single point threading help

[Dugan]

agree .. With swinging and additional 15 degrees one would get 45 on one side...
So back to what is said back in post #7 good to look over a protractor to see a/about 29 - 30* to then know how your compound is numbered.

This is another good thought I did not consider.
I was engaging the half-nut when No. 4 came around.
I have a deft feel for engaging the halfnut and start to move the lever about halfway right before it hits my number and then "feel" the halfnut engage the lead screw into full engagement.
As opposed to just slamming the lever into engagement right before No. 4 pops up.
BUT- Knowing that using any whole number I could also engage on number 1, 2, 3 or 4.
I sometimes will engage on number 3 if I get tired of waiting for number 4 (70 rpm is slow).
I know what the lever feels like when it starts to catch on top of the leadscrew instead of in the lead screw (threading on top of a thread).
The tool tip/ insert is square to the chuck.
I did not square to the piece being turned because it is held by the 4 jaw with the part dialed in with no runout.
Therefore the piece itself square and inline with the chuck centerline.
I do not believe the part was not deflecting because I was turning between centers with a steady rest.
My live center has zero deflection/runout on my indicator - the needle on the gauge doesn't even bounce while spinning.

So----
The toolbit is square -perpendicular all that good stuff.
I'm thinking:
I possibly did not engage half nut on the same number 4. Maybe used No.3 on last few passes. (should not matter)
Or my 29 degree setting was not true 29 degrees.
I have not ran into this before hence the posting.
I've ran some equipment and done many setups.
Ran Akebono, Fadal, CNC in G code- Hardinge, Colchester, Bridgeport - Manual. Blah Blah Blah
I know many of the tricks this and that and am excellent at math.
and suddenly it looks like I used a an 80 degree cutting tool to cut a thread.
Tripped me out!
So of course I posted knowing even with what experience I have, I'm not in manufacturing any more and many of you have more experience and may have done or seen this before when I have not ran into this problem in the past...
Whatever mistake it was I had not made this mistake in 25 years.
So- Screw it Im gonna Pythagorus the whole thing.
Set my compound take a cut and figure the long leg in relation to the hypotenuse.
With this method one could set their compund to 29.1 dead nuts if they wanna.
Just didn't wanna...cuz I have an angle checker and used it instead.
NOT my stamped in protractor since yeah they are close but not close enough.
Might be my angle checker is off a degree. Guess I'll have to send it in to the Dept. of Weights and Measures.
Regardless
I am grateful for all your guys responses and the problem has been resolved.
The compound feed angle was not less than 30 degrees - simple as that.
BTW - this was not a customers barrel but a scrap barrel used for checking and changing setups such as when changing from 3 jaw to 4 jaw and setting up new tooling.
And I'm glad I ran the setup to discover the problem before hand.
I always run a scrap piece and dial things in before running a new setup.
The T-15 insert with toolholder was a new tool I was trying out.
Was hoping it was not the tooling. (I did contact the Mnfg to ask their opinion yesterday to double check if their insert I was using was right for the material being cut).
It's all good fellas.

 

[Matt_Maguire]

There’s no standard (I know) that tells lathe makers how to graduate the compound. If it’s marked “0” then it’s parallel to the cross slide. If it’s marked “90” then it’s square to the ways. Both are right, you gotta do the figuring after that & which way to go…

If someone is still confused they can set one inside tail of the fish gage against a shoulder/face on the part and match the compound side to the fishtail side for 30° & bump it a bit. IIRC you can get 3/8” or so of that inside edge on a square shoulder bumping the other side end...

The best reason for 29.5° I ever heard/read was to reduce the thrust load on the half nuts. Old timey, with most lathes using babbit in the half nuts this was prolly pretty wise. When doing this it was also advised to reduce the backside clearance angle to around 3°ish to make it ride the backside of the previous cut better & help the tool push forward into the cut. I’m talking too much…

@ henrya → I like that “chicken groove” bit. Actually though, it has very much to do with dealing with what engineers call a “notch”, as it does making it easier for the machine shop. Threading trail out marks, improper radius’s and surface finish can get you busted.

