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parrisw
01-12-2010, 01:44 AM
Ok, first time using the lathe today. So I set the spindle for as slow as it would go, not sure what speed that is. I turned a brass piston pin, that came out nice, pretty good finish. Then I made a steel pivot pin for my log splitter, I couldn't find the right size, so why not make one since I now have a lathe, so I just turned down a bolt to a pin, maybe its not the best material, but the finish came out a little rough, its fine for its purpose, but would higher speed be better? I'm using a carbide bit, that has replaceable tips.

Thanks

Machinist-Guide
01-12-2010, 01:55 AM
The larger the work piece the slower the RPM
The smaller the work piece the higher the RPM

parrisw
01-12-2010, 01:56 AM
The larger the work piece the slower the RPM
The smaller the work piece the higher the RPM

Good tip, thanks. What would be a good book for me to get to solve some of these common questions, so I don't have to ask here too much.

Machinist-Guide
01-12-2010, 02:01 AM
Thats what forums are for.
Here is a link to a few lathe videos for beginners that may help.
Some of these videos were made by a retard machine shop teacher
Some were made by me:)

http://www.machinist-guide.com/machine-tools.html

Machinist-Guide
01-12-2010, 02:05 AM
Here is a link to a good book on Amazon

Lathe Book (http://www.amazon.com/dp/B000KJL1KO/ref=nosim?tag=machinist-guide-20&linkCode=sb1&camp=212353&creative=380549)

parrisw
01-12-2010, 02:11 AM
Thanks allot man, your a great help, I've seen some of your video's on Youtube, they're really good.

lakeside53
01-12-2010, 02:15 AM
Your bolt was probably some form of mild steel.. which can be difficult to get a good finish with carbide and a lower power lathe. Been there... Also.. "carbide" inserts can range from plain awful to real nice. As to be expected, you get what you pay for. I used the common and cheap TT inserts from Enco for a while; then I bought some coated USA inserts (about 5X the price) - lol - I saw the light...

The Surface Feet/minute you need depends on many factors, but the starting point is the actual material type. Use the SFM tables as a starting point, then vary those for your particular situation. With carbide, I look to the color of the chips to fine tune, particularly when roughing. Finish may require higher speeds and fine feeds, but in some materials that can work against you. Many variables... and the learing curve can be (still is!) frustrating at time.

There is a ton of discussion to be had about speed/feed on this and other forums. I have a handy "slide rule" calculator for milling, drilling, turning.. came free from some random end-mill supplier. Gets me in the zone.

Goggle for "surface feet calculator" etc... Tons of data out there... and here..

dp
01-12-2010, 02:16 AM
Bolts can be a lot like M&M candies - hard on the outside, soft and chewy in the middle. Once you've digested the literature take some time to experiment with similar bolts turning fast and slow, deep and shallow. The books are guides, not laws, so don't feel you're breaking a rule. The rules change a lot when using HSS vs carbide, too, so practice practice practice.

parrisw
01-12-2010, 02:20 AM
Your bolt was probably some form of mild steel.. which can be difficult to get a good finish with carbide and a lower power lathe. Been there... Also.. "carbide" inserts can range from plain awful to real nice. As to be expected, you get what you pay for. I used the common and cheap TT inserts from Enco for a while; then I bought some coated USA inserts A(about 5X the price) - lol - I saw the light...

The Surface Feet/minute you need depends on many factors, but the starting point is the actual material type. Use the SFM tables as a starting point, then vary those for your particular situation. With carbide, I look to the color of the chips to fine tune, particularly when roughing. Finish may require higher speeds and fine feeds, but in some materials that can work against you. Many variables... and the learing curve can be (still is!) frustrating at time.

There is a ton of discussion to be had about speed/feed on this and other forums. I have a handy "slide rule" calculator for milling, drilling, turning.. came free from some random end-mill supplier. Gets me in the zone.

Goggle for "surface feet calculator" etc... Tons of data out there... and here..

Thanks Andy. I did today feed a slow as it would and spindle slow, will try faster spindle speed's. The carbide's that I got were cheeper ones but seem to cut well, I think I'll need to get something better if I do allot of steel though, they worked great on the brass. I'll just keep playing and see what happens.

parrisw
01-12-2010, 02:21 AM
Bolts can be a lot like M&M candies - hard on the outside, soft and chewy in the middle. Once you've digested the literature take some time to experiment with similar bolts turning fast and slow, deep and shallow. The books are guides, not laws, so don't feel you're breaking a rule. The rules change a lot when using HSS vs carbide, too, so practice practice practice.

