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mf205i
02-17-2010, 03:53 AM
This one goes out to Docn8as. I wanted to thank you for the tip on the shear grind. I tried it in the past, but I didnít have much success. This evening I was making a part out of some A36 and I tried it again with 20 degrees off of vertical. The finish looked like the part came off a grinder, an absolutely unbelievable finish for mild steel. In 40+ years of doing this I had never heard about this grind. It is so easy and the results are so good that I find it a puzzle that it is not widely used.
Thanks again, Mike

Hal
02-17-2010, 06:48 AM
Mike
Do you have any picture of the grind or the link to the grind thread?


Hal

Black_Moons
02-17-2010, 07:27 AM
one thing iv wondered is exactly what way do you feed a shear bit?

I mean, assumeing a bit that slants down from right to left, do you feed it towards the headstock?
(like this bit: http://www.gadgetbuilder.com/VerticalShearBit.jpg (taken from http://www.gadgetbuilder.com/VerticalShearBit.html )

Id assume so, but it kinda looks like it might work the other way too?

And as for center height, I assume just any height where the 'peak' of the works radius contacts the shear area? Does the shear bit have any problems with really big diamiters?

Carld
02-17-2010, 09:37 AM
That is just a left turning tool upside down in the holder. Surely you have to run the spindle in reverse to cut with it like that.

Just how is this setup used? Is this thread intended to start another long debate?

Bob Ford
02-17-2010, 09:48 AM
Carld,

The tool cuts on the face not the top edge. In practice set the top edge above the center of the work. Cuts from tail stock to headstock. It is only for light finish type cuts, .003 or less.

Bob

Davidhcnc
02-17-2010, 10:18 AM
This is what he is talking about. Make one and try it.:)

http://homepage.ntlworld.com/david.hull35/CNC/shearbit.jpg

Dunc
02-17-2010, 10:48 AM
On Davidhcnc's photo, exactly where/what is the cutting point/tip?

Spin Doctor
02-17-2010, 11:07 AM
On Davidhcnc's photo, exactly where/what is the cutting point/tip?

Its the edge between the angled face and the back clearance

Davidhcnc
02-17-2010, 11:08 AM
.
http://homepage.ntlworld.com/david.hull35/CNC/shearbit%20002.jpg

mf205i
02-17-2010, 02:47 PM
. Is this thread intended to start another long debate?
The thread was intended to thank Docn8as.
Mike

allthumbs9
02-17-2010, 03:12 PM
That looks like a lathe version of draw filing. That might work for light, finish cuts.

mf205i
02-17-2010, 03:22 PM
Thanks David for posting the picture. That is what I was talking about except that I had a larger diameter part and I had good results with the face more vertical, 15-20 degrees off of vertical. If it chatters, go more vertical.
Mike

Carld
02-17-2010, 04:13 PM
As they say, a picture is worth a thousand words, most the time, and I can see where it cuts and how it works.

I would not waste time using that cutter, I can do as good or better with a lathe file plus a lathe file will work up to a shoulder and that tool will not. Then you would have to file it near the shoulder and that is rife with problems if your looking for an exact diameter.

For those that can't, won't or don't know how to use a lathe file (a lathe file is not a common file) it may be a good thing.

Thomas Staubo
02-17-2010, 04:44 PM
For those that can't, won't or don't know how to use a lathe file (a lathe file is not a common file) it may be a good thing. Would you care to explain to us ignorant soles (me) what a lathe file is, please?

.

MuellerNick
02-17-2010, 04:49 PM
I would not waste time using that cutter, I can do as good or better with a lathe file

Your cutters must be really terrible!


Nick

small.planes
02-17-2010, 05:25 PM
Better ground on a piece of round HSS and used in a split holder, you can change the angle of the edge then. I have one round here somewhere, made it for my unimat. Light finishing cuts only.

Dave

BadDog
02-17-2010, 05:36 PM
I have and use a 12" "lathe bastard" file frequently, but I still find the "shear bit" quite useful at times, particularly on HR steel. I don't use it as much as I used to since I got the ultra-fine finish Cermet insert a while back, but it's a useful tool that provides options that don't include trying to hand file very precise parts.

Toolguy
02-17-2010, 05:41 PM
A lathe file, also known as a long angle lathe file, has the teeth at a steeper angle to the edge than a mill file. It also has safe edges with no teeth so it only cuts on the flat sides. It has more of a shearing action and doesn't load up the teeth as much as a mill file on a rotating piece. You do still need to check it often and clean it with a file card to avoid making grooves in the workpiece.

Doozer
02-17-2010, 05:51 PM
The toolbit pictured is known as a skiving bit.

--Doozer

oldtiffie
02-17-2010, 07:23 PM
They Do work well - very well - usually as a finishing cut.

