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Author Topic: HSS trepanning toolbit.  (Read 4635 times)

Offline NeoTech

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HSS trepanning toolbit.
« on: October 05, 2012, 10:02:17 AM »
So my uncle came to me cause i have machinery and wanted a piece of cast iron cut out of a square piece (squarish).
Anyway he wanst a 150mm hole in this bugger.. and its about as large as my chuck can handle.. so fine.. i set it up and tried to imagine.. how the hell a tool bit for cutting a disc out of this would look like. After some struggling and broken parting bits so i gave up.

After some thinking and (images googling) i have come up with a grind that .. well could work.. but im not sure.. cause ive never done this in the lathe.


Would this work?! Or will have something come flying at me ?!
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Machinery: Optimum D320x920, Optimum BF20L, Aciera F3. -- I have not failed. I've just found 10,000 ways that won't work. http://www.roughedge.se/blogg/

Offline DICKEYBIRD

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Re: HSS trepanning toolbit.
« Reply #1 on: October 05, 2012, 10:17:44 AM »
Here's one I ground a while back for a 1.9" hole.



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Offline DICKEYBIRD

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Re: HSS trepanning toolbit.
« Reply #2 on: October 05, 2012, 10:24:06 AM »
Oh, almost forgot; I had bad chatter problems until I turned the tool upside-down, put it on the backside and reversed spindle direction.  Cut like buttah then!

edit: Oops, sorry, come to think about it, I didn't turn the tool upside-down, just reversed spindle direction.  That was done a while back & my  memory ain't what it used to be.
« Last Edit: October 05, 2012, 11:41:53 AM by DICKEYBIRD »
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Milton in Tennesee

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Offline NeoTech

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Re: HSS trepanning toolbit.
« Reply #3 on: October 05, 2012, 02:47:24 PM »
ooh så the tool should match the circle check.. *see i have my work cut out for me tomorrow then*
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Machinery: Optimum D320x920, Optimum BF20L, Aciera F3. -- I have not failed. I've just found 10,000 ways that won't work. http://www.roughedge.se/blogg/

Offline philf

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Re: HSS trepanning toolbit.
« Reply #4 on: October 05, 2012, 04:58:09 PM »
Quote from: NeoTech on October 05, 2012, 02:47:24 PM
ooh så the tool should match the circle check..

Neo Tech,

You must have side clearance on both sides of the cutter or it will almost certainly jam and break!

The radius of the cutter on the outside should be smaller than the radius of the hole (R) you're trying to cut. The radius on the inside of the cutter should be larger than R-T (where T is the width of the cutter).

Does that make sense?

A drawing would make it easy to understand but I haven't had time.

Phil.
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Phil Fern
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Offline Fergus OMore

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Re: HSS trepanning toolbit.
« Reply #5 on: October 05, 2012, 06:42:18 PM »
You should simply draw one circle at the inside of your job and at the same centre draw the outside of the intended cut.

Then draw a line horizontally through the centre of the circles.

As stated, the top of the  trepanning tool should touch the horizontal line and have the side shanks waisted so that  it would fit the curvature with enough side relief not to bind or nip.

If you don't get a tool like that you will probably get the job being flung out of the chuck, the tool broken and a possible strained chuck.

You will only learn the true amount of damage- on your return from hospital :bow:
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