Another shear tool

Inspired by Tony Foales carbide shear tool version I had to make mine in a different way without the use of a milling machine. I had a ½ square braised carbide tool which I turned the shank down to a 3/8 dia to fit a square tool block from my cutter grinder which fits my tool holder, this does have the facility to vary the shear angle to suit different materials. Apart from the excellent finishes it produces it is very useful for work hardening steels which do not allow a small final cut to size, this tool will shave off a tiny finishing cut. These tools do have a limitation when working to a shoulder but raising the tool close to the bottom edge will do for most items.

Attachment 38174
Attachment 38175
Attachment 38176
Semi hard cast steel

Thanks Olderdan for yet another (seemingly) simple, versatile tip!
"-Dang, why didn't I think of THAT!":)

Changing the shear angle this easily will probably improve finish even more,
also being able to cut up to a right shoulder, should that need arise...
Sometimes feeding from the chuck can improve the finish even further.

I'm already off to the tool scrap bin, where a few oversize shank brazed carbide tools sits.
I'll just have to turn them down to fit!
Up until now I've been using a 4x4 mm HSS sitting in a DIY-ed lo profile V-block in the tool holder for a shear tool...

Cheers
Johan

Olderdan, do you have a link for the ½ square braised carbide tool ?

Ralph

Ralph, that looks like a C-8 type brazed carbide bit.

https://www.ebay.com/sch/i.html?_fro...l+C-8&_sacat=0

Olderdan, thanks for the great post. I've found shear tools great for certain jobs, but to date mine are all HSS. I'm not familiar with the type of clamp that you chucked up to hold the carbide bit in the lathe...it looks like it would be very handy for certain tasks (obviously like this one). Could you perhaps tell me what that is called, and even better where I can find them. THANKS!

John

Alan,

I am glad to know that my post inspired at least one person. I love your ability to change the angle, but do you do that?

John, it is a clamp type driving dog for between centres work, I had centred the blank in the 4 jaw both ends. It was given to me by a retiring turner it has no makers mark and have not seen another like it, it has left and right hand threads so stays central and balanced.

Tony, I have not used it much as I have only just made it, The ability to change angle is just a byproduct of the way I had to make it.

Quote:

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Originally Posted by metric_taper

Ralph, that looks like a C-8 type brazed carbide bit.

https://www.ebay.com/sch/i.html?_fro...l+C-8&_sacat=0

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Thats the one, I should have mentioned in my post that using a braised tool bit does require the ability to be able to sharpen it.

Just sharing a few experiences from my uses:

Shear tools can just take one or two thou - use something else for roughing.
Let the piece cool after roughing if you aim for really tight tolerances.
(Use the compound at 3-ish degrees for controlled DOC into the tenths range)
Cutting edge has to be really sharp and can dull pretty fast, though geometry isn't critical.
(Some people reported meagre results when using inserts, where the cutting edge hasn't been ground & honed)
Really fine feed, cutting oil and only a few hundred rpms for super finish.
As the tool doesn't exert any high tool pressure, it cuts cool and deflection is minimal even for long stickouts.
(I use it for instance for checking if my lathe cuts tapers).
Excellent for finishing difficult materials: "Mystery metals", rebar, cold rolled, copper and even lead.

YMMV

Johan

Reading through Tony's original post is loaded with information:
https://www.homemadetools.net/forum/...the-work-59276

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Thanks olderdan! We've added your Shear Tool to our Machining category,
as well as to your builder page: olderdan's Homemade Tools. Your receipt:

<div id="blocks"> <div class="block b1 pngfix"> <div class="bimg"> <div> <a href="https://www.homemadetools.net/homemade-shear-tool"> <img src="/uploads/243656/homemade-shear-tool.jpeg"/> </a> </div> </div> <div class="head pngfix"></div> <div class="left pngfix"></div> <div class="right pngfix"></div> <div class="blockover b1 pngfix"> <div class="title"> <a href="https://www.homemadetools.net/homemade-shear-tool">Shear Tool</a> <span> by <a href="https://www.homemadetools.net/builder/olderdan">olderdan</a></span> </div> <div class="tags">tags: <a href='https://www.homemadetools.net/tag/machining'>machining</a>, <a href='https://www.homemadetools.net/tag/shear'>shear</a> </div> </div> </div> </div>
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Thanks for posting that tool, it's the same technology with the use of an particular angle on a radius tool than we use on the shaper for superfinishing ?

