Internal threading help

[DCP]

Internal threading

In South bend - How to run a lathe

For external threading it says to set the com-pound rest to 29 degrees to the right. Says nothing about internal

So I am watching a YouTube video and the guy says for internal threading you set the com-pound to 29 degrees to the Left

I know people set the com-pound to 29 29.5 and 30 degrees

So what do you guys do for Internal threading

Thanks

[Nobade]

I like to run my threading tool upside down, so I am cutting on the side away from me. That way I set the compound and cross slide exactly like I do for external threads. This way all that muscle memory I have built up over the years doesn't make me drive the tool into the work instead of pulling out of it at the end of the thread.

[MBTcustom]

X2 what Nobade said. Leave the compound set at the same place, run your tool upside down and cut the threads on the opposite wall. Not only is this a safeguard against ramming the tool into the threads by doing what you are trained to do with external threads, but also because this way you are not leaning over the lathe and making adjustments to the compound dial, (can be dangerous)
While we are on the subject of internal threads, I will tell you a trick. If you need a very small internal threading bar, grind all the threads but one off a tap. profile it with the grinder but do not touch the one cutting tip that is left. You will have a miniature threading bar that has a guaranteed 60* tip that is absolutely square to the shaft of the tool.

[elk hunter]

I still do internal threading the old way and you do set the compound at 29 to 30 degrees TO THE LEFT for internal threads. That way you're feeding the threading tool down the face of the thread as you progress into the thread. If you don't already have one, you may want to find a college level text book on machine tool operation. It should give you detailed explanations of how and why you set up in certain ways.

[Cap'n Morgan]

+3 What the guys said!

Another trick is to set the cross-slide handle in a horizontal position. That way you won't accidentally plunge the tool into the part when disengaging.

[dragonrider]

Goodsteel wrote>
"I will tell you a trick. If you need a very small internal threading bar, grind all the threads but one off a tap. profile it with the grinder but do not touch the one cutting tip that is left. You will have a miniature threading bar that has a guaranteed 60* tip that is absolutely square to the shaft of the tool."

40+ years in the machine trade and I'm still learning, Thanks Goodsteel that is a great tip. And I may need it soon.

[gzig5]

Goodsteel wrote>
"I will tell you a trick. If you need a very small internal threading bar, grind all the threads but one off a tap. profile it with the grinder but do not touch the one cutting tip that is left. You will have a miniature threading bar that has a guaranteed 60* tip that is absolutely square to the shaft of the tool."

40+ years in the machine trade and I'm still learning, Thanks Goodsteel that is a great tip. And I may need it soon.

Just make sure the thread you leave is a full one, after the lead taper on the end of the tap, which can be 5-6 threads on some taps.

[John Taylor]

Every one forgot to mention that the lathe must be run in reverse when the tool is turned over for inside cutting. I leave the tool right side up and cut on the opposite side with out disturbing the 29 degree angle of the compound. All adjustments are the same as cutting external threads except the moter is running the opposite way. The idea of 29 degrees is that most of the cutting will be with one side of the tool bit and the other will be making a very light cut. I usually grind a small boring bar to do this work. I did see a machinist use a tap for internal threads once. he did not grind any of it, used as is. The hole was larger then the tap but the number of threads was correct.

[DCP]

Well

I thought I was begining to understand
Why do you need to cut with the motor in reverse



Every one forgot to mention that the lathe must be run in reverse when the tool is turned over for inside cutting. I leave the tool right side up and cut on the opposite side with out disturbing the 29 degree angle of the compound. All adjustments are the same as cutting external threads except the moter is running the opposite way. The idea of 29 degrees is that most of the cutting will be with one side of the tool bit and the other will be making a very light cut. I usually grind a small boring bar to do this work. I did see a machinist use a tap for internal threads once. he did not grind any of it, used as is. The hole was larger then the tap but the number of threads was correct.

[John Taylor]

Well

I thought I was begining to understand
Why do you need to cut with the motor in reverse

Go to the bottom of the hole and cut on the way out. Leave the lathe setup for right hand external threads. It is a bit to get the brain to think about.

[danski26]

Awsome tip goodsteel!!!!!!!!!!!!!

