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Black Forest
02-24-2012, 06:27 AM
I finally understand why my threading tools are able to tip. This allows for the helix angle relief. But do I then grind the top of the tool to be flat inline with the through axis of the work? Meaning parrallel to the lathe ways.

Or do I leave it at the tippied angle? It seems to me that then the included angle of the cutting tool would not be correct....

Confused in the Black Forest!

The first picture is looking from the top down.
The second picture is looking at eye level to the back of the cutting tool.
http://i853.photobucket.com/albums/ab91/burnandreturn/threadingtop.jpg
http://i853.photobucket.com/albums/ab91/burnandreturn/threading1.jpg

Highpower
02-24-2012, 07:01 AM
http://www.practicalmachinist.com/vb/general/aloris-axa-8-threading-tool-how-set-up-238756/

1 Yes
1 No

Flip a coin?

big job
02-24-2012, 07:24 AM
If I understand the ? correctly It will depend on the tool holder. If
the holder has a built in rake I think its 16.5* then you will have to
grind the top flat. Holders with no rake you leave it flat. At least
thats what I do. Not being good with words, my order of steps are
for a new tool blank
1-determine if the holder has a rake then grind the top flat if not
leave it alone
2-now grind the sides to 29* or whatever
3-I usually grind a slight radius on the cutting tip slightly
generally most common on Lantern style tool holders have rake
most quick change holders hold the tool flat. sam hope this helps

Black Forest
02-24-2012, 08:16 AM
The cutter is presented with the top flat.
http://i853.photobucket.com/albums/ab91/burnandreturn/threadingendview.jpg

Black Forest
02-24-2012, 08:19 AM
The bottome tool holder is the one I am asking about.
http://i853.photobucket.com/albums/ab91/burnandreturn/threadingsidebyside.jpg

JCHannum
02-24-2012, 09:07 AM
Theoretically, yes, you should grind the top to produce the perfect thread profile.

In actuality, any error will be so minimal that it would take far more inspection equipment than any HSM has available to identify it. As long as the threads produced are presentable and functional, there are many other things to worry about.

I use the Aloris threading tool discussed in the PM thread in a home made BXA sized holder. This is similar to your threading tool and is adjustable for side clearance angle also. When sharpening, I do it with the cutter in the holder on my T&C grinder, just skimming the top. This sharpens it as well as grinds the top to the preset angle. I don't get too hung up over the side angle. It can be set with a protractor, but unless very coarse threads are being cut, I just kind of eyeball it. You do want to remember to change it for RH vs LH threads.

These cutters are great, and reasonably priced. The holders are easily enough made in the shop if the price is unacceptable. The 60* threading blades come in three sizes for 4, 6 and 10 or more TPI and are large enough to last a lifetime with proper care.

Black_Moons
02-24-2012, 11:28 AM
Yes, you change the angle some when you tilt it.
No, it does not likey matter enough to notice.

Yes, the top now has side rake.
No, a little side rake won't hurt anything.

If you really care, you should get one of those insert holders that has 'toping' inserts, one for each pitch basicly.

Personaly, I just use square HSS bits I ground into threading bits, and just grind lots of side relief to take care of the helix angle.

Black Forest
02-24-2012, 11:34 AM
I have all the threading inserts for all the different pitches I use.

But I also have these very cool retractable threading tool holders. Makes it very fast and very easy to thread. The threads I am getting are fine and look good. I just wanted to know if I really wanted them correct if I should flatten the top of the cutting tool.

philbur
02-24-2012, 11:42 AM
Trouble is once you've laid hands on more than $1,500 worth of threading toolholders (when new) cutting tool angles that were good enough aren’t …. well .... good enough.;)

Phil:)

justanengineer
02-24-2012, 12:02 PM
Whether or not to flatten the top of the tool (aka rake angle) is a matter of preference, and is entirely situational, just as "pushing vs dragging" when doing conventional turning. I almost always "drag" the bit when turning, and also use a negative (tipped down into the thread) rake angle for threading as I find it a bit easier on the tool. Contrary to what some on here have or will say, its entirely personal opinion, and many professionals do it both ways. To support this to the naysayers, many carbide manufacturers recommend negative rake and dragging, and many carbide holders are manufactured this way.

