grinding the tool will be more than repaid by improved quality and consistency of the slot. The tool could be created by offhand grinding, but would require patience. A cutter grinder would make the task all the easier.
If you haven't used small end mills, you may struggle a little. As size is reduced, they demand greater spindle speeds, and perform poorly if it's not available. What you'll discover is that they break as if they're made of glass. Carbide is more rigid, but still eager to break.
To limit breakage, you'd be well served to drill the opening, then clean it out using an end mill. As drilling requires a full hole, the material between holes would be best removed by pecking, until the web is removed. Using a 1/16" end mill, you could then walk the ends and sides of the slot, leaving only a thou or two to be removed by the simply broach. Properly centered over the created slot, a single push (using the quill of your mill) would clean all four corners and size the slot.
I'd suggest a similar operation to the one where I thought the open end slot was the one in question. The difference being I'd use the center of the vise, but I'd still set a permanent stop, so pieces can be removed and replaced without losing register. By using a sacrificial parallel (made of aluminum), you can machine directly in to the parallel. The stop would be created by machining a step in the parallel, which would then be clamped permanently in the vise (that's where those ¼" tapped holes really shine).
An alternate to the step in the parallel is to clamp a small piece of stock on top of the parallel, using the end as your stop. Both methods work just fine.
H
How do I make this?
Re: How do I make this?
Wise people talk because they have something to say. Fools talk because they have to say something.
Re: How do I make this?
Thank you Harold for your wisdom. Without guys like you, we would be stumbling around in the dark.
Mr.Ron from South Mississippi
Re: How do I make this?
As Harold pointed out, a 1/16" end mill needs to be run at a very high speed and that speed is not available on my 6 x 26 knee mill. Due to the thin walls, I feel a broach would distort the hole and put the piece out of shape. The only other option is to drill and hand file. I would hate to spend $20-$30 for a 1/16 end mill and have it break almost immediately; drill bits are much less costly.
Mr.Ron from South Mississippi
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Re: How do I make this?
Broach (and drill) first, and in a fixture.