Bent thread

[HopperParticipant @hopper]

Posted by Mick B1 on 14/11/2022 10:18:39:

That die is a basket case. If it's properly-hardened HSS, it's hard to imagine how the teeth could've become so severely blunted.

+1.

[JasonBModerator @jasonb]

But if it is "severely blunt" how did it manage to cut the thread in the first post, apart from being wonky it's cut reasonably well and any tearing is possibly due to having to cut over depth on one side as it went off course.

I'm inclined to thing it is a problem with the method, Martin has had similar problems cutting threads in previous posts.

Although I don't reduce diameter and seldom chamfer an end if you put your second piece of metal back in the chuck and make the taper shallower you may get it to start, something like 20-30 degrees. Leave the tailstock loose on the bed and apply plenty of pressure with your right hand to the end of the tailstock while turning the diestock with your left,

Edited By JasonB on 14/11/2022 13:18:28

[Martin Shaw 1Participant @martinshaw1]

Right, some welcome further stuff. Apart from my technique which several of you have been kind enough to point out the correct way, I have found two other issues which at best won't help.

The adjusting screw on the die stock is badly formed at the point and the screw slot is far too shallow which rather makes it unadjustable, and more importantly I found the tailstock wasn't locking to the bed securely enough. Rotating the feed was pushing the tailstock away rather than onto the work so I've adjusted it to lock better.

I am also going to replace the die, whatever the circumstances around it there is no doubt it is poor. I will also see if I can fix the diestock or replace it. Has anyone a reputable supplier other than Drill Services, I was thinking Tracy Tools as I've had stuff from them before.

I will also look at single point threading as a separate exercise, some Youtube videos have helped explain things on that front.

Regards

Martin

Edited By Martin Shaw 1 on 14/11/2022 18:53:19

[Bill PhinnParticipant @billphinn90025]

In order not to prolong your difficulties unnecessarily, Martin, it really would be beneficial if you could directly address some of the more salient points various people have raised:

Before attempting a cut, did you open the die to its maximum internal diameter [within the limits imposed by the diestock's own ID] by driving one of the die holder's screw points into the split and leaving the other screws loose?

How has the die managed to get into such an advanced state of wear? I find it hard to believe that Drill Service sent you a worn-out die instead of a new one. I've only ever ordered two items from Drill Service but they were first class. And, as Jason says, if it was in that state when you received it from Drill Service, how did you manage to cut the cleanly cut threads you've shown us in your opening post?

It looks to me like you've been trying to cut threads with it on something either very abrasive, or very hard, or very oversize, at some point after you cut the cleanly cut threads visible in your opening post's image.

This thread is about a bent thread. Please be straight with us.

[Martin Shaw 1Participant @martinshaw1]

"Before attempting a cut, did you open the die to its maximum internal diameter [within the limits imposed by the diestock's own ID] by driving one of the die holder's screw points into the split and leaving the other screws loose?"

Yes but as I explained above I have discovered a faulty screw in the die stock.

"How has the die managed to get into such an advanced state of wear?"

I have no idea beyond something I've done wrong. The two threads in the first post were done by hand in the vice on Saturday afternoon and thereafter nothing further beyond

"It looks to me like you've been trying to cut threads with it on something either very abrasive, or very hard, or very oversize, at some point after you cut the cleanly cut threads visible in your opening post's image."

I appreciate your trying to help but this is assumption on your part, and incorrect as well.

Dave said

"From what Martin has said, he did almost everything right:

• Known metal, leaded Mild-steel, easy to machine
• Diameter of rod turned down 5% less than M10
• End of rod chamfered to help start the die
• Bought a reassuringly expensive die from a reputable supplier
• Die backed off frequently to break swarf
• Undercut at the shoulder
• Cutting oil applied"

I believe I did as well, that it hasn't turned out is what is being explored and I think a combination of useful posts has pointed me in the direction to take. My post immediately before yours detailed my further actions and having done them I will let everyone know the outcome.

