turning tapers.

[wm460]

I want to turn a taper 75mm long, 12mm down to 4mm.
Is there any charts that tell you what degrees to use?
Ms Google has let me down.

[nadroj]

Using my calculator's trigonometry functions, I make the angle you need to set your compound to as 3.057 degrees approximately.
You could try to set that, take a cut, measure, readjust, recut, etc, until you get the radii you want over the 75mm length.
You might want to try it on a test piece before committing yourself.

Jordan

[Oddjob1]

Whenever I had to calculate anything I would draw it to scale, measure and bingo! Got the answer that way. My teacher hated me for that! I think to do your thing my way I would simply put the blank in the chuck, measure the length, turn each end to the required Dia, then the rest is easy hey!:D

So what are you making?

Oddjob1

[wm460]

Thanks for your replies, I will try the 3.057 degrees.
I have no idea of how to use my calculator's trigonometry functions, I'd better learn.
I am making a pen insertion tool, Pen Tube Insertion Tool - Rockler Woodworking Tools (http://www.rockler.com/product.cfm?page=18424)
1, for practice and 2, because now I just grab the nearest pen or pencil and use that and the next time I want to use them they are nicely araldited to the bench or somewhere.:D:D

[neksmerj]

I've got it easy. Just draw it using Autocad, and wallah.

Attached is my dwg.

Ken

[nadroj]

Not that it matters here, but your Autocad drawing gives 3.053 degrees. I wonder how come the difference from my calculator?

Jordan

[neksmerj]

Hi Jordan,

I just did the calc on my HP 15c calculator, and came up with the same angle, 3.0529 degrees, each side of centre.

My triangle is 75mm long x 4mm high with Theta, the angle, between the two long sides.

tan theta = 4 divided by 75

theta = artan 0.0533

theta = 3.0529

Ken

[nadroj]

You're correct, Ken. I was wrongly using COS instead of TAN.

Jordan

[pipeclay]

Glad you fellas cleared that one up quickly,otherwise there might of been 50+ posts argueing the decimal point.

[nadroj]

"She'll be right" eh?
Oddjob's graphical method has a lot going for it, though.

Jordan

[Metmachmad]

So how does one accurately get 3.0529 degrees?

[wm460]

So how does one accurately get 3.0529 degrees?

good Question,
How do you work out the degrees on this lathe?
Would each division be 2.5°?

http://i511.photobucket.com/albums/s356/wm460/fuji253.jpg

[Dave J]

You could put a piece of true round stock in the chuck (or machine a piece true) sticking out say 100mm then put marks on it 75mm apart.
Then set up a dial indicator on the tool post or compound, set the compound at approximately 3 degrees and bring the dial indicator in to touch the round stock in the chuck and set it at zero on one of the 75mm marks.
Wind the compound towards the other end and the dial indicator should read 4mm difference, if not adjust and try again until you get it.

Dave
PS
Is that grease your using in the ways? They should really be oiled.

[nadroj]

So how does one accurately get 3.0529 degrees?
Repeating from the 2nd message in this thread:

"You could try to set that, take a cut, measure, readjust, recut, etc, until you get the radii you want over the 75mm length."

Jordan

[Dave J]

Going by this thread on another forum the taper was finished on Sunday.
The Home Machinist! • View topic - Turning Tapers. (http://www.chaski.org/homemachinist/viewtopic.php?f=42&t=88693)

Dave

[wm460]

You could put a piece of true round stock in the chuck (or machine a piece true) sticking out say 100mm then put marks on it 75mm apart.
Then set up a dial indicator on the tool post or compound, set the compound at approximately 3 degrees and bring the dial indicator in to touch the round stock in the chuck and set it at zero on one of the 75mm marks.
Wind the compound towards the other end and the dial indicator should read 4mm difference, if not adjust and try again until you get it.

Dave
PS
Is that grease your using in the ways? They should really be oiled.

I was following Tuning Your Mini-lathe on Frank J. Hoose web site and he was using white lithium grease .

