Threading stainless.

[NeoTech]

Well gonna start off and say im terribad at threading. (see previous thread about lathe setup).

Well now i hade som stainless.. I tried to thread it.. it broke my carbide tips.. and it broke my HSS tool..
Im guessing god didnt want stainless steel threaded from the begining. ;)

Well i resharpen my hss (the good thing with hss tools) and i went at it again.. took lighter cuts (0.02mm)
and well.. chipped again.. thats some hard stuff right there.. And well threading 0.02mm at a time.. that will
take frickin forever.. so i figure.. there must be trick to it!. =)

And yeah i threaded a piece of aluminium and it worked after i knocked of the tops of the thread so it didnt jam
in the nut. ;)

[Pete.]

Grind up an ACME thread tool - you won't break the tip off that!

[DaveH]

NeoTech,

Any idea of the type of stainless - 303, 316 ???  Also the size of the bar and the thread.

Some types are easier than others 
 
DaveH

[NeoTech]

No idea.. its mysterious stainless.. its kinda gummy actually.. a 12mm rod i have alot of.. i turned it to 9.8 so i could thread a M10/1.5 on it.
But well turning metric so i never disengage the halfnut. so when "turning off" and i back off it has more or less welded to the rod and when
i back off i hear "click" and the tip is off.. so annoying..

And Pete, the weirdo homemade tool you sent me, is AAawsome turning stainless with.. 1.5mm at each pass easy and i can go fast.
But well yeah the threading bit is ruined then. *whistling* gonna have to learn to make threading tools myself ;D

[DaveH]

NeoTech,

You will have to use lots of cutting fluid.
To stop the tips breaking the tip has to be fully withdrawn from the work piece before it stops.

Perhaps the best way would be to turn (set) the top (compound) slide to 29deg and screw cut it that way - if you are not already doing that way.
 
DaveH


 

[NeoTech]

Well im not sure.. my compound when set to zero is parallell to the work. (the turning handle is pointing to the right). And then its degreed 60 degree either way.
So i figured i just set it to 60 degrees case if i set it to 29.5 i just cut one side of a V thread.. it get flat on side. (yeap tried it, didnt work).

But, hmm backing off before.. I need an extra arm or.. 2..  but it makes sense.. thats probably where it fails..

[andyf]

You need to set it at 60.5 degrees to the lathe bed, Neotech. That's 29.5 degrees away from perpendicular. Then, the leading edge of the tool does almost all the work, with the other side taking just a slight shaving off that flank of the thread to clean it up so it doesn't get tiny steps cut down it.

And it helps to turn a run-out groove round the work where the thread is going to end, before you start threading. Then, you can stop with the tool in clear air.

It looks like you have chosen some pretty hard stainless steel, though.

Andy

[NeoTech]

Yeah in retrospect it was a really bad choice of material to try with.. i have some mildsteel but its even worse, dont get a clean cut it looks all teared up. Funny enough it worked on aluminium. 

[BillTodd]

A little extra speed usually helps with stainless (especially if using carbide) . You'll have to get quick with the cross-slide handle (or buy a hardinge ;))

I always thread with the top-slide set at just under 30°

Imagine the /\ of the thread extending out wards - the top slide should point/feed  in the direction it is cutting at the angle of the /\ 

 \ for RH external and LH internal
/ for LH external and RH internal

Sharp tools and the right cutting fluid help.

[Pete.]

And Pete, the weirdo homemade tool you sent me, is AAawsome turning stainless with.. 1.5mm at each pass easy and i can go fast.

It should be - it's Deloro Stellite 100. I was down to my last few stubs (hence the weirdo tool) but then I found a load of it at a local place.

In case anyone is wondering, the 'weirdo tool' is 20mm of stellite brazed tangentially to a piece of mild steel. It's awesome for holding it's edge - kinda half-way between HSS and carbide.

[NeoTech]

Yeah, thats something you should do a tutorial on how you made and grinded.. it would prob. help a few others as well.. i use it for all my hogging now a days..  havent figured out how to sharpen it though without messing it upp.. so i just let it be atm ;D

[nel2lar]

NeoTech
Threading is not that difficult, there just a few things you must remember. First, new to threading you need to start one a soft metal and practice. When starting you need to set your compound to 29.5 degrees and set the cutting tool parallel to the work. Next thing bring the tool up to the point it touches the material (metal) at this point set your cross slide to "0". You must turn your carriage out at the end of your thread. If you do not have a thread gauge which indicates the position to start your thread. The better way is to #1 back the carriage off and turn the lathe off never disengage the half nuts then reverse your tool past the starting point. Stop the lathe now is the time that required concentration for the carriage must be dialed back to "0" then advance the compound a couple of thousands then start lathe in forward. This is the process for threading repeat the step from #1 advancing the compound only until your thread is finished. If the diameter is small you might want to use a follow rest. Also when threading chuck up as close leaving out no more than you need. If the thread is long you will need both a follow rest and a tail stock with a center.
I hope this will help and not add more question.
Nelson Collar



May the Lord Direct Your Steps
"When injustice becomes law - resistance becomes duty."