As to your other question about the angle of the tool bit relative to the ways, it should always be perpendicular to the ways when threading, not at an angle as shown in your second 3d model.

Black Forest
02-24-2012, 12:29 PM
As to your other question about the angle of the tool bit relative to the ways, it should always be perpendicular to the ways when threading, not at an angle as shown in your second 3d model.

No I don't think you are right on this. Tilting the cutter allows for clearance of the helix angle. The cutter holders are designed to tilt to allow for clearance.

Black Forest
02-24-2012, 12:32 PM
Trouble is once you've laid hands on more than $1,500 worth of threading toolholders (when new) cutting tool angles that were good enough aren’t …. well .... good enough.;)

Phil:)

I know exactly what you mean. I also have much more than 1500 Euros invested in just threading inserts not counting the holders for right, left, internal and external . I normally just use the threading inserts now.

I need to single point some rather large pitch threads soon and the helix angle will be a factor I think. Therfore my original question regarding the rake.

PixMan
02-24-2012, 12:35 PM
I have all the threading inserts for all the different pitches I use.

But I also have these very cool retractable threading tool holders. Makes it very fast and very easy to thread. The threads I am getting are fine and look good. I just wanted to know if I really wanted them correct if I should flatten the top of the cutting tool.

I was thinking, BF, that an interesting little project that would result in a perfect tooling solution would be to adapt some form of the lay-down threading insert tool holder onto those cool retracting MultiFix holders.

That would give you the best of both worlds in that you'd have the retractable holders but now with perfect thread form inserts doing the cutting. You probably already have that with the internal (threading bar) holder, and just need to adapt the external one.

Black Forest
02-24-2012, 12:37 PM
Today Phil I actually thought of you. I was looking at my retractable threading tool holder and I thought about you telling me to take it apart to see how it locked back. I had a small chuckle and then I considered taking it apart but I had no time.

Black Forest
02-24-2012, 12:39 PM
I actuall thought of doing that Pixman. It wouldn't be that difficult to pull the HSS cutter holder out and make a new shaft and graft on the end of an external insert holder.

Great minds think alike!

justanengineer
02-24-2012, 01:00 PM
No I don't think you are right on this. Tilting the cutter allows for clearance of the helix angle. The cutter holders are designed to tilt to allow for clearance.

Ahhh....my mistake. I did not take note of the axes in your model. In that case yes you are correct. Dang fancy holders confusing me. Top of the morning to you btw...@ noon.

Carld
02-24-2012, 01:02 PM
I have never seen a threading insert holder that is adjustable to tilt the insert to follow the helix. I don't see any advantage to doing so. I have used 1/4" to 1" square HSS tools with a ground 60 deg V to thread for years and shortly before retiring the shop owner bought a QCTP and some tooling, one of which was an insert threading holder. It was not adjustable and I liked using the insert type so much I bought a QCTP and insert threading holder for my shop.

I have always contemplated what is happening while metal is machined. My thoughts on threading is as long as the side clearance of the leading side is sufficient to clear a given helix your good to go. The top of the cutter should be flat and in doing so the cutter is attacking the thread cut with a positive angle due to the angle of the helix.

I don't see any advantage to having the top of the cutter equal to the angle of the helix or even in a negative posture. The positive angle of the cutter helps to take some of the force of cutting the thread out of the picture where as a "0" on negative attack would put extra force to cut the thread and tend to lift the work on the cutter. That could cause a malformed thread and undue stress on the cutter in my opinion.

Black Forest
02-24-2012, 02:00 PM
Ahhh....my mistake. I did not take note of the axes in your model. In that case yes you are correct. Dang fancy holders confusing me. Top of the morning to you btw...@ noon.


You probably just drug your butt out of bed!