They can work wonders on a planer or a shaper - the bottom face is flat but the edge is "sheared-off" to say 30>45+ degrees. The ends of the cutting edge are "radiused-off" with a hand hone. The cutting edge is hand-honed to be razor sharp. The ram speed (shaper) has to be pretty slow but the cross-feed can be almost the width of the cutting tool. Beautiful flat finish. I've seen the pattern over 1/2" wide off a planer and up to say 1/4">3/8"+ on a shaper. It is ideal for marking-out tables and I've seen it on mill tables as well.

It works very well on cast iron and brass - steel too if taken carefully.

You can get a similar effect with a HSS lathe tool bit with a largish end/nose radius on a tool with a fair bit of side and back rake - edges well hand-honed as well.

Shearing cuts make life a lot easier - try a router cutter with zero spiral against a conventional spiral-toothed end-milling cutter and you will son see the advantage of shearing cuts. Same for spiral-fluted slab mills or side-and-face cutters as compared to straight-toothed cutters on a horizontal mill.

Same with a wood-worker's hand-plane with the blade cutting edge at an angle (ie not at 90*) to the line of cut as compared to having the edge at 90*.

Knives and razors are other good examples.

BobWarfield
02-17-2010, 07:39 PM
You certainly can touch up a finish with a lathe file, but I would think this is a better tool if you are pursuing an accurate round diameter for shaving little bits.

In any event, it's another interesting variation.

Cheers,

BW

Carld
02-17-2010, 08:39 PM
MuellerNick, no the lathe tools I grind are sharp and sometimes I hit them with a diamond hone if needed and the inserts are used as is.

The lathe file has been described so the only thing would be to post a photo but if you go to Enco or any supply house and look up lathe file it would be something any machinist should have a few of. The lathe file cuts very fast and doesn't load up as bad as a standard angle file.

If I want a smooth surface I put a round nose on the cutter and then if I want it even better I use a smooth cut file and or emery cloth. lathe tools always leave marks like a thread.

Using a lathe tool usually gives a more even diameter over the length of the work than a file but a good machinist with a file can get very good results. It's just a learned skill.

I may try that idea, if I grind the tool just right and set the height just right it might cut to a shoulder as well as a file would but I am more curious about the surface finish it produces.

MuellerNick
02-18-2010, 02:41 AM
@Carld:
I know what a lathe file is. I have one and frequently use it.

But frankly speacking, this...
"I would not waste time using that cutter, I can do as good or better with a lathe file"
... is simply nonsense.


Nick

J Tiers
02-18-2010, 08:47 AM
The geometry of the "shear bit" is completely wrong for a hogging cut.

But that is not what it is for. It does work nicely, and has one or two very strong advantages which I am NOT going to talk about here, because they may appear in a magazine article.

Carld
02-18-2010, 08:56 AM
Nick, you can consider it nonsense if you wish but it's not to me. I will try the shear tool to see what it does but I still say I can have as good a finish just as fast with a file and or emery cloth.

With a file I don't have to set up a tool or change a holder, just grab a file or emery cloth and finish the work. I don't see any nonsense in that at all.

I will report back my findings though.

MuellerNick
02-18-2010, 09:52 AM
but I still say I can have as good a finish just as fast with a file and or emery cloth.

Er ... pause ... looking upwards, top of the computer screen ... er ... ah! "Home Shop Machinist"!

I'm sorry for having interrupted your ... er ... program. ;)


Nick

mochinist
02-18-2010, 11:07 AM
Er ... pause ... looking upwards, top of the computer screen ... er ... ah! "Home Shop Machinist"!

I'm sorry for having interrupted your ... er ... program. ;)


Nickyou guys seem to like the advice/comments of pro's when you agree with it, as soon as you don't the fact that this is a "home shop" site is brought up. ;)

For the record I've never tried that style of grind, but if it works its as it seem to do, it is just another option to get the job done. There are a lot of ways to do the same jobs, do whatever way works for you.

Carld
02-18-2010, 11:15 AM
That's right mochinist, and in about 40 years of doing machine work, visiting shops and working in shops I have never seen that method used. That's not to say it's not used in working shops, I just haven't seen it and I have seen and worked in a lot of shops.

I am not saying it won't work, I am saying it may not be worth the effort and if it was such a good idea it would be used in some of the job shops I worked in.

As MuellerNick, pointed out, this is a home shop machinist site and the ideas presented are geared to and from home shop machinists and may not relate to working machine shop practices.

MuellerNick
02-18-2010, 12:11 PM
you guys seem to like the advice/comments of pro's when you agree with it, as soon as you don't the fact that this is a "home shop" site is brought up.

Woot? I mean, I'm using shear bits on the shaper. They make a superb finish. So I know what one can get out of it.*)
I also do have a lathe file and -drumroll- even use it. So I also do know what finish it makes.
So I'm in the state of being able to compare both. And if one says that he can make an at least as good as finish with a file ... top of screen ... or his lathe bits are a horror (that's how it started).