Good luck,
Matt

 

[Dugan]

View attachment 246638
BTW - here is a piece of Alum. threaded with the exact same setup.
Same compound Angle, tool, tool height, etc etc.
I used the Aluminum piece to setup before turning the stainless.
Once it hit stainless, one thing did not look like another.
So the problem needed to be figured out.

 

[MattiJ]

im sure I will get flack for this...

I don't get the HSS insert thing...if you are going to pay high quality carbide insert price why not use carbide inserts?
strength of HSS is utilty and affordability.
strength of carbide insert is convenience and repeatabiltiy.

seems like all the cons without much pros.

someone is going to say you can resharpen them by rubbing the face, but I'm not buying it...the flanks are going to see some wear too.
and you got no chip breakers either.

these are great BTW-
LAYDOWN THREADING TOOL

I don't get the (AR Warner) HSS insert thing either. Some (hobby machine folks) advocate them for general use in small machines but you get better geometry with carbide (AR warner HSS inserts are zero rake without chip breaker).
For threading coated carbide(mitsubishi VP15TF) works better than HSS has ever worked for me.

 

[Dugan]

BTW - A fish gauge even if it does set the toolbit correctly relative to the workpiece
.... does not tell what the compound angle is set at

 

[Dugan]

I don't get the (AR Warner) HSS insert thing either. Some (hobby machine folks) advocate them for general use in small machines but you get better geometry with carbide (AR warner HSS inserts are zero rake without chip breaker).
For threading coated carbide(mitsubishi VP15TF) works better than HSS has ever worked for me.

I dunno either honestly.
I've machined more complicated things in production facilities and decided to start doing my own barrel work nowadays.
upon seeing what other "smiths" use and like for the particular steel worked with....many swear by the AR Warner inserts...Similar to how many like Momax Cobalt steel
I do gotta say the T-15 is very tough and holds up well.
Plus customer service is there and they answer their phones to take orders and ship quickly.
I've also read that one can get a better/finer/sharper? cutting edge with HSS than with Carbide
(similar to how Carbon steel will take a keener edge better than any stainless blade. Although I can't verify this)

 

[rke[pler]

The best reason for 29.5° I ever heard/read was to reduce the thrust load on the half nuts. Old timey, with most lathes using babbit in the half nuts this was prolly pretty wise. When doing this it was also advised to reduce the backside clearance angle to around 3°ish to make it ride the backside of the previous cut better & help the tool push forward into the cut. I’m talking too much…

I think that setting the compound at an angle makes the thrust on the halfnuts consistent since the cut is always mostly on the leading face of the tool, so the tool isn't tempted to follow the work. It think it might decrease the cross slide thrust as well but with a good setup you shouldn't notice this (work stiff enough or running a follower).

 

[awander]

It’s not the angle of the compound or deflection in your tooling that caused that. I would be willing to bet that you engaged the lead screw on the wrong position. Gotta watch that thread clock carefully. On most lathes (at least every one that I have ever used), certain thread pitches will thread properly on all positions, where other pitches require you to engage on specific clock positions to ensure you are following the position of the previous cut. It’s not hard to accidentally miss and catch the wrong position, thereby cutting a double thread. Looks like you did that about halfway through.

I see no evidence of a double thread in the photo in post #1. But it sure DOES look like the infeed angle was way too much.

 

[Dugan]

I don't get the (AR Warner) HSS insert thing either. Some (hobby machine folks) advocate them for general use in small machines but you get better geometry with carbide (AR warner HSS inserts are zero rake without chip breaker).
For threading coated carbide(mitsubishi VP15TF) works better than HSS has ever worked for me.

Yeah - I mostly used carbide before as well.
Just ordered some TPMC 32 Carbide inserts
Will compare.

 

[iwananew10K]

my my only argument against HSS is when it comes the inserts.....Its VERY hard to beat a properly ground and honed STICK of HSS.

