Starting a thread on the lathe with a die

All discussion about lathes including but not limited to: South Bend, Hardinge, Logan, Monarch, Clausing and other HSM lathes, including imports

Moderators: GlennW, Harold_V

RSG
Posts: 1541
Joined: Fri Feb 04, 2011 9:59 am
Location: Ontario, Canada

Starting a thread on the lathe with a die

Post by RSG »

I'm about to thread some 303 stainless with a 5/16-18 die and find it difficult to start the thread. I am using a die holder I made and so far the only way I've found to start the thread is to put pressure on the die with the tail stock but even then it's tough. Any suggestion would be appreciated.

Ron
Vision is not seeing things as they are, but as they will be.
Mr Ron
Posts: 2126
Joined: Tue Dec 22, 2009 12:36 pm
Location: Vancleave, Mississippi

Re: Starting a thread on the lathe with a die

Post by Mr Ron »

You need to put a chamfer on the end of the rod so the die can get a grab. Some pressure is also needed to get the die started. After it is started, the die will self feed.
Mr.Ron from South Mississippi
User avatar
Steggy
Posts: 1976
Joined: Tue Jun 28, 2011 9:19 pm
Location: JB Pritzker’s Hellhole
Contact:

Re: Starting a thread on the lathe with a die

Post by Steggy »

RSG wrote:I'm about to thread some 303 stainless with a 5/16-18 die and find it difficult to start the thread. I am using a die holder I made and so far the only way I've found to start the thread is to put pressure on the die with the tail stock but even then it's tough. Any suggestion would be appreciated.

Ron
As said above, some pressure is required to get the die started, which is no different than when manually cutting threads. A gentle chamfer assists in getting the die started and also helps to center the die so you don't get askew threads. Once the die has cut three or four threads it will self-feed.

Although 303's chemistry makes it less difficult to machine than other austenitic stainless alloys (e.g., 304 and 316), you must flood the die and workpiece with cutting lubricant as you are threading. Also, run your lathe very slowly to minimize heating. Inadequate lubricant and/or excessive speed will likely result in a raggedy thread and die damage. My go-to lubricant for any stainless machining, including thread cutting, is a mixture of mineral spirits and petroleum-based cutting oil, 10 percent mineral spirits and 90 percent oil.
———————————————————————————————————————————————————————
Music isn’t at all difficult.  All you gotta do is play the right notes at the right time!  :D
User avatar
liveaboard
Posts: 1971
Joined: Sun Dec 08, 2013 1:40 pm
Location: southern Portugal
Contact:

Re: Starting a thread on the lathe with a die

Post by liveaboard »

Cut stainless with a die?
It never worked for me, but maybe you have better dies than I ever did.

Tappy newyear!
[groan]
RSG
Posts: 1541
Joined: Fri Feb 04, 2011 9:59 am
Location: Ontario, Canada

Re: Starting a thread on the lathe with a die

Post by RSG »

Thanks for the replies, the chamfer idea is good but I guess I should have been more clear to begin with. There is an internal thread as well that is 12-24 and the face of the thread lip is important to have a flat on it so the internal threaded component can snug up to it. Here's a picture of what I'm doing. Either way what you are saying is I do need some pressure on the die to get it started, which is what I was doing, so thanks for confirming that.

Image
Vision is not seeing things as they are, but as they will be.
RSG
Posts: 1541
Joined: Fri Feb 04, 2011 9:59 am
Location: Ontario, Canada

Re: Starting a thread on the lathe with a die

Post by RSG »

Oh, and BDD, thanks for the lube recipe. I'll give it a try.
Vision is not seeing things as they are, but as they will be.
User avatar
GlennW
Posts: 7284
Joined: Sun Apr 15, 2007 9:23 am
Location: Florida

Re: Starting a thread on the lathe with a die

Post by GlennW »

I'd single point it if you want a nice thread that is concentric with the shaft.
Glenn

Operating machines is perfectly safe......until you forget how dangerous it really is!
John Hasler
Posts: 1852
Joined: Tue Dec 06, 2016 4:05 pm
Location: Elmwood, Wisconsin

Re: Starting a thread on the lathe with a die

Post by John Hasler »

RSG wrote:Thanks for the replies, the chamfer idea is good but I guess I should have been more clear to begin with. There is an internal thread as well that is 12-24 and the face of the thread lip is important to have a flat on it so the internal threaded component can snug up to it. Here's a picture of what I'm doing. Either way what you are saying is I do need some pressure on the die to get it started, which is what I was doing, so thanks for confirming that.

Image
Face off the chamfer after all the threading and tapping is done. I'd single-point it, though.
spro
Posts: 8016
Joined: Mon Feb 20, 2006 11:04 pm
Location: mid atlantic

Re: Starting a thread on the lathe with a die

Post by spro »

So the 5/16 X 18 is already internally threaded with 12 X24. What sort of set screw or pilot are you using inside? I've had to use something, especially when using a die.
User avatar
tornitore45
Posts: 2077
Joined: Tue Apr 18, 2006 12:24 am
Location: USA Texas, Austin

Re: Starting a thread on the lathe with a die

Post by tornitore45 »

When machining a part from scratch, if the thread is too delicate or too large that requires a lot of starting pressure I turn a little undersized spigot for about a 10-20% thread, it help start centered and feed. Then is turned off and chamfered.
Mauro Gaetano
in Austin TX
RSG
Posts: 1541
Joined: Fri Feb 04, 2011 9:59 am
Location: Ontario, Canada

Re: Starting a thread on the lathe with a die

Post by RSG »

Glenn, I thought about doing it on the lathe but I'm not well versed on threading up to a shoulder that small and I have about 14 to do as well. I wish I could do it, it's one skill I've avoided perfecting.

I do like John and Mauros ideas and will give them a try today.

Thanks for the input guys and Happy New Year to the board!
Vision is not seeing things as they are, but as they will be.
John Hasler
Posts: 1852
Joined: Tue Dec 06, 2016 4:05 pm
Location: Elmwood, Wisconsin

Re: Starting a thread on the lathe with a die

Post by John Hasler »

I like the idea of a spigot turned to the minor diameter rather than just a chamfer. If it's about as long as the die the die will be perfectly aligned when it starts cutting the first thread.
Post Reply