# Relieving Attachment for making TAPS



## SmithDoor (Jul 5, 2014)

:noidea:Has any one made a Relieving Attachment for a lathe 
Use for making small taps acme, square, Buttress Threads and small gear hobs

http://www.lathes.co.uk/hendey/page11.html

Dave


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## Charles Lamont (Jul 5, 2014)

Eureka attachment, info from various sources:

[ame]http://www.youtube.com/watch?v=Wg0V36H6HsU[/ame]

Model Engineer ran a two part article by D.H. Chaddock and Ivan Law  starting in the February 6, 1987 issue. pages 138-139 and finishing in  the March 6, 1987 issue, pages 280-281

The Eureka tool is described in:
 Gears And Gearcutting by Ivan Law
 No 17 in the Workshop Practice Series
 ISBN 0-85242-911-8


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## SmithDoor (Jul 5, 2014)

Like the video it looks like  it is just for milling cutters not taps and hobs

 Dave




Charles Lamont said:


> Eureka attachment, info from various sources:
> 
> http://www.youtube.com/watch?v=Wg0V36H6HsU
> 
> ...


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## MCRIPPPer (Jul 5, 2014)

it seems like you would need another gear set to drive an eccentric or something, as well as the lead screw gears in order to cut a tap.



what if you had a profiled cam that was mounted on the spindle that somehow was linked to the cross slide.


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## SmithDoor (Jul 6, 2014)

One part is keeping the Clearance: Primary 3°-10° Relief adjacent to the cutting edge this change to the size. 

 Mainly use for  making small taps acme, square, Buttress Threads  and small gear hobs. If you ever try making small parts is hard to thread less than 1/2" on a lathe

I am looking at putting a cam on spindle or gearing from the thread gear train 



MCRIPPPer said:


> it seems like you would need another gear set to drive an eccentric or something, as well as the lead screw gears in order to cut a tap.
> 
> 
> 
> what if you had a profiled cam that was mounted on the spindle that somehow was linked to the cross slide.


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## SmithDoor (Jul 19, 2014)

here is some old photos


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## Hopefuldave (Jul 19, 2014)

Holbrook supplied a comprehensive kit for their toolroom lathes:
An 8:1 spindle speed reducer that sat on the ways ahead of the spindle and engaged with it, with a matching spindle nose and indexing assembly;
A cross-slide mounted relieving slide with an internal cam to advance and retract the tool;
A secondary gearbox driven from the reducer to drive the cam-operated slide via an universal-jointed splined shaft.

By varying The ratio between the spindle and cam you could get different numbers of flutes, whole-number ratios gave straight flutes, fractional gave spiral flutes. As the slide operated independently of the cross-slide and topslide, it could be used in conjunction with the taper attachment or even the profile copy attachment, and the leadscrew was available for "threading", it made almost any tap, milling cutter or hob possible!

There are some good pics of the relieving kit in the Model C brochure, which is on the Yahoo Holbrook group...


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## SmithDoor (Jul 20, 2014)

Thank you
I have join the group I also upload some photos I on internet and posted them.

Thank you
Dave




Hopefuldave said:


> Holbrook supplied a comprehensive kit for their toolroom lathes:
> An 8:1 spindle speed reducer that sat on the ways ahead of the spindle and engaged with it, with a matching spindle nose and indexing assembly;
> A cross-slide mounted relieving slide with an internal cam to advance and retract the tool;
> A secondary gearbox driven from the reducer to drive the cam-operated slide via an universal-jointed splined shaft.
> ...


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