Member postings for Robert Turner 1

A 'Roving bridge' is designed so that a horse towing a barge can cross from one side of the canal to the other without having to disconnect themselves from their boat. That's why the ramp one one side has a big loop. Without the loop, the tow rope would tie itself in a knot around the bridge.

Theres something very serene about canals, though 200 years ago, they must have been very busy carrying the materials and products of the early industrial revolution. From a design/engineering point of view, they are fascinating. They had no tensile materials to build from and very limited ability to pump water. Basically all they had to work with was gravity.

Thank you everyone for all your help. I did consider the Boxford collets, but the 1/2" limit is too restrictive, plus getting a set out here to Halifax, Nova Scotia would cost $$$$. I found some section drawings of the 'Bison' Collet chuck and the collet threads are indeed used to both pull and screw at the same time, so I'm not worrying about wrecking the collets each time I use them. I also notice that the Bison chuck has an oiling point next to the thread, so I will be including one of these.

I realized a long time ago that my engineering hobby would be characterized by plenty of time, but no money, so I think I will have to live with the compromises inherent in my 'Tommy Bar' design. The overhang of the front of the collet from the spindle nose will be 85mm and as the 90mm dia chuck body will be screwed directly onto the spindle, I don't expect too much chatter.

Thanks for the replies - I think I will have about 12 turns of the thread engaged when the 'pulling' part of the action starts. If it looks like this will strain the threads too much, I might add an external locking ring with a coarser thread that pushes a set of pins onto the face of the internal nut.

The other reason for considering 5C collets is that there is more likely to be second-hand ones available.

By the way, does anyone make ER collets for hex or square bar? That would be one of my main reasons for wanting to use collets - I will be making a lot of nuts and bolts for the beam engine and my three-jaw chuck has had 45 years of abuse in a training college....

Hello all - I have been 'lurking' on these forums for a while, and I have a question about making a Collet Chuck for my Boxford AUD.

First a quick introduction: I'm not trained as an Engineer, but I have built lots of full-size hobby projects, such as Wind Turbines, Furniture, a car, a motorbike etc etc. I have had my lathe for about 10 years now and I am working on my accuracy (and patience!) with a view to making a model beam engine.

I don't have much budget, so I have been making various tools for the Boxford out of bar stock, like a cross-drilling jig and a Dividing head.

I realized that I will need more accurate workholding to be able to make a model, so I decided to make a 5C collet chuck, as it seems to have the biggest range of sizes and shapes (Hex and square are handy collets to have). My design for the chuck is pretty simple and it uses a captive 'nut' inside the body to thread onto the end of the collet, tightened up with a tommy bar through a slot. My question is this: will I wear out or damage the threads on the collets by using them for the full force of the collet closing 'pull' while tightening? It struck me that when you have a drawbar you thread it into the collet first, then use the thread on the drawbar to do the heavy pulling. I don't want to use a drawbar, as the whole point of the 5C collet is to hold long bar through the spindle bore - my 3MT collets only allow me to hold a workpiece about 3" long.

Maybe I am worrying too much - It's not going to get heavy industrial use. I would appreciate it if someone with 'real' industry experience could assist......

Sorry for the long rambling post