PixMan
02-24-2012, 05:46 PM
I have never seen a threading insert holder that is adjustable to tilt the insert to follow the helix. I don't see any advantage to doing so. I have used 1/4" to 1" square HSS tools with a ground 60 deg V to thread for years and shortly before retiring the shop owner bought a QCTP and some tooling, one of which was an insert threading holder. It was not adjustable and I liked using the insert type so much I bought a QCTP and insert threading holder for my shop.

I have always contemplated what is happening while metal is machined. My thoughts on threading is as long as the side clearance of the leading side is sufficient to clear a given helix your good to go. The top of the cutter should be flat and in doing so the cutter is attacking the thread cut with a positive angle due to the angle of the helix.

I don't see any advantage to having the top of the cutter equal to the angle of the helix or even in a negative posture. The positive angle of the cutter helps to take some of the force of cutting the thread out of the picture where as a "0" on negative attack would put extra force to cut the thread and tend to lift the work on the cutter. That could cause a malformed thread and undue stress on the cutter in my opinion.

Just what type of carbide insert threading tool is that you have? I'm guessing it's an on-edge Top Notch or TNMC style. Those have clearance angles ground (or molded) into the insert for thread flank clearance.

Most laydown external and the larger internal tools for 16, 22 and 27 size triangular insert holders have a interchangeable carbide anvil/shim underneath the threading insert to adjust the inclination angle of the insert to match the thread's lead angle. You can see it under this insert:

http://img.photobucket.com/albums/v466/kenm10759/Dads%20shop/IMG_1187-r.jpg

I have a full set of the anvils from -1.5º to +3.5º for the IR/EL and ER/IL holders. The advantage is in that the inserts have straight (or nearly straight) side flanks and need that tipped angle to follow the lead angle without rubbing. They work nice, and make for a stronger insert.

rohart
02-24-2012, 06:33 PM
The tilt of the top ? Well, this is the first time I've thought about it.

But I've often worried about the freedom my tool, tool and carriage, or tool and top slide, however you do it, has to 'overtake' the thread. As Just said, it's a matter of dragging or not.

So if you leave the tool flat topped and then tilted, so there is side rake, that is going to make sure of the drag, which will take up all play in the carriage/top slide, and my worries will be over.

And whether you're cutting righties or lefties, the tool is always tipped 'forward' so the drag is always 'backward'. I think ?

Highpower
02-24-2012, 07:21 PM
Theoretically, yes, you should grind the top to produce the perfect thread profile.

I use the Aloris threading tool discussed in the PM thread in a home made BXA sized holder. This is similar to your threading tool and is adjustable for side clearance angle also. When sharpening, I do it with the cutter in the holder on my T&C grinder, just skimming the top. This sharpens it as well as grinds the top to the preset angle.

Jim,

So you do angle the bit for the helix and regrind the top as below for each thread?

http://img.photobucket.com/albums/v82/Highpwr/Temp/threading1.jpg

JCHannum
02-24-2012, 09:10 PM
Jim,

So you do angle the bit for the helix and regrind the top as below for each thread?

No, I eyeball the helix angle when initially setting the cutter up and leave it at that angle when grinding. I don't go through a lot of exercises to set the helix angle or grind the top to match.

These cutters don't usually require grinding unless chipped. I usually just touch up the top with a hand stone to maintain sharpness.

Carld
02-25-2012, 12:42 AM
Yes PixMan, mine is a Dorian upright insert TNMC. I don't need an insert for each thread pitch. I would hate to have to buy an insert for each range of pitches. That could get expensive. I still use HSS and HSS Cobalt 1/4" to 3/4" cutters and have a fixture to grind the 60 deg V and 10 deg side relief. Sometimes using HSS is better than the carbide for me.

dp
02-25-2012, 02:14 AM
If you tip the tool then the cutter will present negative rake to the thread. Depending on the material being cut that might matter. I don't have a surface grinder but I have my pretty damn handy poor man's surface grinder which is just a radial arm saw and an xy table. I don't use the radial arm at all except to place the grinder over the work. When I cut an Acme thread I rotated the cutter then ran it under my PMSG to level it. That gave me the desired rake, preserved the helix relief, and form factor.

