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andy_b
12-31-2008, 05:58 PM
and it didn't involve a threading dial or breaking anything. :)

i needed to make an adapter that i had been promising my brother for about a year, and finally said, "what the heck, let's do it".

http://home.ptd.net/~hamrdog/images/threads.jpg

the object on the left is a muzzle break and i needed to make an adapter to fit the muzzle that the break came off of. since it would be a giant pain to try and test fit an entire rifle with the adapter on the lathe, i made up the handy-dandy gauge (the second item from left). the fine thread (36 tpi) is the part i did, the item was a large bolt in its prior life and the coarse threads are what's left of it.

the third item is my first attempt. again, the weird spiral is an artifact left over from the item's prior life as an even larger bolt that the previous one. :) the external threads are 24 tpi and i cut them a bit too large in diameter. by the time i found that out i had already cut the adapter off and removed it from the lathe. i didn't feel confident enough that i had it re-centered, so i made the fourth item. that one was made from some CRS i had, and i put some knurling on it just to try out my cheap knurling tool (which i had never used).

the insert in the photo is just a view of the internal threads (the 36 tpi ones). surprisingly, it wasn't too bad cutting them. i had the lathe backgear engaged and was running it pretty slow, so it was easy to stop it before anything crashed. one negative to running it that slow was i think my surface finish would have been better at a higher speed. my chances of crashing or breaking things would have also been better, so i just stayed with the slow speed.

anyway, i was happy to actually accomplish something useful over my long holiday break, and i did learn some new skills. i think once i get a threading dial it will make things go quicker since i won't have to keep stopping the lathe and then running it in reverse half the time.

thanks to everyone on the forum for the tips they post and inspiration for me to try this!!!!

andy b.

Bob Ford
12-31-2008, 06:46 PM
If I have threads to cut that are difficult I do not use the motor. Loosen the belt and turn by hand. This way it is very hard to crash.

Bob

Carld
12-31-2008, 11:03 PM
The threads look pretty good to me and if that's your first attempt at threading you did good. Your right about the thread looking better if cut at the right speed and you'll find the right speed over time. It looks like your knurl needed a harder push to make the diamonds stand up. It takes a lot of pressure to knurl some metals.

andy_b
12-31-2008, 11:55 PM
Bob,

a year or so ago i was attempting some threads (i actually made a post about it) but had the wrong tpi selected and several other problems. i tried turning the lathe by hand and decided at that time that if my only solution to cut threads was to do it by hand, then i wouldn't be cutting any threads. :) the finish was terrible and it was taking forever.

Carl,

yes, this would be my first completed thread (and second, and third and...). i'm still afraid of crashing, but i have a variable speed DC motor on the lathe, and i started on slow and ended up on fast (which was still slow :) ). i think next time i'll still keep it in backgear, but put the drive belt on the middle pulley. as for the knurling, you guys always post that you have to really ram the knurler into the work to cut the knurls. this was the first time i used it, but i definitely can see where you have to just go for it and ram the tool in there. i was being a bit gentle. i think knurling takes a knack to do, just like threading. i'll eventually get the hang of it.

andy b.

Ken_Shea
01-01-2009, 12:09 AM
Agreed, fine looking for a first, not shabby at all for that matter.
Is that black pipe ?
That does not produce that polished look that you have seen on some threading.


Ken

Your Old Dog
01-01-2009, 07:51 AM
I'm not real good at threading either and I'd be happy with those results. I made handcrank for my quill similar to what Evan made for his and I crank it by hand. It's funny how crossing the threading hurdle and being able to thread on the lathe seems to empower you as a machinist :D

HSS
01-01-2009, 08:11 AM
Looks good Andy, now turn some internal threads. I turned my first internal thread last night and it turned out good. ( or is that "turned in" good)

Pat

Carld
01-01-2009, 08:37 AM
Andy, I thread from 75 rpm to about 200 rpm depending on the lathe speeds and the material I am threading. Most the time I use 75 and 120 on my lathe at home. The best way to get good threads is to spend a lot of time threading and it's best to start on say, 12 tpi and when that works good then go to finer threads. The fine threads are the most troublesome and requires sharp tools and good skills. It helps to have a set of thread files to clean the burrs off the thread. I also use a small jewelers triangle file to clean the threads and a fine cut flat file to dress the tops of the threads.

Sometimes no matter what you do the threads don't cut real clean. When cutting a thread that will not cut clean it's best to take fine cuts and clean the thread and then try the test nut on the thread. It's real easy to go undersize when threading crappy material that won't cut clean so be carefull.

There's more hand work in threading than many will admit to on manual lathes.

Sparky_NY
01-01-2009, 11:18 AM
I used to be unhappy with the finishes I got when I threaded steel, then I learned a tip (from here I think) about using a lube.

When they thread black iron pipe they use a threading oil otherwise the threads are all galled and the die wears right out. Threading on the lathe is a very similar process to a pipe die. I already had some and tried using pipe threading oil (just a dab on each pass) and it makes a world of difference.

The oil I speak of is Rigid dark sulphur threading oil and can be got a home depot and many other places. If you know any plumbers I am sure they would give you some. It only takes a little bit, I use a flux brush to apply a little on each pass.

Carld
01-01-2009, 12:43 PM
Yep, a sulfur cutting oil is best for threading and makes nice threads. I use it all the time and not just for threads.

The Fixer
01-01-2009, 12:55 PM
Cutting oil makes a world of difference, whether u are using a carbide or hss it's a must.
al

Circlip
01-01-2009, 01:37 PM
And before you "Ram" the knurling tool into the job, either make or obtain a "Caliper" or "Clamp" type knurdling tool, they're much kinder on the spindle bearings. On threading, don't you just love it when it all comes together?

My first one was a two start 1and1/2" x 1/2"pitch square form at "Tech" 45 years ago for a comparator stand, it prooved that the thread indicator does work.

Regards Ian.