That's right, Okapi - AFAIK the geometry was originally discovered for shaper finishing tools,
and for lathe work there seems to be consensus regarding <3 thou DOC, slow speed (<500 spm) and ultra-fine feed.
Tedious to watch while turning, but then there's always some coffee to drink too...

Some machinists report not having good results with carbide inserts, as they don't have very sharp cutting edges
(their rounded-off edges are a design trade-off for keeping up those crazy high speeds & feeds and big DOCs).

As I want to experience this further by comparing carbide tip and HSS shear tools for small work finishing-
I just winged this together from a discarded 5,5 mm masonry bit:

Attachment 38227 Attachment 38228 Attachment 38229

Clamp from a 12 mm square hot rolled, drilled and turned in the 4-jaw, slot cut with a hacksaw, a 15 min job.

Small, easily tweaked for different shear angles and turned over for either HSS or carbide -
just have to hone their edges before trying.
Though carbide needs some careful low speed fine diamond grit to hone properly, HSS sharpens more easily, but gets dull faster...
Compromises, compromises - the fun never ends!:)

Cheers

Johan

-Well, what do you know?
Lacking impulse control, I suffered an irresistible urge to take the tool (or the stock, rather) for a spin at work.
So, with the tool only ground on a greenstone grinder - NO lapping whatsoever - I just gave it a whirl.

Chucked a 15 mm coarse-turned piece of hot rolled, spun it at 450 rpm,
0.04 mm/turn at the lowest available feed, and a 2 thou cut lubed with 50-50 waste oil and kerosene:

Attachment 38230

Turning the Carbide from right to left with a 10-ish deg shear angle acquired a "nearly ground" finish on this POS.
Did a repeat cut at a mere half a thou DOC with amazingly good result, given the worn-down lathe.
Swarf is very fine, wisp-like, and stuck in the oil film at the very fine cut.

Then, turned the tool end over end to see how the HSS would improve the finish further
(as per my previous experiences & reports from other, REAL machinists):
First a Carbide close-up:

Attachment 38231

Then the HSS over the already good, previously cut Carbide finish:

Attachment 38232

The result speaks for itself - in stark contrast to my and others' experience...
The carbide (though even NOT honed) cuts nicer than the HSS does - EVEN with a smooth starting finish...

Bliss! Yet another day of counter-intuitive results! I've experienced and LEARNED something even today!

Maybe some here can find this piece of info interesting or useful!

Cheers

Johan

Oh, well...

Home from work, no "next of kin" around, so I tested a few more materials in my "Walk-In Closet Shop"
after honing the shear tool's edges with a 1000 grit diamond lap.

First (left in pics below) a rough CCMT 10 thou cut at 900 rpm and medium feed;
then 250 rpm w fine feed @ 2 thou DOC for Carbide (center) & "HSS" tip (right) @ 2 thou DOC.
No cutting oil, and a shear angle of 13 degrees.

Al 6082 (CCMT and Carbide hardly distinguishable, "HSS" inferior):

Attachment 38235

Hot rolled (Carbide excellent, "HSS" inferior to the CCMT):

Attachment 38236

Gas Spring Cylinder (Machined hotter than hot rolled (Carbide somewhat better than CCMT, "HSS" inferior):

Attachment 38237

Mystery But Free Machining Stainless (Amazingly good and cool CCMT cut, equals Carbide, "HSS" sucks again):

Attachment 38238

Conclusions: Masonry bit shank NOT from HSS - cutting edge got completely deteriorated on stainless and tool steel.
Cheap CCMTs from BangGood were very fast and amazingly successful in giving a good finish on "the usual suspects".
Carbide, when properly honed did darned well, but really takes its time to achieve it. YMMV.

I'd better be careful with my assumptions in the future, when comparing these with a REAL HSS shear tool.

Hope someone can find some useful info, inspiration or "Schadenfreude", patiently staying with me this far.

Cheers

Johan

A few bonus pics:
Attachment 38239 Attachment 38240

I have gotten some really good results with Aluminium and HSS, I have some carbide tools coming to try them.
Ralph

Johan,

Not all carbide is equal. I am pleased that what was in a masonry worked so well but it might be worth trying others. The tips in those drills are compounded for toughness with sharpness and the ability to hold an edge of secondary concern. On the other hand the carbide for turning aluminium is compounded with a fine structure which can be sharpened to a keener edge and retain it longer.