[DCP]

So if I feed and cut on the way in. Do I leave the lathe running forward

I dont believe I have a reverse on the motor.

Lead screw and cross slide have a foward and reverse Its a Logan (Wards)

There must be a half a dozen ways to do this:roll:

Go to the bottom of the hole and cut on the way out. Leave the lathe setup for right hand external threads. It is a bit to get the brain to think about.

[Nobade]

Nooo! If you are cutting internal threads on the side away from you with the tool upside down you do not run the spindle in reverse. You run it normal and cut going in, toward the chuck. If you cut coming out you will produce left handed threads.

If you keep the tool right side up and cut on the side away from you, then you will need to run the spindle backward. That's why I turn the tool over.

[DCP]

OK lets see if I got this

Cutting a internal thread

Set com-pound to 29 degrees to the Right
Set up your inside thread tool upside down
Now feed tool toward chuck in forward (the normal direction)

I will cut thread just like I would a external thread but inside and on the side away from me

Does anyone wear a face shied or bullet proof vest when running one of these [smilie=l:


Thanks






Nooo! If you are cutting internal threads on the side away from you with the tool upside down you do not run the spindle in reverse. You run it normal and cut going in, toward the chuck. If you cut coming out you will produce left handed threads.

If you keep the tool right side up and cut on the side away from you, then you will need to run the spindle backward. That's why I turn the tool over.

[John Taylor]

Nobade- I thought you were talking about reversing the tool on the side facing you, my bad. I like to see what the tool is doing so I run it right side up and reverse the motor. Picture may help. There are more ways to skin a cat.http://i95.photobucket.com/albums/l132/johnptaylor/IMGP1505.jpg

[Nobade]

Yep, that works too!

[machinisttx]

Don't run the spindle in reverse if you have a thread on chuck. You'll be very disappointed if the tool hangs up using that method. ;-)

[whopist]

I made this Thread Setup Cheat Sheet for myself some time ago.

It did not convert well for computer viewing and I didn't make a lot of notes for public eyes, but here it is.

Maybe it helps a little.

http://i264.photobucket.com/albums/ii165/whopist/ThreadSetup.jpg

[HollowPoint]

I've been practicing on PVC pipe for the past couple of weeks as time permits. Once I got to the point where I thought I was doing it at least close to the right way I switched over to aluminum rod to practice on.

It's working but, I get the feeling that something still doesn't seem right; and I hate like heck to ruin the project I have coming up that will require threading.

I've also viewed and re-viewed all the YouTube videos I can. Some are better than others and a couple seem to contradict the others so, it can get kind of confusing.

Here's a question for the experienced Lathe operators about threading in general.

Once you've set up your lathe and your compound is set at 29.5 degrees; which do you use to actually feed your threading tool into your work; is it the Cross-Feed or the Compound-Feed or both?

If you use a Center-Gauge to position your threading tool just right, it seems as though if you use your Compound you'll be feeding more forward than directly into part you're trying to thread.

I tired it both ways with PVC pipe. My results were clearly better when I used the Cross-Feed.

In the videos I've eluded to, I've watched as these guys seem to make adjustments on both the Cross-Feed and the Compound-Feed before each pass.

Can one of you guys clarify this for me. Since my question has to do mainly with external threads, I hope this isn't seen has a hijacking of this thread. I think the same questions applies to internal threads as well.

I couldn't quite make out the details of the diagram that WhoPist posted. Looks like it might be of some help to me.

HollowPoint

[Nobade]

I always set the cross feed to zero and advance the tool with the compound. That's why it's at 29.5 deg - so as you advance it, the tool cuts on the leading edge and not on the back side like it will if you advance with the cross feed.

[DCP]

Don't feel your hi jacking the thread

I got mine made and it works. But it's not pretty

I started on the back side tool up side down fed toward head.
Well it worked at first then when I started the cut it would pickup (or jump) the whole compound[smilie=b:

I turned the tool up, lined it up and cut it on the front side, Man it's ugly.

I would take a picture- but its so ugly it might break the camera.





I've been practicing on PVC pipe for the past couple of weeks as time permits. Once I got to the point where I thought I was doing it at least close to the right way I switched over to aluminum rod to practice on.

