cutting a taper

[oregonsteam]

I am looking for some advice about cutting a taper on my unimat lathe. I want to make a model ship's cannon with a 1 degree taper to the barrel. I can adjust the head of the lathe to cut the taper, but the tailstock won't adjust off center. How do I secure the other end of the barrel? I tried to make the taper with just one end in the chuck, but there is too much deflection to make a smooth cut. How do you secure the other end of the material? Any advice is welcome.


Thanks,


Mike

 

[Deanofid]

Okay, I'll ask the questions;
How long is the work piece?
What is the diameter?
What material?
What other tools do you have? Tail stock accessories and etc.?
Compound slide?

Give us something, Mike.

Some info would help with answers.

 

[AlanHaisley]

Mike,

This

I can adjust the head of the lathe to cut the taper, but the tailstock won't adjust off center.

sounds like the Unimat does tapers same as a Sherline: rotate the headstock. If that's so, I think that you want to turn the taper between centers using a lathe dog and faceplate to drive the part.

Alan

 

[oregonsteam]

I just have the standard 1960's era unimat lathe. I want to taper a 3.25" piece of .5625 brass for a model cannon. The slide has two independent lead screws. Thanks for your help.

Mike

 

[d-m]

Some one should chime in here a wile back I saw a adjustable live center that you could offset instead of the tail stock for cutting taper. I looked for the thread but can't find it. It was basic and looked easy to build. I want to think I saw it on one of marv's (mkolts) posts.
Dave

 

[FIXIT]

Hi What you should have/need is the 'taper turning top slide'

this is one for the unimate3 but should fit


where are you located



Steve

 

[FIXIT]

Just a quick add on

I've just read the post from Deanofid

"What other tools do you have? Tail stock accessories and etc.?
Compound slide?"

Unimat call it a taper turning top slide but it's proper name is "compound slide"



Steve

 

[Tin Falcon]

Mike :
there are three methods of cutting tapers.

1) taper attachment- offers repeatability not sensitive to length on part.
2) tail stock offset method- offset dependent on length of stock
2a) offset attachment for tail stock
3) compound method good for short steep tapers.
Here is a good primer on lathe operations page 30 of the pdf starts talking about taper turning and it gives formulas.


http://www.metalworking.com/tutorials/army-tc-9-524/ch7.pdf

there are plans for a tail stock offset attachment here:
http://www.john-tom.com/ElmersEngines/ShopWisdomRevNov07.pdf
The plans for the taper attachment are near the end of the file lots of tips to read good info.
Hope this helps
Tin

 

[AlanHaisley]

Mike,

there are three methods of cutting tapers.

1) taper attachment- offers repeatability not sensitive to length on part.
2) tail stock offset method- offset dependent on length of stock
2a) offset attachment for tail stock
3) compound method good for short steep tapers.

Add 1 1/2: With Unimat like yours, as with Sherline, tapers can be turned by rotating the headstock. A short taper might be turned holding the piece in a 3 or 4 jaw chuck. Longer tapers probably between centers with a lathe dog to drive the work.

For your cannon, you need a dead center for the headstock spindle along with a lathe dog and a faceplate. Another center in the tailstock and you should be good to go. The cannon will need to be overlength so there is a surface for the lathe dog to hold onto. Given the way that cannons usually look, you will need to plan out other machining operations and allow for ways to hold the piece as you go along.

Alan