Thread: What causing this "galling"?

OK success. That indexable thread tooling from ebay that Matt suggested worked. Not at first though, but I figured out that SLOW (85 rpm) and LIGHT cuts (.001 per pass toward the end) worked.

I cheated when it was 95% there and ran a die over it. The point of this exercise was to be able to make threads on a boat prop shaft, now it looks like I can. After that I can go back through these posts and learn how to do it really right.


Video to show what worked for me here:

YouTube

Originally Posted by FlyinChip

Hi all, I was slowly cutting threads using HSS and had this what i call galling issue. Then I bought a Carbide 60 degree cutter and had similar issues. I went a little deeper and the tip broke off, so scratch one brand new bit. Slow speed. Not sure why this happening but I'm not very experienced.

Somehow it seems like maybe the 1018 steel part metal quality may be an issue?

Stumped!

threads galling by Chris P, on Flickr

Change your material to 12L17 or another free machining Steel. I think you'll find the problem gone. If your requirement is 1018 go to the store and purchase a pound of lard. Mix some with low cost 30 weight oil and try again.

Roger

How's that saying go? The sun even shines on a dog's ...

I am surprised that even worked at that low an RPM. I would have expected to see chip weld, BUE and micro chipped carbide edges. Oil must have saved your butt. Would like to see a close-up of the thread finish without the die work.

When I ran faster, the chip was getting blue and hot. BUT I was also taking a bigger bite. Not sure, but running slow and light cuts did it. The cut was still slightly ragged IIRC. Never seemed to get totally away from that tearing issue no matter the tooling or speed or depth of cut. But it got to not bad with this slow/light method. Hopefully this hybrid method will get the 304 threaded which is the main task.

Originally Posted by FlyinChip

Hopefully this hybrid method will get the 304 threaded which is the main task.

If this is for a marine application use 316 rather than 304, much better corrosion properties in that environment.

Got a great deal on the 304. Boat is trailered.

While they are costly I sure like carbide inserts. Since almost every part I make is threaded, threading inserts give me consistency. The internal inserts have tail mark, indicating correct depth, going to deep will leave another groove or mark. For lube Magic Tap Extra works great on 304 as well as 416.

Originally Posted by FlyinChip

Got a great deal on the 304....

You might change your mind about that when you're threading it, that is if you count your time as worth something.

Try some 303 just for shits and giggles.

not to be a downer for your enthusiasm, but threading 304 is somewhat different than threading 1018. If you have some extra shafting, you might want to try it. One of the issues with stainless is work hardening, which is not a problem with 1018. If your tool rubs instead of cutting, you will work harden the material, which makes it EXTREMELY hard to cut. The cure is to use sharp tools, very good lubricant, and not to take off too little material in a cut. Stainless like to have a continuous cutting action. If you do not have enough pressure on the tool during the cut, it may not actually cut. Feeds and speeds are really important here. As others have mentioned, I like to use carbide threading inserts. Tap Magic (for stainless), Anchor Lube, or other good cutting fluid is really pretty essential.

I find it interesting that one can look at a bunch of inserts and not see the rake attitude on many. I thing the rake attitude is very important and for mild steel one cant beat having some positive rake attitude.
Back rake or side cutting angle rake is important.

https://www.mscdirect.com/browse/tn/...navid=12107172

Here one that states positive rake /likely cut with less compacting and cutting pressure, but not the angle..

https://www.mscdirect.com/product/details/02161032

Agree some times positive is how the inset sets in the tool holder..and the angle to the part..
Guys grinding HSS bits learn real quick how the rake angle affects the ability to cut.


How to read carbide inserts:
Carbide Milling Insert Nomenclature

Got the job done. I'm glad buck posted the carbide insert nomenclature link, because all I have is a cheap Shars carbide insert tooling set, which has worked really well and looking back I see that some of them are for aluminum, others steel, alloys etc.

3/8" Indexable Carbide Turning Tool Set

Anyway, recently picked up a few old lots of HSS of numerous sizes some cut, most are blanks.

