Insane Hydraulics
Bold and audacious blog about fluid power
So, a friend of mine came by the other day, and he brought "gifts" - a bunch of cylinder parts from an old Komatsu digger:
He was looking for new seals, and, of course, we were happy to help him with that, but as I was taking measurements of the o-ring and seal grooves - he asked me a question, and... this post was born. On a side note - whenever you need to determine a seal size, your best bet is always measuring the respective grooves/cavities and never the seals - that is... if you have access to the "hard parts", of course.
- Dude, how do you measure them internal grooves? You can't really stick a vernier in the gland, can you?
- Well, of course you can't! I have a tool for that, don't you have one?
- Nope!
- Great! Got fifteen minutes? Let me make one for you! All we need is a couple of bolts, and a piece of threaded rod:
You'll need a lathe, too (ideally). I can totally see how one could craft a tool I am about to show you with a power drill, an angle grinder, and a steady hand, but a lathe really turns this (pun intended) into a half-hour job! Let me show you how simple it is. And please, note that I mention dimensions merely "for the sake of completion" - they are absolutely arbitrary, it's the idea that counts, and, quite obviously, there are about a thousand ways it can be changed or improved.
In this particular case, I have a couple of M10x60 bolts and a piece of an M6 fully threaded rod. First, I rounded the hex head of the bolt to the diameter of 16 mm and then cut it down to a width of about 1.5 mm:
Then I drilled a 5-mm hole through the bolt, cut an M6 thread about 20 mm deep, and then turned the bolt around and drilled a 6 mm hole 45 mm deep - thus leaving about 15 mm of M6 thread on the other side:
Finally, I made an equal "nail-head" on the second bolt, drilled a blind hole about 20 mm deep, and also cut an M6 thread into it. Basically, I ended up with something like this:
I also made an improvised locking nut from a piece of another M10 bolt (totally optional). As for the assembly - I tightened the rod into the "blind hole bolt", threw on the "through-hole bolt" and the locking nut, and got the following contraption:
As you can see, this is basically a linear caliper, and here's how you use it - you slide the brims into the groove you need to measure, open it up by turning the through-hole bolt out till it's tight in the groove, secure its position with the locking nut, and then pull it out and measure the width with a normal vernier:
I do know that things like internal groove micrometers (and other specialized tools) exist, but I still defend the idea that every shop should have a tool like this one. It is easily replaceable, its length is limited only by the size of the rod you manage to source, you can use it to "caliper" other stuff (blind holes, for one), it takes about half an hour to make and literally costs cents - and last but not least - there's no such thing as "too many tools!"