Author Topic: Top Rake  (Read 3917 times)

Arbalest

  • Guest
Top Rake
« on: October 31, 2012, 09:25:53 AM »
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 ...  :naughty:

Online steamer

  • Global Moderator
  • Full Member
  • *****
  • Posts: 10328
  • Central Massachusetts, USA
Re: Top Rake
« Reply #1 on: October 31, 2012, 09:45:07 AM »
Arbalest,

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

Dave
"Mister M'Andrew, don't you think steam spoils romance at sea?"
Damned ijjit!

Goldstar31

  • Guest
Re: Top Rake
« Reply #2 on: October 31, 2012, 10:43:00 AM »
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

  • Guest
Re: Top Rake
« Reply #3 on: October 31, 2012, 11:14:39 AM »
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.

Online Dan Rowe

  • Full Member
  • ****
  • Posts: 745
  • Dripping Springs TX USA
Re: Top Rake
« Reply #4 on: October 31, 2012, 01:59:22 PM »
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
ShaylocoDan

Arbalest

  • Guest
Re: Top Rake
« Reply #5 on: October 31, 2012, 03:18:22 PM »
Thanks Dan, very helpful.  :ThumbsUp:

Offline Tin Falcon

  • Full Member
  • ****
  • Posts: 430
  • Down Jersey USA
Re: Top Rake
« Reply #6 on: November 18, 2012, 10:31:47 PM »
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

Offline Bezalel

  • Full Member
  • ****
  • Posts: 376
  • - Skype:Bezalel2000
Re: Top Rake
« Reply #7 on: November 19, 2012, 01:23:06 AM »
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.)   :thinking:


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
Queensland - wet one day, humid the next