How do I cut this taper

[WolfieParticipant @wolfie]

OK the next piece of my engine I want to build is this piece as per the diagram.

Now as you can see its tapered. OK I can work out the taper angle with schoolboy trig drawing a line horizontally from the lower end of the taper. This gives me a right angled triangle of 2 5/16 length and 1/16 high. So the taper angle is 1.5° (tan-1 1/16 divided by 2 5/16)

 

But heres the question. Once I have set my slide to the correct angle, what sort of tool do I use to cut the taper without touching the shoulders at either end?

Edited By Wolfie on 28/12/2011 19:24:29

[WolfieParticipant @wolfie]

[JasonBModerator @jasonb]

You actually form the sholdes by turning. Are you machining this from round and then squaring the ends or from sq/rectangular and then just turning the middle?

 

The one at the big end (left of drawing) can be done with your usual turning tool or one with a small radius such as you get on indexable tools. For the small end you will need to change for something with a more rounded end or corner. I have some cranked brazed tip tools that are handy for this but a bit of HSS ground to shape will be fine.

 

J

[Les Jones 1Participant @lesjones1]

Hi Wolfie,

The angle should should be tan-1 of 1/32 divided by 2 5/16 which is

tan -1 0.01351 so the angle is 0.774 Deg.

You forgot to use the difference in the radius rather than the diameters.

 

Les.

[WolfieParticipant @wolfie]

 

The angle should should be tan-1 of 1/32 divided by 2 5/16 which is

tan -1 0.01351 so the angle is 0.774 Deg.

You forgot to use the difference in the radius rather than the diameters.

 

 

Ooo yeah ta!

 

How do I set my compound slide at an angle of less than 1° grrrr

 

And I’m making it from a round bar.

Edited By Wolfie on 28/12/2011 20:51:19

[Sub MandrelParticipant @submandrel]

Probably not the textbook way of doing it, but I use a ‘V’ tool which leaves a straight edged cone at each end, I then swap to round-nosed right and then left hand tools to form a curved transition instead.

 

In more adventurous days past you could carefully blend the radius in with a file carefully worked in the rotating corner., assuming you wear full body armour…

 

Neil

[Terry LaneParticipant @terrylane]

‘How do I set my compound slide at an angle of less than 1° grrrr’

The taper being purely cosmetic, you will get it close enough by simply eyeballing the graduations on the top slide base – set it to the ‘under’ side of the 1° mark.

[JasonBModerator @jasonb]

To set your topslide you can mount a DTI in the tool holder exactly on centre height touching teh work and then wind the topslide over a length of 1″, in that distance it should move 0.0135″ (1/32 div 2 5/16″)

 

J

[WolfieParticipant @wolfie]

Sounds good. One thing about this lathe, the gradations for the top slide are on the side facing away from me. I’m over 6 feet tall and I struggle to see them. Seems a bit of a strange failure on an otherwise excellent machine.

 

I was going to turn the top slide round to face me but the damn thing is handed and doesn’t fit the other way on. And to cap it all theres an oil hole right where the 0° mark should be so you can’t mark it. I’ve marked 5° instead.

[NJHParticipant @njh]

Hi Wolfie

 

I would try it on a bit of scrap bar first and adjust until it looks right – the exact taper is not critical and with the set-up run(s) you will avoid b*****ing up the proper connecting rod.

 

Cheers

 

Norman

[Terry LaneParticipant @terrylane]

Since the dims are given in fractions I should think that ‘rule measure’ is plenty close enough. As for the grads – they still make mirrors y’know!

 

Inspection Mirror 

Edited By Tel on 29/12/2011 03:05:30

[Brian PriceParticipant @brianprice19431]

Posted by Wolfie on 28/12/2011 20:46:37:

How do I set my compound slide at an angle of less than 1° grrrr

 

And I’m making it from a round bar.

Edited By Wolfie on 28/12/2011 20:51:19

Hi Wolfie

I would hold the left hand end in you 4 jaw with soft packing pieces, put a sacrificial centre centre hole on the right hand end (so it can be removed when finished) and set up the taper offset using the tail stock. Use a DTI running along a predetermined length of the parallel bar to check the off set is correct, of course allowing for radius v diameter mix ups

 

And don’t forget to reset the tail stock back to the original position

 

I hope this helps

 

Brian

http://www.eBolt.co.uk

Edited By Brian Price on 29/12/2011 10:14:19

[Author]

Posts