Machining for Hobbyists-Getting Started

July 29, 2015

Surprisingly complete and easy to understand book that can be used to supplement training on the job for beginners, and a nice reference for those with a year or so on the job. Machining and measurement principles and techniques clearly explained.

A nice easy to understand supplement for newcomers to machining.

A nice easy to understand supplement for newcomers to machining.

I was genuinely surprised  to find some really great nuggets like “the Basic Nomenclature of Measurement ” which clearly defines:

  • Nominal size
  • Allowance
  • Limits
  • Tolerance
  • Basic Size
  • Unilateral Tolerance
  • Bilateral Tolerance
  • Precision
  • Accuracy

…in just a little over a page.

Nice graphics, sample calculations, and well done explanations on how to read a micrometer, vernier, as well as tables with feed and speed data for various types of materials for specific machining operations. very focused coverage of the essentials of the topics.

Do not confuse this book for a hobbyist project catalog.

This is a very clear and understandable text that explains the “how, why, and what” of machining and the use of  tools of our craft.

Nice photos too.

What I like the most is how the author really distills the information down to useful essentials. And makes them understandable.

 


5C Collets Are Cool- Somma Tool

February 15, 2012

In order to machine precision parts, you need to first hold the workpiece securely, accurately and precisely. 5C collets do just that.

5C collets are the result of 100 years of continuous improvement.

Work can be held using methods other than collets- 3 and 4 jaw chucks come to mind, as well as vises-  but for continuous high volume work with barstock, collets are ideal.

Here are 7 reasons Somma Tool says 5C collets are cool:

  • Collets are easier (and faster!) to set up than chucks.
  • Collets are more concentric. With chucks, tolerances stack up degrading concentricity.
  • Collets more affordably provide higher precision.
  • Collets more affordably provide higher accuracy.
  • Collets provide high holding force. As the collet is pulled axially into the bushing, the tapered sides compress radially generating static friction (holding force).
  • Collets are versatile- they can be made to hold over capacity stock; they can have steps built in; come in extra long sizes as well as have internal stops.
  • Emergency collets are available that can be custom bored to your exact need.

Hardinge invented the 5C collet back in 1901. It became a preferred choice for precision workholding in lathes, mills and grinders. Exacting standards, special alloy steel, heat treatment and spring tempering combine to assure accuracy and durability at low cost. The 5C collet became an industry standard. 5C collets range from 0.5 mm (thats 0.0196″ ) capacity to 1-1/16″  round; 5C collets hold up to 3/4″ square and and 29/32″ hex.

PMPA member Somma Tool sells 5C collets from Hardinge.

Thanks to Matt at Somma and Tom at Hardinge  for teaching this ‘steel guy’  7 reasons why 5C collets are cool.


Speaking of “Resolution”

December 1, 2009

Our industry works with some pretty amazing resolution and precision as our stock in trade. There are shops that look at tolerances in thousandths of an inch  (0.001″) . The thickness of a sheet of copy paper is around 0.003″,  and so a shop that can hold “half a thousandth,”  is saying essentially, that their total variation is on the order of one-sixth of the thickness of that sheet of copy paper. One-sixth of the thickness of a sheet of paper!

Some of our shops look at tolerances in terms of microns- that is millionths of a meter. A human hair can be anywhere within the range of 50- 120 microns, the average hair is probably  somewhere around 100 microns.

This means that the micron-calibrated  folks are measuring at precision levels that divide a human hair in about a hundred thicknesses, and a meter in millionths. That’s pretty impressive.

So I ran into this item  talking about about half a meter resolution, and I said, “Half meter resolution. Woo hoo- what’s the big deal? Thats no big deal.”

And then I saw what half a meter resolution looks like. From 684 kilometers (call it 425 miles ) up, taken while moving 7.5 km/second (thats 17,000 miles per hour, more or less.)

This is nothing compared to the photo on their site use the link below.

From Geoeye-1:  The Dubai Air Show. (Go to this site, and keep clicking on the picture until you see it in all its glory.) Want to see the Hoover Dam?

So while I continue to be impressed by the accomplishments of shops whose tolerances are anywhere from say a third of the thickness of a sheet of paper to one one-hundredth of the thickness of a human hair,  I have a new found respect for the resolution of, say, half a meter.  And I think we’ll all certainly be a bit more careful when we’re laying out by the pool…

So what is your best “resolution” or tolerance that you can hold, or held, under any circumstances? We’re looking for your stories, so drop us a line.

Satellite Imagery from Satellite Imaging Corp.

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