Threads coming out with an angle

[Cattleman99]

Hello, I have a small Grizzly G0750G lathe that works well for most things. I’m currently working in threading some muzzles, and I have noticed that the threads all have a forward angle towards the muzzle. Things thread on fine, but the angle bothers me. Any idea how to fix this? I’m not sure how to post a photo.

Compound is set at 29.5 degrees, tooling is square to the work piece via fish gauge. 60 degree single point threading

 

[JS]

Purchase a better machine or figure out how to tighten or fit your lathe to remove any slack backlash or looseness in the machine itself.


That being said hobby machines are not allowed here..

Please use generic terms while referencing hobby equipment.

 

[Rudd]

Some compounds are marked differently - the crank should be at about 5 o'clock when you look straight down on the compound, i.e, 29.5 off perpendicular to the spindle axis, or stated another way 60.5 off the spindle axis.
If you had it the "other" way - say 3:30 or 4 - i.e., 29.5 off the spindle axis, infeeding with the compound would give the results you describe.

 

[Bobw]

Some compounds are marked differently - the crank should be at about 5 o'clock when you look straight down on the compound, i.e, 29.5 off perpendicular to the spindle axis, or stated another way 60.5 off the spindle axis.
If you had it the "other" way - say 3:30 or 4 - i.e., 29.5 off the spindle axis, infeeding with the compound would give the results you describe.

At least 10 times a year.. The SAME EXACT THING.

"I know its set right"

"no its not"

"But it says 29.5"


There was just one of these threads a couple of weeks ago..

I don't understand how its so hard to visualize that if you are
feeding in at a steeper angle than the thread flank, you are
going to wipe out the thread flank. Especially when somebody is
literally sitting there and WATCHING it happen.

 

[Gordon Heaton]

. . .I don't understand how its so hard to visualize. . .

Well, people see what they expect to see. Some 'authority' said 29.5* so . . .

For the O.P. :What isn't usually mentioned is that part about every lathe not being marked the same way. Another way to 'look' at it is that the compound slide must be at the same angle as the right-hand edge of the thread cutting tool. In other words, line a ruler up with the right flank of the cutter and it should extend parallel to the compound. If it slashes across the compound at a noticeable angle, it isn't right.

Now I know that lining anything up with a tiny cutting edge can be difficult, but in the case of alternate degree markings the difference will be obvious.

 

[Conrad Hoffman]

I've had the problem when everything is set up right. Check the tool height and check that the clearance angles are sufficient.

 

[EPAIII]

I posted some instructions on posting photos here:

https://www.practicalmachinist.com/...sing-boards-image-hosting-350499/#post3176881

There are other methods, but that will get you started.

Hello, I have a small Grizzly G0750G lathe that works well for most things. I’m currently working in threading some muzzles, and I have noticed that the threads all have a forward angle towards the muzzle. Things thread on fine, but the angle bothers me. Any idea how to fix this? I’m not sure how to post a photo.

Compound is set at 29.5 degrees, tooling is square to the work piece via fish gauge. 60 degree single point threading

 

[johnoder]

Common sense helps too. If you on purpose set the compound at a low angle in relation to spindle axis it will produce crap threads - every time

The common sense tells me that if I want to feed the tool along the flank of a 60 degree thread profile, I had better have the compound set about 29.5 OFF THE FACE OF THE FACE PLATE - never mind what it says on the degree index

ON EDIT

Hint - pick up that little "fishtail" tool Mr. Starrett made for you - and slap one side of the point against the self same face (chuck, face plate, dog driver) with fish tail pointed back at you and look at the picture that makes. THAT is the same picture you want the compound to make

 

[tdmidget]

Guess those barrels are fucked up. Why would you do that to a finished part not knowing what you are doing?

 

[Rob F.]

Purchase a better machine or figure out how to tighten or fit your lathe to remove any slack backlash or looseness in the machine itself.


That being said hobby machines are not allowed here..

Please use generic terms while referencing hobby equipment.

I think that Grizzly IS allowed ONLY in the gunsmithing sub-forum. Since the OP is doing work on a gun barrel he could have posted outside of his sub-forum by mistake?
Otherwise I agree, do not mention the unmentionable machines here.

 

[Rob F.]

That being said hobby machines are not allowed here..

Please use generic terms while referencing hobby equipment.

I think that Grizzly IS allowed ONLY in the gunsmithing sub-forum. Since the OP is doing work on a gun barrel he could have posted outside of his sub-forum by mistake?
Otherwise I agree, do not mention the unmentionable machines here.

 

[Illinoyance]

It seems to me that OP should have learned to single point thread BEFORE working on firearms.

 

[Milland]

It seems to me that OP should have learned to single point thread BEFORE working on firearms.

If I had my face and fingers near an exploding charge, I'd want to be pretty sure I knew what I was doing before trying to change anything...

 

[DDoug]

Guess those barrels are fucked up. Why would you do that to a finished part not knowing what you are doing?

Well it threaded on "OK"...so that's all that matters....

 

[Rob F.]

He said it was on the muzzle so probably wont ever have to unthread it. More like, find the part (muzzlebrake?) downrange.

 

[CAMasochism]

He said it was on the muzzle so probably wont ever have to unthread it. More like, find the part (muzzlebrake?) downrange.

Some JB Weld will take care of that.

 

[Illinoyance]

Ideally he would cut off the messed up threads and re-thread the barrel, assuming the barrel would still be legal length.

 

[thermite]

It seems to me that OP should have learned to single point thread BEFORE working on firearms.

Maeah,, Darwin's ghost still has to eat...

At least firearms are not as much "in your face" as cellphones, motorcars, drugs, congenital idjuts in their "all of the above" combination, yah?

Population got lazy. Thot we could clean-up our local communities by sending various tribes of truants off to Washington, DC to bugger each other, leave us in peace?

Darwin's ghost is like to die young - health issues off over-eating.

 

[Cole2534]

If I had my face and fingers near an exploding charge, I'd want to be pretty sure I knew what I was doing before trying to change anything...

Since the burning is a deflagration instead of detonation I don't think it's technically an explosion.

Sent from my SM-G973U using Tapatalk

 

[john.k]

Its a muzzle brake,worst can happen is its flying downrange........red loctite is your friend...........some say you got to be crazy to set off powerful explosions inches from your head...not me.