How to fix a statistical measure to analyse my data?

Hello everyone,
This is my first time posting here. So I am a Chemical Engineer working on quantifying the strength of my materials. Basically I synthesise beads and press the beads using a piston and see what load they are breaking.So for each sample I'll repeat the test 20 times, and note down the load for each run. I'll calculate mean and the standard deviation for each sample.

My question is what statistical measure I use for analysing my data properly? I do the same test using two different instruments, I need to compare the data between these two machines. I need to quantify the following things for each sample in each instrument -
1. Repeatibility
2. Accuracy

My aim is to use this statictical measure to screen the samples, right now I was using S.D/mean percentage, and if the S.D/mean percentage was coming above 20 percent I would ditch that sample, saying there is too much variation in strength of individual beads. Is there any other measure that I can use that will be more effective for my task?

Sorry if my question sounds too vague, I don't have much working knowledge of statisics other than the basic highschool level knowledge.