 

[jim rozen]

I think that setting the compound at an angle makes the thrust on the halfnuts consistent since the cut is always mostly on the leading face of the tool, so the tool isn't tempted to follow the work. It think it might decrease the cross slide thrust as well but with a good setup you shouldn't notice this (work stiff enough or running a follower).

Reasons to single point thread per the HTRAL bookd:

1) the cut will load the leadscrew against only one flank of the threads and as such will reduce wander, especially for finer threads.

2) the chip will come off only one side of the tool. Sounds trivial but for coarse threads being done as direct plunge will have the
two chips (one from each side) impinge on each other towards the tool center. This is undesireable.

3) 29 degree threading has less total tool cutting edge buried in the work. This tends to reduce chatter, especially when doing coarse threads.

 

[Dugan]

my my only argument against HSS is when it comes the inserts.....Its VERY hard to beat a properly ground and honed STICK of HSS.

Some people have all the time in the world to have a dip, grab some coffee and enjoy a nice grinding session at the Baldor.
But at only 12 bucks a pop per insert with 3 cutting tips at your disposal already ground like a jewel....it is a big time saver to just lossen a screw and insert a new one if it chips or goes dull.
A triangule shaped cutter with 3 tips costs less in time factor...than grinding one stick of HSS.
10 minutes is worth 15 bucks.
If one can grind a tip in 3 minutes or less that's pretty good. Any more time and money is lost.
At one shop I worked at---we would run the setup and a lot of the tooling was HSS.
After every run the drill bits and Counter sinks were simply thrown away.
New ones were inserted and a new run was made.
This actually cost less than carbide or grinding and sharpening most tooling.

 

[michiganbuck]

Originally Posted by Illinoyance
Why HSS? At the speeds most people are able to thread HSS is a suitable tool. There is no need for the heat resistance of carbide. It is easy to touch up the edges of the HSS tool and saves the expense of the carbide insert. With a bit of regrinding I can change the flat on the end of the tool to suit any thread pitch. I can also add top rake or side rake to improve cutting conditions.

Car2: Also, HSS is good when you need something extremely sharp. Recently needed to make small M1.4x.3 ss studs pressfit onto nuts, on an HLVH. I tried several threading tools, including brazed carbide, brazed carbide honed with diamond, and a full-form insert carbide tool (supposedly suitable for this pitch thread). None of these were sharp enough, and/or suitable angles, to keep from deforming the part, and even with a mini-follow rest they weren't working. The HSS tool shown below was the trick, honed and polished by hand, with the ss wire held in a collet as short as possible, 3-4 passes at around .003 feed (on crosslide). The 3-point honing guides shown (not my original idea, saw something similar somewhere), are used to keep the angles consistent while sharpening the tip of the tool; I use the mylar templates to adjust the screws on the guide since they

Plus you can touch up the angle with an aluminum oxide wheel..I like HSS tool bits with top rake for aluminum..

*Still nothing wrong with using carbide.. The modern good lathe hand uses both.

 

[David Utidjian]

BTW - A fish gauge even if it does set the toolbit correctly relative to the workpiece
.... does not tell what the compound angle is set at

Well... it can be used to check it. Long side of the gage against the compound, side of the tip against the chuck face, 30 degrees. Check your compound degree marks and bump it half a division clockwise, 29.5 degrees (or close enough.) Can't get the compound close enough to the chuck face, no problem, place the angled tip between the side of the work and the compound, bump half division clockwise... yer almost done. ONLY after the compound is set (to whatever angle) lay a long side of the fishtail along the work and set the tool tip into the largest 60 degree notch on the other long edge. If you are using a QCTP and inserts you most likely have to loosen the tool post to set the tool angle correctly.

Do you even have a fishtail gage? They are as basic to lathe work as the chuck key and a 0-1" micrometer.

To reduce errors in using the gage on small diameter work Starrett, B&S, and others used to make a neat little V-block that snapped on to the long side of the gage.

 

[iwananew10K]

I will add since this applies to gun work....a 27 degree infeed covers BOTH 60 degree and 55 degree threads...you will encounter both so if you make a mark once you establish that your life will be a little easier.