Nick

*) Just recently, I experimented once more a bit with that. As I do have a dedicated lathe bit grinder with diamond wheels and diamond lapping wheels and coolant and bells and whistles. I'm getting a finish on the shaper (with CI) where you can even see the *minute* errors the gears in the drivetrain generate. As long as you look at the surface in the right angle.

Here's a picture of that grinder: <http://www.maschinensucher.de/ma2/A646456.html> Mine only has two stations, not four like the one in the description. For 220.- EUR, I simply couldn't resist. :)

oldtiffie
02-18-2010, 04:51 PM
Woot? I mean, I'm using shear bits on the shaper. They make a superb finish. So I know what one can get out of it.*)
I also do have a lathe file and -drumroll- even use it. So I also do know what finish it makes.
So I'm in the state of being able to compare both. And if one says that he can make an at least as good as finish with a file ... top of screen ... or his lathe bits are a horror (that's how it started).


Nick

*) Just recently, I experimented once more a bit with that. As I do have a dedicated lathe bit grinder with diamond wheels and diamond lapping wheels and coolant and bells and whistles. I'm getting a finish on the shaper (with CI) where you can even see the *minute* errors the gears in the drivetrain generate. As long as you look at the surface in the right angle.

Here's a picture of that grinder: <http://www.maschinensucher.de/ma2/A646456.html> Mine only has two stations, not four like the one in the description. For 220.- EUR, I simply couldn't resist. :)

Thanks Nick.

It seems that only you and I know or have seen or used the shear bit on a shaper (or a planer). It works well on a lathe too - very well at times.

Or does it only exist in your case in Germany or in my case in OZ (Australia).

Or is it that because its not known of or has not been used or thought of in the USA that it not only does not but cannot exist? Or perhaps were are being ignored as "ill-informed" (ie bull-$hitting - again??!!).

I used it as an Apprentice under/with Tradesmen from here, the UK and Europe (Dutch, Austria and Germany mainly) - as they all certainly knew about it and used it. I used it as a Tradesman as well.

I have no problems with using a file - "emery paper" and a honing stone too - in a lathe as it is "class of finish" as well as size or "class of fit" that count.

"Class of Fit", Tolerances (and limits) as well as "Class of Finish" need a lot more attention here.

I checked your link. Nice work and nice shop/machinery.

MuellerNick
02-18-2010, 05:32 PM
It seems that only you and I know or have seen or used the shear bit on a shaper (or a planer).

Certainly not! It is well known on a shaper in the USofA.
I do know that shear bits are used on a lathe, I seldomly do. But even on a lathe, it's know in the USA. I do have a book (about 1920 I guess) describing it. Lost secrets? ;)

The advantage of a shear bit is, that you can "dust off", a no-go with carbide inserts.


Re emery paper:
In my eyes, it's only a last resort. I always try do get along without it.


NB:
The link is not my shop. It's from a tool dealer (not related in any way).


Greetings to OZ! I love that country!

Nick

GadgetBuilder
02-18-2010, 06:37 PM
Thanks Nick.

It seems that only you and I know or have seen or used the shear bit on a shaper (or a planer). It works well on a lathe too - very well at times.

Or does it only exist in your case in Germany or in my case in OZ (Australia).

Or is it that because its not known of or has not been used or thought of in the USA that it not only does not but cannot exist? Or perhaps were are being ignored as "ill-informed" (ie bull-$hitting - again??!!).
...

A link ( http://www.gadgetbuilder.com/VerticalShearBit.html ) in the third post of this thread has a reference to this bit's use on shapers in "Machine Shop Practice Vol.2" pg 14-15 by Karl Moltrecht, a USA author - so it's not unknown here.

HSM (a USA source you may have heard of :D) in Jul-Aug 1997 published "Grinding Tool Bits for a Smooth Cut" by Frank Burns which describes application of the shear bit in a lathe.

John

oldtiffie
02-18-2010, 07:45 PM
Thanks John (GadgetBulder) and Nick (MuellerNick).

It took some winkling out though didn't it?

I do enjoy reading your web site John - very well laid out, very useful and informative.

Thanks Nick.

I guessed that it was another shop when I re-read your post later. When I said "emery paper" I meant the cloth-backed type or the "wet and dry" stuff.

'nuther one for the shaper/planer - grind a tool for "tuff stuff" so that it has positive front and side clearance as well as positive side rake but with negative back rake. The tool will contact the work on the cutting edge and start to cut before the front/point of the tool does. It saves the front/point from the high impact load as the load comes on gradually on the side cutting edge first. Works pretty well on a lathe as well.

You can get a pretty good finish too on a horizontal mill by locking the spindle/arbor and mounting a spiral slab milling cutter on it and (with the spindle/arbor locked) just take a light cut and use rapid traverse in the table.