But using the ebay thread insert/holder I cut the threads into the 304 shaft and STILL had a little of the same surface ripping as with the other tooling and the 1018 steel... so I simply got it close, and just ran the Bosch 3/4-10 die over it making acceptable. Actually, the die looked to be "rocking" a little for the first inch then ran true, weird. But the nut likes the resulting thread works just fine for its purpose, but need to keep getting a better finish. I think if really right, it should be smooth as glass?

As to cutting the taper, that worked fine with the Shars insert holder and light, slow passes. Setting up the taper I used a feeler gauge at the left side closing the gap at the start, and the prop fits perfect.

Still learning but this job is at least finished acceptably.

I see your cutting threads on a 9" South Bend lathe. That's where I learned to cut threads on, but with hand ground threading tools. Took me a long time to grind my threading tools perfectly and get a nice honed edge on them, to get a nice shiny thread with. I was around 10-11 years old when I cut my first thread and sliced my finger open from those stringy shavings from the aluminum I was cutting on. I probably have not ground a threading tool in nearly 40 years, all insert threading now. Have times have changed. Ken

Originally Posted by 4GSR

I see your cutting threads on a 9" South Bend lathe. Ken

Close! It's a Heavy 10...

Used insert tooling for the threads and still had not great finish but the die fixed it good "enough" getting smooth cutting, thats chapter two!

Originally Posted by FlyinChip

When I ran faster, the chip was getting blue and hot. BUT I was also taking a bigger bite. Not sure, but running slow and light cuts did it. The cut was still slightly ragged IIRC. Never seemed to get totally away from that tearing issue no matter the tooling or speed or depth of cut. But it got to not bad with this slow/light method. Hopefully this hybrid method will get the 304 threaded which is the main task.

I know this is an old thread. But my experience with carbide, is "blue and hot" is what you want. Run the speed fast enough that the chips are at least a straw yellow. Blue is even better. The other thing you can try, because at the high speeds you don't get much time to stop the thread before crashing into the shoulder, put the tool on the back side of the lathe and run in reverse and cut from the shoulder out. Ie, cut from left to right. use all the same 29.5 degree tricks. and keep cuts light because you may not have as much rigidity with the tool in that position.

Post 111 kind of looks like the roration direction would go to loosen the prop?
gree a nut and cotter pin would hold it.

I still say a positive rake angle and tail support make a huge difference in mild steel threading.

A job done is a good job.

there's nothing like a good spring cut in fall ! all kidding aside yes you will be surprised how much cuts on a spring cut

Originally Posted by rogertoolmaker

Change your material to 12L17 or another free machining Steel. I think you'll find the problem gone. If your requirement is 1018 go to the store and purchase a pound of lard. Mix some with low cost 30 weight oil and try again.

Roger

This is really good advice. I'm mainly a hobbyist but when I was teaching myself to do single-point threading some 25 years ago, I discovered that 1018 is not much good for threading. I was making a replacement axle insert for a Harley-Davidson sidecar and it needed to be a 5/8-18 thread. First effort with HSS and 1018 steel yielded similar result to the OP's picture.

I switched to 4140 and with the exact same setup, I made a very nice thread. I've since used 12L17 and it's also very nice.

Originally Posted by FlyinChip

Hi all, I was >>>>>>slowly<<<<<< cutting threads using HSS and had this what i call galling issue. Then I bought a Carbide 60 degree cutter and had similar issues. I went a little deeper and the tip broke off, so scratch one brand new bit. Slow speed. Not sure why this happening but I'm not very experienced.

Somehow it seems like maybe the 1018 steel part metal quality may be an issue?

Stumped!

threads galling by Chris P, on Flickr

Look at your key word.

Oh I tried a number of of speeds and tooling after that... as I posted, ended up getting close then running a die over for the final cut.

Would like to get back after this and master the real issue though

Originally Posted by FlyinChip

Oh I tried a number of of speeds and tooling after that... as I posted, ended up getting close then running a die over for the final cut.

Would like to get back after this and master the real issue though

FlyinChip with a heavy 10 you should be able to get beautiful near perfect threads with not using a die.

But a die is fine/ok because done is done and your latest threads look good.