up side down threading

jackie schmidt said:
Nothing wrong with upside down threading. The cuts are generally lightbenough as not put much stress on the lower gib plates that keep the carriage from rising up.

And you are correct. When cutting metric threads on a Lathe to a shoulder with an American lead screw, it is easier since you cannot disengage the half nut.
Click to expand...

I like the idea.....will try it next time.

Mort
 
I've noticed

the English and Ausies don't ever disengage the half nuts onest they begin. Works better if the machine has a break tho.

Pete
 
Has anyone here cut acme threads ?.....I've done a couple of female threads ( still have the highspeed tools ground to a template) and I don't remember any problems. Of course this is 50+ years ago and today I can't remember why I walked into the next room......I know there was a reason, I just have to think about it.

Mort
 
dmort said:
Has anyone here cut acme threads ?.....I've done a couple of female threads ( still have the highspeed tools ground to a template) and I don't remember any problems. Of course this is 50+ years ago and today I can't remember why I walked into the next room......I know there was a reason, I just have to think about it.

Mort
Click to expand...

I've cut acme threads, inside and out. I thread conventionally, compound set to 1/2 the included angle of the thread although all the other approaches work as well. The only real 'trick' is, if you're grinding your own tools, make sure there's generous side relief so the tool below the cutting edge isn't fouling the thread.

GsT
 
GeneT said:
I've cut acme threads, inside and out. I thread conventionally, compound set to 1/2 the included angle of the thread although all the other approaches work as well. The only real 'trick' is, if you're grinding your own tools, make sure there's generous side relief so the tool below the cutting edge isn't fouling the thread.

GsT
Click to expand...

After some basic instruction I always ground my own tools.....not that there wasn't some trial and error but I became fairly proficient. Tools that were dedicated to specific jobs appearance
became important. Some of my utility bits have been ground so many times ( left and right) they don't have an obvious identity....like what the hell is this? If a job came in and I didn't
didn't have anything close, I would use a utility bit instead of starting with a blank.

My cutting tools range from 3/4 to 5/16 and most are Cleveland Mo Mak Colbalt and with a Rex here and there.....and yes,proper relief is very important.

Mort
 
dmort said:
After some basic instruction I always ground my own tools.....not that there wasn't some trial and error but I became fairly proficient. Tools that were dedicated to specific jobs appearance
became important. Some of my utility bits have been ground so many times ( left and right) they don't have an obvious identity....like what the hell is this? If a job came in and I didn't
didn't have anything close, I would use a utility bit instead of starting with a blank.

My cutting tools range from 3/4 to 5/16 and most are Cleveland Mo Mak Colbalt and with a Rex here and there.....and yes,proper relief is very important.

Mort
Click to expand...

HSS for the win.

When done correctly they have a far finer 'grain' structure than anything in carbide.

For the finest quality work, who cares if it only lasts a few minutes as long as I can finish the job.

More than once I have used carbide for most of the task and then used a fresh sharped HSS bit for the last few thousandths of an inch.

You can make spectacular surface finishes this way.

And sharpening on translucent Arkansas stones still beats the diamond ones.

The diamond does most of the work, but then a very few honing strokes on the Arkansas.
 
I started with hss and have ended up using all carbide except for a few specialized tools. Even the cheap Chinese carbide on eBay leaves a great finish at high speeds. Prices are very low for carbide inserts considering the amount of use you get. You can’t go wrong either way. Just a preference
 
brickeyee said:
HSS for the win.

When done correctly they have a far finer 'grain' structure than anything in carbide.

For the finest quality work, who cares if it only lasts a few minutes as long as I can finish the job.

More than once I have used carbide for most of the task and then used a fresh sharped HSS bit for the last few thousandths of an inch.

You can make spectacular surface finishes this way.

And sharpening on translucent Arkansas stones still beats the diamond ones.

The diamond does most of the work, but then a very few honing strokes on the Arkansas.
Click to expand...