You can do the same on a vertical mill with and end mill and a locked spindle. The vertical mill can cut on the horizontal by using a disc cutter but the "tram" has to be off-set both for left-right and "nod" (forward-back) so the the cutter contacts the face at mid-way (45*) between "X" and "Y" (ie at NE, SE, SW or NW).

It is similar to the way a cylinder lawn mower works/cuts.

But you do need very sharp cutters!!

You can feed across by say 1/16">1/8" at a time.

Carld
02-18-2010, 11:41 PM
I hope a reasonable person would excuse the fact that I haven't seen this tool before and the reason is I have not been exposed to the use of a shaper or it's cutters.

This week has been a lousy week rife with issues and today my truck would not run, well crap.:mad:

After using my wifes car for some errands that the cold weather and snow kept me from all week I finally felt like going to the shop.

I just got through grinding a piece of 1/2" Rex aaa into a right hand turning tool and guessing by the photo in the link I ground the angles by eyeball. They turned out to be about 15 deg side clearance and about a 20 deg angle on the front top to bottom with about 10 deg from side to side on the top. I did not grind the top because that surface does not cut in this use, I just ground the right side and the front.

When I flipped it over it looked much like the tool in the link. I put a piece of cold roll in the chuck and turned it with a left turning brazed carbide cutter at 300 rpm at .004" feed and .010" DOC. The piece looked good with some tool marks visible. Then I put the shear cutter in a holder, set the height, fed the tool in till it touched, moved the cutter off the work, fed it in about .004" to give .002" on a side and set the feed at .002" and 300 rpm and started the cut. It peeled the metal off in long curls. At the end I disengaged the feed, backed out the tool, moved the carriage and stopped the chuck and looked at the finish.

The finish was better than the carbide tool gave but still had a machined look. Then I picked up a near new Simmons 12" NUCUT file and made two passes over one end of the turned area, stopped the lathe and inspected the finish. The two areas looked much the same except the filed area had more shine to it. I didn't try emery cloth but I know from experience some 320 emery cloth would produce a near polished finish.

So my conclusions are, the shear cutting tool would be very handy if I needed to take a thousandth or two off a shaft and keep the diameter constant along the cut. It may be real good when machining a piece of crappy steel the just won't turn nice. Just leave about .020" and finish it out a with several light cuts to finish diameter. We'll see if that works when the chance comes.

Any one that has used the file as much as I do knows it takes care and practice to keep the diameter constant. It's not near as hard to do with fine emery cloth because it mostly polishes and cuts slower depending on the grade. With the shear cutter tool you should get a uniform diameter the distance the cutter is used on the shaft. For those not experienced with a file and don't want to learn how to file the shear cutter may answer their prayers.

I will still use a file most the time as I don't see the shear cutter as a total replacement of the file. The shear finish and filed finish were the same except for the polished appearance from the file. I will keep the shear cutter handy for occasional use as needed, who knows, I may use it more often as time goes by depending on the job.;)

Does that make you happy MuellerNick? I really don't understand why your so snippy about my posts about using a file. It was my opinion which I am entitled to and there was no reason for you to diss me over it.

Now I have a question, what are the best angles to grind the reliefs to?

From my test I am thinking 30 to 40 deg on the right side and the other angles would be ok. That would give more shearing action. As it was cutting I could see that if the side angle were more it would peel the metal off better and maybe give a better finish and the front clearance could be less to make the cutter work more near the axis of the work. As it is it cuts under the center line of the shaft and you can't change that without changing the front clearance angle. Maybe it does better cutting under the center line, it didn't seem to be a problem.

I will experiment with some angles. Has anyone experimented with the angles and what angles do ya'll use? I am working out a tool shape in my mind to enable it to cut close to a shoulder and a few experiments may turn something up.

oldtiffie
02-19-2010, 02:49 AM
Carl.

You can mount an end mill in an adaptor in your lathe tool post - the cutter is tangent to the job. If you can tilt the cutter left-right - to vary the shear angle - so much the better. Make sure the cutter is very sharp.

Low speed and high feed are what is required.

The end milling cutter - if able to be raised/lowered as well will give you a lot of cutting edge, and if the cutter is held by the shank the tool/end mill may not even have to be re-indexed.

As the cutter can also be rotated, the "hook" (aka top/back rake) can be varied as well.

It is the ultimate "tangential cutter" that is so bloody expensive.

None of this is new - it is just a variation on a principle or a theme.

As I said previously, I use the file and "wet and dry" in my lathe. If I only have a thou or less to go - out comes the file etc. as I have to get both the size and the finish right.

