Rule of thumb of when to use a steady rest or follow rest?

[Wonderclam]

This is for the PM-1127 lathe.

What's the rule of thumb when using a steady rest and follow rest? I know that if you have your workpiece sticking out more than 3 or 4 times the diameter of the workpiece, you have to support it with the tailstock.

But what about the steady rest?

 

[MontanaLon]

Interested in hearing the real answer to compare it to what I was taught. What I was taught was any time the work stick out from chuck was greater than 4x work diameter and you couldn't use a tail stock the steady rest was the way to go. For the steady it was any time the work length exceeded 16 times diameter for stock less than 1 inch in diameter. I always thought that was a bit conservative as I never was able to create any meaningful deflection in a 1" diameter piece of stock of any material without causing the belt to slip on the lathe. Light cuts are easier than setting up the follow rest properly.

 

[mikey]

The rule of thumb I use for unsupported work is 2X the diameter; beyond that, use a live center.

A steady rest has many uses but perhaps its most useful is when you have a work piece with an OD bigger than your spindle can pass. In that case, it has to stick out of the chuck and requires support. If it is solid then you use the steady rest so you can face and then center drill it before bringing in your live center. If it is hollow then you use the steady rest to put a 60 degree chamfer on the inside so you can use your bull nose center. Sometimes the work piece is odd shaped and you need to use a "cathead" that looks like a spider; the cathead has a round surface that the steady rest can ride on.

As far as I know, there are no established rules for a follow rest, although I could be wrong. I use a follow rest rarely because my HSS tools don't deflect much but there are times when the work piece is obviously too long and deflection is a certainty. I don't hesitate to use a follow rest if I think I need it, and this is especially so if I need to hold tight tolerances or if I have a lot of stock reduction to do on the part. If I don't have a lot of turning to do, I usually wrap a piece of stiff paper to pull the work piece into the tool, lube it well and hold it by hand and go; this works better than you might think.

One trick that is useful when using a steady rest is when you want to avoid marring the finish with the fingers of the rest. Use a piece of heavy paper and put it around the work, under the fingers, then clamp the paper to the frame of the steady rest. Put some oil under the paper and proceed to work as usual. The paper usually prevents any significant marring, and what there is comes off easily with a bit of polish if required.

 

[darkzero]

I don't really follow any rule of thumb on when to use a steady rest or follow rest. I just use them when needed as in if I can't make the cut without chatter/deflection. I don't use them for the same purpose so to speak. It depends on the workpiece (size, length, material) & operation.

So here I'm using a live center, well it's a bull center but whatever. The workpiece is large enough in dia so it won't deflect under tool pressure. Now if the work piece was say 1/2" in dia rather than 3.5" dia & I needed to turn the entire length of the OD then a live center probably wouldn't have been sufficent as the workpiece would probably deflect towards the center & cause chatter.



That's when a follow rest would be used along with a live center. The follow rest supports the workpiece near the cutter so it prevents the work piece from deflecting as the cut traverses. Don't mind the details of this pic, it's all I had on hand. Don't know if anyone has actually done this & I didn't know what to expect before trying it but I'm knurling a piece of 5/8" dia titanium that's 24" long from left to right (luckily it worked out). Of course normally there would be a cutter. Although it's called a follow rest I like to have the follow rest support lead in front of the cutter so it doesn't mar the newly machined finish that is being cut.



A steady rest would be used when the workpiece is long & you need to machine the end of the workpiece and/or some area far away from the chuck or live center. Like boring out just the end of a long tube like I was doing below. Or say if you needed to put a center drill in a very long rod that was too large to fit through your spindle bore.




There are other ways to use both types of rests but this is how I mainly use them. Follow rest for long length smaller diameters while traversing & steady rest for long length end work or far away from any supporting end.

 

[darkzero]

One trick that is useful when using a steady rest is when you want to avoid marring the finish with the fingers of the rest. Use a piece of heavy paper and put it around the work, under the fingers, then clamp the paper to the frame of the steady rest. Put some oil under the paper and proceed to work as usual. The paper usually prevents any significant marring, and what there is comes off easily with a bit of polish if required.

Thanks for the tip Mike. I've always wondered what people did to try and protect the finish, I'll have to try that sometime. I've never used rollers before, only brass tips but I hear rollers can still mar the finish a bit. I've seen people make shields to prevent chips from getting under the rollers. The tube above was the first time I ever used the steady rest on this lathe, I was surprised that the brass tips didn't mar the finish at all this time.

 

[mikey]

Rollers will definitely mar the finish, which is why I rarely use them. Brass works better for me. I use that paper trick all the time, especially with aluminum. It tends to produce a burnished surface if I do a lot of machining on the piece but it polishes out quickly. Not my idea; I think I got it from the late Ian Kirby of the UK.

 

[darkzero]

I see. I'm going to buy a new steady rest cause that one that came with my lathe is a piece of junk. I wasn't expecting much of it & I did have to modify the the length of the fingers so I could fit that tube but I'm seruously gonna toss tbat thing it the trash.

The replacement will come with rollers but I think I will make brass tips for it instead. I've never had chips get under the brass tips. I could see how easily chips would get under rollers.

Do you use anything special for lube? I used Vactra #4 for that tube, that seemed to make the most sense with what I had on hand. At the local college all they really had was cutting oil, actually I'm not even sure it was cutting oil cause it seemed like they used that same oil for everything (lubing machines also).

 

[mikey]

I actually just use hydraulic oil and it seems to work fine. I like to use paper from a retail store catalog. Yeah, stupid, but the paper tends to be a bit heavier and has a gloss on both sides. Besides, I can always read the catalog if I get bored ...

 

[ThinWoodsman]

What's the rule of thumb when using a steady rest and follow rest?

At the risk of oversimplifying, and repeating what has been already said:
Use a steady rest when the workpiece would wobble due to stickout (think of what happens when you run a couple feet of stock out the back of the spindle).
Use a follow rest when the force of cutting will deflect the workpiece (think of a thin rod bending away from a threading tool).