Free Metalworking Project Plans: Spring Center (Metal Lathe, Mill)
Material: Steel
Units: (in)
If you’re just starting out in metalworking, it’s not a bad idea to learn how to run a lathe. The first project I ever completed on the lathe was the Spring Center pictured below. At first glance it may look a little complex, but it’s pretty simple once you break it down into steps. If you’ve never used a spring center it might be a little unclear why this object would be useful, but it is!
So what’s a spring center good for? Basically it helps the user tap a hole.
To use the spring center, insert it into the chuck on the mill, drill press, or lathe tail stock. Advance the spring center toward the tap until the spring is fully compressed. Begin tapping as you would normally, but let the spring center apply pressure to the tap while you concentrate on turning the tap itself. As a side note, the photo showing the spring center in use also illustrates a handy way to protect a part from damage. Thin pieces of metal (in this case a sacrificed diet Pepsi can) can be used to prevent the vise jaws from marring the part.
Using the spring center will help you start a tap with ease because it helps maintain tap alignment along the axis of the hole being tapped. All you have to do is concentrate on not breaking the tap!
The spring center is a great “First Project” for the lathe. Once complete, you’ll turn to it over and over again the whenever you need to tap a hole.
In addition to the machined parts, you will need a suitable spring (which can be purchased or made from piano wire, welding wire, or any other suitable spring steel), and a cap screw.
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Update: Pictures of TroyO’s Spring Center
TroyO recently completed his own version of the Spring Center and he took pictures of the process. Below are pictures of the steps he used to complete his Spring Center, along with a description of each step by TroyO himself. Thanks for sharing TroyO!
“Here’s a shot of the completed project.
Here is a closeup of the slot… that’s right off the wanna-be mill, no cleanup other than sandpaper to deburr the edge. (I was surprised taking a close look at it… I expected some chatter marks but it’s really smooth.)
Here’s a picture to show how I used the socket head screw.
The image blow shows how I clamped the Spring Center in the QTCP tool holder to cut the slot. Pretty much just like a bit… I did some cleanup of the shaft after I milled it to clean up the marks from the set screws. I should have thrown a shim between the screws and shaft… ohh well. Note the same concept would work just fine in a turret toolpost, you’d just have to shim it until you got it on center. Secondary note… if you think ahead and machine the shaft to 3/8″ you could also hold it in a 3/8th boring bar holder.
To make sure that the part was aligned perpendicular to the chuck, I brought it flush to the face of the chuck, then locked down the toolpost.
Then I set the height using a centering guage… I could have used a dial indicator in the chuck as well and set it to the highest point. (A centering guage might make a nice project addition… but they are dirt cheap, LOL. I think I got it for $6.) Once I had the height dialed in I locked in the toolholder… now it’s square and on center and ready to cut.
Here’s what it would look like while making a cut (well, if the bit was spinning and the slot wasn’t already there, LOL).
Here’s a shot showing how I made the recess for the socket head screw. I used the same process for drilling the hole, although I stopped a little short and finished the through hole by hand after removing it. (I didn’t want to drill in to the QCTP holder.) I also started the tap a few turns after drilling but before removing the part from the toolholder. It’s a bit sloppy procedure-wise finish drilling a partly tapped hole, or to finish tapping without a guide and just counting on the feel to keep things straight, but it worked.
That’s it. I hope the pictures of my setup will be of use to someone!”
- TroyO
Thanks TroyO! I’m glad you took the time to share. Especially since you came up with a way for others to complete this project without using a mill. Now this project can truly be considered a lathe-only project!
For those of you who would like to make your own Spring Center, here are the plans:
Spring_Center.pdf (57.0 KiB, 4,159 hits)
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Tags: Beginner, Lathe, Mill, Units (in)
January 27th, 2009 at 11:52 PM
You can also use a spring centre to help with centring a 4 jaw independent chuck
January 31st, 2009 at 2:52 PM
I hadn’t thought to use the spring center in this way. In fact, I’m not even sure if I understand what you mean. Take a look at the link below and let me know if this is what you’re referring to. Thanks for the comment!
http://www.homemetalshopclub.org/projects/pmpcntr/pmpcntr.html
February 6th, 2009 at 4:49 PM
I would sure like to download the adjustable boring head plans, but when I follow the link I get a file that Adobe cannot open, says it is damaged beyond repair. Can you offer another source for the plans? Great site BTW!
