Finishing crankshaft Journals

[Basil]

Moving along with my Seal Major 30cc build. I have the crankshaft partially machined and the journals oversize. I am not sure what steel is supplied with the hemmingway kit but it is good and tough. I am machining on a small Myford. Is there a specific carbide insert which works particularly well on finishing the Journals? I have been reading that Carbide tools designed for aluminium are sharper and can produce a better finish when used with light cuts. The carbide tools pictured appear rounded. I am looking for something that might give a better finish before I dive in on the critical cuts. Thank you.

 

[teeleevs]

Your crankshaft looks long and spindly, you can setup a toolpost grinder using a small angle grinder, this will avoid the cutting forces pushing things out of line, finish off with finer and finer grades of emery tape. Should be fine. Ted from down under

 

[Basil]

Thanks Ted. It's not too bad as far as rigidity is concerned and I was looking at turning with maybe a modified carbide parting off tool. The more I think about it though I'm going to go with your suggestion and give grinding it a try, first oversize to see how it works out. I also will be making the cam soon and grinding could work very well for that. On ordering up grinding wheels would you go for a wheel that is the full width of the Journal 1/2" or something narrower? I do have a few diamond truing bitts I picked up years ago. Should I look at different grits? I have a couple of angle grinders also. Thanks again Ted

 

[teeleevs]

Hi Basil, the 2 gears for this oil pump came out of early Toyota Crown Wagon rear window winders, they were about 2 inches long and hardened steel. My friend Gil has a 4 inch angle grinder setup for toolpost grinding and it works magic with a very thin disk, just worked back and forth over the area, didn't even need to polish up after.
Thanks for the inquiry, Ted

 

[Basil]

I have just ordered this 125x5x30 Surface Grinding Wheel Model Tool Post for Hard Steel Grinder White | eBay . I also pulled this from my box of old past projects. I've been down this road before! About 25 years ago when I ground this up. The plan was to build an inline 4 from OS FS20 parts. Got busy with work and had to put it to one side. I plan to finish this build (God willing ) . I am aware you have to be very careful around unguarded grinding wheels. They're scary things.

 

[gpcoe]

A VCGT type insert is probably best if you're looking for sharp grades. There are various types available. I have used the C shaped variants for finishing stainless without trouble. Like you mentioned, light depth of cut. They are like razors and should be treated delicately.

 

[Basil]

From the images they do look very sharp. Thanks

 

[Richard Carlstedt]

For really good journals, you may wish to "Superfinish" them
https://en.wikipedia.org/wiki/SuperfinishingI did this on my crank and the finish is superb.
I used a old Remington electric razor found at a junk shop and modified it.
The thing you want is free and fast vibration ! the wooden block is a snug fit for the medium India stone (300-600) and the stone should be narrower than the journal as the vibration is not only forward and back, but a sideways movement as well.. add Oil and after 30 seconds of light pressure on a rotating crank you get great finishes ....and low friction..invented by Chrysler 90 years ago
You do not have to glue it together, the wood block has a tight fit on the prongs and my fingers hold it in place during work. I think any vibrator would work..and OIL ! ( not shown for clarity )
Rich

 

[Basil]

That's very interesting! So your creating an orbital action and with the part rotation ending up with what could be described as a type of crosshatch finish instead of a linear finish. Many thanks. I'm learning lots here.

 

[teeleevs]

Wow we learn something new every day

 

[rickhann]

Neat! I use an old electric tooth brush to lap in valve seats on my engines. Just make a flexible coupling using a short piece of vinyl tube between the tooth brush shaft and the valve stem. A few seconds later and "Bob's your uncle!"