threading problems.....

higgite said:
If you’re cutting threads with the compound, close is not always good enough if you want to cut good 60 degree threads. There have been a multitude of posts on here about folks cutting screwed up threads (pardon the pun) because they set their compound more than 30 degrees from perpendicular to the spindle axis, or less than 60 degrees from parallel to the spindle axis if you prefer. But, like others have pointed out, if you use the cross slide to advance the cutter, the compound angle is irrelevant. Hope this clears up more confusion than it causes.

Tom
Click to expand...
Thanks Tom, that's where I was headed, just couldn't get it in print.
But, if you're tool is ground with a good edge & angle and the tip set right with your work the angle of your compound can be off a bit (plus or minus a degree) and you'll cut good threads.
Like Tom said though if you use the cross feed it'll work.
 
Bob Kelly III said:
Howdy guys !
Savarin...... well no i don't use a fish tail gauge.....don't have one !
and I ground the cutter by guess and by golly but I am sure it is very close( famous last words right ?)

Ray....... HAHAHAHA well you know....that may well be why the nut don't fit on the thread I made !!!!!!
I'll try it again with 13 TPI thanks ! ( very tactfully stated I must say .... I'm thinking..... hay stupid your trying to put the wrong nut on there that's why it don't fit ! HAHAHAHHAHA

My Machinery's hand book burned up in the Ranch fire darn it... and I have not had the funds to buy a new one yet.... i can't check those things very easily..... it would make a dandy locking nut on that rod ! for a one time use ! LOL......thanks Ray !

later guys !
Bob......
Click to expand...
Sorry about the ranch fire Bob, building a library takes a long time. The text book "Machine Shop Operations and Setups" 4th edition is my goto book in addition to this website and a loose leaf note book full of downloads are my trusted sources of information. I hope you have been able to get your thread cutting problem corrected. Having a tool that needs repair is personally very frustrating If your Logan lathe is like my Clausing you will be making new things for a long time, but at the lathe's speed and capability. Threading is fun but time consuming and I go at it some what differently. The 60` threads mean each side is the same length so I use my cross slide set at 29.5` to cut the depth equal to the pitch. When I get close to depth I start trying the nut, again time consuming but keeps you from having loose nuts.
Have a good day
Ray
 
I've had good luck with the 29.5deg. infeed if that means anything...( good graphics !)
.....
I tried a test threading today, sense I have a reverse switch now on the lathe....
WHAT A DIFFERENCE !
I was only cutting PVC plastic pipe 1" in diam. but it went so easily that it was hard to believe I was threading !
.... I got everything set up and then just locked the half nut and left it locked throughout the whole threading practice
I was doing 13 TPI as that seems to be very common.... but the operation was so easy... I didn't even bother to use the compound
just the cross slide and although the scratch pass was fairly deep I had fully formed threads in about 6 or 8 passes ! so it didn't take all that long at all
.... towards the end I only gave it 5 thow increments on the depth of cut and it worked real good on the PVC.
you need to pay attention to the depth of cut in threading I have found.... but being able to reverse the motor sure made the process much, MUCH easier..... i think I will be using this method from now on, as even a kid could do it... the only thing you have to remember is to back out the cross slide before you reverse...... and if I made up one of the Aussie's flip up threading tools I wouldn't have to do that....
...... just add depth and reverse.....add depth and reverse ! do that a few times and your done ! LOL
I was quite impressed !
it was taking my lathe about 3/16" to 1/4" to stop in cutter movement and I wasn't in back gears ....i just slowed the VFD down to 20%
.....
I finished the re make of the Expanding mandrel for the Lathe indexer ,and bored the 5/8" hole through the 3" wide flat pulley that I have yet to drill any locating holes into ....so I am still stuck with saw blades for the time being.
.....the aluminum gear I made for replacing the chewed up idler gear is working great... no signs of ware at all.
....
so the next project is probably going to be a hand crank for the spindle....i could use one of those ! <grin>
later !
Bob..........
 
Congrates on making threads! Doing the movements in a routine order is most important. If you will cut some more threads using your cross slide only you will see the cutting tool is probably cutting on both sides of the point. If at some time your threads are ragged this may possibly be corrected by adjusting the cut depth with the compound rest where the left side of the cutter is removing the material. You have crossed a major hurdle by producing good looking threads.
Have a good day
Ray
 
Rock_Breaker:
The help I received here made all the difference in the world....
the things that made the biggest difference on my machine and on me were....
1. Super Sharp tool.....(a piece of old file works but not for long soon you will be ripping the threads out when it dulls)
2. finding the slop in the lead screw was a major changer ,hitting the mark on the thread dial is much easier when the tooth is actually there !
3. getting the Routine down.... so you don't have to think about it.... and remembering where you were on the depth of cut.
4. Several types of threads being practiced HELPS ! from 28 t.p.i. to 10 t.p.i the finer the thread the sharper your tool needs to be !
5. practicing on everything I can find helped allot ! it mainly reinforces the routine, but it IS NECESSARY !

With the addition of the reversing switch on my Logan lathe I can now put the lathe in reverse.... so I can leave the half nut locked
and I was really surprised at how much that helped ! all your left with then is In and Out and reversing and thread depth which really uncomplicated the single point threading for me !
......
thread cutting is using a forming tool ! if your not dead on with the point of that threading tool your threads will show it !
...
Bob.....
 
BOB,

You hit on some things I missed. IMHO threading is one tool a hobby machinist must be familiar with. Being able to cut threads has given me more confidence to make tools and do repairs. Another threading capability is being able to reset the lathe to repair worn or damaged threads. In my case it starts with measuring (identifying) the thread, then setting each function as if starting a new thread after putting the old threaded piece back in the lathe. It is called "serious concentration" here.
Enjoy your shop
Rock_breaker
 
I'm wondering if a Special threading tool just for the repair of damaged threads would be worth considering one that doesn't cut away the bent over porton but pushes it back into shape..... a simple bevel on a HHS threading cutter on both sides to "DULL IT " and go in till the threads are pushed back into shape but no further....
I wonder if that would work or not ..... obviously the severity of the damage would vari but for light stuff that a nut will go over but not easily
this may well be the better action than cutting off the dents and leaving holes..... though in my experience I've never had a problem with doing that
when I discovered my first thread file I went around on the ranch and repaired every damaged thread I could find ! especially on the tractor
as everything that had exposed threads had massive dents in the threads..... but cleaning them off sure made it operate good again !
..... I however would be reluctant to use a good HSS thread cutter to this task..... one you were considering tossing is a real good candidate for the experiment ! just round the cutting edge over .... oil real good and see if the idea works !.....you'ed be chasing the threads.... so after everything is all set up and ready to go hand placing the cutter / deformer into a area with no damage then tightening down the cutter should get you there for repeatable passes right ?
any opinions on that idea ? is it worth the bother ?
.....
Bob.......
 
An interesting idea Bob!

My first thought is that this tool would be pushing material back into a stronger material mass which would take a lot of energy. Heating it would also affect the larger mass (bolt) and possibly twisting it. PM me as I have an Idea.
Have a good day
Ray
 
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