Mounting stock. 3 jaw or 4 jaw chuck and fixed steady use.

I have this bolt about 1.2 inches in diameter and 7.2 inches long. As can be seen it has some corrosion mostly removable with a wire brush and file. I have cut the large square head off so have no 'true faces'. I want to reduce the diameter and cut a 12 TPI thread into it. I will probably lose the existing thread as this is to be a test piece. I initially mounted it in a 3 jaw with the intention of centre drilling the threaded end so I could then support it but as the Sieg mandrel is not big enough bore to accept the bolt I really have too much hanging out of the chuck. I then thought about using the fixed steady which came with the lathe but now I am in unknown territory never having used a steady. The steady is the type with 3 'pointed' bronze supports but the top doesn't hinge open.

I am concerned that the surface of the bolt may be too rough on the bronze supports. I'm guessing that setting the bar up in the steady is similar to setting it true in a 4 jaw chuck. Should I be using the 4 jaw chuck rather than the 3?

I could cut off the existing thread to shorten the bar but will still need to face both ends at some point and reduce the diameter to get it down to size for thread cutting and for turning the register portion behind the thread.

So, looking please for advice on the sequence of machining process's I need to face the ends, reduce the diameter and cut the threads.

Edited By Nige on 24/06/2018 20:22:17

Best to throw the bolt in the scrap bin or a box of useful for another job stuff. If you have a steel stockholder nearby buy a bit of EN1A to play around with. My local (12 miles away) stockholder has an offcuts/short bar rack and is very cheap for a cash sale.

I would use the 3 jaw. Hold the plain end in the chuck. Move the steady as close to the chuck as you can and adjust the fingers to touch all around. Then slide the steady up to the last parallel bit and fix the steady to the bed. Lubricate the fingers with some oil. This will hold the bolt steady enough to drill a centre hole. You can then remove the steady and and use a centre in the tailstock. Chris is correct in that this may not be the best material to use but you will learn a lot from attempting it.

HTH,

Rod

Hi Nigel If you want to turn this as a test piece I would firstly clock it up true on the outer right end complete end and centre drill the end. Use revolving centre to support the bolt whilst you clean up the place where the steady is to run. Wind back the steady suports and slide the along tge bed until it is in correct place, after winding back the tailstock. I use a piece of one thou shim and wind in the first bearing screw till it just nips but not push the piece, repeat for other two screws. Try running the lathe and listen. I would just nip the top screw and at the same time oil the bearing area. Try a cut but keep an eye open for heat build, up don't run it to fast, and chattering you have to just get used to the support that you get from a steady.

David

I would agree with Chris. Dump it and get something decent. Particularly on a small lathe.

Roy

Thanks guys. The whole point of this exercise is using what I have and learning the techniques to achieve the aim. Under ideal conditions it might be possible to choose a different bit of metal but the question would be exactly the same one if that was a nice looking piece of EN1A with the same dimensions. 😀

Thanks Rod and David for the suggestions on mounting and use of the steady 😀

Nige

Knock all the nasty corrosion off with a file or emery tape first. You can do this with the bolt held in a bench vice. Then do as Rod says, set the steady jaws on the bolt at the chuck end and then slide it down to the right so it bears on the last bit before the threaded section. You may have to temporarily loosen one of the brass points to move the steady. Then reset it once in position. Put plenty of oil on the bolt to lubricate the brass points on the steady and then drill your centre hole.

You say the bolt had a square head, most likely its a very low carbon steel and as others have said, not nice to machine. Don't worry about snapping your first threading tool, its happened to most of us when we get some 'lumpy' material.

Or just mark out each end, centre drill and clean it up between ctrs. Then set your steady as per Rod's method to face the ends.

As has been said bolts can be horrible material to turn, not just the metal but stresses and hardness set up when forging the head and rolling the threads. You won't learn if it is your thread cutting method or the metal that is at fault when you get poor results and loose the tip of your tool.

Cut it in half and have two test pieces! Now only about 2 1/2 times the diameter overhang, so no real problem, if careful.

What grade bolt? I would suspect it is not plain mild steel!

