Top Rake

[Arbalest]

Does anyone know the angle used on English pattern tool holders:

http://img.tjskl.org.cn/pic/z24ea07a-600x400-0/turning_tool_holder_english_pattern.jpg

I'm assuming this is so you don't need to grind the top rake?

I'm asking as I'm part way through a ball turning jig and I'll need to make the tool holder soon and this is one of four options!
The other ones are tangential, round insert & triangular or rhomboid insert. Decisions, descisions ... 

[steamer]

Arbalest,

I believe they're 16 degrees.   I don't have any anymore so I can't check.

Dave

[Goldstar31]

If it is a ball turning jig, then I would be loathe to use an English Tool holder at all.
It simply is far too clumsy for this purpose. Fine with a flat top for brass or with various rakes for other metals- on other tasks.

Of course, none of us know which of the many designs or even what you are using.
Professor Dennis Chaddock actually drilled some holes in an old softened file, and then re-tempered it. His many Quorn ball handles emerged in a night and there you have it. I made the ball handles with a home made boring head- a la George Thomas for my Quorn and went back  to using my home made tool for many more purposes.

I may have got it wrong- for you but not for me.

[Arbalest]

Thanks guys. I don't plan to use an English pattern holder (far too big),  just use the same angle on the ball turners tool post.
I'm making a version of Steve Bedair's tool.

[Dan Rowe]

I dug my holders out and the Armstrong and Ready Tool Co. ones have about 15⁰, the J.H. Williams holders are about 7⁰. It seams like there was a difference of opinion as to what the angle should be.

Dan

[Arbalest]

Thanks Dan, very helpful. 

[Tin Falcon]

IIRC 15 degrees.  but I have used zero top rake and it still cuts fine.  like any other tool geometry  the best angle is determined by the material being cut. and ranges from 0 for brass to 35 for aluminum. so i guess the real solution is make a QCTP  with a built in rocker and set the back rake depending on material.
Tin

[Bezalel]

I was curious about the question so I looked it up.


The Correct name for the Pictured tool holder is a "Weston" tool holder. ( According to the ninth edition "Workshop Practice" 1947.) A British publication


This reference also refers to the angle in question specifically as "front rake" and that top rake is the angle of the top of the tool relative to the radial angle from surface to center of the job.    Which would mean that top and front rake are only the same angle at center height.
 
So for tools not on center height, Lower gives less top rake, higher gives more, but the front rake remains the same- (I guess there is a quick cheat in there for cutting brass if all your tools are set up for cutting Ali - I haven't tried it.)   


The Bad news is this particular book doesn't say what the standard angle should be on a Weston toolholder

I guess Weston is a brand name -  are they still around?

Bez