Sherline lathe - holding limits of three jaw chuck

[BiggerNoise]

I have recently started trying to use the Sherline lathe that I inherited from my Dad. I'm completely new to this and starting with the most basic cuts.

I chucked some 6061 aluminum stock that I got from Amazon. Roughly 2.5 inches long and an inch in diameter. I was trying to do a basic right to left cut.

The "first cut" section of the manual talks about taking fairly aggressive cuts from the stock (up to 50 thousands). What I found was that I could make a 5 thou cut fairly easily and a 10 thou with some concern, but at 15 thou, it was less than .100 down the material when the material would grab the cutter and climb it, wrenching it out of alignment.

Today I picked up an optical tach to verify that my speeds were about right.

I also center drilled the tail and set up a live center to support the tail. Then I could make much better cuts (did .035 before I quit for the night).

So, my question is: is this normal? The sample cut videos on the Sherline site don't show a tail support, but the piece is both shorter and thinner.

If it is normal, how do people support the tail when facing it off?

 

[mikey]

Welcome to HM!

A Sherline lathe is capable of much more than you are experiencing. Perhaps if you answered some questions, we might be able to help more.

• What kind of tool are you using? Did you grind it or was it the preground HSS tool set from Sherline or are you using carbide?
• Was the tool tip at center height?
• What was your speed? Did you use any cutting fluid like WD-40?

When you need to face a work piece that is longish, use the steady rest to support the far end. Once faced, you can center drill it to accommodate your live center. Remove the steady rest, insert the live center and you're off.

The key to unlocking the performance of the Sherline lathe is your tooling. With a turning tool optimized for aluminum, I have taken a 0.100" deep cut (0.200" reduction in diameter) on this lathe and produced a mirror finish in the process. A good tool will also enable you to make precision cuts with relative ease. Given how important these tools are, the best option will be to learn how to grind them and there are some good resources to learn how to do exactly that on the forum.

 

[BiggerNoise]

Thank you for the reply and the welcome. I've been looking at the various online galleries and some of the profiles in Joe Martin's Tabletop Machining and have no doubt that the issue is not on Sherline's end .

Tooling:

I started with the preground tool that comes with the lathe. Since I'm learning everything at once I bought a set of preground bits from Amazon (Accusize). These tools are a compromise shape, so I don't expect to remove a full .100. There's a couple of blanks in the odds and ends that came with the tool, so I certainly intend to learn how to grind these pretty soon. I'm just trying to get basic operations down first.

I welcome opinions on the merits of this approach. The learning curve is approaching vertical, and I'm looking for ways to flatten it a bit.

Centering:

I did adjust the height of the tool tip such that it just touched the bottom of the height adjustment accessory, so it's centered or very close.

Speed:

I was going for about 500 RPM, but tried higher or lower. I think I was in the ballpark, but didn't have the tach until yesterday.

I was cutting dry until yesterday when I added some Tap Magic to the surface. I don't know if that helped or not. I was dry until the .035 cut. I was getting very long strings for chips and I thought that might help break them up. (I know that's another problem, but I think it's a general one, so I'll do some more reading before I come back for help on that).

 

[EricB]

6061 gets sticky with heat and will weld to the edge of the tool. You need higher rpm (500-1000 SFM) and a cutting lubricant. A lot of folks use WD-40 (a light mineral oil) on aluminum.

 

[BiggerNoise]

Thank you. I'll give WD-40 a try and double check my feed rates.

 

[mmcmdl]

Welcome to the site !

 

[mikey]

Tooling:

I started with the preground tool that comes with the lathe. Since I'm learning everything at once I bought a set of preground bits from Amazon (Accusize). These tools are a compromise shape, so I don't expect to remove a full .100. There's a couple of blanks in the odds and ends that came with the tool, so I certainly intend to learn how to grind these pretty soon. I'm just trying to get basic operations down first.

Centering:

I did adjust the height of the tool tip such that it just touched the bottom of the height adjustment accessory, so it's centered or very close.

Speed:

I was going for about 500 RPM, but tried higher or lower. I think I was in the ballpark, but didn't have the tach until yesterday.

I was cutting dry until yesterday when I added some Tap Magic to the surface. I don't know if that helped or not. I was dry until the .035 cut. I was getting very long strings for chips and I thought that might help break them up. (I know that's another problem, but I think it's a general one, so I'll do some more reading before I come back for help on that).

