I feel embarrased asking this - but I'm struggling to cut a 8mm thread with a die - I get it started then after about 3/4 of a turn it strips - what am I doing wrong? - using MS rod about 7.8 mm diameter.

I am starting the thread then backing off slightly then cutting about 1/10th of a turn then backing off etc.

When I've cut threads, I normally have a bit of pressure on the die at the start so that it takes to the rod there after I let the die pull itself.

The other thing, I normally do 1.5 - 2 turns before backing off at the start.

One final thing, if the die is blunt, it can also have the effect of chewing the rod.

Hope this helps.

Cheers

Ian

don't take this the wrong way, but you haven't got the die upside down have you? most a a leading face.

Use some cutting fluid or oil to lubricate the die and rod.

You also need to make sure the die goes onto the rod squarely.

Its hard work, but you'll get there. Give it a bit of welly

David

good luck - I 've tried and it is very difficult to get a square thread. Depending on what it is you want it to screw into or hold together, that may be acceptable.

To start it off, put the rod in a drill press and file a conical end - you can always cut that end off afterwards, unless you have cut the rod to length.

the way to guarantee a squrre thred is to use a lathe.

As nib1980 says - make sure the die is the right way up. There should be writing on one face of the die; in most cases this should go towards the rod.

It helps to have a little bit of a chamfer at the end of the rod (just 1mm or so) to get the die started.

I was taught to do 1/4 turn, then back until it clicks (when the swarf is broken off), then another 1/4 turn, etc.

Try as hard as you can to keep the die totally level for the first few turns, with a steady downward pressure to help it start cutting. On 7.8mm rod you shouldn't have to try too hard.

Just make sure that you're not doing the dumb trick I once did - I just couldn't get a thread started once... until I found that I'd picked up a left-hand threaded die!

HTH,
David

Have you got the stock set right? For the first cut you need to tighten the middle screw first to spread the die. Then on the second pass, unscrew the middle one, tighten the outer two.

quote:

---

Originally posted by owelly
Have you got the stock set right? For the first cut you need to tighten the middle screw first to spread the die. Then on the second pass, unscrew the middle one, tighten the outer two.

---

Hi All - thanks for the advice - eventualy got it right by turning the first 7mm down .5mm that got it started properly - unfortunately my die isn't split so can't set penetration so after all the hastle find the thread is too tight on the nuts - will have to buy a split die

Must learn how to cut threads on a lathe some time, although I think my gearbox is Imperial so not sure if you can cut metric threads.

quote:

---

Originally posted by owelly
Have you got the stock set right? For the first cut you need to tighten the middle screw first to spread the die

---

I don't bother to use the feeds to cut small threads on my lathe - I just use the nose of the tailstock to hold the die stock in line, and turn everything by hand. I either rotate the die-stock, or pull the chuck round, while GENTLY feeding in the tailstock, just enough to keep things straight.

Well worth putting the lathe out of gear, or ensuring that the mains is completely off (pull the plug out) before trying this!

When cutting threads on a lathe using a die I don't feed the tailstock, just push it along by hand keeping a steady pressure towards the headstock while turning the chuck by hand.
Otherwise there is a chance of cutting a thread which has a compound pitch of the die and tailstock threads.

HTH

If I'm using the lathe, I hold the the die stock in the four jaw and the bar in a chuck in the tailstock and just leave the tailstock free to travel, lowest speed and bob's your uncle!!

Tapping: hold the job in the chuck, revolving centre in the tailstock. Hold the tap against the job with the tailstock and use a spanner to stop the tap rotating, lowest speed and go for it.

To cut metric threads on an imperial machine you need a 127 tooth change wheel in the gear train somewhere.

Regards
Davie


[Edited on 22/5/07 by daviep]

quote:

---

Originally posted by trikerneil
Otherwise there is a chance of cutting a thread which has a compound pitch of the die and tailstock threads.

HTH

---

Most of the time at least up to M6 threads

I lock the die in my small vice, and put e rod in a small battery power hand drilling machien (whatsitcalledagain?) and then run the drill slowly using a little presure and when it grips let the die pull the rod through.

I've never tried doing thet on M8 but suppose that would work also,

only the the rod is not connected to for instance..... euhm the car? would take a serious drilling machine and strong arm to pulle that of

grtz thomas

All good advice and tips.

However the best advice I can give is design so you do not have to cut male threads! Home cut male threads are generally awful, they are full of stress raisers and the material not really strong (otherwise you wouldnt be able to cut it)

If I need a male thread I will buy a stud (or bolt) and use that into a tapped hole using 638 Loctite to hold it in.

If it was a threaded adjuster (ARB drop link for eg) I would use tube with welded in tapped threaded inserts.

John

If its not a split die, its the wrong one for the job! If its a 'die nut' then these should only be used to clean up threads that are already cut.

As mentioned before as to how to use one, you should be using a split button die.

Tried to buy a split die at my local Nut & Bolt shop on Friday - don't have in 8mm.

Anyway have subsequently found that running the tap that came with the die set I used through the female part I was using sorted the problem.

Obviously I have an an off-standard set.