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View Full Version : Setting a Precision Taper Without a Master or Angle Blocks



Andre3127
12-02-2016, 04:01 PM
https://www.instagram.com/p/BNcvb9oBMT_/?taken-by=andre_shop3127

Using a parallel bar indicated true to the lathe longitudinal axis, I set my compound to a very precise angle without the need for a standard or reference taper. Using known angles, some trig, you can compare compound rest in-feed distance to indicator reading to calculate your angle. I won't bore you with the math, but one thing to note is you need to make sure the indicator spindle is parallel to the test bar, and it needs to be re-squared after every adjustment of the compound.

I used this to turn a #7 brown and sharpe taper for a collet block. The taper turned out perfectly.

Mike Amick
12-02-2016, 06:30 PM
So what you are saying is ... HERE is another way to cut a taper.

But .. HERE is going to remain a little bit of a mystery.

I promise .. I won't be bored.

Andre3127
12-02-2016, 06:36 PM
So what you are saying is ... HERE is another way to cut a taper.

But .. HERE is going to remain a little bit of a mystery.

I promise .. I won't be bored.

Does this help?

http://i.imgur.com/rIGffcm.png

Math is simple. Find specs in taper per foot, then divide your numbers into ones that can be handled on your lathe. For instance...

.5" included taper per foot is the standard for (most) Brown and Sharpe taper tooling. Divide it in two, since we only turn one side of the taper, for .250" taper per foot. Now divide that by 12 to get taper per inch, then multiply by however may inches your compound slide can travel without binding. In my case, 2" before I got tired of cranking (and was the length of my taper)

So, for 2.00" of compound infeed I needed my dial indicator to read ~0.0415" to be set to a theoretically true taper.

Paul Alciatore
12-02-2016, 10:01 PM
Back in the Jan-Feb 2009 issue of Home Shop Machinist I authored an article titled "Setting Up Accurate Angles - Inexpensively". You can see it here.

https://www.dropbox.com/s/6hx2gq491h6c7zn/AngleGauge.doc?dl=0

In it I explain how a set of angle gauge blocks can be used to set up almost any angle, with accuracy. It includes the use of the same principle that a sine bar operates on but you do not need to have a sine bar or gauge blocks. I substitute lengths of wire or drill bits that can be precisely measured with a micrometer for the gauge blocks. However, it does involve some math so a scientific calculator will be useful (or Excel). And it includes a discussion of how to calculate the accuracy that you can expect with the method so you are not flying blind.

Mike Amick
12-02-2016, 10:02 PM
A while back I asked how to find the location of a third bolthole. nonsymmetrical pattern. It went on for a day or so
with people saying it was easy ... but .. failing to actually explain how. Finally someone posted a really neat
diagram explaining exactly how to do it.

I printed it out and saved it ..

Now I will add this one to it ..

Thanks Andre

Andre3127
12-02-2016, 10:30 PM
Back in the Jan-Feb 2009 issue of Home Shop Machinist I authored an article titled "Setting Up Accurate Angles - Inexpensively". You can see it here.

https://www.dropbox.com/s/6hx2gq491h6c7zn/AngleGauge.doc?dl=0

In it I explain how a set of angle gauge blocks can be used to set up almost any angle, with accuracy. It includes the use of the same principle that a sine bar operates on but you do not need to have a sine bar or gauge blocks. I substitute lengths of wire or drill bits that can be precisely measured with a micrometer for the gauge blocks. However, it does involve some math so a scientific calculator will be useful (or Excel). And it includes a discussion of how to calculate the accuracy that you can expect with the method so you are not flying blind.

Hi Paul, your method is great for many things (especially setting up parts in a mill vise!) however much different from my method. You do not need any angle references (although you do need a known flat block/bar) and can interpolate any angle you desire with no standards or reference angles.

Do adjustable angle angle gauges exist? Like adjustable parallels but for angles.

Andre3127
12-02-2016, 10:32 PM
A while back I asked how to find the location of a third bolthole. nonsymmetrical pattern. It went on for a day or so
with people saying it was easy ... but .. failing to actually explain how. Finally someone posted a really neat
diagram explaining exactly how to do it.

I printed it out and saved it ..

Now I will add this one to it ..

Thanks Andre



It's just another way to get to a singular problem, I'm sure many have done it before but I'm glad I was able to bring it to your attention. Feel free to screenshot and save the Instagram picture, who knows how long that stuff will be hosted or if my account gets compromised. I will add a real picture (not a link) soon.

