Using a 3-jaw and soft jaws to cut eccentric shaft.

[thehomeengineer]

Hi All
This is a really easy way to cut an eccentric shaft with little effort. No difficult clocking of a 4-jaw to get the correct throw. But you do need a 3-jaw that can be fitted with soft jaws.

This is the method I use:

D1-4 Milling auxiliary plate used to locate the 3-jaw while machining the soft jaws. This is clocked to get the spindle concentric to the plate. Once concentric the table is moved to the desired off-set. (You do not need the auxiliary plate just clamp your chuck to the mill table and clock)


Using an end mill, the same size as the shaft diameter to be held is used to cut the jaws. The jaws are moved in using the chuck key and the end-mill is simply raised and lowered using the quill like a drill to cut the jaws. The jaws are moved in a small amount using the chuck scroll after each cut until there is enough of a diameter cut in to the soft jaws to hold the shaft diameter.


With the chuck remounted in the lathe the eccentric diameter can be machined. The photo shows the first few cuts made.


Eccentric diameter machined to required diameter. This photo also shows the offset diameter machined in to the soft jaws.


Completed shaft


Safety Note:
Normally when machining soft jaws in a lathe it is recommendable to place a piece of bar or a ring in or around the jaws and tighten. Two reasons for this, the jaws will be held secure to ensure good finish and accuracy. The second and most important if the jaws are not tightened against anything and the chuck is started at high speed the scroll can release the jaws and potential you could have three missiles whizzing around the workshop. This is especially common on old badly worn chucks. The chuck rotates but the scroll doesn’t keep up and the jaws can be released. This is not just soft jaws. So never start a chuck at high speed when there is nothing clamped in the chuck.
Forgive me if I am telling you how to suck eggs.
The Home Engineer

[DIYer]

Thanks thehomeengineer! We've added your Eccentric Shaft Cutting Method to our Machining category,
as well as to your builder page: thehomeengineer's Homemade Tools. Your receipt:

Eccentric Shaft Cutting Method by thehomeengineer

tags: machining, chuck

[Wmrra13]

Great tip, thanks!

[philipUsesWood&Brass]

Thank HomeEngineer, and your small SAFETY Tip: My Opinion is Safety First can not be OVEREMPHASIZED.

philip, from the Great Pacific NorthWET.

[Toolmaker51]

Personal Safety is a far more 'local' endeavor than versions administered by departments, agencies, etc. Not hazards like those of chemicals, loose electricals, etc that can transpire hidden from view.
When inspectors [often without physical background in a trade] make judgements; tainted by their own apprehensions more than what I might call probability.

I'm usually comfortable working mill/ lathe/ drill without safety glasses. One single occasion with a lathe, roughing journals on 6" Ø 4130 very heavily, threw perfect wide blue chips, a fairly consistent arc landing 6-8 feet away. Put on good wrap-around safety glasses. A few would deflect, projecting them wildly.
Caught one between left eyelid and brow. Sizzled a few seconds. Ouch.
Instead of bouncing off and being little more than an irritation, lens & frame HELD IT IN PLACE. I knocked glasses off, cool water released the chip easily.
Oh thanks, Mr. Administrative Oversight and concern of increased insurance premiums. I should have saved the chip, bronzed for display in your cubicle.

I self treated first aid; eye cup+boric acid. Part of being a 2X veteran [45+ years machining, 26 USN] our tendency to remain cool-calm-collected.
You haven't lived until crusty pus of seared skin takes 10-12 days to clear itself up. Kept it clean, washing it frequently. No scar, no impact on vision.
And no more prescription 'safety' glasses.

to Philip, from the Great Pacific NorthWET. Lol. I spent time stationed in your North Wet; calling it "World's Biggest Carwash". Had until then never seen such deluges, even here in the Midwest rarely in that scale.
For those unfamiliar with Cascade Peninsula, its rightly called a rain forest. Quite different than what's close by to their east!

[TSiArt]

As Mike Row (I think he said it) and other people say "safety third".

Toolmaker51, It could not have been said any better. And i had similar situations with glasses and eye balls but no burning flesh yet. I can't stand wearing them cause I'm limited with those horse blinders on what I can see and I almost walk into people before.

[philipUsesWood&Brass]

Personal Safety is a far more 'local' endeavor than versions administered by departments, agencies, etc.

>>> To Consider my concern for Personal Safety, I only suggest looking at my Avatar ! ! ! <<<

to Philip, from the Great Pacific NorthWET. Lol. I spent time stationed in your North Wet; calling it "World's Biggest Carwash". Had until then never seen such deluges, even here in the Midwest rarely in that scale.
For those unfamiliar with Cascade Peninsula, its rightly called a rain forest. Quite different than what's close by to their east!

Toolmaker51, YES, Washington has an Official RAIN FOREST, just not a "Tropical" one!!!! I once camped out on the North tip of the Peninsula, in a VW Bus, We had to stake it to the Big Trees, to keep it from Rocking in the WIND !!!!

I had lived up there for several years, before I heard one kind of RAIN described as "A Light Oregon Mist, MISSED Oregon & HIT us" ! ! !

philip, in the Calm Today, Great Pacific North WET

[Okapi]

Thank HomeEngineer, and your small SAFETY Tip: My Opinion is Safety First can not be OVEREMPHASIZED.

philip, from the Great Pacific NorthWET.

Philip, I'm not a wood turning specialist but working under the supervising of a specialist with some toxic woods, I've a good solution for you, the poly-carbonate helmet which makes you another idea for your avatar.

[philipUsesWood&Brass]

Yes, that could work ! ! !

And if I painted some of it I could use it for a "Robot Costume on Halloween, If I "did Halloween!!!!

I am kind of hooked on my "design though: those Safety Glasses are "covering" Prescription lenses, so I can insert colored leses for silver soldering, or stay clear, My NEXT step is to add in an LED Light that will focus at approx. 18 inches for extra light when needed!

I like that hood though!

thanks!

philip

[Okapi]

I've found a very good use for that protection at the metal lathe, when working with some brittle brass, you have small chips in ears, eyes coming from behind your glasses and in your clothes, with that item you just have some in your slip…