February 6th, 2009 at 5:33 PM
I’m sorry you’re having trouble with the plans. I’ll check on it when I get home. If all else fails I can always email the plans to you directly.
Do you happen to have an old version of Adobe Reader? Have you tried to open any of the other plans? Have you tried re-downloading the plans? Make sure you save the plans to your hard drive (don’t try to open them from inside the browser, save and then open instead).
If none of those suggestions help, let me know.
February 6th, 2009 at 7:32 PM
I just checked the plans. They downloaded fine for me. If you’re still having issues let me know and I’ll e-mail them directly to you. Sorry for the trouble.
February 7th, 2009 at 7:33 PM
I downloaded a newer version of reader and it took care of the problem. Thanks!
July 24th, 2009 at 1:56 PM
While this project looks exciting, i think i need a little more hand-holding on my first lathe project.
For example, i have no idea how to achieve the 30 degree conical turning. I mean, i have the idea of where to put the tool, but how do i advance into it to get 30 degrees? Perhaps something to do with the compound angle that I’m missing?
Is there another project (with pedantic instructions) that i should maybe try first?
Thanks for any help!
July 24th, 2009 at 8:05 PM
Hi Tsaavik,
You’re right, this project can seem daunting at first. In fact, it was the first project I ever completed on a lathe and I got stuck in a few spots. The other limitation this project has as a first-time lathe project is the slot for the set screw, which really needs to be cut on the mill. So in all reality, it’s kind of a lathe/mill first projet. You can cut the slot on the lathe, but you’d have to secure the part to the cross slide (preferrably via a milling attachment) and cut the slot with an end mill that is held in the chuck (or better yet, in a collet if you have a collet closer for your lathe). Those limitations aside, here are a few pointers.
First, the 30 degree angle (a 60 degree total, or “included” angle) is indeed cut with the compound. To do so, set the compount at 30 degrees from the axis of the part. If your compound is set to zero degrees (so the tool is cutting along the axis of the part, and the handle of the compound is pointing toward the tailstock, or toward 3 o-clock), turn the compound 30 degrees in the counter clockwise direction. The handle for the compound should swing toward upper right (or about the 2 o-clock position) and turning the handle should move the cross slide toward the lower left (or toward the 8 o-clock position).
Once you’ve set the cross slide at 30 degrees, you’re ready to start cutting. Take little cuts in the same way that a pencil sharpener cuts a new pencil. What I mean by that is, if you stuck a pencil in a pencil sharpener and turned the pencil one rotation, the 90 degree edge of the pencil would be slightly chamferred. Another rotation of that pencil would make that chamfer larger, until eventually you’ve got a point on the pencil. Do the same with your cuts. Take a little cut to just barely chamfer the 90 degree edge, then take another cut a few thousandths deeper until eventually you’ve got a point on the end of the part. Make sense?
The other problem you might run into is drilling out the hole in the other part. Use a center drill first (always), then a small bit, maybe a 1/4″. Don’t bury the bit all the way into the part, doing so might cause the bit to break. Drill that 1/4″ hole a half or maybe 3/4″ deep (dependign on the lenght of the drill bit and the quality of the drill bit you may be able to go deeper). Once you’ve got the hole 1/2″ or so deep, chose another bit between 1/4″ and the final size – like a 3/8″ bit. Drill that hole to the same depth as the first. Then pick a drill bit that is at the final size (I don’t have the plans open, but I think the final diameter is .500 or 1/2 inch). So pick a 1/2 inch drill bit and drill that to the same depth. Then do the entire process over again (1/4, 3/8, 1/2) until you’ve got the hole to the proper depth. If you were to just center drill and chuck up a 1/2″ bit you’d run into problems. Your lathe might not have the HP to drill such a large hole all at once, your bit might wander or cut a non-round hole, or your bit might start to slip in the chuck. You want to try to avoid all these things. Also, use cutting or tapping fluid while drilling the hole, and retract the bit ever 1/8″ or so to remove the chips that build up.
Now, if you really want that hole to be perfect, you need to drill it slightly undersized (like .480), then bore it a little larger (like .498 or .499), and then ream it to size (.500). That’s the best way to get the hole perfect. I didn’t do that with my project because I wasn’t trying to get a perfect hole. I just needed it close. It’s up to you. If you have a .500 reamer and a boring bar, go for it. If not, don’t worry about it.
The hole for the set screw can be drilled and tapped on a drill press using a v-block or even just a vise, but a v-block will help you drill the hole perfectly perpendicular to the axis of the part. Tap the hole at the same time (avoid removing the part between drilling and tapping to help ensure that your tap starts straight).
