Holding tapered bar in a lathe chuck.

[Thomas ClarkeParticipant @thomasclarke78224]

I would like to know who one would go about holding a tapered bar in the chuck if it is possible. I look forward to any answers on this matter.

 

Thomas

[HOWARDTParticipant @howardt]

Depends on diameter, length and taper, as well as the purpose for holding it.  The ideal way is to place it between centres and drive with a drive dog.  Anything small in diameter you would hold a parallel diameter and turn the taper outside the chuck.  If the taper is below about 8degrees you could probably make a bush with a matching internal taper and hold the part in that as it would be a locking taper, if larger you could push a centre against it to hold it in place.  Just some ideas, I am sure you will get plenty more.

[Andrew CrowParticipant @andrewcrow91475]

<p style=”text-align: left;”>You could make a split collar that could be pushed onto the taper to compensate for the difference in diameter if its quite a big difference or even just wrap some sheet metal or even tape around the smaller diameter.</p>
Andy

[peter1972Participant @peter1972]

What do you want to do the the tapered bar when it is held by a chuck?

[old martParticipant @oldmart]

Soft jaws for a scroll chuck can be bored to hold many odd shapes. If your chuck has top jaws held on by SHCS, you could make your own soft tops out of mild steel or aluminium.

[Thomas ClarkeParticipant @thomasclarke78224]

I would like to add a threaded hole at the bottom and create a dome at the other end. I have a ball turning attachment but this can’t be used while there is a revolving centre at that end. I could create the dome before I add a tapper to the bar but that would mean using a centre punch on the top of the dome to hold the revolving centre leaving its mark after the work.

 

[Peter Cook 6Participant @petercook6]

Drill & tap the hole before cutting the taper. After cutting the taper, make a parallel  arbour that screws into the threaded hole, grip that in the chuck and use a fixed steady close to the other end to machine the dome.

[JasonBModerator @jasonb]

large female ctr will support the domed end and allow you to turn the taper after shaping the dome

[Andrew CrowParticipant @andrewcrow91475]

When you turned the taper make a split bush at the same setting, you can then hold either way round to do the other operations.

[DalboyParticipant @dalboy]

Can you make the blank 1″longer to start with? Place the blank into the chuck and turn the dome on the end. Reverse the blank and turn down the last inch to the minor diameter and droll through the !” plus the depth of the threaded section and thread this.

The extra can be held in the chuck and by making a small adaptor to fit over the revolving tail stock with a reversed V which can be pushed against the domed end then turn the taper, finally part off the extra 1″ hopefully the parting off will leave a pretty clean end.

Hope that makes some kind of sense.

[mike TParticipant @miket56243]

Jason, That’s an interesting suggestion.

Can you explain each step in more detail.

[cedric 1Participant @cedric]

No need for a split in the bushing. Just drill and bore or ream a tapered hole in a piece of round bar held in the chuck. Then tap the tapered pin into the tapered hole firmly. It will hold well enough to dome the end. Then tap the pin out with a rod through the spindle hole.

Another way might be to turn your taper, then drill and tap the hole in the small end, then part off at the other end using a HSS form tool ground to give the radius with parting tool incorporated. Angle the parting section so the “tit” in the very centre is left on the scrap, not the job.

How big is the pin BTW? And how many do you need to make? Is the taper a standard dowel pin taper, or morse taper etc where a reamer could be used to make a quick bushing?

[mike T]

On mike T Said:

Jason, That’s an interesting suggestion.

Can you explain each step in more detail.

Take your piece of bar and face one end, spot drill, drill and tap your thread.

Hold in chuck to face the other end to overall length and form the dome.

Take an odd piece of rod, turn down the end and thread to fit the hole in your part.

Screw the part onto that threaded arbor which will drive it and also allow you to turn the taper right to the end (you can cut into the arbor)

Put a female ctr in the tailstock and bring that up to support the domed end

Turn the taper

[JasonB]

On JasonB Said:

 

Put a female ctr in the tailstock and bring that up to support the domed end

Turn the taper

For small pieces you can buy something like THIS I have one which I use when wood turning.

 

[DalboyParticipant @dalboy]

Not sure what happened but the link did not come out try again Look HERE

[JasonBModerator @jasonb]

You can also turn a 60degree cone into both ends of a short piece of rod, slip that onto your existing ctr and away you go. 3D printing would be another option.

[old martParticipant @oldmart]

Having seen the picture after replying, I would also start with a longer bar and drill and tap the end as deep as possible. Then turn it round and produce the round end. Using a concave ball bearing centre (which everyone should invest in) hold the threaded end in the chuck with enough sticking out to be long enough to be able to taper turn. If you don’t mine having a conventional centre hole on the rounded end you can use a normal centre to steady it when taper turning. Part off at the small end of the taper. If the metal is already cut to length, use the thread to secure the end to a pre drilled extra piece that fits in the chuck.

[Andrew Crow]

On Andrew Crow Said:

…make a split bush at the same setting, you can then hold either way round…

That statement might need additional clarification.

If you have the thick end of the taper in the bush towards the headstock, the cutting force will try to push the item out of the bush. This might be of concern if trying to drill the thinner end of the piece.

[Andrew CrowParticipant @andrewcrow91475]

Not sure how big the OP’s job is but I it’s about 6 to 8 inches long, a bush about 3 inches long split through once and partially split in two other equally places should be able to hold in a 3 jaw chuck while drilling.

Andy

[DC31k]

On DC31k Said:

On Andrew Crow Said:

…make a split bush at the same setting, you can then hold either way round…

That statement might need additional clarification.

If you have the thick end of the taper in the bush towards the headstock, the cutting force will try to push the item out of the bush. This might be of concern if trying to drill the thinner end of the piece.

I think I would turn the taper first, with a tailstock centre in the small end. Then drill and tap the hole. And then flip it around in a bushing to dome the big end.

[Howard LewisParticipant @howardlewis46836]

To add to the conflicting advice, do the easy jobs first, while the material is parallel.

Make the blank, drill and tap the end, reverse in chuck and form the dome.

Then screw onto a threaded arbor, and use Jason’s suggestion of a hollow centre in the tailstock, to support the domed end while the taper is cut

If you make the threaded arbor, and then do not disturb it , the thread should be concentric.

If the taper is longer than the Top Slide travel, you will have to turn the taper between a centre in the headstock and offset the tailstock. The hollow centre will accommodate the offset, but lubricate it.

Howard

 

[Martin ConnellyParticipant @martinconnelly55370]

If you have a morse taper extension/adaptor with a parallel section make the taper to match that morse taper. You can then hold it in a chuck.

Martin C

[cedric 1Participant @cedric]

How big is this pin?

[Pete RimmerParticipant @peterimmer30576]

I’ve been modifying MT4 arbors by cutting off the tang and drilling&tapping the end for a drawbar thread. I purchased an old MT4 cpstan turret sleeve and cut the end off. That allowed me to knock the arbors gently into the open-ended sleeve and hold the parallel outer diameter in the chuck. There’s no need for any other method of securing it holds the taper firm enough for turnong, parting and drilling.

 

[DiogenesParticipant @diogenes]

Peter, does that really hold them firmly enough for the drilling op. from the small end ? – useful if so..

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