^^^^ this ^^^^

"HSS seduces the workpiece, carbide rapes it"
 
alinwa said:
^^^^ this ^^^^

"HSS seduces the workpiece, carbide rapes it"
Click to expand...


That is a scary image to contemplate.

You can also make HSS scary hard if you choose the correct stuff.
It does get brittle though.

Sort of like carbide.

HSS is far better on interrupted cuts than carbide though.
 
brickeyee said:
HSS for the win.

When done correctly they have a far finer 'grain' structure than anything in carbide.

For the finest quality work, who cares if it only lasts a few minutes as long as I can finish the job.

More than once I have used carbide for most of the task and then used a fresh sharped HSS bit for the last few thousandths of an inch.

You can make spectacular surface finishes this way.

And sharpening on translucent Arkansas stones still beats the diamond ones.

The diamond does most of the work, but then a very few honing strokes on the Arkansas.
Click to expand...

Funny how different we all are. I have found carbide with fast deep cuts makes the best finishes. Carbide can make spectacular finishes also.
Curious what you meant by “far finer grain”??
 
Mram10 said:
Funny how different we all are. I have found carbide with fast deep cuts makes the best finishes. Carbide can make spectacular finishes also.
Curious what you meant by “far finer grain”??
Click to expand...

The crystal structure in HSS is finer than any bonded together carbide.

In HSS you are down to the atoms.

Face centered or body centered atoms.

Heat, quench, temper (if needed), hone the final edge.

Martensite is a body-centered Tetragonal crystal lattice and very hard.

A carbon atom is inside 8 iron atoms. That fine a grain.
 
brickeyee said:
The crystal structure in HSS is finer than any bonded together carbide.

In HSS you are down to the atoms.

Face centered or body centered atoms.

Heat, quench, temper (if needed), hone the final edge.

Martensite is a body-centered Tetragonal crystal lattice and very hard.

A carbon atom is inside 8 iron atoms. That fine a grain.
Click to expand...

Is that noticeable to the eye? My carbide leaves a better finish to my eye, but I haven’t looked at it under a microscope
 
Mram10 said:
Funny how different we all are. I have found carbide with fast deep cuts makes the best finishes. Carbide can make spectacular finishes also.
Curious what you meant by “far finer grain”??
Click to expand...

What speeds, feeds and DOC are you using with carbide inserts? I’ve been playing around with some but HSS is still leaving a better finish for me.
 
Depends on the insert, but they leave the best finishes fast and deeper cuts. 780rpm is my usual, but really like 1000+ if I’m not too lazy to switch the pulley. Depth is generally .020-.050. Feed is usually .010. I’ve never gotten great finishes at .005” or less. Probably need to play with speeds and feeds for that light of cuts.
 
You need a VERY tight setup for light cuts and best surface finishes.

The lightest play or flex messes the surface finish up very quickly.
 
brickeyee said:
That is a scary image to contemplate.

You can also make HSS scary hard if you choose the correct stuff.
It does get brittle though.

Sort of like carbide.

HSS is far better on interrupted cuts than carbide though.
Click to expand...

When cutting welded up tapers in ships rudders we used HSS. Carbide couldn't handle it.......Just like you said.

Mort
 
brickeyee said:
The crystal structure in HSS is finer than any bonded together carbide.

In HSS you are down to the atoms.

Face centered or body centered atoms.

Heat, quench, temper (if needed), hone the final edge.

Martensite is a body-centered Tetragonal crystal lattice and very hard.

A carbon atom is inside 8 iron atoms. That fine a grain.
Click to expand...

I knew all that but thought I should read it anyway.


Mort
 
I also know everything, but feel I should respond ..... letting everyone know that I already know what they are telling me .... ;)
 
Mram10 said:
I also know everything, but feel I should respond ..... letting everyone know that I already know what they are telling me .... ;)
Click to expand...

I do learn something every day here...... today I learned that millennials can be of any age


I'm simply sideswiped.......hornswoggled...... flabbergasted that is......
 
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