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From: Bob La Londe <none@none.com99>
Newsgroups: rec.crafts.metalworking
Subject: Re: Those Cheap Diamond Inserts
Date: Tue, 20 Aug 2024 11:23:19 -0700
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On 8/20/2024 8:48 AM, David Billington wrote:
> On 20/08/2024 07:50, Charlie+ wrote:
>> On Sun, 18 Aug 2024 17:02:31 -0700, Bob La Londe <none@none.com99> wrote
>> as underneath :
>>
>>> On 7/30/2024 2:44 PM, Richard Smith wrote:
>>>> Bob La Londe <none@none.com99> writes:
>>>>
>>>>> On 7/29/2024 11:38 PM, Richard Smith wrote:
>>>>>> I heard diamond
>>>>>> * works for Ali because it has no solubility for Carbon
>>>>>> * does not work for irons/steels because the hard tool 
>>>>>> "disappears" by
>>>>>>      solution into the iron
>>>>>> ?
>>>>> My apologies.  I didn't at all mean something like a PVD diamond
>>>>> coating.  DCMT is a diamond shaped insert.  Typically your find them
>>>>> coated with TiN, uncoated, and occasionally with TiAlN or AlTiN
>>>>> coatings.  My point was these small geometry inserts that work so well
>>>>> in under power under-rigid machines like the typical import 7-8 by
>>>>> 10-16 mini lathe also work on a heavier machine.  If the big boy
>>>>> inserts don't work these still do.  In this case I was cutting 304
>>>>> stainless steel. It improved the finish, didn't require sharpening,
>>>>> had less heat input, and did the job much faster net elapsed time.
>>>>>
>>>>> FYI:  I do a fair amount of aluminum cutting, and generally I've found
>>>>> bright sharp uncoated tools do the best job and have the best material
>>>>> removal rate for me and leave a good finish.  Diamond was popular when
>>>>> I first started cutting aluminum on machine tools, and more recently
>>>>> ZrN has become the popular coating.  I've tried them and the simple
>>>>> fact is a coated tool isn't as sharp.  They might work better for
>>>>> larger tools on larger machines, but on middle weight machines with
>>>>> limited horsepower (5 or less) a bright sharp uncoated tool works best
>>>>> for me. For high speed flood coolant makes the tool last without chip
>>>>> welding, but coatings do not.  On smaller tools horsepower isn't even
>>>>> a factor as the tool can't take it anyway.
>>>>>
>>>>>
>>>>> -- 
>>>>> Bob La Londe
>>>>> CNC Molds N Stuff
>>>> Thx for this detail.
>>>> Interesting yes certainly.
>>>> Sorry "got the wrong end of the stick".
>>>>
>>>> I used cutting insert tooling - aagh - 30 years ago.
>>>> Vertical milling shell-cutter on steel.
>>>> Did well - they'd never seen steel chip ejection like a chain-saw
>>>> cutting timber.  Took a visit from the rep. who explained this is how
>>>> the tooling is supposed to be used :-)
>>>> Coated carbide inserts - coating the gold coloured one - a Ti 
>>>> nitride(?)
>>>> coating - for this steel.
>>>
>>> Pushing it harder and harder.  As I once offended Jim a little (sorry
>>> Jim) over... time is money.  Even if you are doing something for fun,
>>> favor, self... time is still your most valuable nonrenewable resource.
>>>
>>> I needed to make another batch of stainless mold cores today.  (Stock
>>> design that uses upto nine (9) 1.5in diameter cores to varY the size of
>>> the casting.  That's 18 cuts to true them up after they come off the 
>>> saw.
>>>
>>> My new inserts arrived a few days ago ago, but I wantedif I could bump
>>> up the speed a bit with that little hobby lathe size insert.  I had been
>>> using at at 300 RPM in low gear.  That's a starting SFM of 117 if I have
>>> done the math right.  I am sure there are folks pushing big turning
>>> centers orders of magnitude faster, but this is after all only a bigger
>>> import lathe.  Its still an import lathe, and while its relatively
>>> heavy, its light for its size.
>>>
>>> Of course the SFM drops as the diameter is reduced.  Maybe I could go
>>> faster if I cranked up the speed as I reduced the diameter, but this is
>>> a single phase gear head lathe.  The motor just turns one speed.  The
>>> time to stop it and change gears would eat up any time savings.
>>>
>>> Just for the heck of it I decided to see how much faster I could start.
>>> At 460 RPM the insert was still doing fine.  Still using the same insert
>>> I used when I started this thread.  I don't mean the same type.  I mean
>>> the same insert.  That means the insert was hitting the outside of the
>>> stock at 180 SFM.  The number doesn't sound much bigger, but the part
>>> time was definitely faster.
>>>
>>> A couple ends with an intact insert at that speed and I decided to try
>>> the last couple parts at 755 RPM.  296 SFM.  That was significantly
>>> faster.  Part time was a lot shorter, and the insert still looks like
>>> when I started.  (I'll look at under magnification later)  It wasn't so
>>> fast that I had any issue keeping up, but it was fast enough I couldn't
>>> do anything else, like move the stock in the saw to cut the next rough
>>> blank.
>>>
>>> Now that I have spares I think next time I cut a batch of these cores I
>>> am going to push it until I chip an insert to see just what they will 
>>> do.
>>>
>>> Please bare in mind that these are relatively light cuts.  The blanks
>>> come off the saw at about 1.4" to 1.41" and get trued to 1.375".
>>>
>> Interesting thread Bob, thanks, is this example the type of tool you are
>> talking about? Never come across the diamond tipped versions of inserts
>> but my original machining in industry experience was in the 1960's! Only
>> hobby level now..
>> https://www.ebay.co.uk/itm/115334715488?_nkw=diamond+inserts+carbide+lathe&itmmeta=01J5Q723XNA0GREWTN8RFZEQK2&hash=item1ada7c1860:g:YyUAAOSwUtJiUKWN&itmprp=enc%3AAQAJAAAA4HoV3kP08IDx%2BKZ9MfhVJKnC8gu8jBQODZUzjY6nfSpuZas%2FJzGcWIYLgG5EPfxVgG0wH1c4QdrYrUHqD4z98NSE8atbz28SHAAsTTB%2FvXsdw1KSXcN7%2Bx6cwyg%2FcKXwvDq3eEqXZbpx%2Bzxtc0f0%2Fp0BsyoIUtnlZlJQI86p6TyhETkaZsGuuwYw1Ayo2CHAORe6WE1WiaDElO8xogeQY1mItmsxVxjRLhavW15vEW5hMGkyR8srWzmxrGq4dX%2B9yZ23zhsDDiiDdifsQ%2Bk8r7IRPefZ9T%2FppdLbpKF%2FwpjM%7Ctkp%3ABk9SR_S-iOetZA
>> It says for non ferrous but you are using on stainless without any red
>> spark? Can they be touched up if/when the edge goes?  I know its only a
>> single but looks uncheap to me!  C+
> 
> If you read Bob's post 30/7/2024 he clarifies he's not talking about 
> diamond tipped inserts but diamond shaped rhombic inserts.
> 


That's true, but I did run across a reference (Stefan Gotteswinter video 
maybe) to an actual diamond attached to a tool.  There are also coatings 
that are called diamond, although most are actually DLC "diamond like 
coatings."


-- 
Bob La Londe
CNC Molds N Stuff


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