Who provides/cuts their own surgical tubing?

[Ronsonic]

To cut the tubing I use a single edge blade and lick it first. The wet acts as a lubricant so the tube cuts smoothly without the cut edges grabbing the blade as it passes. And yes, saliva makes a better lubricant for latex than water.





Snarky replies in 3 2 1

[peskywinnets]

Just got back from the friggin Casualty dept.....when they asked me how I got my tongue injury ... "thurgical thoobing".

[FunkyKikuchiyo]

... Did you run out of KY?

Someone had to say it.

[peskywinnets]

... Did you run out of KY?

well, after all, this is a "tradesman's" forum ....*and* wide open to all new entrants.

[Joe Gwinn]

Interesting. I have stopped using it to insulate cores, but I still use it for the outsides. It isn't the best dielectric out there, but I'd hardly call it "highly conductive" as Dave says. Then again, I don't have a perfect way to test dielectric strength, just a couple meters.

I think you want to measure the resistance (in ohms) per square of the tape, versus the dielectric strength (in volts per inch to cause breakdown).

Measuring ohms per square is easy. First thing to know is that it makes no difference how big the square is, so long as it's square and has terminals on a pair of opposite sides of the square. So, arrange two pieces of copper, brass, or aluminum sheet to be as far apart as the tape is wide, and use a piece of tape perpendicular to the edges of the gap to bridge the gap, and measure resistance between the two sheets of metal. This assumes that the adhesive is conductive.

If not, attach the tape to a piece pf plastic, put the piece of plastic tape-side-down on the two pieces of metal, and put a brick on the piece of plastic, ensuring that the tape is pressed into firm contact with the two metal sheets.

Alternately, paint stripes on the tape with shielding paint, and press the conductive stripes into contact with two pieces of bare wire.

[FunkyKikuchiyo]

Joe, those are great suggestions. My DMM is of mediocre quality, but I'm sure I could get something useable for my own purposes, if not lab quality.

What I HAD been doing is putting each piece of tape I wanted to test onto a clean scrap piece of steel, and I'd measure capacitance with my extech with one probe on the tape and the other on the steel. I figured the lower the capacitance, the better suited it is as a dielectric - even if it doesn't correlate directly to the actual dielectric strength. I have no idea if this method really tells me much of anything, but it gave me a way to compare several different materials that I was using, and it also seemed to match my results as I swapped things and just listened. I was also able to test a myriad of other materials besides tape.

[Joe Gwinn]

Joe, those are great suggestions. My DMM is of mediocre quality, but I'm sure I could get something useable for my own purposes, if not lab quality.

What I HAD been doing is putting each piece of tape I wanted to test onto a clean scrap piece of steel, and I'd measure capacitance with my extech with one probe on the tape and the other on the steel. I figured the lower the capacitance, the better suited it is as a dielectric - even if it doesn't correlate directly to the actual dielectric strength. I have no idea if this method really tells me much of anything, but it gave me a way to compare several different materials that I was using, and it also seemed to match my results as I swapped things and just listened. I was also able to test a myriad of other materials besides tape.

Hmm. What problem are you attempting to solve?

[FunkyKikuchiyo]

No problem in particular, I just would like to be able to have some way of comparing my options. Much of pickup design for me has been a matter of just making a series of small, seemingly insignificant decisions that can add up to something more pronounced. I've had enough experiences with varying qualities/characteristics of insulators in audio that I wanted to at least give it some thought.

In the particular case of my pickups, it is a steel blade core that is grounded, so I had imagined that capacitance to the core (and to ground) would darken the sound. I also use the tape as an outer wrap, but I haven't given much thought to smaller electrical properties for that purpose. I've been using the 235 for that because it is strong, looks okay, and doesn't goo up.

[Joe Gwinn]

In the particular case of my pickups, it is a steel blade core that is grounded, so I had imagined that capacitance to the core (and to ground) would darken the sound. I also use the tape as an outer wrap, but I haven't given much thought to smaller electrical properties for that purpose. I've been using the 235 for that because it is strong, looks okay, and doesn't goo up.

You are right that proximity to the grounded steel core will increase the capacitance of the coil. To reduce coil-core capacitance, a bobbin or a thick layer of tape is effective. In either case, the inner windings are spaced away from the core by the thickness of the dielectric. Capacitor - Wikipedia

You can measure the dielectric constant of the Scotch 235 black masking tape by building a simple parallel-plate capacitor, measuring the capacitance, and solving the p-p equation.

However, the capacitance of masking tape will probably vary greatly with humidity, so a plastic film tape may be a better choice.

[FunkyKikuchiyo]

However, the capacitance of masking tape will probably vary greatly with humidity, so a plastic film tape may be a better choice.

That is more or less what I ended up figuring out. It is reassuring to know that my piddling is consistent with normal electrical theory! I certainly wasn't going to count on wax penetration to do the job for me, and the various film tapes were amazingly good, even when they weren't as thick. Space is a huge issue for me, so a couple thousandths can really make a difference. I don't think the 235 was all that bad - I still use it for alnico rods - and its structural properties makes me want to always have it on hand for other things. It doesn't tear around corners, it stays down when you press it, etc.

[Joe Gwinn]

That is more or less what I ended up figuring out. It is reassuring to know that my piddling is consistent with normal electrical theory! I certainly wasn't going to count on wax penetration to do the job for me, and the various film tapes were amazingly good, even when they weren't as thick. Space is a huge issue for me, so a couple thousandths can really make a difference. I don't think the 235 was all that bad - I still use it for alnico rods - and its structural properties makes me want to always have it on hand for other things. It doesn't tear around corners, it stays down when you press it, etc.

The effect of humidity can become large, but the effect considerably lags the cause.

The issue is that the dielectric constant of water is about 80, while that of most plastics and waxes is more like 3, so if doesn't take much absorbed water to make a difference.

However, if the gap between coil and core is large enough, the resulting capacitance may be small enough to not make a big difference when it changes.

[Jim Shine]

A pharmacy can get it for you. It is literally surgical tubing. Last time I bought it that way, a good sized spool was about $35.