People slam this use of the radial arm saw but it is damn handy and quick to set up :)

beanbag
02-25-2012, 02:52 AM
I finally understand why my threading tools are able to tip. This allows for the helix angle relief. But do I then grind the top of the tool to be flat inline with the through axis of the work? Meaning parrallel to the lathe ways.

Or do I leave it at the tippied angle? It seems to me that then the included angle of the cutting tool would not be correct....

Confused in the Black Forest!


It partially depends on if you are planning to do a radial in-feed, alternating in-feed, or the usual compound at 29 degrees infeed.

Assuming the latter, the change in geometry from tipping is not a big issue as the angle does not change significantly from 60 degrees. You should mainly regrind the top so that you have a neutral top rake.

This is one of the nice things about the carbide inserts - they already have the top rake built in so you can do all styles of in-feed.

PixMan
02-25-2012, 08:50 AM
Yes PixMan, mine is a Dorian upright insert TNMC. I don't need an insert for each thread pitch. I would hate to have to buy an insert for each range of pitches. That could get expensive. I still use HSS and HSS Cobalt 1/4" to 3/4" cutters and have a fixture to grind the 60 deg V and 10 deg side relief. Sometimes using HSS is better than the carbide for me.

I buy at least one, though usually two of the full-form inserts at a time, as needed or as a bargain appears on Ebay. Even that can get expensive, but since it's spread out over (now 6) years, I hardly notice the money and have a nice collection.

I also still use some HSS threading tools, and have a sine bar vise and nice surface grinder to make the tools. It's rare though, as I so love the smooth finish and perfect form I get with the inserts. Knowing the tough grades allows the slower speeds of a manual machine to be used successfully.

Martin0001
02-25-2012, 09:38 AM
Yes PixMan, mine is a Dorian upright insert TNMC. I don't need an insert for each thread pitch. I would hate to have to buy an insert for each range of pitches. That could get expensive. I still use HSS and HSS Cobalt 1/4" to 3/4" cutters and have a fixture to grind the 60 deg V and 10 deg side relief. Sometimes using HSS is better than the carbide for me.
I am very much with you.
I just cannot find much justification for carbide tooling for threading except of production where machine time is at price.

I use HSS with all satisfaction and I have constructed a simple jig to work together with off hand grinder which aids greatly in shaping a cutting tool (it works base on *tangential grinding*.
I would only recommend "Screwcutting in the Lathe" by Martin Cleeve where all threading tricks which I might ever need are well explained.
Mentioned jig for toll forming is also described there.

I have found HSS excellent for cutting various threads in stainless (even in cold drawn, high tensile stainless, OK we don't go to extreme values there, 700 MPa ultimate tensile strenght is typical) and I have also made a number of threads in titanium TiAl6V4.
Believe it or not but with good cooling this Ti alloy seems easier to thread than a carbon steel and thread looks like if ground, just off the knife.
Stainless also brings about superior finish.

And my machine is a good ole ML7 of Mayford, albeit bearings (plain) are new and very carefully adjusted.

So I would never invest $1000 + in some sets for insert based threading for amateur work.
In any case carbide tooling is *less* forgiving than HSS.
You need *more* rigid machine to deploy it successfully and exploit its advantages.

PixMan
02-25-2012, 10:34 AM
So I would never invest $1000 + in some sets for insert based threading for amateur work.
In any case carbide tooling is *less* forgiving than HSS.
You need *more* rigid machine to deploy it successfully and exploit its advantages.

I have perhaps 1/3rd that amount in total invested, and it was done over a period of 6 years. While I have collected a good number of pitch-specific inserts in that time, I certainly started out with and still use the 16ER-A60 "partial profile" inserts quite a bit. I happen to really appreciate the perfect thread form I get with cresting inserts. To each his own.

The advantages of carbide insert tooling include far more than the higher speeds and productivity rates that a commercial shop requires. I respectfully submit that it is a common misconception that only rigid machines with high speeds can use it, and that modern carbide insert tooling is "less forgiving" than HSS tools. That's a gross generalization on the part of both types of tools because I've managed to break HSS in places where carbide has performed well, and vise-versa.

