Turning brass thimbles

[jdbondy]

My model of Pride of Baltimore 2 requires some thimbles. The model is in 3/16" scale, so the thimbles would have to be pretty small. I tried cutting segments of 1/16" brass rod with a Dremel cutting wheel and peening them with a jeweler's punch, but the results were not consistent or satisfactory.

 

I recently acquired a Sherline metalworkers lathe, used and at good cost. So I am finally having to learn how to properly use it for metal turning. To this point I have only used it to turn some wood pens. So the first step was to clean the sawdust out of all the crevices of the lathe...

 

I purchased 3/16" brass rod stock and cut off a suitable length (about 2"), then faced the cut surface smooth. (Oh, to get to this point, I had to learn how to grind my own cutting tool, then mount it so it was at the appropriate height. A process in and of itself.) Then I used a center drill to just barely touch the surface and create a dimple so my smaller drill bit wouldn't wander when drilling a center hole. I used a 0.031" drill bit (which required purchasing the small collet that accommodates such small bits, yet another step...) to drill a depth of about 0.1".

 

I turned the outer dimension to 0.050", then used a triangular file to carefully file a groove into the outer surface of the cylinder near its end. Then I parted off a thickness around 0.025-0.030". Getting to this point required extensive trial and error as I learned how to eliminate vibration of the parting tool so it wouldn't fracture the cylinder instead of parting off the final product, and also learned how to adequately sharpen the cutting and parting tools. But it was worth the effort to get such a consistent product. Three photos are attached, the final picture obtained after blackening with Birchwood Casey. Thanks for the tip, Dr. Toni Levine!

 

 

JD

[jdbondy]

PS, I just can't quite figure out how to make my images appear smaller in my posts! I substantially reduced their size (25% of original size) using Paint but that didn't seem to do it.

 

JD

[mtaylor]

JD,

Don't sweat the picture size.  As long as you're under the max and it loads, that's the important thing.  Usually, clicking on the picture will open it full size.   Having said that, Chuck recently increased the display size on what shows in a post and they look larger.  

[jud]

Those 3 jaw chucks are seldom concentric with the rotating C/L.  Two choices, a face plate and turn between centers with a centered head stock or oversize stock so you can true it up, both quick and useful methods. Don't see much about turning between centers on this site but I expect there are some here who use the method. 4 jaw chucks also are good except for the setup time and not often used for turning of round stock. There are instructions on line that will allow you to true up your chucks but they will never reach the precision of collects. Looks like you are getting a good start with you machine knowledge, that with your own observations will be serving you well in years to come.

jud

[mtaylor]

Jud,

You can also true up the chucks...  put a quarter as far back as you can get it and close the chuck.   Use an "inside" cutting tool to very gently kiss the inside of the chuck clamps.  Takes some time but it's worth it.    Just don't feed the cutter fast.. very slow and just so it barely takes material off.  

 

I got this from an old machinist way back on MSW 1.0.  Sadly, he's no longer with us but he knew his lathes and milling machines.

[Jose Gonzales]

Hi JD,

 

I did something a little simpler - I used brass tubing 1/8 " dia. , and cut it with a tubing cutter (from K&S) that I got at my LHS. In between the cuts, I used the cutter to etch a little groove in the middle of the ring (I etched the groove first, then cut out the ring). I used these thimbles for the slings on the fore and main courses of my Revell 1/96 Constitution.

 

Cheers,

Jose

[Richard Griffith]

Another method is similar to Jose's except I use a center punch to flair out both sides of the tube.  Be sure to anneal the brass to make it soft.      Duff

[jdbondy]

Thanks, everyone. Jud and mtaylor, I suspect that the error lies more with the tailstock, as it currently has a lot of play in it. I'm going to invite a machinist friend over to see what he thinks. I'll keep it in mind that we could true up the inside surfaces of the 3 jaw chuck.

 

Jose and Duffer, I have just put in an order for a K&S tube cutter! We'll see how that goes; I think it's going to be hard to beat the quality of the turned thimbles.

 

Hopefully I'll get around to creating an actual build log of my model...

 

JD

[wefalck]

What lathe do you have ? It may be worthwhile to invest into collets, if your lathe spindle has a taper for them, or into a collet chuck. This gives a much better and concentric grip on thin material - and is also safer, because you are not bothered by the jaws and can work closer to the chuck, which eliminates chatter.

 

Of course, the tailstock needs to be checked for alignment.

 

Why do you use a file to make the groove ? A tool in the slide rest would be safer and more efficient - or are you using a wood lathe ?

[jdbondy]

Hi Wefalck,

 

The lathe is a Sherline 4400.  I am using a collet on the tailstock of course; I guess you are suggesting another collet for the headstock. 

 

I used a file to cut the groove because I was just too lazy to go back to the bench grinder and create another cutting tool for making the groove! The file worked fine but I agree that another cutting tool with a pointed tip would be more optimal and reproducible.

 

I received the K&S tube cutter recently but I can't get it to work on the relatively small size of the brass tubing I have (1/16"). I'll put it away for when I have larger tube that needs cutting.

 

JD