bench vise valve spring compressor psi checker, accurate?

how accurate are they & which one should I get? thank you for your time.

they can vary with ambient temps. use a "checking " spring for comparisons. I use one for my little stuff but wouldn't consider one for any serious race stuff.

Used to sell one that was accurate within 1%. They're made by an old funny car racer friend of mine. Bench-tested every one. He also sells 'em to Summit, Jeg's, maybe Speedway, which they re-brand as theirs.
You can PM me if you like for his phone #.

the one I have is the 300lb version and was bought thru Powerhouse (comp cams). have no idea who makes them.

The one I have is way off

There are only two realistic factors for accuracy (or not).
What you're looking at is a piston in a cylinder exactly 1.00 square inch in area, and a pressure gauge. Both have to be accurate and if they are, the device is accurate.

As it is much easier to produce a cylinder that is 1.000 square inches, the major source of inaccuracy is the pressure gauge. SO, if the pressure gauge is accurate to within 1%, that is what the device's accuracy is, as well. If one wanted to be idiotic, the distance the centerline of the gauge is above or below the centerline of the cylinder counts too, but it is usually much smaller than the gauge's inaccuracy.

IMHO it is much easier to be inaccurate about measuring the distance between the vice jaws than any other part of this process. If one wishes to be super accurate buy a super accurate gauge and have it calibrated by a deadweight tester traceable to the National Institute of Science and Technology, before the series of spring tests.

There are other less accurate ways to assure accuracy.

R.

The Proform tester I bought was JUNK. The one I bought from topside some years ago is consistent and pretty accurate, based on what my calibration spring and other "known quantity" springs read.

LSM
Not cheep but great tool

A friend bought one of the Proform bench top units that uses the hyd cylinder with the pressure gage on it.
Brought it down to the shop and we checked it against a PAC calibration spring...... it was waaaay off.

It got sent back.

pretty sure the one I have is some kind of liquid filled. reads high at cooler temps. at room temps it's pretty good. I think it does better if it's "cycled" a couple of times before taking a final reading. they're not professional quality by any means but for the guy messing in the garage on stocker type stuff they're ok. the "test" spring that comes with them is a helps.

Damn! I think I might try a bathroom scales in a drill press! (I read about that once).

you just have to keep in perspective what your buying. if you want $1000 performance then your not going to get it for $100. as a tool the one tester I have has helped me a lot but I respect it's limits; and, (just an opinion), I think the 600lb one is silly.

Exactly

They are easy to screw up if you try checking coil bind. Forgot to remove pressure gauge before checking coil bind height and over ranged the gauge.
Might have to get a load cell like:
https://www.omega.com/pptst/LC302.html

I would never try to check coil bind with one of these gauges.

One of the tricks is the oil type & volume; that took some figuring out. The reject rate on the gauges themselves varied, but sometimes 30% were off more than the 1% benchmark we thought acceptable, or they didn't give linear/progressively accurate readings.

I found that the readings on the gauge I have match up very well with the advertised numbers (when I can find them) for the assortment of springs I have. as I've said, I only use this tool for single springs for my driver type stuff. for me it's a useful tool, but it's not a substitute for the professional type testers.