Lathe "How To" Questions

[studysession]

Hi -
I have a lathe and been using it for a few months now. I am not sure how to do something though. Attached is a picture of a center. I want to learn how to properly do the long taper on the one end like that.

I am not sure how to do it. I know how to make the nice sharp point on the one end, but not the long taper on the other.

Any help would be appreciated.

[DACMACHINE]

Originally Posted by studysession Hi - I have a lathe and been using it for a few months now. I am not sure how to do something though. Attached is a picture of a center. I want to learn how to properly do the long taper on the one end like that. I am not sure how to do it. I know how to make the nice sharp point on the one end, but not the long taper on the other. Any help would be appreciated.

2 ways that I know of

1 - some machine have tapers attachment that fallow whatever angle you chose

2 - machine a blank leaving ~ 3/4" tailstock on the end (where the 60deg would be) drill centers both sides
- put a small piece of stock in the chuck and turn a 60 deg

- put the blank back on, 3/4" on the chuck center use a drive dog to clamp the piece

- offset your tail stock 1/2 the difference if the ods ( 2"-1" = .5/2 =.250" offset) must be done with indicator
- take your cut
- flip blank, put in chuck and machine 60deg

this should work, might not be very accurate
your best bet is to just buy a new center

Hope this helps
Dan

[studysession]

I do not want to make a new center, just want to be able to make something with same kind of taper. Now sure how to do it.

THANKS

[DACMACHINE]

The way I mentionned will work for long tapers

basically your putting the workpiece on 2 centers

and take a cut, offsetting the tailstock gives the angle

[Mcgyver]

assuming three things 1) the centre pictured has a centre drill at the other end, which it almost for surely does, 2) you have an indicator and 3) you have another centre for the tailstock.

place a piece of steel in the three jaw, face and carefully centre drill. Now mount your centre between the centre drilled pad at the headstock and centre in the tailstock. What you are going to do, with the aid of indicator mounted on top of the compound and touching the side of the centre , is rotate the compound until you get no change in the indicator reading from one end of the taper to the other (feeding it back and forth with the compound screw). When you are done, the compound is now exactly at the same angle as the taper and you can use it to cut the taper.

It is important that you do so with the indicator at centre height. If you have a taper attachment the principal for set up is identical except obviously you're adjusting the taper attachment not the compound.

If you do not have an indicator, and are not willing to buy one (you’d only be delaying the inevitable) your other choice is trail and error with Prussian blue and a female taper. Not an appealing process.

while you've got this set up, turn a bunch of blanks + 3 in larger dia from which to make three tailstock die holders in the three standard sizes. You'll never regret making those and for years to come you'll think back with pride at what a clever devil you were for making 'em!

[out2thow]

TPF = Taper per Foot
TPI = Taper per Inch
TO = Tailstock Offset
D = Large Diameter
d = Small Diameter
L = Length of Work
l = Length of Taper

To offset the tailstock the required amount first make sure the tailstock is set so the part turned has no taper at all (even a few tenths will throw you out) then use the following formula:

TO = TPI x L/2

to cut a #3 morse taper (like in your picture)
First set up your piece between centers using a drive dog to drive it, and cut it straight until you have reached the size you want (aprox .060 larger than the finished diameter) Make sure to use a micrometer and measure both front and back to ensure there is no taper in the tailstock. (adjust if necessary BEFORE you get to the final cut)

Calculate TPI for a #3 morse taper

TPF for #3 MT = .6023" (from reference chart in book)

TPF/12 = TPI
.6023/12 = .0502

say the piece you cut is exactly 10.000" long (be sure to be as accurate as possible)

then TO = .0502 x 10/2
TO = .2509"

Set a dial indicator, with the base on the ways and the dial on the tailstock, (make sure that the dial is square and parallel with the tailstock) unlock the tailstock slightly (you will not be able to adjust it without unlocking it, be sure you part does not fall out) and offset the tailstock in the proper direction for the cut to be taken.

Tailstock offset is great but rarely used in the real world because of it's limitations, you are restricted to long external tapers, and it take a while to set up and tear down. Taper attachment is the most preferred method of cutting tapers, you can do internal/external up to 3.5" TPF and limited by the length of the guidebar on the attachment, the only real drawback is backlash, which is easy to work with if you know how it works.

you can also use the compound slide, but you will not get a good finish, and your accuracy on the taper may not be so good (harder to dial up, you have to use rise/run)

Hope this helps you cut a taper.
-S