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(DIR) Return to: Machine Tools, Machining, and Toolmaking
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#Post#: 62685--------------------------------------------------
Scary Milling
By: Stoker Date: April 14, 2024, 9:24 am
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Yesterday I did a bit of what I have to consider as "SCARY"
milling.
Using a HSS 3/32" end mill on a case-hardened, angled surface,
for a two diameter long "notch" that ended up at the deep end as
being about equal to diameter of the cutter. I had four such
notches to make in a single piece of metal, and by the fourth
cut I was getting definite evidence of grab and chatter that
could well have broken that weak little bit. Clearly, that bit
became progressively duller during its torturous ordeal. I was
expecting for it to snap at any moment, leaving me with this
critical task uncompleted.
I initially tried a plunge cut, but saw that poor little bit
deflect down-slope on the angle, so knew that wasn't going to
work. Coming in slowly and laterally at a fixed depth from open
air allowed me to initiate the movement of metal, but the feed
had to be so slow as to almost qualify as an abrasive rather
than a cutter.
However, by nursing that poor brutalized little mill bit along
at about 1400 rpm and feeding it at less than .010" depth per
cut, I managed to complete all four notches without incident,
though it seemingly took me forever to accomplish each of the
four cuts. I doubt if I was feeding more than a very few
thousandths a second, and still would feel the bit grab and
catch in what must have been almost certain near breakage.
In reality I should have been using a 5/64" end mill but I
didn't have one, and of course I also should have been using
carbide, but didn't have that either, and as actual size of
these notches was not super critical, going a little bit
oversized was an acceptable option in this instance!
Think I was holding my breath the entire time, as this was the
only end mill anywhere near that small that I had, so breakage
would have left me short of completion, and would have meant
needing to buy another end mill and wait for its arrival.
Whew!
#Post#: 62686--------------------------------------------------
Re: Scary Milling
By: MasonvilleEngines Date: April 14, 2024, 9:49 am
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I have more expertise in breaking bits than milling. I find the
small bits thrilling also. Nice you had the patience to
persevere. I try to have two on hand of some of the smaller
sizes I find myself using most.
Len.
#Post#: 62687--------------------------------------------------
Re: Scary Milling
By: Woe is me Date: April 14, 2024, 9:50 am
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Good thing it let you nurse it through. If it would have
snapped, would you raise the chuck
and leave everything as is until a new bit arrived. Seams like
that would leave everything
lined up but it would also tie up the mill. Just wondering.
#Post#: 62688--------------------------------------------------
Re: Scary Milling
By: Stoker Date: April 14, 2024, 9:59 am
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Yes, I would have left the set-up intact until I could source
another end mill. While I almost always have many tasks that I
am behind on, none of them is so critical or pressing as to have
broken down that set-up. However, the actual issue that is faced
every time I wish to use the mill, is moving everything out of
the way so I can get to the mill to make any use of it! ;c)
Weather actually also enters into the "equation" of mill usage,
as the garage (to be read as: Shop) door must be open to make
any use of my mill.
#Post#: 62689--------------------------------------------------
Re: Scary Milling
By: Stoker Date: April 14, 2024, 10:09 am
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[quote author=MasonvilleEngines
link=topic=7121.msg62686#msg62686 date=1713106154]
I have more expertise in breaking bits than milling. I find the
small bits thrilling also. Nice you had the patience to
persevere. I try to have two on hand of some of the smaller
sizes I find myself using most.
Len.
[/quote]
I'm sure there was a time when I did have two 3/32" end mills,
but just as a guess ... I broke the other one sometime in the
past and failed to replace it!?!?
Next time I'm feeling my wallet bulging (may not ever happen)
I'll have to get a mill bit order going .... or should I just
buy another engine instead?!?!
;c)
#Post#: 62691--------------------------------------------------
Re: Scary Milling
By: St Paul Steam Date: April 14, 2024, 1:43 pm
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I feel your anxiety, many is the time I have pushed my little
micro mill waaaay past its stated limits, hence my wanting I
mill on par with your excellent machine. 😀
#Post#: 62819--------------------------------------------------
Re: Scary Milling
By: Weedensteam Date: April 19, 2024, 10:12 pm
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[quote author=MasonvilleEngines
link=topic=7121.msg62686#msg62686 date=1713106154]
I have more expertise in breaking bits than milling. I find the
small bits thrilling also. Nice you had the patience to
persevere. I try to have two on hand of some of the smaller
sizes I find myself using most.
Len.
[/quote]
That is my expertise as well, I have learned the hard way to
alway buy more than one of the small
sizes.
(HTM) https://emoji.tapatalk-cdn.com/emoji1.png
#Post#: 63215--------------------------------------------------
Re: Scary Milling
By: Stoker Date: May 2, 2024, 10:11 am
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While it is generally true that mill bits get progressively more
expensive as they get larger, it is also true that their price
tends to skyrocket as they get small, going under about 1/8th
inch.
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