Yes I noticed that actually, after got the crunchy candy coating off the bolt, it cut better. I actually tried it on a stainless bolt first, and it seemed to machine better.

darryl
01-12-2010, 02:51 AM
What a wide open field- you're going to find that different materials react in different ways, and there won't be a magic number to cover it all. Start with a surface feet per minute, per material, per cutting tool type- then experiment and modify from there. If something seems unusual, ask on this forum. You could easily find three steel rods that look the same and are the same diameter, and each machines differently. A common bolt and a grade 8 bolt, for instance.

I think a very good exercise is to learn how to identify materials. It's pretty easy to tell copper apart from brass or aluminum, but it's not so easy to identify steel bits and pieces. Different alloys look pretty much the same, that goes for aluminum as well. Some materials are really going to frustrate you. Aluminum bronze, for instance. Read about the spark test, use the file test method, maintain identification for materials when you know what they are as you buy them.

This will come up sooner or later- don't even think about using sash weights for anything other than sash weights- :) don't equate bed rails with angle iron, and don't turn any beryllium on the lathe.

There. That's about .00000000000001 % of what you need to know :)

lakeside53
01-12-2010, 02:53 AM
Here's a decent summary with a table of materials for HSS. Carbide speeds can be 2-5X these..

http://en.wikipedia.org/wiki/Speeds_and_feeds

You said you were running "slow".. well...

If your pin was say 1/2 inch mild steel, and you wanted 100 SFM, you'd need 764 rpm... I'd probably try 300+ sfm with my carbide, so that would make it 2292rpm... close to the top speed of my lathe. How does that line up with what you were doing?

Here's two of a zillion online calculators.

http://www.americanmachinist.com/Calculators/SpeedsFeeds.aspx
http://www.a-i-t.com/calculate.html

Carld
01-12-2010, 09:44 AM
400-500 rpm would be a more usable speed for turning what you were. You said you used the slowest rpm and that I will assume is around 100 rpm +/-.

The thing is most the charts give to high a feed and speed for manual machines. If your running the lathe at 2000 rpm or more and not taking a deep enough cut or fast enough feed you will wear the tip of the cutter. High speeds require high DOC and or feed. You also should use flood coolant with high speeds.

To use high speed, feed and DOC requires a heavy duty lathe. What kind of lathe do you have?

Your using insert carbide holders so your looking at an expensive learning curve. You were right to start slow but you didn't try going faster. I usually start at 300 rpm and work my way up or down depending on the material I am cutting. Of course if it's brass or aluminum you can start higher.

Anther good book is How To Run a Lathe by South Bend Lathe Co. You can find them on Amazon and other sites.

EDIT: Just saw your thread on your "new lathe" and saw it's a 9" lathe. I don't think you can or will want to run it at 2000 rpm. The feed/speed charts are a guide for professional machinists on heavy duty machines and you have to use some common sense using the charts.

I suggest you experiment on your lathe and you will find the speeds, feeds and depth of cut (DOC) that yours will handle. If you decide to use the charts DON'T start at the high end, start low and work your way up. Replacing those inserts will get expensive running to fast. Your lathe will do just fine with reasonable speeds and feeds. My second lathe was a Logan about the same size as yours and I had it for 20 some odd years then bought a larger lathe and sold the Logan to my son.

Black_Moons
01-12-2010, 10:18 AM
Don't worry about the finish you get on steel, you could try for 3 days to get a good finish.. get a mirror finish for 2 inchs and then back to the same smudges without touching the machine.. and then be upset that the finish is diffrent for 2" insted of consistant.

There are a few tools and tips and tricks to get better finishs on steel. But right now just focus on the basics :)

Now, if you want to turn some mirror finishs, buy some aluminum! that stuff is wayy easyer to get a mirror finish on and you'll learn just what makes or breaks a finish, so you'll have better luck when you try to get a good finish on steel again.

parrisw
01-12-2010, 10:28 AM
Thanks again everybody, I knew I had lots to learn, so it begins. I've been doing lots of reading.

Thanks

Will

lakeside53
01-12-2010, 12:49 PM
9 inch? oh.. for some reason I thought it was a 12x36. My bad. Yep..faster then you were doing but listen to what Carl says also. And.. on your machine carbide may not be totally suitable... but I use it on my 1hp Emco V10 without any issues.

If you want decent finish on steel without jumping though hoops, buy some 12L14... Finishes like a mirror and so easy to turn.

parrisw
01-12-2010, 06:14 PM
9 inch? oh.. for some reason I thought it was a 12x36. My bad. Yep..faster then you were doing but listen to what Carl says also. And.. on your machine carbide may not be totally suitable... but I use it on my 1hp Emco V10 without any issues.

