Setting up a taper attachment

[metaldestroyer]

Hi all; I would appreciate some suggestions regarding the best method of setting up a taper attachment to achieve an accurate angle. This will be to bore a 5C collet closer bore in a pot chuck body that I have. It would be nice to not muck this one up. I have a 5" sine bar but no experience using it.

Jack

 

[Dan Rowe]

Jack,
There are at least 2 types of taper attachments for a lathe, so the instruction manual should be looked at to properly answer the question.

South Bend lathes have two types of taper attachment the plain type has to be locked to the bed and the taper slide then a shoulder pin is removed to free up the cross slide screw. The telescopic type of taper attachment is simply locked to the bed and taper slide for taper turning.

I hope this was of some use.
Dan

 

[metaldestroyer]

Dan thanks for the reply. My lathe is a 11" Standard Modern to use the taper attachment you remove the fastener for the crossfeed screw and use the compound to advace the cutter. My concern is a method that I can use to setup the taper attachment angle. In the past I would just sweep an object that included the correct angle using a dial indicator and adjusting the taper attachment to obtain a 0.0" difference.

Jack

 

[djc]

...I would appreciate some suggestions regarding the best method of setting up a taper attachment to achieve an accurate angle.

Easiest way is to find something with the same taper you are trying to cut. Chuck it up and dial it in so it runs true. Then adjust your taper attachment so that when you traverse the item, the DTI registers no movement.

If you have a sine bar, chuck up a straight, parallel round bar and dial it in true. Rest your sine bar against this with the appropriate spacers under one end and clock along the top (side) of the sine bar. This requires a couple of extra hands so you have to do a bit of creative 'propping up' or you can make a simple clamp to (lightly) secure the sine bar in the right place.

If you read Guy Lautard's stuff, you will see that for the type of work we do, you don't need to worry unduly about the exact thickness of the spacers. The nearest thousandth of an inch is ample (accurate to about 40 seconds of arc).

 

[Dan Rowe]

I have never attempted this but if your taper attachment has a flat spot to lightly clamp the sine bar to with the angle in the vertical direction if top angle face is set parallel to the taper slide the normal flat or bottom face can be arranged to be parallel to a fixed dial indicator on the bed ways.

Dan

 

[Ed T]

Since the taper you need to make is short, you may want to consider using the angle adjustment on the cross slide. Many of the same set up issues, but less of a hassle. That is one where I think I would play around with the setup on a piece of scrap with some blueing (magic marker) regardless of how you choose to do it.

 

[Peter.]

I don't have a taper attachment, so what I do is set the compound to the angle as shown on the cross-slide. This gets it somewhere near. I put a piece of bar in the chuck, or between centres, and mount a dial indicator to the compound and set it on centre height, level and square to the bar.
Now I choose a distance to wind the compound, say 50mm, and this is the hypotenuse of a triangle described by the cross-slide, the bar and the compound. Knowing the angle I need and the length of the hypotenuse I use trig to calculate the amount the dial should move as I wind the compound 50mm. I just keep winding back and forth 50mm making small adjustments until I hit that figure then I know it's good. You have to start off with it quite close so that you don't generate errors by moving the compound too far and making the dial indicator out of square.