tapered thread on a manaul lathe?

[ian3846]

Hi guys just wondering if it is possible to machine a tapered thred on a manual lathe and if it is how? im thinking along the lines of the buffing attachments people use on there bench grinders you know the thing that sticks out the end and normally virabrates that much it makes the machine useless for anything else.

Thanks

[HelicalCut]

Use a tapered turning attachment or if it is only to hold buffing wheels, try to freehand it.

[ian3846]

yes i had thought of that but i dont really want to spend that much for a one of job. i could knock one up at work in a cnc but finding free machine time is the problem. i may have to look at a different type of mounting. Heck its not even for me but it is for the old man so i would like to help if can.

[Glacern]

Freehanding the taper, as Helicalcut suggested, is not a bad idea.

First taper the shaft with the compound, then thread the shaft completely as you normally would at the largest OD. Then at slow speed, start retracting the cross slide manually with each pass, following the taper by eye. If anything starts to go haywire, just retract quickly. Repeat until finished. Sharp, high positive rake HSS tool bits will help with the slow speed.

[ian3846]

yes know its put like like it seems like a farly resonable idea. I had invisioned trying to thread with the top slide by hand. ill give it a go.

Thanks

[HelicalCut]

To freehand cut a thread, set up to thread as usual and just dial in the compound while the leadscrew is feeding, repeat until finished. Follow the taper in the air a few times before actually taking a cut then watch the chip and try to keep it the same thickness by tuning the compound handle at the right speed.

[gbent]

There are several posts here on the subject, mostly for turning tapered pipe threads. Turn your threading tool upside down, reverse the spindle, and thread away from the chuck (assuming the big end of the thread is on the left). Work out in advance how much you need to feed the cross slide per revolution of the chuck.

Threading away from the chuck and turning the cross slide in gives three strong advantages. You can't run into the chuck because you were busy looking at other things. The backlash is always taken up. If you get confused, just stop turning the cross slide as you are moving away from the material, not into it.

With little practice this works well with the 1:16 pipe taper. I think you are wanting a much steeper taper, so it may be slightly more challenging.

Another method is offsetting the tailstock.

[Conrad Hoffman]

Why not pop a center hole in each end and offset the tailstock? Turn the taper and thread it just as you normally would.

[Racer Al]

Woodturners often freehand threads with a thread chaser. You could use a similar design hand tool - it looks like a cross-section of a bolt perpendicular to a long handle.

If you had a old broken tap or a cheap tap in the right pitch, you could lop off a section with 4~5 teeth, weld it to a handle and quench it to bring it hard again. Not like you're going to use it every day, so I wouldn't wouldn't over-think the hardening.

I'd start by cutting a cylindrical thread, then cut the taper into the piece, then chase manually.

[L Vanice]

Did you realize you can just buy a tapered buffing wheel arbor for $11.00? I would not consider spending an hour or more of lathe work to avoid spending that small amount of money.

http://www.swmetal.com/cart/search?c...d%20Extensions

There may be a Chinese source that charges even less.

The tapered arbors are mostly used by jewelers and dental labs for small work. They come with both left and right hand threads. I have an assortment of wooden hub bristle and wire brushes and small cloth and felt buffs with small pilot holes for the tapered screw arbors. But serious buffing with 6" or larger wheels is usually done with straight 1/2" or larger arbors with nuts and washers to retain the wheel. The wheel will have a 1/2" or larger hole, too big to fit a tapered screw.

If a standard buffing arbor will not do the job, then there are several practical ideas above for making your own.

Larry

[stannp368]

It appears as though your project is not an accurate one. Use a lathe dog & turn your taper between centers using the offset tailstock. Set your thd tool normal to the axis & proceed to cut your thd

[antique iron]

The old man showed me how to cut a pipe thread on a manual lathe years ago. Figure out how much your thread tapers per individual thread. So you cut the thread to the largest diameter. You then continue to cut, each time taking a cut equal to the taper of one thread, then drop the cutter out one thread short of the last pass. For what you are making it would be plenty accurate.

Paul

[AzironaZack]

The Southbend book, How to Run a Lathe: the Care and Operation of a Screw Cutting Lathe, goes into this. It describes the process just as Conrad Hoffman and stannp368 said.

As a beginner I can vouch for the fact that this book is great for beginners. It's a great read and a resource I imagine I'll be going back to over and over again.

[franco]

Here is a photo posted by John Stevenson some time ago showing an alternative set up to cut tapers using a center mounted in a boring head in the tailstock to avoid having to disturb the tailstock setting. This will also work for tapered threads using the normal threading feeds as described by stannp368 above. Note that he has used ball centers because of the large amount of offset of the workpiece.

franco