drilling strain relief holes in phenolic boards

[Luthierwnc]

Hi All,

I'm revamping an older 2nd gen build that will be getting new circuit boards. In casting around other builds, I noticed some makers use eyelets closer to the center of the board and drill eyelet-sized holes near the edge to double the wire from the underside and loop it back down (see Ultrahookedonphonics' 183 build from a couple years ago. Others (like me) don't bother and just run the wires out of the bottom.

Couple questions for people who make 'em both ways:

what are the advantages? and
do you chamfer the edges of the holes and the side of the board so they aren't so sharp?

It looks nice. Just curious, Skip

[ToneMerc]

Skip I do it on many builds because here's what it does for me;yes it a strain relief at the solder pool, it helps to pin the leads in place and it provides a small amount extra slack in the form of a maintenance loop for tweaks/repairs. Yes, I chamfer both sides of the board holes with a 7 and or 45 degree carbide cutter tool. This gives me an excuse to use my precision ammo prep tools for something else....lol

TM

[Luthierwnc]

I was thinking more in terms of a countersink. It is nasty stuff, though. I clean the dust out of the tablesaw and radial saw collector ports since it sometimes throws sparks with a carbide blade. The first time I made a board with the 1/8" FG10 I tried to cut it with a bandsaw. Killed that blade about 3" in.

Thanks and Merry Christmas, sh

[David Root]

That's odd, I've been cutting those boards for years with the same metal cutting bandsaw blade, think it's 24 tpi. Still works fine.

[Luthierwnc]

3-tooth per inch skip-tooth. Hey, it cuts aluminum great! Loud too. Live and learn.

[ToneMerc]

I was thinking more in terms of a countersink. It is nasty stuff, though. I clean the dust out of the tablesaw and radial saw collector ports since it sometimes throws sparks with a carbide blade. The first time I made a board with the 1/8" FG10 I tried to cut it with a bandsaw. Killed that blade about 3" in.

Thanks and Merry Christmas, sh

Skip considering that most boards are either .062, .093 or .125 in thickness there's not much material so all that's needed is to chamfer the inside edge of he hole.

TM

[Luthierwnc]

What I'll probably do is chuck a Dremel cone-shaped grinding bit in the drill press and kiss the holes lightly. Quick, easy, self-centering and there is a dust port on the machine. Thanks, sh

[ToneMerc]

What I'll probably do is chuck a Dremel cone-shaped grinding bit in the drill press and kiss the holes lightly. Quick, easy, self-centering and there is a dust port on the machine. Thanks, sh

Here's the "cone shaped" 7 degree carbide tool I use.

TM

[Luthierwnc]

Ended up using a fluted countersink in the DP at high speed. Half second each hole. A little 220 around the edges and it was a five minute job. Parts are still arriving but as this is a rebuild (of sorts) the major metallurgy and heavy bits are already here.

FWIW, this is the working schematic on the build. It is a hybrid hybrid 2nd gen with an onboard loop, bright, deep (no R/J), simplified PAB. the mid-boost and FET are on the footswitch.

Some members will recognize their own schematics hacked on MS Paint. AFAIK, the 2nd doesn't have a schematic here -- several layout diagrams but not the schemo. Of course this is probably quite different than the originals but it is what I'm starting with. When it is up and running I'll post any changes it took to get it right.

Cheers, sh