You have to keep in mind that the Sherline motor is only rated at 60 watts, or 0.08HP, so the Sherline will never be accused of being a powerhouse. Yet, it can perform like a much larger lathe IF you use the right tooling on it. The preground stuff you get from Sherline is not precisely ground and simply (and poorly) approximates the tool geometry of standard tooling. The stuff on Amazon ... who knows what they are ground to. I cannot recommend either choice but that is not a reflection on you; just a statement of fact. If you need a good set of tools to unlock your lathe, PM me and I will hook you up with someone who can grind good tools that will perform well, at least until you have the time to learn how to do it yourself. If I were you, I would use 5/16" - 3/8" tool bits. 1/4" will work okay but the larger, stiffer bits work much better. Please trust me in this; your tooling is the key to unlocking the Sherline lathe.

All Sherline lathes are different, meaning the center height of each one is different. They may be close but not the same. Likewise, the centering tool they sell may or may not match your spindle centerline. Given that even a thou or two above or below center makes a difference on a precision lathe, it is better to at least confirm the accuracy of the tool you have or make one to fit your lathe. Fingers crossed yours is accurate.

Speed:
RPM = CS (in sfm) X 3.82 / diameter of the work in inches
This is the formula to calculate speeds for a given material. Go here to see the listed cutting speeds (CS) for commonly used materials.

For your material:
RPM = 500-600 sfm X 3.82 / 1" = 1,910 - 2,292 rpm for a 1" diameter piece of 6061-T6 so you might want to increase your speed a bit.

With that said, speeds are a bit tricky to understand. Speeds are important for cutting efficiency and tool life but they are not exact. The calculated speeds in the tables are also for industrial machines with standard geometry tooling using power feeds, not for a little manual feed Sherline. The "tricky to understand" part is that speeds, feeds and depths of cut are tied together in an intricate ballet. The deeper the depth of cut, the slower the speeds will be and the faster the feed will be. Likewise, faster speeds like in the calculations above will limit how deep you can cut at that speed and you will need to adjust the feed by feel. You think the learning curve is near vertical? You're underestimating the curve!

My suggestion is to get yourself some good tools and then play with the lathe. Set your speed somewhere around 1500-1600 rpm and dial in a 0.020" deep cut and feed the tool into the work so that you feel a slight resistance to the feed; the tool will push back and you'll feel the resistance. You want to feed just fast enough to maintain a slight resistance. Under these conditions, the material will string; that is the nature of 6061. If you want this material to chip, you have to take a deeper cut and feed hard and fast and it will come off in chips but for now, accept the strings and be careful because they are sharp. Also keep your hands clear of the strings; they can grab your hand and pull it into the chuck.

Play with speed, feed and depths of cut and you will begin to sense their relationship, how changing one will affect the rest. When I first started on my Sherline, I spent months learning how these three factors work. It was time well spent. Now I no longer even bother checking or calculating speeds for most materials on my lathe. I turn the lathe on, set speed wherever my lizard brain thinks it should be and feed according to what my feel tells me is appropriate.

You have a good machine. I would take the time to learn how to use it. Everything you learn on a Sherline lathe will transfer over to a larger one if you ever decide to step up. I believe I am better on my Emco Super 11 lathe because of what the Sherline taught me.

 

[Karl A]

BiggerNoise,

About six months after I purchased my Sherline lathe, I tried to make two 1-inch diameter washers from a one-inch-long piece of 1.25-inch diameter 1144-steel round stock. I used a pre-ground HSS tool from Sherline. I faced the end and turned down the OD. I got rough surfaces, a lot of chatter, and the piece came loose from the 3.1-inch diameter three-jaw Sherline chuck.

I attribute the cause of the piece coming loose to the significant chatter. I attribute some of the chatter to two mistakes that I made: I installed a left-hand tool instead of a right-hand tool, and I installed the left-hand tool with the top face turned 90 degrees counterclockwise.

I ended up making the washers out of 6061 aluminum.

Karl A

 

[BiggerNoise]

BiggerNoise,

About six months after I purchased my Sherline lathe, I tried to make two 1-inch diameter washers from a one-inch-long piece of 1.25-inch diameter 1144-steel round stock. I used a pre-ground HSS tool from Sherline. I faced the end and turned down the OD. I got rough surfaces, a lot of chatter, and the piece came loose from the 3.1-inch diameter three-jaw Sherline chuck.

