Happy new year, all.
I’m finishing up a headphone amp. I installed a Goldpoint attenuator and purchased a couple of aluminum knobs with the attenuator. All Goldpoint stuff is 6 mm. I installed a selector switch with a 1/4” shaft (not Goldpoint). So the knob is slightly small and won't slide over the shaft. So, I toss the knob(s) or enlarge the hole.
I could probably get this done at a machine shop; but I’d prefer to do it myself, if possible. I,ve got a vise with nylon jaws and a hand held, battery drill. I’d probably buy a new 1/4” bit, just to be sure. The shaft hole is around 3/4” deep, the difference between 6mm and 1/4” is about 0.3mm, so one pass seems enough. There is a set screw, probably need to bring that back a short distance.
So, opinions on please: will this go smoothly or will the drill kick out, wrench the knob out of the vise, toss it across the room and break a window?
I’m finishing up a headphone amp. I installed a Goldpoint attenuator and purchased a couple of aluminum knobs with the attenuator. All Goldpoint stuff is 6 mm. I installed a selector switch with a 1/4” shaft (not Goldpoint). So the knob is slightly small and won't slide over the shaft. So, I toss the knob(s) or enlarge the hole.
I could probably get this done at a machine shop; but I’d prefer to do it myself, if possible. I,ve got a vise with nylon jaws and a hand held, battery drill. I’d probably buy a new 1/4” bit, just to be sure. The shaft hole is around 3/4” deep, the difference between 6mm and 1/4” is about 0.3mm, so one pass seems enough. There is a set screw, probably need to bring that back a short distance.
So, opinions on please: will this go smoothly or will the drill kick out, wrench the knob out of the vise, toss it across the room and break a window?
I've done this many times with a drill press, and it went smoothy. A little oil always helps.
By handheld drill? I dunno. The vice will certainly help.
By handheld drill? I dunno. The vice will certainly help.
You will likely have the best luck reaming the hole to size. Trying to drill that small amount of material usually ends badly because the drill bit will just grab. SOWA - Homepage
You guys are confirming my fears. I’ll Wait and find a machine shop with the right tools. Always cheaper in the long run. Thanks
Let the drill pull itself along, don't rush it. They usually grab when you are asking the drill to move faster through the material than it wants to go.
Why not try drilling a 6mm hole in some scrap stock, then enlarge it to 1/4" with a drill and see how it goes.
Why not try drilling a 6mm hole in some scrap stock, then enlarge it to 1/4" with a drill and see how it goes.
I’d like to practice, but I’ve only got 1/8” stock (this is 3/4”). I drill 1/7 frequently: for a 1/4” hole I’d do three or four increasingly large holes. I don’t know a machine shop, but wood shops and others usually get $5 for a little job. You just have to be polite. If I can’t find somebody, I’ll try it myself.
Without a drill press, you aren't going to get a nice straight hole, and it will be oversize, and slightly tapered.
jeff
jeff
Just the opposite: low revolution, but a super sharp (new) HSS drill bit. And some oil, as it has been suggested. I usually go in 0.5 mm steps.
I've drilled hundreds of holes by free hand, and of corse some moore with different machines.
Make a good marking for a start. Pre drill with about 3.5 mm It's a good choice working on free hand so it won't break.
Start slow and increase speed to when you'll see that it cuts nice.
Some lubricant may do good but isn't necessary. WD 40 or something will work.
Remember that it's the preparing before drilling that gives good precision.
Figge
Make a good marking for a start. Pre drill with about 3.5 mm It's a good choice working on free hand so it won't break.
Start slow and increase speed to when you'll see that it cuts nice.
Some lubricant may do good but isn't necessary. WD 40 or something will work.
Remember that it's the preparing before drilling that gives good precision.
Figge
The question was about enlarging a 6mm hole to 1/4" which would work out to removing about 0.016" of material. That's a lot harder than just drilling a fresh hole as there isn't enough material present for the relief angles on the drill bit to control anything.
Yes, a normal drill bit without the help of a drill press will almost certainly grab, but reamers aren't well suited to blind holes either.
What I sometimes do in similar circumstances (not these exact ones, since I have a drill press) is to modify a drill bit: essentially reducing the cutting angles in this case. It is relatively easy to do, even with a hand-held grinder and no guide or jig, but ideally you would need to make a test before any attempt on the real part: even a moderately thick aluminum plate would be sufficient for that.
What's the shaft made out of? If aluminium, could you sand it down a touch? wrap some maybe 240 grit wet and dry around it and turn it round and round. May not be practical.
Tony.
Tony.
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