If I have, say, a shaft that is say 6" long that has a tolerance of say +0.001"/-0.001" my "HI" and "LO" limits are 0.002" apart. So I can do what ever I like provided that I stay within those limits - filing and "wet and dry" included. If I have a taper of say 0.002" per 1", I am quite entitled to have "saw-tooths" of 0.002" every inch with the top of the saw-teeth at say 0.001" > 0.000" over my top limit. I can file the tops off the saw cuts so that they are within my limits etc.

Its been done that way on "fu*ked" lathes since for-ever and is perfectly legitimate.

I can do a similar tactic on a cross-slide that is worn and/or out of square to get the accuracy I need.

Some of these "gurus" who write those books that are pretty much all the same and that some regard as "Gospel" (or the "Bible"??) have a lot to answer for. A lot of Trade/Vocational Training is no better.

I don't get the least bit "hung-up" if my lathe is not dead level or if it has a twist in it - or if "Rodney's Dad's method" et al won't work. I just do the best I can to set the machine up, and accept it as it is for what it is and get on and use it.

I made it my business and priority to find out what my machines' limitations and capabilities are and I just work within them.

Same with so-called "different" or "new" ways of using machines and tools that don't appear in some of those "Gospels" ("Bibles") and almost certainly not in many vocational training establishments.

This applies to the shear cutting that Nick and I referred to.

MuellerNick
02-19-2010, 03:14 AM
Opps! My posting got lost somehow. :(

This is the finish I get with a CCMT insert.
http://www.cncecke.de/bilder/uploadFiles2008/16348_106769655749_db1.jpg
No stinking file. ;)


Nick

Black_Moons
02-19-2010, 09:06 AM
Heh, I manage to get a reliable mirror finish facing HRS with one of my TCMT insert holders! Oddly enough the same cutter can't turn it worth a crap, but faces like a dream.. oh well, I just leave it as a deticated facing tool. :P

Sometimes the tool that gets you a great finish on one operation can fail on others

Carld
02-19-2010, 09:06 AM
Oldtiffie, I remember someone mentioning using an endmill and that would do a good job set right.

So slow speed, fast feed. What rpm and feed do you run the tool at? Also, what angle do you prefer on the shear part of the tool? Since you have used it a lot who better to ask.

Carld
02-19-2010, 12:44 PM
So, am I to assume only Oldtiffie and a few others use the shear tool but have no opinion on the angles they use?

Does that indicate how prolific the use of the tool is?

Black_Moons
02-19-2010, 02:03 PM
Carld: you could wait for more then 4 hours for a reply.

Carld
02-19-2010, 02:56 PM
NO, NO, I want to know NOW. :eek: :D :rolleyes:

The Artful Bodger
02-19-2010, 03:16 PM
So, am I to assume only Oldtiffie and a few others use the shear tool but have no opinion on the angles they use?

Does that indicate how prolific the use of the tool is?

I use a shear tool on my lathe, by coincidence it is the very same tool I use on my shaper.

For what it is worth I have found that tiny adjustments to the toolpost angle (i.e. rotating on the vertical axis) makes a big difference to how the tool operates. A fine cut shears off tiny curled whiskers and gives a satin finish while a bit more angle shears off a long unbroken spiral chip. That is on a stainless steel shaft of unknown specification.

MuellerNick
02-19-2010, 03:58 PM
Does that indicate how prolific the use of the tool is?

Certainly. You knew that you can do better with a file, even without having tried it.

This kind of discussion needs no further anwers and no further explanations. Try it by yourself and stop wining.


Nick

BadDog
02-19-2010, 04:08 PM
I've used these to varying amounts since I first found them back when I had the Rockwell. I really couldn't say what my angles are (more on that in a minute). I don't use fixtures of any kind for grinding HSS (except threading, and sometimes not then). I just grind them till it looks "about right". Just guessing, but clearance is maybe 5*, not a lot since it is used for only the shallowest of cuts. I generally grind a bit of rake, but probably only 3* or so, and sometimes 0*.

I've reground that thing numerous times, tweaking this and that. Sometimes it just doesn't seem to want to work as well from one use to the next, and that includes edge touch up with hand lap. Feed/speed adjust can sometimes help, but changing shear edge angle a bit can sometimes make a huge difference in finish, or so it seems to me, and angles sometimes work differently at different diameters on the same material. My current bit has 2 edge angles, one about 10* on the lower half, and about 20* on the upper half. I can then move it up or down to see what works best on a given material/diameter.

So, I recently decided try a change on mine, but haven't had a chance to try it out.

I plan to grind mine so that the cutting edge is not straight, but rather an arc (by turning bit somewhat parallel to wheel axis and grinding on circumference) while giving it a bit of rake (tail of bit closer to axis). This would use a larger stick (maybe 3/8 to 1/2"?) and smaller wheel (dremel?) to get enough arc to make a difference, but not a whole lot in any case. That allows moving it up and down in tool post to adjust the angle of the shear edge. And still easily sharpened by touching up the flat end clearance facet.

