Need some input on how I am cutting on lathe

[vigsgb]

I created a very short video with my lathe setup while making a .010 pass on a piece of 12L14 with a tool I sharpened myself and would like some input on what you see so I can learn from people who have done this a million more times then I.

Any input is welcome.

Here is the link to the video on youtube I do zoom in and such to the tool while cutting. [ame]http://www.youtube.com/watch?v=m5AnIF7I1V8[/ame]


Thanks!

 

[rake60]

What is the diameter of your work piece?
What is your spindle speed?

The video looks like you may be running a little fast for an HSS tool.
If you would straighten your tool post and move that tool back into the holder
as far as you can, you will get a much better finish.

Rick

 

[Maryak]

What Rick said + I think your tool would be better if you gave it some top rake and rounded off the cutting edge to about 1/32".

Hope this helps.

Best Regards
Bob

 

[vigsgb]

What is the diameter of your work piece?
What is your spindle speed?

The video looks like you may be running a little fast for an HSS tool.
If you would straighten your tool post and move that tool back into the holder
as far as you can, you will get a much better finish.

Rick

The work piece diameter is 2 inches.

I have no way to tell how fast the spindle speed is.

I will pull that tool back into the tool holder and straighten out the post and see what happens....

Thanks

 

[kvom]

If you don't know your rpm then you can't know the sfm either. Get one of the cheap laser tachometers from ebay.

 

[Tin Falcon]

learn the basics they will serve you well.

surface feet per minute this is published data.
determine rpm from a chart or formula.

gringd the tool bit to propper geometry with a nose radius and hone stone the bit

you have the work suported so good there.
the rule of 2 1/2 keep the tool and unsupported work sticking out less than 2 1/2 times its cross section . so a3/8 bit should only stick out 3/4 of an inch .
also learn to set up the tool so if things move the tool will swing away from the work not dig in. Always check the setup for rigidness and clearance before you power up.
A little cutting oil could also help.
Learn to listen to the machine . your speed sounds fast to me .


when roughing slower speed and faster feed. finishing fast speed slow feed.
Tin

 

[vigsgb]

This is all great information!!! Thanks

 

[vigsgb]

learn the basics they will serve you well.

surface feet per minute this is published data.
determine rpm from a chart or formula.

gringd the tool bit to propper geometry with a nose radius and hone stone the bit

you have the work suported so good there.
the rule of 2 1/2 keep the tool and unsupported work sticking out less than 2 1/2 times its cross section . so a3/8 bit should only stick out 3/4 of an inch .
also learn to set up the tool so if things move the tool will swing away from the work not dig in. Always check the setup for rigidness and clearance before you power up.
A little cutting oil could also help.
Learn to listen to the machine . your speed sounds fast to me .


when roughing slower speed and faster feed. finishing fast speed slow feed.
Tin

Ok things are starting to click now... I bought a tachometer looked at the charts for surface feed rate and found I was cutting at a rate of 1800 and thus the reason why a lot of my chips looked like I was cutting cast iron. So I slowed that down to the recommended cutting rate for a hss tool which was around 200 and did the math = 200 x 4 / 2 = 400 RPM I also brought the tool in and straightened the tool post and used a pre sharpened hss bit and things look much better and have some logic to it now.

I will now copy the profile of the sharpened bit onto my own blank and round the tip some and see what that does.

Now I am off to print out some charts of feed rates drill hole and tap sizes for the wall.

Thanks

 

[robcas631]

You are going to fast! Slow is down! Also adding one drop of oil is not a bad idea. If it smokes you are going too fast! Remember each material has a certain cut rate. It changes on diameter. The smaller the diameter the faster you go...opposite regarding larger diameters. When a bit is curring correctly you should see lots of burrs and a silencing of ........how do I say this the tool as it cuts the material. There are charts regarding material, speed and FPS.

 

[robcas631]

2" diameter steel? I supplied a basic chart on how many feet per minute you should be moving at. Each metal has a different cutting speed and maximum depth. I noticed that you didn't use and oil to lube your bit? For steel I use regular car oil. You are doing good because you are creating decent burrs. Typically HSS needs a lower cutting speed than carbide. Let's find your diameter and find the correct speed range. 2"x Pi = 6.28" being that is 1/2 a ft. 200' -260' FPM = 400 to 520 RPM @ a cut depth of 0.004." A carbide bit At the same cut depth = 800 to 820 FPM = 1600 - 1640 RPM. I also do not have a dial in speed though I know my maximum speed is about 2700 RPM. Assuming the speed control is linear, you should be running at 14%.

Too much Math...so lets get down to business. I recommend you start experimenting with depth and speed. Add one drop of oil to the tip of your HSS tool and take 0.01" deep or less cut depth. Start at a slow speed until you start getting a really long burrs. Also the bit should cut without making a lot of noise. I've had burrs 10 ft long!

I am sure there are other reference charts but check this out for starters.​

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http://littlemachineshop.com/Reference/CuttingSpeeds.php​

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Contact me if you have questions. Perhaps I will make a video.​