cutting a longer taper

[richard.nott]

wanting to make some alignment pins from 3/4" and 7/8" hex stock that are 15" long and have a 6" long taper on one end. my lathe will only cut a taper a little over 3" would appreciate a suggestion on getting out to the length I need. one questions I like to ask is it practical to cut what I can and then move the carriage in?

 

[mfrick]

You can offset your tailstock and cut a long taper very easy, the only limit is the length of the bed of the machine. The other problem you will run into is being long and skinny you may get some chatter so you will have to play with speed and feeds and tool grind.

Mike

 

[Mike1]

If you have a boring head put that in your tail stock, make a centre for the boring head and offset the boring head to your taper requirements, this will save you having to offset the tail stock and you can use the power feed to machine the taper for it's full length.
Mike 1

 

[richard.nott]

if I've got my figures correct i'll need 1 1/2* of taper not for sure how many degrees of off set that would be. if I do this with an offset able boring bar will I need to use a faceplate and a drive dog . so far this looks doable but will have to us slow feed with the hex stock. the taper i'm going to need with 3/4" hex stock is 3/8" at the small end tapering to full size a six inch length.

 

[Charles Lamont]

You say 'alignment pin'. If all we are talking about is a podger, then turning the taper in steps using the topslide will be adequate and easier.

 

[mfrick]

I your going to offset tailstock and or use the boring head yes you will need to do the job between centers.
Mike F

 

[Jennifer Edwards]

Here is s link that will calculate the angle of offset required to develop a taper of any length. Just input the beginning diameter, ending diameter, and length the program will give you the necessary angle.
I am always surprised by how small an offset you need.

http://www.magafor.com/841/uk.htm

Jenny

 

[Mike1]

Jenny, That's a good useful link.
Mike1

 

[Mike1]

Jenny, That's a good useful link made a note of that.
Mike 1
Two replies ??

 

[Hengeveld.gerard]

Thank you Jenny, it makes my life so much easier,

Gerard

 

[petertha]

The thing you have to be aware of with the offset tailstock method (or boring head in tailstock = same effect) is that the length of your rough stock may well be different length than the finished taper length.For example if your finished tapered arbor will be 3" length & you have some extra material on either end so the stock is 5", now your TS will have to be displaced over 'more' in order to achieve the same target taper angle. This is a bit different than adjusting a taper attachment bar to the target angle. Once its set, it doesn't matter where along the work you cut the taper, it will be the correct angle.

But for between centers taper turning, you need some method to validate the taper cutting angle & it may well be a trial & error procedure. I've only done this once & the part allowed for an undercut on either side of the taper. Since I could measure the large & small diameters somewhat close and I knew the length in between, I could calculate the actual angle. The nice part of a boring head is you can dial in correcting offset in small increments, typically 0.001" or better on most common models. But again, realize you are adjusting the point where the TS center cone is engaged, not the small diameter itself. So needs a little bit of trig math.

If this is all common knowledge no problem, but sometimes its not so obvious the first go round... he says with firsthand experience

 

[Hengeveld.gerard]

Many thanks for the update,