"Please be straight with us." I very much have been and the other useful posts in return would suggest so, I'm sorry if I didn't explain things adequately enough for you.

Kind regards

Martin

[Bill PhinnParticipant @billphinn90025]

Posted by Martin Shaw 1 on 14/11/2022 21:20:22:

"Before attempting a cut, did you open the die to its maximum internal diameter [within the limits imposed by the diestock's own ID] by driving one of the die holder's screw points into the split and leaving the other screws loose?"

Yes but as I explained above I have discovered a faulty screw in the die stock.

So quite possibly the split remained closed while you cut the two threads you say are the only threads you've cut with that die from new.

Posted by Martin Shaw 1 on 14/11/2022 21:20:22:

"It looks to me like you've been trying to cut threads with it on something either very abrasive, or very hard, or very oversize, at some point after you cut the cleanly cut threads visible in your opening post's image."

I appreciate your trying to help but this is assumption on your part, and incorrect as well.

Assumption can be perfectly logical and excusable when an adequate explanation for some event [in this case a very worn die after only two cuts in mild steel] isn't forthcoming.

[HopperParticipant @hopper]

Tracy Tools taps and dies have been good when I ordered them in the past.

 

 

Edited By Hopper on 15/11/2022 04:11:49

[JasonBModerator @jasonb]

last few Dies I have bought have been from ARC but their M10 needs a 30mm holder so you may not want to spend out on both. And that will also open up the unsplit die debate.

Also bought a few metric ones from Rotagrip made by Volkel not their cheaper offerings.

Dormer from MSC is another option but quite spendy and again at least 90% of Dormer dies are solid like many makes these days.

[not done it yetParticipant @notdoneityet]

It can be a pain to set up for single pointing a short thread on a hobby lathe. I find it a pain, as invariably (well quite often) I need metric when set up for imperial or vice versa. But the advantages of concentricity and parallelism, plus the savings on wear and tear on (relatively expensive) dies makes it worthwhile. A QCGB does help, mind – as reverting to a normal cutting feed-rate is easy.

[HopperParticipant @hopper]

Posted by not done it yet on 15/11/2022 09:09:46:

It can be a pain to set up for single pointing a short thread on a hobby lathe. I find it a pain, as invariably (well quite often) I need metric when set up for imperial or vice versa. But the advantages of concentricity and parallelism, plus the savings on wear and tear on (relatively expensive) dies makes it worthwhile. A QCGB does help, mind – as reverting to a normal cutting feed-rate is easy.

Agreed, but hardly seems worth it for a 10mm thread though. Ordinarily you can whizz it on nice and straight and clean with a die and be done with it. I rarely bother with screwcutting unless it is something special or diameter over 1/2" (13mm) or so. But I have boxes of good old HSS dies and taps scavenged up over the years at rummage sales etc so no worry about wearing them out. And you can always sharpen them with a Dremel grinder.

Making a hand-crank for the lathe spindle for threading was about the best thing I ever did. Close second would be the tailstock die holder set and spring centre tap guide I made. You can just whip threads up in no time with no struggling with dieholder handles and spinning the chuck by hand etc etc.

[Nigel McBurney 1Participant @nigelmcburney1]

