Sherline Machine right for the job or too small?

[elementalrage]

Let me preface this by saying, I am new to the machinist world and am grateful for the members' knowledge here. I do have a strong knowledge of software and can use 3D programs.

I need to make some small pieces (see graphic), but a lot of them (200+), so I want to use a CNC lathe. I would look for a company to make them, but I would rather learn the trade and end up with some machinery in the shop to play with after the work week is done.

I have a ~$2500 budget which should get me a Sherline 4400 Lathe, the 6731 CNC Upgrade Kit as well as Mach 3 software and some accessories (chuck, hss bits).

THE QUESTIONS ::

The piece in the graphic is rougly 1.5" long. If I use 3/8" 6061 stock is the Sherline CNC going to take forever to make each piece? There is not much metal coming off each pass.

Also, is buying a lathe this small going to be a huge waste of money OR is this suitable for the task? I know stepping up to a higher end CNC machine will add several thousands to the price - is there a better option?

What would be the best starter chuck to buy? I want quick repeatability and accurate within a 0.002".

Thanks!

daren

 

[stevecmo]

daren,

I'm not sure I understand your concern. You did say aluminum, right? You're only talking a total depth of cut of .110" if you start with 3/8" material. Do I assume correctly that the largest diameter of the finished part is .185". If so, why are you starting with 3/8" material? Why not use 1/4"?

Regardless, I don't see a problem. The Sherline should make quick work of this.

Steve

 

[DMS]

I agree, the sherline should have no problem with that. They are small, but capable machines from what I have seen.

Now, if you plan to do larger pieces, that may be a reason to look at larger hardware, but for stuff on the scale you are describing, you should be just fine.

 

[elementalrage]

daren,

I'm not sure I understand your concern. You did say aluminum, right? You're only talking a total depth of cut of .110" if you start with 3/8" material. Do I assume correctly that the largest diameter of the finished part is .185". If so, why are you starting with 3/8" material? Why not use 1/4"?

Steve

I meant 3/16"... yes, 6061 aluminum.

Would 1/4" be better to use in case of dimensional issues with the 3/16" stock?

daren

 

[rebush]

Daren: You'll have no problem running those pieces on a Sherline. I've run alot bigger than that with no problem. You should have no problem with .002 tolerance and repeatability with the standard three jaw chuck. Sherlines are very accurate machines. Roger

 

[elementalrage]

Well, everything sounds great guys. Looks like I'll be making the purchase and then really start pestering you guys. ha!

Since I have video and camera equipment, I'll post some pics after I get it and set-up.

Thanks to all!

daren

 

[mikey]

On a work piece 1.5" long and 0.185" OD you car going to have to use a live center, regardless of the chuck used. The OEM Sherline live center is okay but not sure if it will hold 0.002". The 3-jaw chuck is pretty good - within 0.003" if I recall correctly. However, a more accurate system is a collet system. If you are going to work with 1/4" or 3/16" stock then the Sherline collet/drawbar system will work. If you want to pass the stock through the spindle then an ER chuck would be better and nearly as accurate. For what you are looking at an ER16 or ER25 chuck will work great. I use an ER32 system on my lathe and it is excellent.

The reason I raise the chuck issue is that you are looking at 200 pieces that have to be faced, turned and parted off. A collet will be faster and more accurate. Just a thought.

 

[elementalrage]

On a work piece 1.5" long and 0.185" OD you car going to have to use a live center, regardless of the chuck used. The OEM Sherline live center is okay but not sure if it will hold 0.002". The 3-jaw chuck is pretty good - within 0.003" if I recall correctly. However, a more accurate system is a collet system. If you are going to work with 1/4" or 3/16" stock then the Sherline collet/drawbar system will work. If you want to pass the stock through the spindle then an ER chuck would be better and nearly as accurate. For what you are looking at an ER16 or ER25 chuck will work great. I use an ER32 system on my lathe and it is excellent.

The reason I raise the chuck issue is that you are looking at 200 pieces that have to be faced, turned and parted off. A collet will be faster and more accurate. Just a thought.

I greatly appreciate the info!

 

[mikey]

I just did a check on my Sherline OEM live center (not the adjustable one) and it has 0.0008" of runout so your 0.002" requirement is not a problem.

I also wanted to reassure you that while the Sherline 3 jaw chucks are accurate to 0.003" they are quite good. The 4 jaw independent chuck is truly excellent. Still, with 200 pieces to do I would be looking at a collet system if I were you.

 

[D.C.Clark]

You might enjoy my video of mass production on a Sherline:

http://youtu.be/PubBx9K4bUo

For your application, I would turn all the diameters in one setup. That will ensure that surfaces all are coaxial regardless of how the material is held. With light finish cuts, and the right tool, you should not need a live center.

I'd install the rear mount parting tool on the back of the cross slide.

http://www.sherlinedirect.com/index.cfm?fuseaction=product.display&Product_ID=58

This will allow you to face, turn, and part the work in one CNC operation with no tool changes. The automatic material feed as in my video is even possible by feeding the work through a one-way roller bearing held in the chuck.

http://www.mcmaster.com/#drawn-cup-roller-bearings/=li3m5s

Alternatively, hold the work in an end mill holder. You would then only need to loosen a set screw, advance the workpiece, and restart the program.

This is really a very quick and simple job. I'll set it up on my lathe later today and post some photos.

David Clark in Southern Maryland, USA