If you want decent finish on steel without jumping though hoops, buy some 12L14... Finishes like a mirror and so easy to turn.

What's 12L14? I take it that a grade number?

lakeside53
01-12-2010, 07:24 PM
It's a "leaded steel" or once known as "screwcutters steel" as it was commonly used for threadcutting. "Free machining" - very easy to turn. Not a good choice if you want to weld onto it. You can also get 11L44 and others, but it's harder to find (around here anyhow..)

Wonderfull stuff on a small lathe, or when mild steel finish really counts (and you want it "easy").

Here's a link to check out some common steels :

http://www.onlinemetals.com/steelguide.cfm

parrisw
01-12-2010, 07:36 PM
It's a "leaded steel" or once known as "screwcutters steel" as it was commonly used for threadcutting. "Free machining" - very easy to turn. Not a good choice if you want to weld onto it. You can also get 11L44, but it's harder to find (around here anyhow..)

Wonderfull stuff on a small lathe, or when finish really counts.

Here's a link to check out some common steels :

http://www.onlinemetals.com/steelguide.cfm

Thanks andy great help.

parrisw
01-12-2010, 07:38 PM
Here is a piston holder I'm working on.

http://i278.photobucket.com/albums/kk107/parrisw/IMG_2627800x600.jpg

http://i278.photobucket.com/albums/kk107/parrisw/IMG_2626800x600.jpg

lakeside53
01-12-2010, 07:55 PM
Maybe I'm missing something, but... why not just chuck the piston in a 4 jaw? You can put plenty of pressure across the pin area, and a reasonable amount higher up on the skirt.

parrisw
01-12-2010, 08:16 PM
Maybe I'm missing something, but... why not just chuck the piston in a 4 jaw? You can put plenty of pressure across the pin area, and a reasonable amount higher up on the skirt.

I would but, I don't have a 4 jaw yet. Soon to come hopefully. In the meantime this will do, and something for me to learn on. Plus once I get this done, it will be faster then a 4 jaw. If I'm within a couple thou, its fine for a popup.

lakeside53
01-12-2010, 08:26 PM
Any project is a good project. You only learn by building things!

Faster? ha, with a little practice you'll find a 4 jaws is about the same setup time as a 3 jaw ;) hey...I might have a 4 jaw for your lathe...

parrisw
01-12-2010, 09:11 PM
Any project is a good project. You only learn by building things!

Faster? ha, with a little practice you'll find a 4 jaws is about the same setup time as a 3 jaw ;) hey...I might have a 4 jaw for your lathe...

Cool, ya, i just like building things. 4Jaw you say huu. You have my attention now!! I'd love one.

parrisw
01-12-2010, 09:23 PM
I also need a drill chuck with MT2, got anything in that department you want to sell?

lakeside53
01-12-2010, 09:31 PM
most likely.. PM me.

hornluv
01-12-2010, 10:32 PM
Nobody gave the formula for figuring the RPM, so I figured I would. It is (SFM x 4)/Diameter. On the lathe, the diameter will almost always be the diameter of the part unless you're making a hole, then it is the size of the hole (either through drilling or boring). BTW, if you want some SFM figures to start with, I tell my students to use 150 SFM for brass and aluminum, 90 for mild steel, 50 for tool steels and mystery steels, 40 for stainless, and 100 for bronze. These are very conservative figures. They're pretty much the low end of the range of cutting speeds given in most charts. As mentioned, carbide can be run at least 2x faster than HSS.

parrisw
01-12-2010, 10:40 PM
Nobody gave the formula for figuring the RPM, so I figured I would. It is (SFM x 4)/Diameter. On the lathe, the diameter will almost always be the diameter of the part unless you're making a hole, then it is the size of the hole (either through drilling or boring). BTW, if you want some SFM figures to start with, I tell my students to use 150 SFM for brass and aluminum, 90 for mild steel, 50 for tool steels and mystery steels, 40 for stainless, and 100 for bronze. These are very conservative figures. They're pretty much the low end of the range of cutting speeds given in most charts. As mentioned, carbide can be run at least 2x faster than HSS.

Thanks allot. Another dumb question but how do I know what my SFM is? I know I can change my gear box levers to get higher feed rates, but how do I know what does what, it only gives the ranges for thread cutting.

lakeside53
01-13-2010, 01:49 AM
I''m not familiar with your lathe... but are you confusing your feed box with spindle speed? SFM only has to do with spindle RPM and work size.