Reading all the comments, It appears that the workholder er collet is very good,these collets grip and dont slip if tightened to spec, the material ie 1a leaded should produce good threads easily without the need for specialised lubricants ,the commercial die holder looks ok though I would prefer the type where the body holds the die firmly,i am not keen on separate inserts. the 45 degree lead is ok on this material a 30 degree is preferable on tougher materials. I think the problem is a rubbish die,it may be marked hss but its the manufacture thats the problem.Get a good ground thread hss die from a known manufacturer and the problem will disappear. Cutting a thread by hand with the work in a vice is difficult and takes a lot of practice and is to be avoided. Holding the die in the tailstock is the easiast method to cut a thread for the amature modeler, modern commercial tallstock holders are a bit too complicated and cost a lot of cash. During my training I spent a lot of time on a Boxford, the commercial tailstock die holder was simple, short length of 1/2 inch dia rod,possibly hardened to reduce wear was held in the tailstock chuck,the die holder about 4 ins long just slid onto the rod,no key ways or any method to prevent rotation, it had a heavy knurl along most of its length and a cross hole for a tommy bar , the die was held and adjusted by the usual 3 pointed screws. In use BA threads were cut with the lathe running and the holder gripped in the hand and pushed towards the work,when a shoulder was reached you just relaxed your grip on the dolder and then spun it off by hand ,on larger threads the tommy bar was used with the lathe spindle stationary. This type of holder can be home made using either mild steel or aluminium for the body and silver steel for the rod thatgoes in the tailstock chuck,no need to make morse taper shafts. I have a lot of these home made holders which cost nothing ,the largest holding 3/4 bsp as I thread water pipe when restoring full size stationary engines,I thread under power using a decent sized tommy bar which is prevented from turning by a steel bar held in the toolpost,Dont use the lathe bed.When I started my engineering work over 60 years ago ,there was never any problem with either carbon cut thread or hss taps and dies,though in the last 30 years i have sent a die and a number of taps back to suppliers as they would just not cut ,with duff taps some just start cutting and then just jam solid.Nowadays I rarely need taps or dies but if I do have to buy one I bite the bullet and pay a lot extra for ground thread HSS. A comment was made about why does a toolpost stud need to be relatively precise,well the nut needs to be square to the axis of the stud in order to maintain a firm grip. How would I do this stud,both my lathes have imperial lead srews so I would use a die , if it was imperial over say 1/2 inch i would screwcut with a chaser.

I only use die holder and vice for jobs like extending the thread on coachbolts or cleaning up damaged threads, I have a WD set of whit taps and dies 1/2 to 1 inch whit made in 1940 and typical goverment,no expense spared,solid metal case with hard timber insert in army green, a polished all over sliding block tap wrench and a die holder which has separate iserts to hold the dies,so the dies can be set to size and the setting held,each die holder has a built in guide to keep the thread square ,though it would take a strong soldier to cut one inch Whit threads ,it cost me £40 and I think the tap wrench alone was worth that as that is the most used part of the set.

[Mike HurleyParticipant @mikehurley60381]

Posted by Hopper on 15/11/2022 09:49:59:

Making a hand-crank for the lathe spindle for threading was about the best thing I ever did. Close second would be the tailstock die holder set and spring centre tap guide I made. You can just whip threads up in no time with no struggling with dieholder handles and spinning the chuck by hand etc etc.

+1 for that!

[Mick B1Participant @mickb1]

Posted by Martin Shaw 1 on 14/11/2022 18:52:42:

…

The adjusting screw on the die stock is badly formed at the point and the screw slot is far too shallow which rather makes it unadjustable, and more importantly I found the tailstock wasn't locking to the bed securely enough. Rotating the feed was pushing the tailstock away rather than onto the work so I've adjusted it to lock better.

I am also going to replace the die, whatever the circumstances around it there is no doubt it is poor. I will also see if I can fix the diestock or replace it. Has anyone a reputable supplier other than Drill Services, I was thinking Tracy Tools as I've had stuff from them before.

Martin

The central screw for opening the die-split is often quite unsuitable – a dog-point is generally useless unless the split has an especially wide vee. Sometimes I've made a new one from a capscrew with a little tommy-bar through its head and a turned 40 – odd degree incl. vee point. This'll open up the die till it's hard against the holder's I/D, but it'll also put a lot of stress on the tapped thread in the mazak holder – remains to be seen how long that'll last.

Cheap(-ish) sets of very adequate metric taps and dies in some stuff they call 'tungsten steel' are available from Machine Mart. They work well enough for everything I routinely do and I only need to buy a new set every couple of decades, and that's usually cos of broken taps in difficult materials rather than worn-out dies.

[Anonymous]

Posted by Martin Shaw 1 on 14/11/2022 18:52:42:

…thinking Tracy Tools as I've had stuff from them before.

