Thread: turning tips

Harold hall describes setting the compound to .6 deg, or 1 in 100 (actually .573deg)to get super fine DOC. .1mm compound feed will give you .001 DOC etc. You just need to use a sign bar setup to create the angle. He shows a bar, set parallel in the tool holder and then a 1mm drill bit is used with a mark 100mm from the end of the bar against a test bar between centers to create the angle. Or you could make the sign bar setup that retromilling showed a few months ago here https://www.woodworkforums.com/f65/yo...ml#post1456944.
The book in question is Lathework a complete course and can be had off ebay for about $15 delivered. IMO well worth it.

Ewan

hi mate. whose Harold hall? you know in the back of my head i was thinking 10 deg doesn't equal.
a 1 in 10 ratio. im not shore what DOC means. Well i think i get it but what does it stand for.
i picked this up from an instructor during my apprenticeship. Problem is i quite often think ill be right and don't offset the top slide.
i only mentioned it because a few others i know that are good machinists didn't know about it.
thanks for posting that link. I had been wondering about an accurate way to set my compound slide of set to cut different tapers. brilliat

Originally Posted by azzrock

hi mate. whose Harold hall? you know in the back of my head i was thinking 10 deg doesn't equal.
a 1 in 10 ratio. im not shore what DOC means. Well i think i get it but what does it stand for.
i picked this up from an instructor during my apprenticeship. Problem is i quite often think ill be right and don't offset the top slide.
i only mentioned it because a few others i know that are good machinists didn't know about it.
thanks for posting that link. I had been wondering about an accurate way to set my compound slide of set to cut different tapers. brilliat

Hi Aaron,
If you haven't heard of Harold Hall then get prepared for some serious reading and youtube watching. He has several videos on machining and workshop techniques plus his own website full of things to make

My metalworking and other interests. Harold Hall

Up until 12 months ago I had never machined with a DRO (Digital Read Out) and now I have no idea how I managed any accuracy at all. Consequently thats what I use for the very fine dimensional accuracy.
DOC stands for Depth Of Cut.
Thanks again for the mahr indicator, it has been very handy.

Phil

Azzrock what trade did you do?
DOC is depth of cut.
I had never heard of that setup with the compound either,but then again I've never read any of the Hall books.
Only real problem I can see in the compound method would be having measuring gear on hand that reads that fine.
Then you would either need to make or buy a Sine bar.
How much oversize was suggested before starting to use the compound method?

Originally Posted by pipeclay

Azzrock what trade did you do?
DOC is depth of cut.
I had never heard of that setup with the compound either,but then again I've never read any of the Hall books.
Only real problem I can see in the compound method would be having measuring gear on hand that reads that fine.
Then you would either need to make or buy a Sine bar.
How much oversize was suggested before starting to use the compound method?

There is no suggestion on when to start using the compound method. I guess with .1 or so to go? One thing that is very important taking such fine cuts is the tool height. If the tool is just over center height, all it will do is rub. Hall suggests being under center by .05....no mean feat to get your tool set so accurately without using a height gauge.

Halls books starts simple and get more difficult as you go into them. Most projects are used for the next project, so the test bar is the project before the bore gauges which have to be turned to such precision.

Ewan

This method is also described in Ch 2 of the Hercus Textbook Of Turning. 5.75 degrees on the compound equals 1:10.

Originally Posted by Steamwhisperer

Hi Aaron,
If you haven't heard of Harold Hall then get prepared for some serious reading and youtube watching. He has several videos on machining and workshop techniques plus his own website full of things to make

My metalworking and other interests. Harold Hall

Up until 12 months ago I had never machined with a DRO (Digital Read Out) and now I have no idea how I managed any accuracy at all. Consequently thats what I use for the very fine dimensional accuracy.
DOC stands for Depth Of Cut.
Thanks again for the mahr indicator, it has been very handy.

Phil

hi phil hows it going. every time i see some steam equipment i think of you. funny that.

here is a beauty.
Attachment 207305
i think it looks ok in blue..

yah i dont have much of an opportunity to use a dro. i have in the past. used them. ,Some times when they where fitted to machines we where all ways steered away from
using them by the people teaching us..
what sort do you use. and on what.
i remember them being on all the milling machines and some of the lathes when i was learning my trade. The instructors discouraging there use. saying "you cant rely on them." from memory they wouldnt of been cheap ones either. i think after training i used them and liked them ( and thought what where those crazy old buggers caring on about) that was a long time ago.
glad the dial and stand worked out ok.hope they help to keep all that kuta old equipment running.

hi pipe clay thanks for the questions . how have you been.
as for my trade im just looking at the certificates one says
Fitting and machining trade(machining strand).
the other
fitting and machining trade(general engineering strand).
from NSW dept of tafe
i agree with the measuring equipment could be hard to find. epically in the form of a digital vernier.
more to the point with this its handy when you find your self slightly oversize and you don't wont to give the cross slide hand wheel a nudge. I don't think it was intended to be used to arrive with a strange fractional or decimal size diameters..
So normal measuring equipment could be used.
every know and then even using the best techniques you may me 1 or 1/2 of a thou over size and if a spring cut doesnt get you on size.If set up for it. This techquine work well.
I have found it handy recently a few times.
um i think its stuck in my mind because we were very competitive and would want all our work going to the marking hut within tolerance and emery paper was simply not available.
it maybe more useful for hss cutting.

I just thought it strange that you were unaware of the meaning of the term DOC.

Originally Posted by Ueee

There is no suggestion on when to start using the compound method. I guess with .1 or so to go?

Ewan

thats the problem ueee i would say 0.3mm for a finishing cut
so about there. offset the compound slide and hope you don't have
to use it.
good comment about center height. something i need to pay more attention to.

Originally Posted by jack620

This method is also described in Ch 2 of the Hercus Textbook Of Turning. 5.75 degrees on the compound equals 1:10.

well done a book we all probably have a pdf of. Ill have to read it past the first chapter.

Originally Posted by pipeclay

I just thought it strange that you were unaware of the meaning of the term DOC.

i know strange is a good word for it.

Maybe when he was learning they just used the term depth of cut and not DOC. Some simple abbreviations have you scratching your head, and then once you work it out or find out what it means the penny drops, I have done it myself with some.

Dave

thanks dave.

Originally Posted by azzrock

thats the problem ueee i would say 0.3mm for a finishing cut
so about there. offset the compound slide and hope you don't have
to use it.
good comment about center height. something i need to pay more attention to.

I think you need to keep the DOC bigger with carbide as it needs to take a decent cut to work properly. With hss though you can take tiny cuts, to the point where all you get is dust, not chips. You can use the same technique for facing by turning the compound by 90 deg.

Ewan