Sensitive tailstock for mini lathe

[dk0Participant @dk0]

The idea is to design a small rotating tailstock with a key feature: it can be preloaded using disc springs to ensure constant force on the center of the shaft being machined. Furthermore, the small tailstock with a 12mm cylindrical shank can be easily mounted on the drill chuck without having to change the Morse taper every time.
What do you think, could it be useful and functional? Thanks.

[JasonBModerator @jasonb]

I’d rather use the one that I have with no preload then I can feel the cut whatever diameter drill I’m using. Would not want the same force on a 0.3mm drill as a 1mm drill.

[Michael GilliganParticipant @michaelgilligan61133]

Excellent concept, but I fear the drill chuck might have too much run-out

MichaelG.

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Edit: My post crossed with Jason’s

… I concur

[JasonB]

On JasonB Said:

I’d rather use the one that I have with no preload then I can feel the cut whatever diameter drill I’m using. Would not want the same force on a 0.3mm drill as a 1mm drill.

Sorry, maybe I didn’t express myself well, unfortunately English isn’t my native language.

I mean that the rotating tailstock has a constant load because, after a little work sometimes stops rotating because the rotational force is greater than the friction of the center point. However, if the load remains constant due to the disc springs, the shaft support is guaranteed.
Mounting the small rotating tailstock onto the drill chuck is simply a matter of practicality.

[Michael Gilligan]

On Michael Gilligan Said:

Excellent concept, but I fear the drill chuck might have too much run-out

MichaelG.

.

Yes it is true,  it’s probably not perfectly centered but it is the same eccentricity

with which you get the drill center because it’s the same drill chuck.

[cogdobblerParticipant @cogdobbler]

<p style=”text-align: left;”>It sounds like there is something wrong with your revolving tailstock centre. It should not stop revolving like that. Try pulling it apart and lightly greasing the bearings and check the spindle is not contacting the body at the back end under load. You may even need new bearings. Some are made with poor quality bearings.</p>
A spring loaded tailstock revolving centre will allow the cutting forces of the tool to deflect the end of the job. It needs to be solid mounted and the tailstock locked in position.

[DiogenesParticipant @diogenes]

Not sure how a rotating centre can ‘relax’ itself once set and locked?

..normally the problem is that if the work heats up it will bow / exert too much pressure..

[dk0Participant @dk0]

Frankly, the opposite has often happened to me: the tailstock tends to stop after a while due to the cutting pressure which unloads the force on the center, deforming it, and also the drag clutch generates overheating, widening the center.

Ps. Finally, the rotating mass of the traditional tailstock is disproportionate to the small diameter of the center of the workpiece.

[Peter Cook 6Participant @petercook6]

Taig do something that resembles what you are talking about for their micro lathe. Available from Rotagrip in the UK.

Body is just under 1/2″ in diameter. It has longish needle roller bearing in the end to carry the sideloads, and the centre is spring loaded. It’s not too difficult to make additional centres that fit.

[bernard towersParticipant @bernardtowers37738]

Yep got one and find it pretty darn useless

[dk0Participant @dk0]

This could be the concept with two radial needle bearings and one thrust bearing.

The body diameter is 18mm the cylindrical shank diameter is 12mm and the overall length is 60mm.
It could be a small and practical device to use as a tool on the drill clutch.

 

 

[PeteParticipant @pete41194]

It’s actually something that’s available on industrial quality live centers, and with an industrial price to match. https://www.riten.com/products/live-centers/spring-loaded-concentric-live-centers/

However what you seem to be experiencing with your current live center certainly isn’t normal as others have already said. I’m only guessing, but you haven’t always been using far too much screw pressure from the tail stock hand wheel in the past? Forcing any live center with too much pressure can or could ruin the bearings quite quickly. All you need is to just seat the 60 degree live center into the previously center drilled hole in the shaft, then lightly pre load it a slight amount to fully take up any tail stock feed screw backlash, then lock the tail stock quill.

At most, the center might need retracting a tiny fraction if the shaft heats up during longer periods of turning to compensate for it expanding in length. Too much tail stock feed screw pressure is also hard on the lathes head stock bearings as well. I suspect you now need either new bearings for your live center or a replacement if I’m understanding the issue your having correctly.

 

[old martParticipant @oldmart]

You would be better to make use of the Morse taper, soft ended blanks can be boughtto build up the tool. As mentioned drill chucks are not likely to holdthingstrue enough,unless you are lucky. It would be worth checking your chuck first for runout with it holding a new drill that is the same size as the arbor of your tool.

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