With a square head it could well be wrought iron, you may see inclusions in the area where you cut the head off, but you will if you can turn it. 99% of my metal comes from scrap, some is soft , and tears giving a rough surface, other stuff is hard and needs a carbide tool, but I can now usually find a good bit of scrap. My first thread was cut on a bit of cast iron, using a tool made from an old file.

Ian S C

Take care when machining long rods that are only gripped by the length of the chuck jaws. You are taking a walk on the wild side!

The danger is that long work can cam out of the chuck when you try and cut it. Then the other end flails about with a good chance of it jamming between the chuck and something solid like the saddle or tool-post. Bang! If it jams there's a good chance of serious damage to the lathe; dented ways, twisted tool-post, stripped gears, crunched tool, strained bearings, and a dead motor / electronics are all possible. If the rod doesn't jam, it might damage the operator instead.

Rods longer than 4 or 5 times their diameter are surprisingly bendy and they also act as a lever. A typical cam out occurs when the tool pushes the spinning rod away rather than cutting metal. Sooner or later the tool digs in and exerts enough force to crowbar the rod out of the chuck's grip. The cure is to make certain the work is supported throughout. It's not unusual to see long work supported by a fixed steady and by a travelling steady as well as the chuck and tail-stock centre.

I'd approach the job as described by Rod: drill a hole and use a tail-stock centre. Well worth doing for the experience, but take reasonable care.

Dave

Nige: If you're passing by I'll give you a length of free cutting steel.

Andrew

How do we feel about wearing rings in the workshop? My ex-GPO friend had a gory booklet showing finger injuries sustained after slipping a couple of feet on telegraph poles. (And then being caught by the harness.) I suppose catching a ring in a lathe might also end in hospital.

Which is why a rod in a steady that appears to be centred according to a dti can be well off the lathe centre - an effect that I observed recently when putting centres in a 13" length of 30mm diam. silver steel.

Rod (usually off centre and not very bendy)

I don't, but then again I'm not married, so there's no need.

But if I was I'd take it off. I do wear a watch, but I always wear long sleeve shirts. Otherwise no loose clothing and I never wear gloves when running the machine tools. I mostly wear goggles when machining and I've recently bought a proper pair of slip on safety shoes. Good move since I've dropped the traction engine rear wheels twice while trying to rivet the spokes. I've also got a bag of ear plugs for use when using DIY power tools, especially the angle grinder. And in case of boo-boos I've got a first aid kit, eyewash and fire extinguisher on the wall by the door.

Some while back I got an old tatty jersey caught in the lathe feed shaft. Darn good job the power lever was on the saddle; I don't think I would have been able to reach the headstock. I don't have enough hair to worry about getting it caught, although I did so when a kid and in the 70s there was a fashion for long hair. Fortunately not serious, but it still hurt.

Andrew

Edited By Andrew Johnston on 25/06/2018 17:40:02

Just keep your hand with the ring on it away from the moving chuck etc. Don't use your hand as a brake to slow the chuck down and stop it after cutting off the power, just let it come to a rest naturally. And you shouldn't be putting your hands near swarf spirals etc anyway. So no big drama re rings and lathes really, if common sense is applied.

Rings are probably more of a danger when climbing ladders or even stairs with poor handrails. As in the phone pole example, the danger is when you slip and grip on to rough surfaces to support whole body weight under movement.

I remember a training film (back when talkies were a new thing!) that showed how a bloke ended up bodily in a skip of scrap metal after pushing a bale of scrap off the loading dock. His ring caught on a piece of wire etc sticking out of the bale and pulled him into the skip along with the bale.

How about boring a short length of stock, concentric to the OD, to be a close fit over the threaded portion. Then run the fixed steady on that? (Similar in principle to a cat head, for those who are familiar)

No need to overcomplicate it. A fixed steady on the existing plain section will hold the piece plenty securely enough to drill a centre hole in the end.

A few weeks after one of my work mates was married, he was removing the battery from a Cessna 185 on a cold and frosty morning, and managed to short the spanner and wedding ring, welding the ring to the spanner and causing quite a deep burn to his finger. Don't know about other times, but the ring never came back to work.

Ian S C