[NeoTech]

hehe only one.. i have a dial chaser..  for turning threads.. but i cant figure out how u use it for metric threads.. =)

[andyf]

hehe only one.. i have a dial chaser..  for turning threads.. but i cant figure out how u use it for metric threads.. =)

You can't. If you have an inch leadscrew, the threading dial won't work for metric threads, and vice versa.

You have to keep the half nuts engaged thoughout, and reverse the motor to run the tool back ready for the next pass. Cumulative backlash between spindle and leadscrew usually means the tool will widen the groove by cutting on the other flank as it returns, unless you withdraw it before reversing.

Andy

[NeoTech]

yeah i guess thats problem, i dont know what type of leadscrew its is on my machne.. i havent figured that one out yet. =)

[nel2lar]

NeoTech
If you have a dial indicator, you will have the info you need to determine metric or inch. Set the DI and turn the crank one turn ( mark spindle and turn one rev ).
Nelson Collar



 
You can't escape the responsibility of tomorrow by evading it today. May the Lord Direct Your Steps
"When injustice becomes law - resistance becomes duty."

[NeoTech]

Uhm oki, if i did this right im guessing its a metric screw in this machine.

So i guess i should be able to use the chase dial when cutting threads.. But not really sure how. (god i hate this machine manual).

[AdeV]

This video might help?

Basically, the thread dial rotates at a certain ratio to the leadscrew; threfeore, so long as you always engage the drive at the same point (when one of the numbers passes the marker), the tool will follow the same path as on previous goes, so you cut one deep thread instead of lots of shallow ones.

Exactly how your thread dial works will depend on your lathe. I'm lucky - mine works on both metric and imperial as I can cut both threads straight from the gearbox, but TBH my experience of single-point threading is similar to yours (broken tips), so I'm lazy and tend to use taps & dies these days.

[Darren]

Since I made a swing tool I've not looked back, small threads, large ones, it does them all with ease

[NeoTech]

Ah ok, yeah my lathe can turn both metric and imperial according to the gearbox. (have been pondering about that). And the chase dial can be attached with different "teeth" speeds i guess it is. I have just set it at 36 and havent bother anymore after that.. I thread with engage and backing off with it engaged atm. but it would be faster when doing large/long pieces (which i will be needing to in the future) to be able to run it with the dial.. But its a learning process.. i just need to figure it out. =)


A swing tool you say.. i saw something about that on hemingway... wondered what it was for actually. =)

[AdeV]

You can work out how well the thread dial works in various pitches fairly easily; chuck up some scrap material & turn it so it's turning true; then set a very light cut (0.001-0.002", 0.02-.004mm), get everything turning, then engage the half nuts as the thread dial indication "1" touches the marker (you don't have to be nanometer accurate, the nut will engage only when the dial is in the right place, unless you're way off).

Turn a short spiral, then back the tool out & disengage the half nut. back the carriage away from the work, feed the tool back in to the same depth as before, wait for the thread dial "1" to come around again, and repeat. You should find the tool following the same spiral. If it does, try again, but engage on the "2", "3" and "4" of the thread dial. Again, it should always follow the same spiral; or maybe you'll end up with 2 spirals (one for odds, one for evens). If you get the 1 spiral, try again on the 1/2 marks.

Now turn the spirals away so you've got clean stock again, change from metric to imperial (or vice versa), and repeat the exercise. If you get random spirals each time, then you can't use the thread dial in whatever range your lathe is set to. It's also worth trying on a few thread pitches, to make sure it behaves the same way no matter what.

I ought to try that myself tbh, I've never actually done it on my lathe...

[Darren]

Here you go ... a swing threading tool .... made a while ago and used quite often ...

http://madmodder.net/index.php/topic,2462.msg25986.html#msg25986

[Fergus OMore]

I think that someone should do a bit of explaining about this 'Swing Tool' business.

Actually it was a 'patent applied for' situation by the late Kenneth C Hart or as he was known in most circles under his his pen name of Martin Cleeve.

As far as I can gather Cleeve could not afford to continue  the financing of the swing tool and the application lapsed. Nevertheless, he continued to develop the tool and several modified tool holders were published in 'Model Engineer' and finally in 'Engineering in Miniature'.

At present, there is a write up and drawings in his 'Screwcutting in the Lathe' and Hemingwaykits is selling a variant which is from castings rather than the fabricated constructions which Cleeve described.

For those who want to follow the principle, there is still a set of old drawings on the net in Popular Mechanics.

Perhaps it worth adding that Cleeve also published a simple jig to sharpen screwcutting tools in his excellent but sadly posthumous book.

[NeoTech]

Ahh cool there is some history.. As a swede... This hobby isnt that spread out.. and as somewhat.. "young" guy.. i have no clue of what you just talked about. im guessing some paper and a couple of books i could google down? =)

[andyf]

There seems to be some confusion arising here between Martin Cleeve's Retracting Toolholder (which requires a lever to be pulled to withdraw the tool from the work) and the Swing-Up Toolholder design shown on this forum a year or so back (which doesn't).

The Swing-up is very simple to make; Cleeve's is more complicated.

Andy