Paul Alciatore
12-03-2016, 12:33 AM
Andre,

Adjustable angle gauges of course do exist. Some with scales (usually called protractors) and some that are just two blades that can be set at any angle to each other.

https://www.bing.com/search?q=adjustable+square&pc=MOZI&form=MOZTSB

and

https://www.bing.com/search?q=protractor+head+square&qs=AS&pq=protractor+head&sk=AS2&sc=8-15&cvid=97E29E3D2F2C4A709CA9BA3366282966&FORM=QBRE&sp=3

I have at least two protractor heads for my adjustable squares. And I guess you could call a sine bar an adjustable angle gauge: you adjust it with gauge blocks. The problem with all of them except the sine bar is getting an angular accuracy that is better than a few minutes of arc. Even with a Vernier scale, it is hard to get better than 5 or 6 arc minutes of accuracy without a worm gear with a Vernier scale or a sine bar with gauge blocks.

You could even make your own adjustable angle gauge. Take two pieces of flat, ground stock (1/16" x 3/4" x 6"), drill a hole in the end of each, and add a pivot (tight fitting screw and thumb nut). That's it. There is a version made for carpenters. But you still need an accurate way to set it to your angle.

Your method focuses on an angle measured with rise vs. run. Mine focuses on a numeric value of the angle. Both can work. And you can easily translate between the two with the tangent function on any scientific calculator.

Tan(angle) = rise/run
and
Angle = ArcTan(rise/run)

I have been able to find new scientific calculators at local stores for less than $5, even less than $3 when they are on sale, like back to school sales at the end of summer. So there is no reason not to have one in the shop. I have several; even one at the breakfast table. I leave calculators and reading glasses scattered around the house and shop wherever I may need them. Even my flip phone will do trigonometry.

Many machinists have made their own sine bars. And you can substitute a number of things for the gauge blocks normally used with them as long as you can measure their thickness accurately with your micrometer. A sine bar translates an angular measurement into a linear one.




Hi Paul, ...<snip>...

Do adjustable angle angle gauges exist? Like adjustable parallels but for angles.

Jaakko Fagerlund
12-03-2016, 01:58 AM
You don't need the bar in the procedure - just use the ways of your machine as your reference. Or like in most lathes, the compound has at least one side machined as a reference flat which runs parallel to the compound travel and can be used to set angles.

In a pinch I've indicated off the chucks surface or previously machined feature if there just hasn't been any space to use my lathes ways.

JCHannum
12-03-2016, 09:04 AM
If you want to set a taper attachment and have a part that has that taper, say a drill with a Morse taper shank, the easy way is to chuck up the part and indicate the taper directly. If you don't have a part, this is an easy method of setting the attachment.

Thanks for posting, I can see the benefits. Knowledge of basic math, including trig and geometry, is pretty much a requisite for layout and machining. I enjoy the problem solving as a means of keeping the brain functioning just like crossword puzzles.

Lew Hartswick
12-03-2016, 09:13 AM
Knowledge of basic math, including trig and geometry, is pretty much a requisite for layout and machining. I enjoy the problem solving as a means of keeping the brain functioning just like crossword puzzles.
Try and explain that to your typical high school kid today. :-(
...lew...

Edwin Dirnbeck
12-03-2016, 10:10 AM
Diameter change per foot.
I have been driving lathes for 65 years and on the rare occasion that I needed to know, I could never remember, what taper per foot meant.SOO, I changed the wording for myself to,DIAMETER CHANGE PER FOOT.To me this is more logical .Edwin Dirnbeck

JCHannum
12-03-2016, 12:35 PM
These are the kids who cannot make change for a dollar in their heads and need an app on their smart phones to figure 15% or 20% tips. It is a crime, but it is not their fault, just a sign of the state of the US education system.

Andre3127
12-03-2016, 06:29 PM
There are at least a dozen ways to turn tapers on a lathe, I just didn't want to adjust my taper attachment since I have yet to clean it up and also didn't want to take apart my compound. Lazyness at its finest!



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old mart
12-05-2016, 11:30 AM
A 2" sine bar is more useful on a lathe than the common 5".
The museum's Smart & Brown lathe has a built in taper turning attachment up to 10 degrees. The instructions emphasize the importance of keeping the tool height dead on the centreline.