What is the advantage of oil?

[Dave J]

Oil will wash out most chips and grit where grease will stick it in their.
You will find it much better using oil.

Dave

[R W]

Whenever I had to calculate anything I would draw it to scale, measure and bingo! Got the answer that way. My teacher hated me for that! I think to do your thing my way I would simply put the blank in the chuck, measure the length, turn each end to the required Dia, then the rest is easy hey!:D

So what are you making?

Oddjob1
As I'm sure there are a great many of us who wouldn't have a clue about trigonometry and are probably not particulary interested in learning it.
To myself your method makes a lot of sense, for many tapers a suitable gauge or template could be made to check the angle setting if desired.

[nadroj]

As I'm sure there are a great many of us who wouldn't have a clue about trigonometry and are probably not particulary interested in learning it.


All the original poster had to do was ask here, and he got numbers - no trig or geometry set needed!

Jordan

[wm460]

Oil will wash out most chips and grit where grease will stick it in their.
You will find it much better using oil.

Dave

What type of oil would you recommend?

[Dave J]

I just use motor oil as it's cheap and does the job, some of the guys on here chased up the proper way oil with tackifiers in it but it can be hard to get in small quantities, you usually have to buy 20 ltr's.

I also mix the 20/80 motor oil with kero to spray machined surfaces of the lathe, mill, chucks, rotary tables and tooling to keep rust away. It's cheap (I usually grab it on a good special) so I am not worried about how much I use. I find spaying it on like this, the kero thins the oil down to spray on then evaporates away and leaves a light coating of oil which is easily removed when needed.

If you do a search on Google you will find a lot of opinions on way oil, some of the guys over in the US swear by the proper grade way oil while others just use whats on hand. With our lathes only being used in the home shop and not in production environment it doesn't really matter what oil as long as it's kept well oiled.


Dave

[Stustoys]

I've used a few different oils. I feel the proper way oil is an improvement over hydraulic/engine oil. (but then, maybe I was just trying to convince myself that I hadn't just blown $120 and I'd have to say that the fit of my slides isn't great so maybe that has something to do with it as well. Also it may just be that the viscosity is what made most of the difference) Is it worth buying 20ltr's for one machine? I doubt it.

I believe from what someone else said that my local oil guy now sells way oil in 5ltr containers. So it could be worth a few phone calls.
Stuart

[wm460]

I cleaned all the white lithium grease off and now using engine oil as I have mob of it.

[Dave J]

Does it feel better now? You will also be able to adjust the gibs properly now as the grease would have given a false reading being thick and sticky. They should be adjusted so there is a slight drag.

Dave

[Dave J]

I just came across an interesting post about using grease for ways. Though it is usually looked down on, this guy seems to have had great results with it.
It starts at post 13
Soo... I greased my ways - Practical Machinist - Largest Manufacturing Technology Forum on the Web (http://www.practicalmachinist.com/vb/bridgeport-hardinge-mills-lathes/soo-i-greased-my-ways-218865/)

Dave

[Metmachmad]

For what its worth I'll add my 2 cents. As a lubricant I don't think anyone could knock grease for its lubricating qualities, as we all know industry runs on the thick stuff.

But I feel it does have some negatives, although only seemily small as a way lubricant.

* As previously described here, grease is much more tackier than oil and as a result it will make adjustment of the gibs much more difficult. The result that for the same amount of drag or feel on the feed/adjusting screws the amount of clearence will more than likely be greater than using oil.

* Due to the extra drag caused by the grease and moreso when it is cold, there will be increased load on the other moving components, potentially increasing the amount of wear and load that they may experience.

* Also as previously said, dirt, dust, swarth (particularly cast iron which is the most detrimental to slides and ways) is attracted and held in grease more readily, potentially increasing wear and scoring to the ways.

[Dave J]

I agree and would never use grease myself, but found that guys claims (with pictures) about the little wear over that period of time interesting.

Dave