Carld
02-19-2010, 09:43 PM
Nick, did any one ever tell you that your a real class A JERK. If not then let me be the first to tell you that you are for certain a CLASS A JERK.

Why don't you find a corner and hide in it.

It takes a lot to get on my sh*t list but your on it now.

BTW, this is the last time I will reply to any of your incite full remarks.

Carld
02-19-2010, 10:06 PM
BadDog, when I grind HSS tools I usually use a pedestal grinder and grind so the cutter is flat against the circumference of the wheel. That puts a slight concave surface on the relief face so moving the tool up and down will change the shear angle in two planes.

I think I will make several shear angles to use. I can have two different angles on one tool and two tools would probably cover everything. Since you said one angle don't work on everything that should work.

After a lot of thought the fact that it would be easy to get a uniform diameter the length of the work may come in handy. Even if it is not a high finish I can file or emery it to the desired finish without removing much metal.

I'm not sure if the finish with the shear tool would ever be a near polished finish but that is not what I would be using it for. My purpose is a uniform diameter the length of the work with an acceptable finish. As know not all metals will machine smooth but the shear cutter may over come some of that. Also, on short areas it's still easier to file it but a long run takes time to file to a constant diameter.

It's worth experimenting with for just that purpose alone to me. Since I got the truck running again and some of the other pressing issues are done I can play a little now.

Carld
02-19-2010, 10:09 PM
I want to apologize to the rest of the members for loosing my cool with Nick but that is the way it went and it's done.

Boucher
02-19-2010, 11:41 PM
This type tool is workable and has a specific purpose. I have two versions ready for use in tool holders. When GadgetBuilder posted his link some time back I tried his version. I had previously tried a little different version on cutting a long somewhat chatter prone Brass cylinder. I have two Lathe files some 320 grit cloth backed abrasive roll and about four Cratex abrasive sticks of varying grits right on the same shelf with the shear bits. Having a long relationship with the files, I probably grab them more often as my tool of choice. That is my comfort zone. The beauty of this site is that we all can learn from one another faster than we could figure it out on our own.

Oldbrock
02-20-2010, 02:11 AM
I have never seen this cutting tool in all the sixty plus years I've been machining. Going to grind one up tomorrow and try it. On second thoughts, it's our 56th wedding anniversary tomorrow and Man U is playing Everton so my day may not include a visit to the shop but will try it soonest, Peter

oldtiffie
02-20-2010, 02:51 AM
BadDog, when I grind HSS tools I usually use a pedestal grinder and grind so the cutter is flat against the circumference of the wheel. That puts a slight concave surface on the relief face so moving the tool up and down will change the shear angle in two planes.

I think I will make several shear angles to use. I can have two different angles on one tool and two tools would probably cover everything. Since you said one angle don't work on everything that should work.

After a lot of thought the fact that it would be easy to get a uniform diameter the length of the work may come in handy. Even if it is not a high finish I can file or emery it to the desired finish without removing much metal.

I'm not sure if the finish with the shear tool would ever be a near polished finish but that is not what I would be using it for. My purpose is a uniform diameter the length of the work with an acceptable finish. As know not all metals will machine smooth but the shear cutter may over come some of that. Also, on short areas it's still easier to file it but a long run takes time to file to a constant diameter.

It's worth experimenting with for just that purpose alone to me. Since I got the truck running again and some of the other pressing issues are done I can play a little now.
Carl.

A suggestion.

Use round HSS tool bits (instead of square") and put the tool in a boring bar adaptor in your tool-post (pointing forward).

You can tilt the shear tool in the boring bar adaptor and can further adjust the tool by swinging/rotating the tool post - all in a minute and without re-grinding the tool.

Simple, easy and versatile.

krisfarm
02-20-2010, 05:18 AM
Carld,
I use shear bits quite a lot for finishing cuts on low grade black bar and find that 15 degrees on the cutting face generally works the best, next time you use shear bit, give this a try drop the lathe speed back. On 1" diameter bar I use 50-100 rpm with coolant and get an almost mirror finish with a .002/.004 depth of cut I use a very light feed as well.The spindle speed seems to have more impact on the finish than the face angle.
Bob

joegib
02-20-2010, 05:34 AM
Use round HSS tool bits (instead of square") and put the tool in a boring bar adaptor in your tool-post (pointing forward).

This form of the tool is described here:

http://i923.photobucket.com/albums/ad80/joegib/Skiver.jpg

This is a quote from LC Mason's book "Using the Small Lathe" published in1963 (though the author didn't claim it as new/original then). As oldtiffie says, it's more flexible than the version made of square tool stock because, held in a boring bar holder, the angle of attack can be altered by swiveling it. Moreover, if you use a runout channel, the not-cutting-to-a-shoulder problem can be pretty much overcome by raising the tool so it only cuts on the "south-western" corner of the diagonal cutting face.