It's working but, I get the feeling that something still doesn't seem right; and I hate like heck to ruin the project I have coming up that will require threading.

I've also viewed and re-viewed all the YouTube videos I can. Some are better than others and a couple seem to contradict the others so, it can get kind of confusing.

Here's a question for the experienced Lathe operators about threading in general.

Once you've set up your lathe and your compound is set at 29.5 degrees; which do you use to actually feed your threading tool into your work; is it the Cross-Feed or the Compound-Feed or both?

If you use a Center-Gauge to position your threading tool just right, it seems as though if you use your Compound you'll be feeding more forward than directly into part you're trying to thread.

I tired it both ways with PVC pipe. My results were clearly better when I used the Cross-Feed.

In the videos I've eluded to, I've watched as these guys seem to make adjustments on both the Cross-Feed and the Compound-Feed before each pass.

Can one of you guys clarify this for me. Since my question has to do mainly with external threads, I hope this isn't seen has a hijacking of this thread. I think the same questions applies to internal threads as well.

I couldn't quite make out the details of the diagram that WhoPist posted. Looks like it might be of some help to me.

HollowPoint

[dragonrider]

Once you have your tool set properly, and your compound set at 29.5 deg. Set your compound dial on zero. Acquire the surface of your workpiece with the tip of your tool using the cross slide. Set your cross slide dial to zero, be sure that you have set the thread cutting gearing correctly. Disengage your cross slide power feed, or set the engagement lever to neutral if your machine allows that. Engage your lead screw. Now you are ready to cut, advance your COMPOUND a few thousandths, no more that five, engage the half nuts when a numbered line lines up with the indicator on the threading dial. Others will give you more information here about how to use the threading dial, that info will be needed in the future but not right now, keep it simple and use the same numbered line each time you engage the nuts. When you reach the end of your cut, disengage the half nuts and move the tool bit away from the workpiece using the CROSSLIDE. Move the carriage to the beginning of the cut and return the cross slide to the zero position. Advance your COMPOUND a few more thou and repeat the process until your are done. Threading requires that each step be done in order exactly, make one step out of order and you will junk your workpiece. The above directions work for inside or outside threads.

Using the compound to advance the tool bit allows the tool bit to cut on only one side of the tool thus reducing the amount of pressure on the point and lessening the chance of breaking off the tool bit tip.

[Reload3006]

only thing i can add is when you get within .005 of finish finish with the cross slide as it will complete the form of your thread.

[HollowPoint]

My initial attempts using the Compound resulted in what I can only describe as overlapping threads. It was a mess.

The starting cut looked beautiful but, every time I advanced the compound even by the slightest amount it was like starting a whole new thread pitch.

I had the day off yesterday so I got a chance to do a general check of my lathe and tighten up my Cross and Compound feeds hoping that this was a contributing factor in the bad results I was getting. Today, if I get the chance I'll install some inexpensive DIY DRO's and practice a few more times before I take the plunge.

I think that once I get comfortable with being able to make good threads it will step me up to another level of metal working on a lathe.

Thanks everyone.

HollowPoint

[dragonrider]

If that is the case I can only think that you have your compound set at the wrong angle. Position your compound center line to be 90 degrees or perpendicular to the center line of the lathe, now swing it to the right to 29.5 degrees. Perhaps I can take some pictures this evening to help out. I will try.

[Simonpie]

My initial attempts using the Compound resulted in what I can only describe as overlapping threads. It was a mess.

Thanks everyone.

HollowPoint

If that's the case, I'm guessing you're throwing the half nuts on the wrong mark.
For a test, do light cuts and just use the cross slide and always throw on the same mark. Don't mess around with odd/even/whole numbers etc. Once that works, try the compound. Once that works try using different marks on the half nuts.

Also, some materials cut nicely on just one side of the tool (29.5 degrees), but others like the higher loads of plunging straight in with the cross feed. Play around until you get a nice surface. Plunging can overload the tip or cause chatter due to the higher forces. You just have to play to find the sweet spot.

