# DIY tangential tool | Diamond Tool Holder and plans in video description



## celsoari (Jul 17, 2020)

How i made my tangential tool / Diamond Tool Holder:


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## brino (Jul 18, 2020)

I've have wanted to build one of these.
I really like your design.
Thanks for sharing it!
-brino


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## celsoari (Jul 19, 2020)

brino said:


> I've have wanted to build one of these.
> I really like your design.
> Thanks for sharing it!
> -brino


Thanks Brino.
cheers
Celso Ari


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## Karl_T (Jul 19, 2020)

Just curious, unless its a HUGE amount of material, I never saw out sections like done at the beginning of the video. Time saved removing material is lost re-trueing up IMHO. Both ways certainly work. Maybe I like my method cause i got a 5hp spindle and carbide insert cutters for hogging.   Corn cob cutters work great too. What is the general opinion here on hobby machinist?


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## celsoari (Jul 19, 2020)

what is IMHO? sorry here we speak portuguese, i am not fluent in english, so i have difficulty understanding some word suppressions



Karl_T said:


> Just curious, unless its a HUGE amount of material, I never saw out sections like done at the beginning of the video. Time saved removing material is lost re-trueing up IMHO. Both ways certainly work. Maybe I like my method cause i got a 5hp spindle and carbide insert cutters for hogging.   Corn cob cutters work great too. What is the general opinion here on hobby machinist?


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## Tozguy (Jul 19, 2020)

IMHO means 'in my humble opinion'

nice work there celsoari. Thanks for showing the video.


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## brino (Jul 19, 2020)

Karl_T said:


> What is the general opinion here on hobby machinist?



Interesting question..........
I guess it comes down to what is easier/cheaper for any given operation.....and that depends on what machine tools are in the shop and whether it's a production shop or a hobby shop. It comes down to a time required for the operation.

-brino


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## homebrewed (Jul 20, 2020)

Owning a small desktop mill, hogging out large amounts of metal is very time-consuming for me.  So I look for ways to speed things up where I can.  Depending on the item I'm making, I may use my bandsaw to rough out some portions.  In others, I will use my slitting saw instead of turning the whole volume of removed metal into small bits of swarf.  If feasible, I also have separated the item into several different pieces and then assembled them into a whole.

I found a design for a tangential tool holder that uses the latter approach, and, in addition, splits the two different angles among two separate parts, rather than needing a complicated setup to mill the compound angle needed for a one-piece approach.  This should work OK for me because I'm using a Norman Patent style of QCTP and can split the angles between the main block (that mounts on the post) and a second piece that will bolt onto a sloped face of the block.  The design can be found in the groups.io 7x12 mini lathe file section, titled "Mini Lathe Diamond Tool Holder.pdf".   Folks who have dovetail-style QCTPs may not find this approach all that interesting.

I'm wondering about a design that uses an even simpler scheme to achieve the required clearances.  Mill an angled vertical slot on the face of the QCTP block, then rotate it by a small angle when you install it on the lathe.  Just one easy-to-mill angle.  Here's a sketch showing the working face of such a holder, with a cutter installed:



In this view, the upper-right corner of the cutter is presented to the work, so I'm showing the back of the holder relative to the operator,  Not shown:  the holder is rotated so the tip of the cutter is pointing slightly away from you.

NOTE:  I edited this because I originally (and mistakenly) indicated that the holder needs to be rotated CCW, and thus can't foul the chuck, but that was incorrect.  The holder must be rotated CW to get the proper relief angles.  However, I still don't think the holder is likely to strike the chuck before the cutter would.  This due to the fact that the chuck jaws extend from the front of the chuck, so there's some leeway there.

If oriented correctly, I'm thinking this holder could also be used to face a workpiece, too.

Not shown:  fixing screws to hold the cutter in place.  Oh, and the grind angle of the cutter isn't right -- it should be arranged so there's some positive rake when it's presented to the work (it IS just a sketch, right?).


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## homebrewed (Jul 20, 2020)

I wrote an OpenSCAD script to more-fully explore my tangential tool holder idea.  Here's what a rendering of it looks like (rotated the proper direction, if the work is on the right):


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## mickri (Apr 29, 2022)

I also use a norman style QCTP.  In addition to the typical square or rectangular holders I have made them with an angle on one side.




  Could do something similar for a tangential tool holder.


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## homebrewed (Apr 30, 2022)

mickri said:


> I also use a norman style QCTP.  In addition to the typical square or rectangular holders I have made them with an angle on one side.
> 
> View attachment 405482
> 
> ...


Yes, the usual approach is to employ a compound angle to get the job done.  But your rendering doesn't look quite right to me -- the cutter's angle component ponting to the right is OK, but shouldn't the other angle be reversed, so the cutter points toward the viewer?

The whole idea of my proposed alternative was to avoid a compound angle, relying on a rotation of the tool holder to provide clearance and provide a kinda-sorta compound angle.  I think the scheme would work OK in some cases but it wouldn't be good for an all-around cutter.  But that's not a total loss -- after all, a boring bar isn't all that great for an all-around cutter either.....


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## mickri (Apr 30, 2022)

I looked at your drawing and duplicated the angled slot on the end of an angled tool holder.  Here is a top view.  Don't know if that helps.


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## homebrewed (Apr 30, 2022)

Your top rendering looks OK.  If the angles are correct, the top face of the cutter would obscure its body.


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## mickri (Apr 30, 2022)

What do the angles need to be?  I will correct the drawing and include the tool bit.


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## homebrewed (May 1, 2022)

mickri said:


> What do the angles need to be?  I will correct the drawing and include the tool bit.


Typical angles for the tool holder are 12 degrees forward (toward the headstock) and 12 degrees back (away from the operator).  This permits both facing and turning, IF no part of the holder is forward of the cutter tip.  This includes the fixing system used to attach the bit to the holder.

The tool bit is sharpened at 20 degrees, so it presents a top relief angle of 8 degrees to the work when it's installed in the holder.


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## mickri (May 1, 2022)

Did another sketch.  This time instead of drawing a dedicated tool holder to fit on the post I drew a holder that would fit in one of my existing tool holders.  It is 1" H x 5/8" W x 3" long.  The bottom is angled 12* tilting the holder towards the headstock and the slot for the tool bit is angled 12* tilting inward.   That should give the required compound angle with two simple milling operations.  I like to use 3/8 tool bits and have the tool bit stick out a bit from the holder.  The slot is 5/16 deep by 3/8 wide.  I haven't checked the height of the tool bit to see where it would be in relation to centerline on my lathe.  Will probably have to make some changes to dial that in.


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## mickri (May 2, 2022)

Did another sketch.  The one in my previous post was too high to work on my lathe.  This one is made from 1/2" square by 3" long steel bar.  The portion that fits in the tool holder is angle 12* top and bottom for a better fit in the tool holder.  The slot for the tool bit is angled 12*.  I also angled the side by the tool bit for better clearance when facing.  Don't know if that is needed and I will make some test cuts before I do that.  Don't know when I will get to this.  I am still in the middle of remodeling my new place.  My garage shop is a mess with barely enough room to walk through it.


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## homebrewed (May 2, 2022)

The required cutter height made a big difference in my version of the tool holder -- The cutter tip is only .620" above the compound.  The only way it would work was to arrange things so the cutter hangs down below the side of the compound.  Like this:


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## mickri (May 2, 2022)

There is 1.1875" from the top of the compound to centerline on my lathe.  I may have to make a dedicated tool holder.


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