Old timer at my shop swore by coolant concentration strips, I thought he was nuts

Guy named Frank with 30 years on a Bridgeport told me to use those titration strips instead of guessing by feel. I laughed it off for months until I wrecked a $400 end mill on a 304 stainless job in Houston. Turns out my coolant was way too weak, strip test showed 3% instead of the 8% I needed. Anyone else get humbled by a simple tool they ignored?

3 comments

3 Comments

the_jamie1mo ago

Titration strips... yep, been there. Had a coolant tank that looked like swamp water and my parts kept coming out rough, spent a week blaming the inserts. Finally grabbed some strips from the Snap-On guy out of desperation, turns out my concentration was at 2% on a system that needed 9. Made me look like a real genius running 4140 at those speeds. Frank was probably laughing in his sleep knowing you'd come around eventually.

the_max9d ago

Hang on, did you just say you ran parts at those speeds with a coolant concentration of only 2%? That's wild, man, I'm surprised you didn't weld the insert to the part halfway through the cut. I've made plenty of dumb mistakes myself, but that one takes the cake.

henry_martinez1mo ago

Funny you mention the Snap-On guy, those strips are overpriced as hell but they work. One thing though, I think you might be mixing up your units there. Most coolant concentration is measured by brix refractometer scale, not percentage like a battery electrolyte. A 2% reading on a refractometer would be basically tap water. Probably meant 2 brix when you needed 9 brix which makes way more sense with 4140. Still, you ain't wrong about the swamp water. That stuff gets nasty fast when the concentration drops off.