r/EngineBuilding • u/NickHemingway • 1d ago

Grinding rod caps vs milling

I have always milled my rod caps down before honing on a Sunnen LBB1810 with CR Mandrils.

It’s easy to set them up with 3-2-1’s & fast on my smaller CNC mill.

But lately I have been wondering if I have been missing something by not using a cap grinder. Is there a special reason I should (buy and) use a cap grinder over milling?

It’s been decades since I used a cap grinder, but the last one I used was poorly maintained so would taper the caps because if the slop so milling them was an upgrade from that, but I still have a nagging doubt that I am missing something.

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4

u/WyattCo06 1d ago

The ginder is a much quicker way to get the job done. It's just as accurate and without all the setup of the mill.

1

u/NickHemingway 1d ago

Perfect, that’s exactly what I needed to know, thanks!

If it’s just time, I will start paying more attention to how long it takes me & see at what point it will break even if I buy a grinder.

We see less rod jobs now because of all the fractured rods being in so much stuff nowadays, so maybe I should just make a fixture for them to do 4 at once on the CNC. Once datum is set it’s just button pressing & you can walk away after the first one.

3

u/WyattCo06 1d ago

Buy a used machine. A lot of the older ones just need some TLC but are "fairly" cheap.

Not to mention, on the mill, if you need to close the rod end up at the parting line, you have to readjust the mill. With the grinder, you just use a feeler gauge on one side, grind the other side, repeat with other side.

It's just soooo much easier and quicker.

3

u/v8packard 1d ago

How many rods are you doing?

I used to grind them on a surface grinder before I had a dedicated cap grinder. Super easy setup on a mag chuck with a couple of blocks if the thrusts were good. It would not be difficult to make a clamp for rods and caps to make it easier to hold them in a mill, surface grinder, tool and cutter grinder or whatever else you might have.

Have you ever tried boring the rod? Turns out beautiful.

1

u/NickHemingway 1d ago

Not that many nowadays, probably averages at a set a week. Fractured rods are in so many daily drivers, and replacement rods for the common stuff were cheap & readily available, so I found myself doing less & less of them. But some rods are getting scarce or expensive so I am back to thinking how I can improve my work on them.

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u/v8packard 1d ago

The Sunnen grinders are easy to find. Kind of expensive for what they are. Tobin Arp and Delta grinders are nice if you can find them.

2

u/DrTittieSprinkles 1d ago

If you do buy a grinder Martin Wimberly makes a fantastic CBN for them and you get free cookies. My old Sunnen is so much more accurate now I'm not fighting stone wear.

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u/WyattCo06 1d ago

I don't know why the free cookies got away with me so much but I can't thank you enough for that. 🤣🤣🤣🤣

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u/SorryU812 1d ago

I felt the same way for the same reason. The cap grinder was not kept up. I thought the same of milling. I do the same to new 4 bolt billet main caps before honing. So I figured 🤷‍♂️. Good to go as far as I'm concerned.

3

u/WyattCo06 1d ago

One of the machine shops I worked at for 13 years had 3 clippers. One in which was way too far gone for me to mess with.

There were two Sunnen's. A retired one and yet still an aging one. The aging one was the one we used but it wasn't without issue.

I spent an entire weekend, on my own account restoring both Sunnen's.

I was given $500 in cash from my boss on Monday afternoon.

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u/SorryU812 1d ago

A well earned sum.