How to make a long thin tapered rod

I have been asked if I can make some items that use a steel rod tapering from 1/4" down to 3/32" over about 7". All I can think of at the moment is to try and turn it but using a special tailstock centre to allow it to be placed in tension and offset the tailstock to set the taper as normal. The taper doesn't have to be accurate, it could be slightly barreled, but does need to be smooth. Any body have any better ideas.

I think this would typically be done using a taper attachment.

If you don't have a taper attachment, turn it between centers and set over the tailstock.

Jim

Don't know anything about your special tailstock center, I assume it has some kind of chuck--but if you were to offset the tailstock in the usual way for tapers, something like that is not likely to work unless it has some kind of swivel joint.

I might try turning the bulk of it off on the lathe, then finish off with grinding, sanding or filing while spinning.

If it doesn't have to be accurate, chuck a 1/4" shaft in a portable drill and grind it while spinning. Start with a coarse wheel, then finish off with a belt sander which would give a fairly straight taper if the sander's platen were long enough.

Or chuck it in a drill press, and use an angle grinder.

Ken Grunke

Hi David, if you have a lathe: use thicker stock material, face on both sides and bore center on both sides w. center drill.

turn between centers, with tailstock set over and use a travel rest. on both sides leave about 1/2" long thick for later use in the chuck then mount the chuck and cut off either end

If you do not have a travel rest you may use some square material, drill a hole and insert a round brass bar with the end cut to a V. This will be just right to avoid too much flex. (Lubricate well: gear oil is just fine).

/jan

David Billington schrieb in im Newsbeitrag: snipped-for-privacy@djbillington.freeserve.co.uk...

If you had a friend with a Swiss-style CNC lathe, you'd be laughing.

Other than that, I wonder if a toolpost grinder would work well. You'd certainly get an excellent finish. Not sure about deflection though.

Regards,

Robin

Just use a steady, home-made is OK. Turn between centers, don't rely on the bending to give you good results.

Jim

Turning it will be a real bitch because you have so much deflection and you cannot turn it too fast. If you could figure out a way to grind it on a simple bench grinder you may have more luck. I'm thinking of something similar to a centerless grinder only with one wheel, the standard rest supporting the bar, and a fixed stop clamped to the rest to take the thrust from the grinding wheel. You would have to spin the rod has you feed it across the wheel. Maybe you could use a slow hand drill to spin the rod. Now the only thing you need to figure out is how to get it tapered. I'm thinking that if you had a tapered wedge, maybe plastic, that was the full length of the bar, and inserted between the rod and the fixed clamp on the rest, you could feed it with the bar to increase the grinding depth and generate a taper. Maybe you could slide a big washer over the bar until it bottom on the hand drill chuck. The plastic wedge would bottom on the washer and push the wedge along with the bar while the bar is spinning. Yeah, I know its real hokey but its a start.

How bout using a tool post grinder with the set over tailstock? Gerry :-)} London, Canada

I had to make a small triblet for the jewellery I make. It consists of a silver-steel rod that tapers from 9mm to 1.8mm over a distance of about

150mm. I turned it on my lathe using nothing but the standard equipment

- I don't have a taper attachment and the top slide travel is only 70mm.

I machined the taper in stages, so the the cutting tool was never more than 30mm from the chuck. I centre drilled the end, set the topslide over to the the required angle, chucked the rod so that only 30mm protruded supported it with a live centre in the tailstock, then started to cut the taper until it got too close to the live centre. At this point I continued the cut by leaving a knob on the end where the centre supported the rod. It got tricky at this point 'cos I wanted to get the end of the taper as small as 1.8mm, but, by using a sharp tool that could cut in both directions, this was finally done. The rod was then extended a further 30mm and, with suitable light cuts, the taper cutting was continued until it met the previous one. The process was repeated until there was no more to cut, then the knob was removed and the surface improved with emery cloth.

It made a very nice triblet that gets a lot of use - in fact I made two, one for a friend.

David Billington wrote in news: snipped-for-privacy@djbillington.freeserve.co.uk:

Radius nosed wheels in your follow rest. Turn between centers.

Greetings David, One thing that may work is to use oversize stock, say 3/8" or 1/2", and turn it down all at once. If you used Ledloy (12L14) I think it may work for you. If I was doing it I'd start with 1/2" 12L14 and centerdrill the end. Then, cut a groove down to 3/32" about 3/16" wide and about 1/4" back from the centerdrilled end. Or, if you dont like that put in a very small center, about 1/16" dia. Anyway, after the parts were all drilled put them back in the machine and turn all at once. If you use the groove method you will need a narrow tool or you will need to enlarge the groove so your tool can get all the way down to 3/32". In case you don't know, 12L14 is a leaded steel alloy that turns so well some folks call it "Dark Aluminum". After turning cut off the end if you used the groove method.. BTW, does your tailstock have enough travel to get the desired taper? ERS

David Billington wrote in news: snipped-for-privacy@djbillington.freeserve.co.uk:

00p....you are correct.

I typed before I gave it much thought..my bad.

Are you concerned about failure in bending due to exceeding the elastic limit or non-destructive flexing? What is the stress level? As long as the stress is well below the yield strength of the steel which alloy you use doesn't matter. All steels have a modulus of elasticity of approximately 30E6. If the max. bending stress in your object was (say)

10Kpsi, mild steel would bend the same amount as heat treated 4340 or High Speed Steel or ...

Ted

Funny, that, that's exactly how I've done it, too.

I was turning tapers, about 380mm long, tapering from 15 to 3.8mm. I started with some 5/8"round bar and cut the taper 80mm at a time, working from the small end to the large. I centre drilled the small end for the rotating centre, not really for support, but to keep it from whipping about. Worked a treat.

Cheers

John

Wooding wrote: || David Billington wrote: ||| I have been asked if I can make some items that use a steel rod ||| tapering from 1/4" down to 3/32" over about 7". All I can think of ||| at the moment is to try and turn it but using a special tailstock ||| centre to allow it to be placed in tension and offset the tailstock ||| to set the taper as normal. The taper doesn't have to be accurate, ||| it could be slightly barreled, but does need to be smooth. Any body ||| have any better ideas. ||| || || I had to make a small triblet for the jewellery I make. It consists || of a silver-steel rod that tapers from 9mm to 1.8mm over a distance || of about 150mm. I turned it on my lathe using nothing but the || standard equipment - I don't have a taper attachment and the top || slide travel is only 70mm. || || I machined the taper in stages, so the the cutting tool was never || more than 30mm from the chuck. || I centre drilled the end, set the topslide over to the the required || angle, chucked the rod so that only 30mm protruded supported it with || a live centre in the tailstock, then started to cut the taper until || it got too close to the live centre. At this point I continued the || cut by leaving a knob on the end where the centre supported the rod. || It got tricky at this point 'cos I wanted to get the end of the || taper as small as 1.8mm, but, by using a sharp tool that could cut || in both directions, this was finally done. The rod was then extended || a further 30mm and, with suitable light cuts, the taper cutting was || continued until it met the previous one. The process was repeated || until there was no more to cut, then the knob was removed and the || surface improved with emery cloth. || || It made a very nice triblet that gets a lot of use - in fact I made || two, one for a friend. || || || -- || || Regards, Gary Wooding || (To reply by email, change feet to foot in my address)