Again, the slot is best cut on a mill. But you could use a drill press with an end mill and an x/y attachment, or you can cut the slot on the lathe if you have a miling attachment for your lathe.
Other than that, everything else should be pretty self-explanitory.
Oh, and to answer your question about an easier “first time” lathe project. I don’t have a set of plans right now that would be easier, but you might try to find the set of plans by South Bend Lathe Works for the plumb bob (it’s Project Number 3). It’s very easy. It’s basically a plumb bob cut from a piece of hex stock. It’s one piece and simple. Another idea (also in the same book of plans) is for a set of punches (center punch, drift punch, nail set, ect). They are also turned from hex stock and can be cut to whatever size you might need.
Here’s a link to the book on e-bay:
Machine Shop Projects by South Bend Lathe Works
Last I looked the book was listed for $12 – worth every penny. You can also try to google the book if the link above is dead. Lindsay Publications also sells the book so include “Lindsay Publications” in your search if you have trouble finding the right book.
If you have any other questions or get stuck leave another comment and I’ll try to help you out ASAP.
Good luck and thanks for visiting!
Tyler
September 16th, 2009 at 10:13 AM
awsome
October 27th, 2009 at 7:52 AM
I just made one of these last night, nice project! Thanks for the site and the plans, it’s great!
I made mine a bit smaller, to suit the stock I had on hand (5/8 Drill rod) but I think it’s still plenty beefy for the job.
I don’t have a mill so I clamped the outer part in to a QCTP toolholder and milled it that way. By first lining up the toolpost against the face of the chuck, then adjusting the height using a centering guage (you could also use a dial indicator) I got everything squared up and in line.
Then I just chucked up a 5/16″ end mill(Remember mine is slightly smaller scale) and took several light passes until I had a nice slot ready to go. It worked like a charm and made it a Lathe Only project!
I used a 6/32 socket cap screw and just took a light pass off the head until it ran through the slot without binding.
October 27th, 2009 at 10:46 AM
Hi Troy,
I’m glad to hear you enjoyed the project. I use my original spring center almost daily (well, at least every day I work in the shop). It has been the most useful shop-made tool I’ve ever made.
I’m also glad to learn of the technique you used. I’ve been trying to figure out how to make this a lathe-only project. I had considered chucking an endmill and holding the part in a milling attachment, but I hadn’t even considered holding it in a QCTP. I need to check, but the part might actually be small enough to fit in the 4-way turret style tool post that some lathes (including mine) come with. If so, that would make it easy for anyone to take your approach to cut the slot.
The only thing I didn’t quite follow was your last sentence. Why did you need to remove material from the head of the cap screw?
Also, could you send a picture of your completed spring center? I’d like to post it here. If you have any pictures of the setup please send those my way as well.
Again, I’m glad you had fun with the project!
Tyler
October 28th, 2009 at 6:13 PM
I only had to take some off the #6-32 cap head screw because the head was slightly larger than the 5/16″ slot.
A regular 1/4″ set screw (Which I think is what is in the plans?) would have been fine in the slot, except the inner shaft size I used was just under 3/8″ so there wouldn’t have been a lot of meat left to hold the 1/4″ set screw.
I also don’t care for the idea of using a threaded set screw shaft as a stop… a nice turned section seems a better fit.
Besides… I had a #6-32 handy and didn’t have a 1/4″ set screw. ;-P
I also used the mill to make a flat on the shaft before drilling/threading for the cap screw.
I’ll go shoot some pics and re-create the wanna-be milling set up.
(My lathe is an HF 8×14, BTW… I could have accomplished the same with the stock turret and shimmed it just like a cutting bit.)
October 28th, 2009 at 10:46 PM
Ah, the fact that you were using a cap screw didn’t register. Now I understand why you needed to shave it down a bit. I actually like your solution better. You’ve got a smooth cap screw riding in the slot instead of a threaded set screw. Nicely done.
I added the images you sent to the post above. Thank you for taking the time to duplicate your original setup and take pictures.
Like I mentioned before, you came up with a great solution by using your lathe to cut the slot. I was always worried that lathe owners looking for a first project would be put-off by the fact that you needed a mill to complete this project. But not now!
Thanks again for your contribution!
November 24th, 2009 at 9:26 AM
Sorry for the very slow response, yes that link to the shop made pump centre was just what I was thinking of with regards centering a independant jaw chuck.