Knowledge is power, experience a good teacher, continuous improvement a virtue.

Carld
02-25-2012, 10:49 AM
I love the threading insert holder and use it slightly more than the HSS. The thing I like about the inserts is if the edge gets dull or chipped you can index a new tip without loosing the thread. With the HSS I have to set back up on the thread and sometimes it is difficult to do.

I agree that you don't have to have a tight lathe to use carbide but it does help. I keep both brazed carbide and insert carbide in my QC holders and use each one on things I have found they work best. Manual lathes depend on the skill of the operator a lot.

I still think tilting the top surface of the cutter so it is perpendicular to the cut enters undue forces while threading and I don't think the cut will be as clean.

Martin0001
02-25-2012, 12:29 PM
@PixMan,
Who knows... maybe a word *modern* is a keyword here...
I was trained about 10 years ago by an experienced engineer (at this time I have resigned from full time job and got a plenty of time free).
I have just decided to work for free in his shop, just to learn.
This guy had some aversion to carbide tooling, arguments were that "they are for those not intelligent enough to operate a grinder properly" or alternatively that "they are not economical to use in traditional setup" and so on.
Mind you, he was using carbide tooling for some general work (lets say standard CNMG 12mm inserts).
Nevertheless threads were invariably made by HSS tooling and quality of job was invariably excellent.
So I have inherited these habits and perhaps the guy had bad experience with older versions of carbide inserts.

btw,
He was not a "caveman type of character", irrationally traditional.
When some corrections on hardened steel were needed he wouldn't hesitate to use CBN tipped inserts (there was no cylindrical grinder in the shop).

@Carld,
You have certain points with re-indexing new tip once currently used one gone damaged, all without losing a thread.
Here is a clear advantage.

Black Forest
02-25-2012, 01:43 PM
In my short involvement with me personally machining my own parts I have learned one thing as absolute. Never say never!

I like to learn as much about a subject as I can. So I try to learn all the different possibilities to arrive at the same end. Then I use my own mind to determine which is best for my situation. Of course that includes my abilities and my machines capabilities. I bought what I thought to be very good and solid machines. Then I went about aquiring tooling to suit the jobs as they came. I use my "machine shop" to support the farm I have here. I am a tinkerer by nature.

My experience is short but I have listened to some very good advice from several sources on this site regarding tooling. If Pixman tells me a certain tool will do this on that machine working with this material it has never been wrong. So I picked a tool company which sells Walter tooling and have pretty much bought most of my tooling from them.

It is very comforting to know when I order many hundreds of Euros of tooling that it will do what I need and expect.

Thank you Pixman for your support!!!

My other very good source to keep me on track is Nick Mueller in Germany. He is very tolerant of my ignorance. He was a great asset to this board. It is really a shame for the rest of you that George Bullis banned Nick from this site for calling Evan on things that Evan wrote that were way off track.

Nick keeps me humble with his knowledge of so many things related to machining. A very smart man he is in fact.

Carld
02-25-2012, 03:56 PM
Hmm, I didn't know Nick was banned. He always had some good info. I too keep an open mind to new processes or tooling but I have limited funds and tend to go with what I can afford. I thought about the lay down inserts for threading but decided against it for economic reasons.

It really all comes down to what will work for each individual and their budget. I am sure everyone picks the best they can afford that will do the job as they desire it to be done.

Black Forest
02-25-2012, 04:27 PM
Hmm, I didn't know Nick was banned. He always had some good info. I too keep an open mind to new processes or tooling but I have limited funds and tend to go with what I can afford. I thought about the lay down inserts for threading but decided against it for economic reasons.

It really all comes down to what will work for each individual and their budget. I am sure everyone picks the best they can afford that will do the job as they desire it to be done.

That sums it up quite nicely Carld.

As to Nick my understanding is that George gave Nick a choice. Lay off of Evan or be banned. Nick chose to be banned rather than let the crap that Evan was putting forth go unchallenged.