 

[Dugan]

I will add since this applies to gun work....a 27 degree infeed covers BOTH 60 degree and 55 degree threads...you will encounter both so if you make a mark once you establish that your life will be a little easier.

There we go...

 

[michiganbuck]

There we go...

Not exactly, at 29,5* and even down to perhaps 20* on the compound you will get an almost correct thread. What will be wrong is that the point end of the tool bit is traveling away from the left side of the form so will change the left side from 30* to perhaps 1 to 3* error, with the angle being less than 30*
The error is corrected with a finish-in feed of .001 to .003 or so, with that last feed coming from the cross-feed not the compound. The cut from this feed will be mostly taking stock near the point correcting the angle on the left side to 30*, Yes it may kick up a slight burr but there is no other way to make the correct thread.

Still I am pushing using the fish gauge. The long 60* or the short 60* can be used for a taper gauge when making a chuck or collet held tickle center. Double thread depth is given on many even that some ^include the nose flat in that number and some don’t, so one needs to know the kind they have. Being sure your angles are right is important because with wrong angles even the wires measure can’t be relied on to make a functioning thread. But fish come in 55 and 60* so one needs to choose the one they want and some come with not having the double depth numbers, Having the double depth numbers is very handy.

^ for example Lufkin and Starrett fish are different.
lufkin has .096 for a 18 thread....and Starrett has .072 for a 18 thread..

 

[michiganbuck]

I like HSS for mild steel and aluminum..Yes I hand sharpen a tool bit many times...Hss for an odd shape or radius you cant find in an insert.. for near exactly the right nose flat...

 

[David Utidjian]

In response to car2 and Dugan:
Yeah futzing around with grinding a fresh HSS blank for each tool change is a PITA but who does it like that? Armstrong makes (or made) a neat HSS threading tool where all you have to do is kiss the top of it with a hard Arkansas stone every now and then. Williams No. 31-L & No. 31-R Cutting Off & Side Tool & Armstrong No. 5 Tools | eBay The Armstrong style tool is not for getting close to shoulders. For that I use an HSS parting blade choked up close to the holder that I have already ground a 60 degree included angle down along the front clearance. Someone makes such a tool but I don't remember who.

I use both HSS and carbide as I see fit. As not to waste time on individual tools for a job I take a little time out as needed and grind up a batch of HSS tools with my favorite geometries. Set up the grinder for the each angle and do them in batches. The all go in a blue akro-mills bin segregated with a paper towel. I have fistfuls of nice sharp HSS tools on hand. Changing them out is almost as quick as changing a carbide insert. Sometimes quicker. As they get so dull or damaged that a quick kiss with a small stone won't renew the edge they get tossed into a red akro-mills bin for later touching up on the tool grinder. As the blue bin empties and the red bin fills up I do another grinding session. Once I built up a stock of tool bits the grinding sessions go very quickly because most of the angles and grinds are already done. Which reminds me of one of the best lines in 'Tremors': Tremors - We Plan Ahead - YouTube

You can even buy them pre ground: 8 pcs H.S.S. Tool Bit Set, Pre-Ground for Turning & Facing Work, 1/4", 5/16", 3/8" & 1/2" - Accusize Industrial Tools and/or HSS indexable inserts from https://www.arwarnerco.com/default.asp (which I think was already mentioned up-thread)

 

[michiganbuck]

That Accusize HSS kit is a very good starter set for an apprentice and handy for a seasoned guy, Although I think one 60* threading bit with a .005 flat would be an asset for the set.
I think every apprentice should use and grind a few HSS bit to understand the value of a grindable tool bit. Suppose a need for a beainged shaft job comes to the shop and the part print asks for a 3/8 radius at the step diameters and there is not a 3/8 radius insert in the shop. That is the value of HSS that an odd need can be made up on the spot. The talent of going over to a pedestal or bench grinder and knocking out a special bit in perhaps 5 minuets is a huge asset for a lathe hand.. Buying whole pack of inserts for the once in ten years need, holding up a job for two hours or perhaps two weeks, or saying we can't do that is out of the question..
I do hope instructors are teaching this.