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Threading issue

Ratz

Aluminum
Joined
Feb 4, 2014
Location
Canada
Hi Everyone,
Hopefully someone can shine some light on this threading business.
See attached photo. Yikes.

This is my practice run on 1” round 4140 hardened alloy I just purchased.
I tried the 4140 annealed and had much the same results, threads pulling.

In the setup I have currently Arthur R. Warner HSS insert TNMC. I have EDGE level
to adjust the height. I tried moving the insert up and down with not much change.
Both inserts are new. Shaft runs nice and true 0.0003” and everything is tight.

In the picture is a second insert I tried with TPMC (carbide gold color), no difference.

The speed tried is 65 and 185, which may be the culprit, but since the thread on the final product is 15mm, length of the thread is 16mm and collar beside it is 25mm, I am paranoid going any faster of fear crashing the tool into the collar. (not in the picture as I am just practicing).

I was even thinking if I need to ran faster to make the shaft where the collar should be, say a 16mm so I will not crash it, and then after the threading if successful press the collar onto the 16mm shaft. Unless of course there is another technique, like cutting threads away from the collar with upside down insert.

I work mostly with stainless and never run into this to be a bother. So obviously, I am just not capable to machine 4140. I am ashamed of this embarrassing picture.

DSCN1379.jpg
 
I was even thinking if I need to ran faster to make the shaft where the collar should be, say a 16mm so I will not crash it, and then after the threading if successful press the collar onto the 16mm shaft. Unless of course there is another technique, like cutting threads away from the collar with upside down insert.

Running in reverse with cutter upside down is exactly what I've done in such close quarters.
 
17 and 48 SFPM on 1" dia. - 350 SFPM would be more like cutting speed. 4140 prehard will thread nicely. Flood coolant or at the very minimum dark cutting oil

Hmm… I may be wrong, but I punched in the numbers. 350 SFPM works out to 22 revolutions per second. Since the length of the thread is 15mm that would give me ¾ of a second to do the cut and stop the spindle before it crashes.

I can see this speed for turning but call me chicken for threading on manual lathe. Maybe I misunderstand your approach.
 
Hmm… I may be wrong, but I punched in the numbers. 350 SFPM works out to 22 revolutions per second. Since the length of the thread is 15mm that would give me ¾ of a second to do the cut and stop the spindle before it crashes. . .

I think he must've meant 350RPM.
 
I think he must've meant 350RPM.

That would make sense. I will see what the cut of thread looks like at 350 and go from there. As I said
185 made me nervous so I just may practice the upside down method going outwards.
Thanks for coming up.
 
350 RPM on a 1" dia is 92 SFPM - suit yourself - but I do see the carbide cutting tools which will be happy at 22 revs per second or 350 SFPM

I never threaded this way, so I will do some practicing.

You will need a relief groove to start in
 
OK, good to know I am not dreaming. I never threaded this way, so I will do some practicing.

Don't try this if your lathe has a threaded spindle. Having a spinning chuck unscrew itself and chase you around the shop is far too exciting for one's health.
 
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I have threaded a lot of 4140 both annealed and hardened, almost every day. screws down to no.6-38 ( if memory serves) and up to 2"-12 always on manual lathes. first, high speed steel properly ground and sharpened is much more forgiving on speed, second a good lard based oil, or even baking lard ( I use it constantly) or dark cutting oil, applied every pass, will help keep your cutter clean, the metal welding to the end of the tool is your worst enemy. My dad threads even slower than I do, I have in the past ran as slow as 65 rpm on 1" bars with good results, just takes a lot of time and light (.005 or less) passes. first pass can be deeper, but need to get lighter with each pass. getting proficient with threading is all in practice...... and good cutting oil, don't be stingy with it!

by the way I threaded the no.6 at less than 100 rpm, speed helps but it's not necessary for a beautiful thread. ( I made thumb screws for a browne and sharp 38" vernier caliper I bough my dad for Christmas,both fit better than the ones in my starrett and looked better too!)
 
I thread a lot of 4140 both annealed and prehard from 1/2" to 1 3/8". I always use Kennametal grade KC5010 it has given the best combination of life and finish. That is on a CNC Lathe using water soluble flood coolant. For 1" threads I would go 500-600 rpm. The right insert I have found is very important. I have a 3.5" long thread I single point at 1,000 rpm, Kennametal NJF3008R20 KC5010 will usually get 200+ on each insert side. The same style in a KC730 will barely make a dozen parts.
 
Hi Everyone,
Hopefully someone can shine some light on this threading business.
See attached photo. Yikes.

This is my practice run on 1” round 4140 hardened alloy I just purchased.
I tried the 4140 annealed and had much the same results, threads pulling.

In the setup I have currently Arthur R. Warner HSS insert TNMC. I have EDGE level
to adjust the height. I tried moving the insert up and down with not much change.
Both inserts are new. Shaft runs nice and true 0.0003” and everything is tight.

In the picture is a second insert I tried with TPMC (carbide gold color), no difference.

The speed tried is 65 and 185, which may be the culprit, but since the thread on the final product is 15mm, length of the thread is 16mm and collar beside it is 25mm, I am paranoid going any faster of fear crashing the tool into the collar. (not in the picture as I am just practicing).

I was even thinking if I need to ran faster to make the shaft where the collar should be, say a 16mm so I will not crash it, and then after the threading if successful press the collar onto the 16mm shaft. Unless of course there is another technique, like cutting threads away from the collar with upside down insert.

I work mostly with stainless and never run into this to be a bother. So obviously, I am just not capable to machine 4140. I am ashamed of this embarrassing picture.

View attachment 264921


You tried 'moving the insert up and down'? What the hell for? Set it slightly below centerline height and it should cut. Looks like you've got it set above centerline, and that just ain't gonna work in this universe.
 
Thank you. There should be hope for me then. I just keep trying with different tools. Interesting is
that my HSS insert by Arthur R. Warner never failed me in 316 and 304 stainless.
 
Can't tell from the photo, but how much stick-out? You keeping it under 3x diameter?

This is my latest trial. Still crappy. Material is sticking out 1.25". Using TPMC carbide 180RPM. This is a second try without chamfered start on this piece of alloy. It was late last night and I forgot.

Come to think of it this is my first fine thread. Course threads always came up nicely in stainless.

DSCN1380.jpg
 
You tried 'moving the insert up and down'? What the hell for? Set it slightly below centerline height and it should cut. Looks like you've got it set above centerline, and that just ain't gonna work in this universe.

I have tried moving insert up and down, just to see if being below and above centerline would make a difference in cut. I have included a picture of EDGE level for everybody to know, that I am using some decent tools to find centerline. Other convincing fact of being on the centerline is during facing I have no nipple left what so ever.
I will keep in mind your advise being slightly below is preferred. Thank you for posting.
 








 
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