[scrapcan]

Great info once again thanks to all.

one thing not mentioned is the 29.5 degree feed-in angle using the compound is for 60 degree thread form types, if you cut other thread form you may need a different compound feed angle. the 29.5 degree setting also lets you know the actual cut depth as you make your depth setting. A direct read dial helps here also. Make sure you know what your dial markings relate to. Just a bit of geometry calculation to find out what the graduations equal at different angle settings will give you this info ( i.e use sin to find depth of cut based on angle length of movement, right triangle formula ). But that will all come to those of us newbies as we progress in making usable threads and lots of chips.

Great info once again thanks to all.

[Cap'n Morgan]

For what it's worth; Once the threading spindle has been engaged, I keep it engaged through the whole operation. After each cut I pull the cross slide and put the lathe in reverse at the same time, then feed the compound while the tool is moving back for the next cut. It can be a little taxing when you're cutting a coarse thread and your lathe runs 160 rpms at its slowest, but you'll get used to it :shock:

[HollowPoint]

For what it's worth; Once the threading spindle has been engaged, I keep it engaged through the whole operation. After each cut I pull the cross slide and put the lathe in reverse at the same time, then feed the compound while the tool is moving back for the next cut. It can be a little taxing when you're cutting a coarse thread and your lathe runs 160 rpms at its slowest, but you'll get used to it :shock:

I tried that very thing today and I was still getting overlapping threads. Frustrating.

On my lathe, if I'm threading metric threads the instructions actually calls for this very thing. Since I wasn't having any luck with 1x14 threads I was attempting to do I decided to try it as if I were cutting metric threads. Still no luck.

The first pass is beautiful but, every pass thereafter falls either a fraction behind or ahead of the initial thread pass; regardless of which method I use.

Upon closer inspections I believe I may have found the problem. I think that this particular little chinese metal lathe has far to much "Back-Lash." (Grizzly 9x19)

I'll see what I can do about it and give it another go after I've tightened it up some more.

Thanks guys.

HollowPoint

[John Taylor]

I tried that very thing today and I was still getting overlapping threads. Frustrating.

On my lathe, if I'm threading metric threads the instructions actually calls for this very thing. Since I wasn't having any luck with 1x14 threads I was attempting to do I decided to try it as if I were cutting metric threads. Still no luck.

The first pass is beautiful but, every pass thereafter falls either a fraction behind or ahead of the initial thread pass; regardless of which method I use.

Upon closer inspections I believe I may have found the problem. I think that this particular little chinese metal lathe has far to much "Back-Lash." (Grizzly 9x19)

I'll see what I can do about it and give it another go after I've tightened it up some more.

Thanks guys.

HollowPoint

Might be a good time to check the gears and make sure they are not jumping a tooth once in a while. Had another shop ask me to look at there lathe because the feed was not working anymore and the problem was the change gear came loose and dropped down.

[HollowPoint]

This little lathe has a bunch of different gears. They all seem to be in order. They all have some play in them so it would be difficult for me to the find the culprit causing my threading problems.

I'll have to scour the internet in search of any info I can find on how to lessen or eliminate the backlash in my feed screw. I hate the thought of having to dismantle it completely in order to come up with a fix on my own.

I've done it before on another bench lathe I had. It was no fun but I did manage to get it fixed. I had to fabricate some Delrin parts that worked out well. Almost but not quite eliminated all
the backlash problems I had with that previous lathe.

I hate it when stuff like this happens. Sure puts a damper on ones enthusiasm.

HollowPoint

[HollowPoint]

I figured out what I was doing wrong.

Boy do I feel stupid. Nuff Said.

HollowPoint

[DCP]

Good for you [smilie=w:

I will take pictures of my working but ugly threads if you tell all :popcorn:



I figured out what I was doing wrong.

Boy do I feel stupid. Nuff Said.

HollowPoint

[HollowPoint]

On my particular lathe (Grizzly 4000) there's alot of play in all the gears. I thought perhaps there was to much play and that was causing my threading problems.

In my search for answers I came across one of the yahoo groups that deals with nothing but this type of lathe. It turns out that I'm not the only one who was experiencing this type of "Over-Lapping" threads problem.

One of the guys who responded to a similar problem being had by the poster actually put together a pictorial/tutorial of exactly how he goes about making threads on a similar lathe.

It seems that I was doing everything right except for one tiny step in the process.