The shank of masonary bits is certainly not HSS. That would lead to a lot of broken bits. HSS is very brittle.

Thanks for reporting your tests, very interesting.

BTW. On aluminium I found no visually obvious difference between HSS and a sharp carbide insert. Same on mild and free machining steel but as you would expect the HSS did not like hardened steel but the carbide worked.

Thanks again, Tony.

The masonry bit was really just a quick find and "suck it and see" thing.

Possible avenue of coming tryouts:
Given the low rpm (over 100 sfpm I get chatter) and the slooow feed: 1 ipm,
I wonder if perhaps having a steep angle (<15 degrees) would be advantageous?
I've experienced better finish, less strain on the lathe, less noise and cooler turning
when going in with a steep shear angle (contrary to most machinists on the Interweb that swear by 25-40-ish degrees).

My thought, and a piece of vector algebra:
Most of the (small, indeed) cutting force will then work "more horizontally" in the bed's longitudinal axis,
where the leadscrew pushes against it,
instead of the force trying to deflect the tip mostly downwards (and less to the tailstock) as in ordinary turning.

I also consider that having a steep angle would equal a smaller nose radius on a conventional tool.

At least my mini lathe lacks some rigidity in the cross- and compound slides,
so deflecting that load off them seems to improve finish,
and also makes even tiny-teeny DOCs possible (if one only could get that carbide crazy sharp).

Any reflections on this are most welcome!

ATB
Johan

It takes a time to read and understand all when english is not your mothers'tongue, but all you wrote is similar as what I've experimented in workshop, using a lot of material with no provenance certified, I've made a lot of try with different cutting material too etc…
And as you said it's not easy to give a permanent solution for finishing, using specific powder cutting steel from Ifanger as specific steel like which named Supercoup here used specifically for cutting with a good surface finish on the lathe, and different carbide tools, I can't have a permanent solution and at each time it need some proofing, just as you said Hss is generally not the better choice, just on small diameters where it is very difficult to have a tool making a minimal force on the turned part.
The use of the tool sharpened like for the shaper with a radius cutting head with an inclination angle of 40-60° makes generally good results for me, but on parts with different diameters is difficult to use on all the length and you have to make a radius cut at the end.
Thanks for making all this testing and pictures, it's need a lot of time and you take it for us!!!

Thanks Okapi for your kind words - actually I wasted less than 2 hours for "the tryouts" (I wouldn't even call them "scientific") .
I learned a lot - for instance that my assuptions aren't seldom clouded by my ever-present eagerness and comfirmation bias.
And, as Tony pointed out: Carbide comes in a lot of varieties, and masonry drill bits don't have HSS shanks.:)
-Christ - I could've just tried the shank with a darned file...

Regarding your English, I don't personally think you have anything to apologize for,
but then English isn't my native tongue either.

All the best!
Johan

Thanks Johan, just as a complement, concrete drills have a shank in a serious quality of steel with a very high resilience and a high resistance to the twist, just try to fold one, then it's a good support for the purpose, I've brazed hard metal on old drill shank to drill bigger holes in concrete, it's very easy to make with very good results.

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Thanks DIYSwede! We've added your Cutting Tip Holder to our Machining category,
as well as to your builder page: DIYSwede's Homemade Tools. Your receipt:

<div id="blocks"> <div class="block b1 pngfix"> <div class="bimg"> <div> <a href="https://www.homemadetools.net/homemade-cutting-tip-holder"> <img src="/uploads/247547/homemade-cutting-tip-holder.jpeg"/> </a> </div> </div> <div class="head pngfix"></div> <div class="left pngfix"></div> <div class="right pngfix"></div> <div class="blockover b1 pngfix"> <div class="title"> <a href="https://www.homemadetools.net/homemade-cutting-tip-holder">Cutting Tip Holder</a> <span> by <a href="https://www.homemadetools.net/builder/DIYSwede">DIYSwede</a></span> </div> <div class="tags">tags: <a href='https://www.homemadetools.net/tag/holder'>holder</a> </div> </div> </div> </div>
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