Joe

Carld
02-20-2010, 10:40 AM
oldtiffie, joegib, the round tool is a great idea. That eliminates the under center problem. While I was reading the article joegib posted I got an idea for grinding a square tool so if I don't have some round HSS I will try some square. The round woud be better because the angle can be adjusted as needed.

I suspected I was to fast on the rpm and feed and that appears to be the case.

I am some times resistant to change but when an idea starts having usable qualities it's worth learning and still keeping the other methods I use. Just the fact that it will cut a constant diameter along the work and clean up tool marks makes it a keeper for me.

Scishopguy
02-20-2010, 12:45 PM
This is a perfect use for the shanks of broken or worn out end mills. I have used them for boring bar cutters for years. Lots easier than making a square hole out of a round one to fit a tool bit. ;)

DaHui
02-23-2010, 09:13 PM
So I've never seen this kind of grind before and decided to whip up a tool today and try it. Holy smokes! I pulled out my best "normal" HSS grind to baseline and I got the usual banding and inconsistent surface on a piece of 1/2 DOM.

Went back over it with the shear grind and it finished up absolutely perfect. Amazing really. Everyone should try this...especially if you haven't. Unfortunately I didn't have my camera but I hope to post a couple of pics soon.

I also didn't measure any of the angles, just eyeballed what seemed to look right. At first I thought I didn't have enough angle on the face but it worked great. I'd guess it was between 10 and 20 degrees.

lazlo
02-23-2010, 09:21 PM
This form of the tool is described here:

This is a quote from LC Mason's book "Using the Small Lathe" published in 1963

Hope this isn't a hijack, but I've never seen Tool E - the "Tailstock turning tool."
How's that work??

joegib
02-24-2010, 04:38 AM
Mason describes it as a "running down tool" intended for use from the tailstock. He says it can be used for the production of fine screws. Rod stock of screw head size is held in the headstock chuck or collet. The bit is is advanced from the tailstock along the workpiece. The outer cutting edges of the bit cut off waste material, the reduced shaft entering the bit's through-hole. Of course, the through-hole is sized to suit the screw's required diameter. A die held in a tailstock holder is then run down on the shaft to cut the thread, parting-off being carried out from the crosslide in the usual way.

The attraction of the process is that the screw shaft is generated by an end cutting tool which also provides back-end support via the through-hole. Likewise, using a die ensures that the screw shaft is supported during the cutting process. That way, all the hazards associated with conventional screwcutting ó side thrusts tending to bend a slender shaft ó are avoided.

I suppose you could carry out batch production of small screws in this way. Set up the running down tool and die in a tailstock turret, with a parting tool on the crosslide and you're ready to go. Screwhead slotting would need a separate operation, of course. Can't say I've ever seen the operation in the flesh either. Maybe it's something more favoured by clockmakers/watchmakers who more commonly need fine screws.

Joe

MuellerNick
02-24-2010, 05:08 AM
I learned to know them as "rose bits".
I made a few up to 6mm Ý. They work quite good and are very fast compared to doing that work with a lathe bit. Always the same diameter and the length of cut can be read on the tailstock.
Surface isn't the nicest one, but good enough for a thread.

Nick

oldtiffie
02-24-2010, 05:13 AM
That's so Joe as regards Tool "B".

http://i923.photobucket.com/albums/ad80/joegib/Skiver.jpg

You know now why I suggested that it be made from round stock HSS. That's why I suggested it. I waited until at least some one had tried it for themselves as some seemed to doubt what I'd said. As I also said previously, the key is a very sharp keen honed edge at slow speeds with higher feed rates and lots of cutting oil. It is a form tool after all - just as screwing and parting tools are. It is essential that the cutting edge neither fails nor rubs.

Toll "E" - as referred to by Lazlo - is also an old tool too. I first ran into it about 58 years ago when I was a First Year Apprentice on an OZ-made (under licence) 6" belt-driven SB clone with a capstan adaptor mounted in lieu of the SB tail-stock. I made a lot of small slender spindles and screws on it.

The tool actually provides the support - as steady or a tail-stock might. It has fairly limited use in a conventional tail-stock as regards length, but if that tail-stock is a capstan or turret it becomes a whole new ball game as some have cross-drilled capstan spindles/spigots. Put a matching bored "tool" in the opposite turret position to support the thread or spindle - and away ya go. Threading can be done in the next sequence using a "Coventry" type (hollow shank) die-head threading tool and you are on you way.

http://www.threadtools.com/Files/Coventry%20technical%20info.pdf

http://www.namco-tooling.com/coventry-dieheads-chasers.html

That cutter "E" which we are referring to, if it has a spigot in the centre works very well as a "spot-facing" tool - or even as a counter-bore in a lathe, a mill or a pedestal drill.