Once this individual engages the threading half-nut, he keeps it engaged until his threads are completely cut. Forward to cut the threads and back out the Cross-Feed and reverse to bring it back to its original Starting Position for the consecutive passes.

It's that "Starting Position" that was messing me up. In my attempts to cut threads I had my "Starting Position" at or near the very edge of my part.

Having my "Starting Position" so close to the part before turning on the lathe or engaging the half-nut wouldn't allow any of the backlash or slop in my feed screw to be taken up before my thread cutter made contact with my part.

It was just a matter of moving my "Starting Position" about one-inch away from the right-side edge of my part. This extra bit of space between my tool and my part allowed enough time for the slack in my gears to be taken up and feed the tool through the same tool-path with every consecutive pass.

Even with all this figured out the finish on my thread was still a little rough looking. Then it dawned on me that I forgot to use cutting oil. Once I applied a little cutting oil the threads started looking really clean; almost like I knew what I was doing.

I've been trying to cut some 14-pitch threads. The threads themselves look good but, my thread gauge is telling me that they're coming out as 13-pitch threads. (not sure if that's the correct terminology; I'm not a machinist, just a tinkerer.)

I've checked and rechecked my gears to make sure they're all in the right place. They all appear to be in the right positions but, I'm still not getting the right thread count. There has to be something I'm missing in my setup procedure. Once I figure that out I'll be a happy camper; or happy threader.

HollowPoint

[Cap'n Morgan]

Don't know about your lathe, but older types often require you change the main gear wheel when cutting either metric or imperial threads. Normally the metric wheel will have 127 teeth and the imperial 120... or is it the other way around? Anyway, using the wrong gear could very well explain your error. The numbers 127:120 are close to 14:13.

[DCP]

Darn now I have to go take pictures[smilie=l:

[HollowPoint]

Don't know about your lathe, but older types often require you change the main gear wheel when cutting either metric or imperial threads. Normally the metric wheel will have 127 teeth and the imperial 120... or is it the other way around? Anyway, using the wrong gear could very well explain your error. The numbers 127:120 are close to 14:13.
Greetings Cap'n:

My metal lathe has the same two tooth-count gear wheels. I've tried using both to see what, if any, change in the thread count would result but, nothing seemed to change. I'm still getting 13 rather than the 14 threads per inch I thought I was set up for.

I'm thinking that the answer to this problem is one of those pesky but incredibly simple answers like the "Starting Position" of my thread cutter was.

I'll go back to that yahoo 9x19 metal lathe users group to see if I can dredge up an answer to this setback. If I have to I'll sign onto that forum just so I can ask someone who knows what they're doing for some input.

I sure wish I was born with this knowledge rather than having to learn it a little at a time. I suspect that life would be boring if I was though.

HollowPoint

[John Taylor]

Check to make sure the lead screw is not for metric threads. In most cases it should have 8TPI. Every once in a while a China lathe makes it to the U.S. set up for metric.

[DCP]

It works. But it's not pretty

Its a 3/4-16 cut in alumimun used carcoal fluid for lube

I started on the back side tool up side down fed toward head.
Well it worked at first 1st 10 or 12 passes.
Then when I started the cut it would pickup (or jump) the whole compound

I turned the tool up, lined it up and cut it on the front side, Man it's ugly.

Hope you dont go blind

[HollowPoint]

"Check to make sure the lead screw is not for metric threads. In most cases it should have 8TPI. Every once in a while a China lathe makes it to the U.S. set up for metric."

I'll have to check that out if I can't come up with an answer to this problem. I signed onto that yahoo site I mentioned previously and posted my question about the problem I was having. I got quick responses. Hopefully one of them will have the answer I need.


"It works. But it's not pretty

Its a 3/4-16 cut in aluminum used carcoal fluid for lube

I started on the back side tool up side down fed toward head.
Well it worked at first 1st 10 or 12 passes.
Then when I started the cut it would pickup (or jump) the whole compound

I turned the tool up, lined it up and cut it on the front side, Man it's ugly.

Hope you dont go blind"

If you could have seen the damage I was doing in my initial attempts to cut threads, the threads you made up would have made you more proud than embarrassed. I think that real cutting oil would have made them look even better.

HollowPoint