Smooth cuts??

[steamer]

" postit note run between the teeth is just right, "


I agree with everything you said Machine Tom....especially the post it note!

I use writing paper some times too.

Dave

 

[lazylathe]

Thank you all so much for the info!!!

I will work on this tomorrow morning and post my results!

I had a feeling it was too fast but lacked the instruction and knowledge to safely do what needed to be done!

Thanks for showing me the right way!

Will post pics tomorrow!!

Andrew

 

[Lakc]

a postit note run between the teeth is just right,

What a marvelous idea for the cheap no brand postit notes we have at work. :bow:
What other practical uses are there for sticky notes that dont stick?

 

[Maryak]

Andrew,

The leadscrews on a lathe are always cutting a thread, maybe not of recognised size pitch etc., but a thread none the less. The idea is to overcome this by:-

1. Using the change gears to make this thread as fine as possible.

2. Grinding your tool so that the cutting surface is greater in size than the pitch of whatever thread your change wheels are set at, meaning it removes the ridges and leaves a smooth surface.

Sometimes it is possible to have a heavy rate of feed, (leadscrew advance), combined with a wide cutting face on the tool and a very light depth of cut and still have a good finish. It is a technique I was taught when machining steel pump shafts. The time saved was astronomical with these 6ft long x 2" dia. shafts.

There are some well proven relationships between speed in ft/min of rotation and speed in feet/min of leadscrew advance and depth of cut, for most of the common metals such as iron, steel, brass, bronze, copper and aluminium which should, if all else is OK, give a reasonable finish to the surface being machined. Most of these figures are for commercial rigid machine tools, for our hobby machines 9 times out of 10, IMHO halving these figures will give reasonable results.

The other important thing is lubrication and cooling which again depends on the metal being machined.

Hope this helps

Best Regards
Bob

 

[steamer]

As Bob has rightly stated, there is a "right" feed and speed for every metal. Most are published in the "Machinery Handbook". This I should have stated. At the time, I thought that understanding the lathe was a bit more pressing. Andrew, once you get through this, get ye a Machinery handbook. A Used copy is fine as this data has only changed since carbide tooling became prevelent. Most of my machining is with HSS, and therefore at a lower feed and speed rate......lots to learn ;D


Dave

 

[websterz]

What a marvelous idea for the cheap no brand postit notes we have at work. :bow:
What other practical uses are there for sticky notes that dont stick?

Tiny little paper airplanes? :big:

 

[lazylathe]

KARMA all around for those that helped!!!! ;D
You guys are awesome!!!!!! :bow: :big: :bow:

I had to go down to 0.0043 to get a nice smooth cut that looks almost polished!!
Will post pics later tonight, i have a model engineers meeting to go to soon!

Thanks for all your help and the pictures posted!!!
It made it so much easier!!!
And now i know one more "trick" to get a smooth finish!!!

Thanks again!!!
Pics up later.

Andrew

 

[steamer]

Cool!

Dave

 

[Brian Rupnow]

So---did you change the feed rate or just take a lighter cut?

 

[lazylathe]

Brian - Lighter cuts made no difference.

I changed the gears and reduced the leadscrew rate to 0.0043" and that made a huge improvement!
Attached is a picture of before and after.
Closest to the chuck is what i was getting and the end section is where i am at now.
I think i can live with it like it is!
A quick go with some compound, fine water paper or polish will really make it shine.

The pic is just after a cut with oil.
Same tool as the last pictures.

Thanks again for all the help and guidance!!
It was really appreciated!

Andrew

 

[steamer]

Hi Andrew,

Glad everything is coming around! Also glad you learned something.....

A couple more observations.....call it the grad class if you like

I wouldn't extend the work much more with out some support from the tailstock in the form of a center.

I think the old rule of thumb is 5:1 (length to diameter)....I'm sure I don't remember it right...and I'll be corrected.

If I was to want a polished turned surface, start by making sure you have a polished cutting tool. If you look under a magnifying glass, you will amazed at how rough a tool looks after it comes off the grinder. All those striations get transferred into the work. Spend some time with a couple of slip stones and bring the cutting edge right up to mirror. You will be amazed at how nice a finish you can get, and how much sharper the tool is! It also means that you will cut with less cutting force....which is always a good thing on any lathe but especially on small lathes...

Keep the over hang of the tool to the absolute minimum. Especially with a round nose tool, but with any tool really. It's stiffness decreases with the cube of the length. and the tool will become a tuning fork in a real hurry!...so choke up on that tool.

Glad your having fun and making chips...keep at it, its very rewarding!

Dave

 

[lazylathe]

Thanks Dave!

That length of material is about 5 inches long.
The other side was center drilled when i first started this adventure and was supported by a live center.
I only turned about a 3/4 inch length outside the chuck and then extended it so that everyone could see the
change in cut.

I am still a bit wary of my first "big" lathe.... :-\
So it just gets used on the lowest speed which seems pretty fast to me!

Now i just need to figure out how to get out of doing yard work... ;D

Andrew

 

[Troutsqueezer]

Now i just need to figure out how to get out of doing yard work... ;D

Andrew

Now you're just being silly. That's impossible.

Ouch! Stop that, Honey! I'll be out there in a minute......I just want to finish typing this........ :big:

 

[lazylathe]

Ouch! Stop that, Honey! I'll be out there in a minute......I just want to finish typing this........ :big:
[/quote]

I see we are all in the same boat here.... ;D
Oh well we will use whatever free time we can get!!!

Andrew

 

[Ned Ludd]

Hi Andrew,
Out of curiosity, where did you get the advice to have your top slide at such a strange angle? Most people would suggest it is at right angles to the cross slide, although some recommend 3 or 6 degrees, to get a very fine in-feed. Others suggest you move the top slide around to 30ish degree, or half thread angle, to the cross slide (not lathe axis) for threading purposes, but this is completely unnecessary for successful threading and I don't suppose you are screw cutting yet
Ned

 

[steamer]

The compound doesn't look so bad...though I'd argue to straighten out the toolpost making it square and parallel....

Dave