Look up your lathe model on http://www.lathes.co.uk/page21.html
It will likely tell you what you need to know.

What is the lathe make/model? Maybe someone can help you with a manual.

And.. failing all that.... use an optical tachometer - less then $40...

parrisw
01-13-2010, 01:52 AM
I''m not familiar with your lathe... but are you confusing your feed box with spindle speed? SFM only has to do with spindle RPM and work size.

Look up your lathe model on http://www.lathes.co.uk/page21.html
It will likely tell you what you need to know.

What is the lathe make/model? Maybe someone can help you with a manual.

And.. failing all that.... use an optical tachometer - less then $40...

Hey its a hercus 9" model a. How does a optical tach work on a lathe? I have and optical tach from my rc days? Is that the same?

lakeside53
01-13-2010, 02:06 AM
The Optical tach senses a "phase change" - i.e. back to white. You put a tiny piece of reflective tape on the chuck and point the laser at it... often you don't need the tape - if I point it at my BP drawbar, it reads the hex nut perfectly - at 6X the actual speed, but hey, I can divide.

Your lathe : http://www.lathes.co.uk/hercus/index.html


But... I have no idea if you have the original pulleys or not. Spindle speed can simply be calculated by factoring the motor speeds against the pulley diameters... or.. turn the motor by hand and count how many times you need to get exactly one turn of the spindle.

parrisw
01-13-2010, 02:10 AM
The Optical tach senses a "phase change" - i.e. back to white. You put a tiny piece of reflective tape on the chuck and point the laser at it... often you don't need the tape - if I point it at my BP drawbar, it reads the hex nut perfectly - at 6X the actual speed, but hey, I can divide.

Your lathe : http://www.lathes.co.uk/hercus/index.html


But... I have no idea if you have the original pulleys or not. Spindle speed can simply be calculated by factoring the motor speeds against the pulley diameters... or.. turn the spindle by hand and count how many times you need to get exactly one turn of the motor..

What tach do you have? I think everything is all orignal. I have the manual, but there is multiple options?? So I don't know excatly what I have.

parrisw
01-13-2010, 02:20 AM
Here is the spindle speed chart. Mine has the 4 pullys, and single speed motor, so I got two options?

http://i278.photobucket.com/albums/kk107/parrisw/spindlespeeds.jpg

lakeside53
01-13-2010, 02:25 AM
I guess it depends on whether you have the "high speed drive"... whatever that means..

Do some simple counting tests when turning the spindle by hand, then factor that against the motor plate rating. Or.. dig out that optical tach.


My tach looks like this : (search Ebay for "laser tach")

http://cgi.ebay.com/Digital-Laser-Photo-Tachometer-Tach-for-Milling-Machine_W0QQitemZ220539421672QQcmdZViewItemQQptZLH _DefaultDomain_0?hash=item33592c83e8

parrisw
01-13-2010, 03:15 AM
I guess it depends on whether you have the "high speed drive"... whatever that means..

Do some simple counting tests when turning the spindle by hand, then factor that against the motor plate rating. Or.. dig out that optical tach.


My tach looks like this : (search Ebay for "laser tach")

http://cgi.ebay.com/Digital-Laser-Photo-Tachometer-Tach-for-Milling-Machine_W0QQitemZ220539421672QQcmdZViewItemQQptZLH _DefaultDomain_0?hash=item33592c83e8

Ya, mine is a little different. Its a hobbico digital mini tach, its optical none the less.

This is it. http://www.hobbico.com/fieldequip/hcap0401.html

lakeside53
01-13-2010, 01:10 PM
Sounds like itls set up for 2 and 3 blade props. If you put TWO pieces of bright tape on your chuck 180 degrees apart, it MIGHT be able to read correctly. Mine works from 3 feet away.

parrisw
01-13-2010, 10:26 PM
Sounds like itls set up for 2 and 3 blade props. If you put TWO pieces of bright tape on your chuck 180 degrees apart, it MIGHT be able to read correctly. Mine works from 3 feet away.

Tried it today on the chuck jaws, it seemed to pick it up but would vary allot if you tilted the tach in anyway.

lakeside53
01-13-2010, 10:43 PM
Turn the motor "n" times until you get one spindle revolution.. Move the belt, do it again... etc. Motor plate rpm divided by your "n" count = spindle speed (at full power, slightly higher for low power use).

I don't know if you have a back gear or the equivalent; if you do, figure that factor also.

