DIY - Micro Polish Your Crankshaft At Home

[Jeff Rice]

http://www.enginelabs.com/news/video-do ... polishing/




(copy)
Here’s a resourceful DIY engine builder who found some scuffing or discoloration on the factory Mitsubishi crankshaft in what appears to be a 4G63 4-banger. Instead of taking the crank down to the machine shop for a polish, he rigged it up in the block using the two forward main caps for support. After a trip to the local home improvement for tape and scrounging micron paper from his shop, he hooked up a big drill and polished the crankshaft by hand. The journals clamped under the main caps were freed up when the crank swapped ends.

The results don’t appear harmful, and the poster says he mic’d the journals. A little bit of searching on the web revealed it’s not all that uncommon to polish a crank in a home shop. EngineLabs found photos on a Toyota forum with a crankshaft stand made from plywood and a bow for the sanding belt made from a yardstick. Again, a drill was used to turn the crank.

Never overlook the ingenuity of engine builders!

Here's another example of DIY crank polishing on top of the workbench. The bow for the polishing strap was made with a yardstick.

[Bill Van Alstyne]

I saw a video about 5 years ago with a guy doing this in his back yard on a small block chevy. It might be ok diy, but I think I'd have a machinist in a shop take care of mine. Bill

[Jeff Rice]

I micro polished the crankshaft when I freshened up the engine in my 1938 Allis Chalmers B.
Put the crank in a 1938 Atlas lathe.
That was 18+ years ago.
Tractor is the most reliable thing on the property.

Just thought it an interesting method.

[PackardV8]

Your opinions and results may vary, but IMHO, precision crank polishing comes under the "Kids, don't try this at home."

I'm regularly in the shop of a large rebuilder who turns out several engines a day. They stopped belt polishing and spent the bucks for a new K-Line micro polisher because even their experienced professional crank guys couldn't hold a consistent finish and dimension with a belt.

Micropolishing machines use a polishing tape backed up by a rigid shoe instead of a flexible belt. Belts are always removing material and there's nothing to control taper. Typically that amount of material a belt removes can be small, but what it did is an unknown until the crank stops turning; if too much or tapered or crowned, that extra material removed can't be put back. Of course, some material has to be removed to achieve the correct surface finish, but less is more. With micropolishing only taking off the microscopic peaks and getting down towards the valleys, and the more peaks removed the more surface area. Another misconception some users have is they think they can put a polishing belt on a crank and because when finished, it's prettier to the eye, they are making it better. Some people think making the part shiny is enough, but it probably then has taper, crown and who knows what else. Even if it is within a couple of tenths, the error is still there. That’s why micropolishers back up the tape up with a rigid shoe; a setup that can’t introduce taper, crown or remove too much. When a journal is done, it's still round, flat and on dimensional spec; there's no chance of operator error.

A bit of irony, is the finish from belt polishing looks shinier to the eye. The shops using the K-Line tape micro polisher have to sell the customer on improved dimensional control, because the journal isn't as bright and shiny.

jack vines

[Jeff Rice]

Good info...

[Jeff Rice]

Here's a thread where you can share your little shop tricks and tips......

[Jeff Rice]

My wife Carrie is a genius. She gave me a long pretzel container a few years ago that has become my wire tie holder. Then she gave me a grated Parmesan cheese shaker bottle. Cool! You can just shake out a wire tie! Then she gave me an even smaller grated Parmesan cheese bottle. So, this morning I decided to separate the wire ties by size. Look at what was in the bottom of the pretzel (wire tie) container ...





Ok... But a potato chip?

[Bill Van Alstyne]

Playing with your toys can make you hungry, and I've seen your stash!!! Good idea for the wire ties. By the way, did you ever get the valves etc. I sent you? Bill

[Jeff Rice]

<snip>By the way, did you ever get the valves etc. I sent you? Bill

Look at the USPS box just to the right of the small zip tie bottle... That's your stuff..

[Jeff Rice]

I am taking an online welding class.
So far it has been great!

https://youtu.be/5nKMycSjraY

[Bill Van Alstyne]

Kind of a cheesy way to weld, but maybe your welding will look like his now!! Looks so simple. Bill

[Jeff Rice]

Made up a little gauge tool for the R2 valve springsmthis afternoon...
Simple thing....



Each side has a specific length, and the numbers were stamped it in so it would be remembered...
It is used with this hydraulic valve spring pressure gauge.
Made up a round anvil piece to go in my Dad's old drill press (s#!tty weld and all)...



Now you just slip the spring in, and read the pressure gauge at each measured point.
You find out real fast when a spring is shot.
(Am going to turn the OD of the anvil down to match the diameter of the pressure tool)

[55commander]

nice an simple but effective

[SilverHawkDan]

I like it. Today I got to experience first hand how having everything in the shop on wheels pays off. Did a bunch of cutting, drilling and welding. Did it outside by the wall. When I got done I blew off the drill press, cutoff saw and saw horse making sure to direct the chips at the wall. Pooled everything inside and then just swept up the chips and dust and threw it in the trash. So nice to not have to clean up half the shop after a work session. I even have a plan for days it is too cold or wet to work outside. I am really loving the new shop. I will take some pictures of the set up Robin and I came up with so everyone can see it and maybe use some of it in their shop.
Dan

[Jeff Rice]

Here's a lil' video of the dimension plates being used to check valve springs on a Stude V8 engine.