Bifurcated tool for crankshaft turning

[vcutajar]

Hi

I am in the process (planning) of making the crankshaft for my single cylinder Westbury's Kiwi. This is going to be my first crankshaft ever. I had a good look at George's crankshaft tutorial (http://www.homemodelenginemachinist.com/index.php?topic=5673.0) from where I got some good ideas. I need to make the bifurcated tool for turning the crankpin (12.7mm long) which both George and Westbury mention.

I have a never used HSS parting tool with a 5mm cutting tip (see photos below) and was wondering if this is an ideal candidate to transform into the bifurcated tool. Any ideas?

Thanks in advance.

Vince

 

[arnoldb]

Hi Vince

That should do just fine for the job - as long as the thinned section is long enough so that the thicker bit of the tool won't catch on the webs while you're machining.

In fact, George mentions that his is made from a parting tool.

Just a bit of grinding and you should be good to go Thm:

Kind regards, Arnold

 

[vcutajar]

Thanks Arnold.

Yes, I forgot to mention that it has to have a reach of at least 1.25" to clear the webs.

 

[tornitore45]

I just finished yesterday a crankshaft using a bifurcated tool.
Observation 1 The tool width must be less than 1/2 the bearing length, this is obvious now but not on the first try.

Observation 2 The resulting 2 cutting edges must be at the same level horizontally.

To be sure I left the QCTP cube loose and scrathed lightly on a suitable surface noticing one mark instead of two.

You advance or retract the cross slide while pressing lightly on the QCTP by hand. This results in a small controlled rotation of the QCTP. Repeat until at the slightest pressur you see two scratch mark. This indicate you are working with both tips.

Finish was so good tha only a bit of wet and dry polish made it shine.

I cut a popsicle stick and a strip of paper to size and run the late in reverse, is easier to keep the popsicle stick centered and you go out of alignment it just lift instead of jamming.

 

[vcutajar]

Thanks Mauro for your notes on using the tool.

I cut a popsicle stick and a strip of paper to size and run the late in reverse, is easier to keep the popsicle stick centered and you go out of alignment it just lift instead of jamming.

I could not understand your last sentence.

Vince

 

[tornitore45]

I could not understand your last sentence.

Vince

After finishing to cut the journals (the eccentrics where the connecting rod goes) you may need to polish to size and a fine luster to reduce wear.
So you spin the CrankShaft on one of the offset center and are supposed to place a strip of abrasive paper righ in the middle of the revolving crank, not an easy thing to do.
If you are angled the least bit the crank slams you down catching the paper strip.

By turning the lathe backward, when you deviate off angle, instead of catching hard it simply lifts the paper and popsicle stick gently and as soonas you correct the abrasive falls back in the groove (so to speek).

The wooden stick is pinced between the srip of abrasive folded over the stick.

I hope this explains it, but if you keep it in mind it will become clear as you go an work on the lathe.

 

[vcutajar]

Thanks Mauro

Now it makes a lot of sense. Did not know that. Thanks for the tip.

Vince