In 5 minutes you'll have your own table.

parrisw
01-13-2010, 11:00 PM
Turn the motor "n" times until you get one spindle revolution.. Move the belt, do it again... etc. Motor plate rpm divided by your "n" count = spindle speed (at full power, slightly higher for low power use).

I don't know if you have a back gear or the equivalent; if you do, figure that factor also.

In 5 minutes you'll have your own table.
Ok, maybe later tonight after the kids are in bed I'll go do some counting.

So turn the motor by hand until the spindle goes 1 turn, while counting the amount the motor has turned, might be easier just to turn the spindle 1 turn while counting the motor. Thanks I'll give it a shot.

parrisw
01-14-2010, 12:24 AM
Ok here are the speeds the way I figure it. Its close to the factory chart. According to the back plate on the motor its a 1725rpm motor.

Belt position

1=862rpm
2=627rpm
3=517rpm
4=363rpm

Back gear engaged.

1=164rpm
2=117rpm
3=88rpm
4=66rpm

lakeside53
01-14-2010, 12:31 AM
Perfect.. now you know! The actual speed may be about 5% slower when the motor is running under load, but your numbers are close enough for calculating SFM!

So.. what SFM were you using when you did your steel and brass turning?

parrisw
01-14-2010, 12:38 AM
Perfect.. now you know! The actual speed may be about 5% slower when the motor is running under load, but your numbers are close enough for calculating SFM!

So.. what SFM were you using when you did your steel and brass turning?

ha ha, I have no idea!! I just chucked it up and went with the slow speed. which was the 363rpm. How do I calculate SFM?

Will

lakeside53
01-14-2010, 12:49 AM
That wasn't so slow on your lathe...

Post 12 and post 27 ;)

parrisw
01-14-2010, 12:55 AM
That wasn't so slow on your lathe...

Post 12 and post 27 ;)

Thanks ya, I just went back and looked at those posts, forgot you posted those links, too much info going into my little pee size brain at the moment! LOL I think I'm getting it now. I'm going to print off a chart and hang it up at the lathe.

Thanks again. This is getting interesting!

Will

parrisw
01-14-2010, 12:58 AM
So when facing a medium to large size piece what do you do about SFM? I just noticed tonight, that the cutting changes when you get to the middle since you SFM slows, just go midway?

lakeside53
01-14-2010, 01:14 AM
Ha.. you are getting it;)

You throw away your pulley system (just leave it for a torque multiplier) and put a 3 phase motor and VFD on the lathe:D

For pieces that don't vary too much in size, you just choose something that "works'. On large pieces, say a 9 inch disk... you may need to stop the lathe and change the speed. It depends greatly on the material and the desired result. Getting a mirror finish across the face of a large stainless (depending on the grade) disk may be quite difficult.

parrisw
01-14-2010, 01:17 AM
Ha.. you are getting it;)

You chuck away your pulley system and put a 3 phase motor and VFD on the lathe:D

For pieces that don't vary too much in size, you just choose something that "works'. On large pieces, say a 9 inch disk... you may need to stop the lathe and change the speed. It depends greatly on the material and the desired result. Getting a mirror finish across the face of a large stainless (depending on the grade) disk may be quite difficult.

Cool thanks. 3phase eh, hmmm sounds pricey!!

lakeside53
01-14-2010, 01:25 AM
1hp motor.. $25-50.. or often free.. VFD - $130-150...

parrisw
01-14-2010, 01:38 AM
1hp motor.. $25-50.. or often free.. VFD - $130-150...

Really eh?? Maybe I just haven't looked, but I never see deals around here like that. What does the VFD do? convert to 3 phase?

lakeside53
01-14-2010, 01:54 AM
yep.. and also ajustable speed, soft start and a bunch of other stuff.

Search on 'VFD".. you'l be buried.. but first figure out your lathe as it was built :)

parrisw
01-14-2010, 01:58 AM
yep.. and also ajustable speed, soft start and a bunch of other stuff.

Search on 'VFD".. you'l be buried.. but first figure out your lathe as it was built :)

Yes. Don't know that I'll ever go to 3 phase?? What about a variable DC motor?

lakeside53
01-14-2010, 12:59 PM
About the same cost... (if you are a good scrounger)... some torque advantages low down but IMO.. VFD is the way to go.. And MUCH easer to find cheap/free 3 phase motors than decent DC motors.

Don't sweat "three phase - that's made "invisible" by the vfd... you still plug it into a conventional single phaser power, and for 1hp, even into a 115v outlet.

parrisw
01-14-2010, 05:10 PM
Sweet I'll definitely keep my eye open for something.