I attribute the cause of the piece coming loose to the significant chatter. I attribute some of the chatter to two mistakes that I made: I installed a left-hand tool instead of a right-hand tool, and I installed the left-hand tool with the top face turned 90 degrees counterclockwise.

I ended up making the washers out of 6061 aluminum.

Karl A

Ouch.

I'm glad to hear that I'm not the only one who didn't get it quite right immediately.

 

[BiggerNoise]

You have to keep in mind that the Sherline motor is only rated at 60 watts, or 0.08HP, so the Sherline will never be accused of being a powerhouse. Yet, it can perform like a much larger lathe IF you use the right tooling on it. The preground stuff you get from Sherline is not precisely ground and simply (and poorly) approximates the tool geometry of standard tooling. The stuff on Amazon ... who knows what they are ground to. I cannot recommend either choice but that is not a reflection on you; just a statement of fact. If you need a good set of tools to unlock your lathe, PM me and I will hook you up with someone who can grind good tools that will perform well, at least until you have the time to learn how to do it yourself. If I were you, I would use 5/16" - 3/8" tool bits. 1/4" will work okay but the larger, stiffer bits work much better. Please trust me in this; your tooling is the key to unlocking the Sherline lathe.

All Sherline lathes are different, meaning the center height of each one is different. They may be close but not the same. Likewise, the centering tool they sell may or may not match your spindle centerline. Given that even a thou or two above or below center makes a difference on a precision lathe, it is better to at least confirm the accuracy of the tool you have or make one to fit your lathe. Fingers crossed yours is accurate.

Speed:
RPM = CS (in sfm) X 3.82 / diameter of the work in inches
This is the formula to calculate speeds for a given material. Go here to see the listed cutting speeds (CS) for commonly used materials.

For your material:
RPM = 500-600 sfm X 3.82 / 1" = 1,910 - 2,292 rpm for a 1" diameter piece of 6061-T6 so you might want to increase your speed a bit.

With that said, speeds are a bit tricky to understand. Speeds are important for cutting efficiency and tool life but they are not exact. The calculated speeds in the tables are also for industrial machines with standard geometry tooling using power feeds, not for a little manual feed Sherline. The "tricky to understand" part is that speeds, feeds and depths of cut are tied together in an intricate ballet. The deeper the depth of cut, the slower the speeds will be and the faster the feed will be. Likewise, faster speeds like in the calculations above will limit how deep you can cut at that speed and you will need to adjust the feed by feel. You think the learning curve is near vertical? You're underestimating the curve!

My suggestion is to get yourself some good tools and then play with the lathe. Set your speed somewhere around 1500-1600 rpm and dial in a 0.020" deep cut and feed the tool into the work so that you feel a slight resistance to the feed; the tool will push back and you'll feel the resistance. You want to feed just fast enough to maintain a slight resistance. Under these conditions, the material will string; that is the nature of 6061. If you want this material to chip, you have to take a deeper cut and feed hard and fast and it will come off in chips but for now, accept the strings and be careful because they are sharp. Also keep your hands clear of the strings; they can grab your hand and pull it into the chuck.

Play with speed, feed and depths of cut and you will begin to sense their relationship, how changing one will affect the rest. When I first started on my Sherline, I spent months learning how these three factors work. It was time well spent. Now I no longer even bother checking or calculating speeds for most materials on my lathe. I turn the lathe on, set speed wherever my lizard brain thinks it should be and feed according to what my feel tells me is appropriate.

You have a good machine. I would take the time to learn how to use it. Everything you learn on a Sherline lathe will transfer over to a larger one if you ever decide to step up. I believe I am better on my Emco Super 11 lathe because of what the Sherline taught me.

Thank you for the detailed reply, I did send you a PM for a tooling contact.

It's good to know that the strings aren't necessarily a sign of doing things wrong.

One question on tool holders:

The height adjustment is a little wonky on the stock tool posts. I have seen that with the quick change sets available from Sherline and Little Machine Shop, the holders have screws that should enable a much more careful setting of height. Any experience with any of these? Or best to just stick to the stock posts?