Smaller Box Tools for a smaller lathe

[greenie]

I needed to make thousands of small 12BA and 10BA Coachbolts for the models I make.
I started to make them on a Unimat 3 lathe using a cutting tool, after many mistakes and it taking a rather long time to make each miniature Coachbolt one at a time, I realized I needed to make the process much quicker and easier.

I have the book by Stan Bray, called MAKING SMALL WORKSHOP TOOLS, on page 67,68,69 and 70 are drawings for a simple box tool with a taper on it, for fitting into the tailstock of a lathe.
Using these drawings as a guide and with a bit of head scratching and a few false starts, I eventually came up with this lot.
It just screws onto the tailstock of the U3 lathe, once the tooltip is set for the correct size shaft for the coachbolt I require, then it's into it and I can make thousands of whatever length coachbolts I need, just set and forget.
The Unimat 3 is very good for this, just push the tailstock up to the Tobin Bronze sticking out of the chuck and then one turn of the tailstock is one millimeter, if I need a ten mill bolt, then turn the handle 10 times, simple as, eh.
Tobin Bronze is a heck of a lot cheaper than brass and is far stronger than brass of the same small diameter, using bronze you will get far fewer breakages than if you used brass for the miniature coachbolts.

Threading the miniature coachbolts is dead easy, I just used a broken screwdriver and drilled a hole into the main pulley, insert this handle and crank away as many times as you want. The bronze does not grab like brass and it is very easy to hold the die in your fingers when doing 10BA or 12BA.

Used the K.I.S.S. principle here, far fewer things to go wrong, just screw on what sized cutter for the different sized coachbolts I need and away you go.

The drawing can be adapted to whatever lathe you might want it to fit.





Psst, K.I.S.S. = Keep It Simple Stupid

[Altair]

Thanks greenie! We've added your Box Tools to our Lathe Accessories category,
as well as to your builder page: greenie's Homemade Tools. Your receipt:

Box Tools by greenie

tags: tailstock

[bigalscorpio]

Hi Greenie, You got me interested in the gadget and the end product but for the life of me I can't imagine the process. How about a few close ups of this in situ or even a video? Also some pics of the bolts before and after with something to compare scale. All the best, Al

[greenie]

OK Al, you should be able to see what happens now -----------

Here's the 12BA box cutter with the front cover removed, showing the two pieces that make up each Box Cutter -

https://i.imgur.com/sPEo2c4.jpg

Simple as, no moving parts at all, the bronze rod just slips into the hole in the front cover, to make the rod stay where it should when it's being attacked by the toolsteel. The 4 cap screws are to adjust the 1/4 inch toolsteel, into an appropriate position, so that it can do it's job properly.


Down to business -------------------

Bronze rod sticking out of the chuck about 20 mm to make a 10 mm coachbolt, the front plate that supports the bronze rod is 10 mm thick, so 10 + 10 = ?

https://i.imgur.com/qdiJEXa.jpg

Move tailstock up so the rod touches the tooltip

https://i.imgur.com/6h6MQlE.jpg

Turn on lathe and start to crank the tailstock forward by 10 turns, remember 10 + 10 = ?

https://i.imgur.com/1vv9VFC.jpg

Remove tailstock and you have an un-threaded 12BA coachbolt by 10 mm long

https://i.imgur.com/bSEpbHP.jpg

OK, now to start to make the 12BA thread, the main pulley has a hole to take an old stuffed screwdriver cut down for a handle.

https://i.imgur.com/jhhFnrg.jpg https://i.imgur.com/KyvxAWK.jpg

Hold the 12 BA Die in your right hand firmly and crank the handle thirty odd times with your left hand, 12BA is about 3.4 threads per mm.

https://i.imgur.com/p6OVSp7.jpg

Bingo, one threaded 12 BA coachbolt fully threaded to 10 mm

https://i.imgur.com/IttEL3j.jpg

Cut it off anyway you can, so you can continue to make as many coachbolts as you might need

https://i.imgur.com/lJIKH9S.jpg https://i.imgur.com/mPiVeW5.jpg

Insert the unfinished coachbolt into a Pin Chuck, to be able to make the domed head on the coachbolts, then into it with a file to round the head off, to finish the miniature coachbolt

https://i.imgur.com/E12iF2Y.jpg https://i.imgur.com/jzXuDkg.jpg

After this, you have a completed 12BA by 10 mm long ready for use on a model.

https://i.imgur.com/ev6aJgM.jpg https://i.imgur.com/M322n2b.jpg



Hope that is enough explanation for you, if you require anymore, please let me know

[bigalscorpio]

Hi Greenie, Right, now I get it, and I love the end result! Those tiny bolts really finish off the job nicely.

I have had for some time a set of tiny taps and dies, it's only a Rolson 59154 set but saying that some Rolson tools are half decent and these seem reasonable quality. I bought them originally for repair work but you have inspired me to have a go at some tiny bolts for one of my mates who has just started scratch building model boats (Cabin Cruiser at the mo) but plans to concentrate on Canal stuff mainly. My set btw is Metric M1 to M2.5 and so far have only been used on steel, which I have to say they seem to cut quite well, clean and smooth. I assume the local Model shop will carry Tobin Bronze rod? Can't wait to try a 1mm thread on some bar. I have never used the M1 or infact anything below M1.4 and most of my use in general has been with the dies..

Keep up the good work and when I get chance I will have a go and try to post pics of my results. Thanks again, Al (Sheffield, UK)

[greenie]

Hi Al, you will NOT find Tobin Bronze at any hobby shop, it is used by all sorts of persons for braze welding bit's to other bits.
Think Engineering workshops, they use it all the time for filling, or welding different bits together.
It is about half the price of equivalent sized brass rod and about twice as strong as brass rod as well.

The tap and die set you have is NOT made from the best metal available, but will do bronze rod or brass quite well.
I have both the metric and MONGREL set as well and only use them on bronze or brass.


https://www.ebay.co.uk/itm/2-4mm-x-2...gAAOSwDipdRMgJ

metric = self explanatory

MONGREL = stupid ridiculous outdated 'imperial' measurement - ie - it's a 'mongrel' to work with after you get used to Metric.