Glenn Wegman
02-24-2010, 07:23 AM
Nice work Carl!

What I find interresting is that John (Gadgetbuilder) has posted about these tools on many occasions and nobody gave them a second look. Suddenly they are the greatest thing and the rage of home shop forums! (for good reason)

Carld
02-24-2010, 08:58 AM
I guess it goes with the saying of rediscovering the wheel. It is a useful tool and while normal cutting tools should do the job most the time there are times when the shear tool will stand out above the rest.

As to filing the work to size it's so easy for short areas it's not worth setting the shear tool up. On long runs is where the shear tool could be a real asset.

I guess you saw the thread Shearing Tool Update also? It has rolled to the third page on the site now and has a lot of photo's of different cuts I made and the tools I used.

The 30 deg shear angle with a 4 to 6 deg front clearance seemed to work the best and the Cobalt and carbide cutters held the edge best.

DaHui
02-28-2010, 04:19 PM
Here is my first effort. No measurements or anything, just eyeballed it. The skiving tool undoubtedly produces the smoothest surface finish. I found it worked especially well on smaller diameters. The stuff in the photos is 1.75" HRS.

http://www.the-alchemist.com/Images/Shoptask/Skivving%20Tool/JPEG/DSC00192.jpg

http://www.the-alchemist.com/Images/Shoptask/Skivving%20Tool/JPEG/DSC00190.jpg

The bands are as follows (starting from the left):

1) SECO DCMT finishing insert
2) Generic TCMT
3) Ground HSS
4) Skiving Tool

Richard-TX
03-02-2010, 12:40 PM
I have been playing with the whole shear cutter idea now for a while and I don't see a significant improvement. As a matter of fact I don't see an improvement at all over my other finishing cutters. My finishing cutters do a better job.

I am going to try some other shear angles but don't hold out much hope.

Carld
03-02-2010, 12:58 PM
If your not getting a fine finish your doing something wrong. I found a 30+/- deg angle is best with a 4-6 deg clearance works best. The shear angle of 30-40 deg is much better than less than 30 deg. Experiment with rpm and feed but I found a rpm of about 190 had less wear on the cutter and the feed I used was .004" with a DOC of .002". That's .002" on a side and any less than that was a problem. Here is a photo with my best results taken from about 3-4" from the work. At arms length it looks to be a ground surface. The cutter in the photo is a HSS 10% Cobalt which had more wear resistance the HSS and a carbide tool had less wear than the Cobalt tool.

http://i82.photobucket.com/albums/j276/yeathatshim/P2230010.jpg

DaHui
03-02-2010, 01:01 PM
Who is going to be the first to set up triangular insert to cut on the side? :) Might not be sharp enough but maybe a diamond wheel can take care of that.

Carld
03-02-2010, 01:08 PM
Strange that you should ask because I had the same idea as I was doing the experiments. The reason I didn't do it is I had a stick of triangle carbide to grind the end on and would have had to make a special holder for an insert. Guess what won out.

I would expect that a 5 deg relief triangle insert mounted at a 30 deg angle would perform perfectly as a shear cutter and being able to index it as the edge wears out would be very handy.

DICKEYBIRD
03-02-2010, 01:09 PM
Who is going to be the first to set up triangular insert to cut on the side? :) Might not be sharp enough but maybe a diamond wheel can take care of that.Now that's a fantastic idea! You wouldn't need a new insert, just use the ones with chipped corners. I got lotsa those.:)

BryceGTX over on Chaski http://www.chaski.org/homemachinist/viewtopic.php?t=84313 posted a ton of great info on the shear bit. He did boring, flycutting and endmill shear cutting bits and posted great explanations & pics.

Peter.
03-02-2010, 01:24 PM
What about grinding a piece of round HSS to make an internal-cutting one? Can't see why it wouldn't work - I might try it out later!

DaHui
03-02-2010, 01:24 PM
Can I not see the chaski images because I'm not registered?

Carld
03-02-2010, 01:24 PM
And, you might want to read this one as a companion info on shear cutting as well.

http://bbs.homeshopmachinist.net/showthread.php?t=39894&highlight=shearing+tool+update

DICKEYBIRD
03-02-2010, 02:44 PM
Can I not see the chaski images because I'm not registered?Sorry, forgot about that. It's worth registering over there too; there's smart fellows there as well.

lazlo
03-02-2010, 02:52 PM
BryceGTX over on Chaski http://www.chaski.org/homemachinist/viewtopic.php?t=84313 posted a ton of great info on the shear bit. He did boring, flycutting and endmill shear cutting bits and posted great explanations & pics.

That's a great thread. He's using a 15į shear angle, which I think was derived from GadgetBuilder's geometry.

Carld
03-02-2010, 02:55 PM
That's the same angle I started experimented with and found it wore faster. The steeper angle has more shear and less rubbing at the same speeds and feeds.