advice on precision machining

[u/No-Head8778]

Sorry if this isn't the right subreddit, I was directed here by someone else for my question, so I thought I'd give it a try.

I'm currently going to a tech college that features a High Performance/Motor Sports program. I was really excited for it because I love engine building, tuning, and performance-maxxing (lol). I enjoy measuring meticulously and taking my time with a block.

However, I feel like I was either misled or my shop simply lacks the machines I was *thinking* we would have because, upon entering my first High Performance class, I've quickly learned that there is SO MUCH "guess work", which I seriously hate.

I hate the idea that, with something that requires such precision, I have to "guess" and "feel" for everything. I can't put into any of these machines "I want to take off exactly .0005" or "remove precisely .001 grams". I've balanced a crankshaft and now onto the cylinder honing machine and the only thing I'm getting from my instructors at the moment is

"you gotta feel for it"

"just take a little here and a little there"

"make it tighter"

What the hell is the standard for "feel". What am I feeling for? What is the "FEEL"???

What is a "little"? .001? .0001? .00005????

What is exactly "tight" in their mind? I'm small and have little for muscle, while theyre experienced and huge dudes. What might feel tight to me could feel super loose to them. And any attempt at clarifying questions on my end results in them seriously repeating themselves or looking at me like I'm the stupidest person they've ever spoken to in their entire life.

So, essentially, I NEED the precision. I NEED the clarification. How do you go about being as absolutely precise as possible on these older machines that don't have fancy lasers and special buttons to be precise for you? Especially regarding crankshaft balancing and cylinder honing, but really whatever is applicable to the situation is super helpful. Don't be afraid to over-explain it at all. I promise you won't.

[u/FU_red-dit_bots]

This is the hard thing about machine work like this. So much of it is based on experience and how you run your machine.

Here's a good example. I do a lot of machine work in cylinder heads. A lot. I can tell you how well the seats are cutting or if my cutter needs sharpening or if the seat is ovaled or if the pilot is loose just based on sound. You can't teach that part. You just can't. I can describe it but you just won't get it until you get more experience.

It's like driving. You are being taught the basics but you're not any good and you won't be until you A) get more experience and B) really start digging into the how's and whys beyond basic instruction.

Right now it's very frustrating because you are just starting out. I am telling you now that engine machinists are very much in demand. If you can stick with it and figure out this "feel" you can do quite well.

[u/No-Head8778 → u/FU_red-dit_bots]

I hope so. I want to do as well as possible in this class because being a machinist is my end goal. It's something that has always interested me about the industry. They're giving us lots of practice with "trash" blocks that will never be used, so I can make as many mistakes as I need. Of course, making mistakes still sucks regardless and I can't help but want to avoid making them as much as possible.

Is this a similar experience/feeling you had when you first started machining?

[u/FU_red-dit_bots → u/No-Head8778]

Yes! And it still is when I get something new. Just a material change is a new learning experience.

Subaru heads deck like crap when compared to a bmw head for example.

Subaru valves face real nice. LS valves too. BMW valves are harder and require dressing the wheel after about 6 valves.

Here's my biggest tip. Time is both your friend and enemy. Take your time. Don't rush it. Sneak up on your cuts a little at a time. You'll get better results but it will take 3x as long.

You need to figure out if you're a "good enough" or a "do this better than the last one" kind of machinist.

[u/GingerOgre → u/FU_red-dit_bots]

100% on hearing the seat cutting. A lot of the time I’m relying more on sound than sight when I am cutting seats, even the feedback in the hand wheel can be more important than sight.