TO-3 Drilling Jig

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I am thinking of producing a jig for drilling the heatsink holes needed for TO-3 devices.

It will be a CNC-milled piece of aluminum roughly the size of a TO-3 device with four drill bushings (will make it as close as possible, may be larger to accomidate the two end bushings). You place the jig where you want the device on your heatsink and use a hand drill to drill the holes. Simple as that.

Would anyone be interested in these? Not sure of a price yet, but probably in the $15-20 ballpark each. Also, any feedback on the design? Could include a 1/8" drill bit as well.

If there is interest, I will post in the Marketplace forum.
 
and me...

I'll take a couple...would you consider getting the same thing done out of steel? or are the bushings steel?

I have used aluminum jigs for other purposes and they work perfectly for a while, but I always seem to slowly enlarge the holes, a steel version, or steel bushings would make this process slower.

Of course I am assuming the cnc process can be applied to any material...

Stuart
 
You can use an old TO-3 case, if you have one, but it won't do much for guiding the drill.

My initial idea was a simple jig and a metal punch to be followed by drilling, but I figure there are a bunch of people out there without drill presses, and drilling straight into a piece of aluminum with a hand drill can be tricky.

The drill guide bushing will keep the drill perpendicular to the surface you are drilling. It also will not wear out (hole get bigger) over time. These things should be the last tool you need for it, which is the way I like things.

I'll make a couple and post some pics.
 
This is a sleeping thread, I know, but a TO-3 drilling Jig would certainly be an answer to my need and I have searched both this site and the wider internet at length without finding anything more practical.

I will soon need to mount 12 x TO-3 cases onto thick T section aluminium which will be the thermal link to my heat sinks. I do have a few old transistors that I could sacrifice and use as templates (with a friend to say if I am keeping my hand held drill upright) but before I do that I wondered how others did it.

Please could you share any hints or tips.
 
Having a template for a single device is not always a great help. It depends on whether it can easily be clamped to the heat sink while it is being used. In a lot of cases it is easier to draw the layout for all the devices on paper, then lightly stick the paper to the heat sink, centre punch the position of all the holes through the paper, remove the paper and drill the holes.
 
Manufacture a steel drilling jig with the 4 holes in the correct position.
If need be, pay a machinist to drill your jig accurately. It would not cost much extra to get two sets of 4 holes in the one jig.
I'd suggest at least 6mm thick and preferably approaching 12mm thick.
 
KatieandDad - That was, indeed, my thought and I don’t need to buy anything as I have some RCA 2N3235s that have sat in my oddments drawer for a few decades. Though on googling them I see someone recently sold them at GBP3 each so perhaps I should rename it my treasure chest :)

franzm, levistubby and frank1 - I guess you are right I should be braver especially as I don’t even want to insulate the transistors from the T piece so I only need to make sure the pins don’t contact the “intermediate aluminium”.

AndrewT - If I don’t get braver I’ll try to find a light engineering shop and every data sheet has the measurements on it!

Thanks to all for this food for thought.
 
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