Personally I no longer buy from Tracy Tools. I got so frustrated with the last set of taps and die that I widlarised them:

Andrew

[Mick B1Participant @mickb1]

Posted by Mick B1 on 15/11/2022 12:13:17:

Posted by Martin Shaw 1 on 14/11/2022 18:52:42:

…

…

Cheap(-ish) sets of very adequate metric taps and dies in some stuff they call 'tungsten steel' are available from Machine Mart. They work well enough for everything I routinely do and I only need to buy a new set every couple of decades, and that's usually cos of broken taps in difficult materials rather than worn-out dies.

The set I meant from Machine Mart is CHT303. The diestock centre screw has the usual fault, and for blind or shouldered holes you may want to grind the points off some of the taps – carefully, they obviously don't dare to call their tungsten steel 'HSS', so you don't wanna get it too hot. But they've served me well for 90-odd% of what I've done this millenium…

[Nick WheelerParticipant @nickwheeler]

Posted by Mick B1 on 15/11/2022 13:33:50:

Posted by Mick B1 on 15/11/2022 12:13:17:

Posted by Martin Shaw 1 on 14/11/2022 18:52:42:

…

…

Cheap(-ish) sets of very adequate metric taps and dies in some stuff they call 'tungsten steel' are available from Machine Mart. They work well enough for everything I routinely do and I only need to buy a new set every couple of decades, and that's usually cos of broken taps in difficult materials rather than worn-out dies.

The set I meant from Machine Mart is CHT303. The diestock centre screw has the usual fault, and for blind or shouldered holes you may want to grind the points off some of the taps – carefully, they obviously don't dare to call their tungsten steel 'HSS', so you don't wanna get it too hot. But they've served me well for 90-odd% of what I've done this millenium…

Mine is the same. And the M10x1.5 has done a lot of work, both in the lathe and vice, in brass, steel and aluminium.

[Bill PhinnParticipant @billphinn90025]

Posted by Mick B1 on 15/11/2022 12:13:17:

The central screw for opening the die-split is often quite unsuitable – a dog-point is generally useless unless the split has an especially wide vee.

The central screw on most of the newly bought, economically-priced three-screw die holders I've got were originally cone points rather than dog points. Sadly, these screws are generally too soft to do the work of opening the split of a split die; they typically get mulched after a few uses. I replaced them early on with Grade 14.9 cone point socket set screws. These are up to the job.

By way of contrast, the secondhand Dormer and Toga die holders I've got had much tougher cone point screws when I acquired them. These didn't need upgrading.

So I do sympathize with this aspect of Martin's problems.

[Martin Shaw 1Participant @martinshaw1]

Todays update, I have bought a new 1" Volkel die from Rotagrip and a new, reputedly drop forged steel, Volkel die stock from another supplier. This is possibly over the top, it certainly wasn't cheap, for what I'm trying to achieve, but I can't see any point in persevering with probably damaged die and stock. It was approaching the point where the workshop wall was going to get dented. I'll see what happens when the new bits arrive, I now have a far better understanding than I did three days ago, thanks all.

Regards

Martin

[jimmy bParticipant @jimmyb]

Martin,

The cost soon be forgotten on quality items.

Looking forward to a further update when the tools arrive.

Jim

[Martin Shaw 1Participant @martinshaw1]

This all ground to a halt after my last post. New dies were ordered from Rotagrip and despatched which was the last anyone has seen them, lost in a Royal Mail office somewhere. Obviously new ones weren't going to be sent until the claim period had expired and this coincided with the coldest spell since I've lived in this house. I could warm the attic workshop with warm air from below and turning the radiator upto full, the fuel bill didn't want to be thought about. As it was the replacement dies arrived on Saturday, meanwhile I had ordered various new threading equipment and consumables, I think I may have had a blind spot here as nothing of threading bits was really up to scratch, a decent set of BA taps and dies is due to be bought in the new year.

Having collected all the bits together a new stud blank was turned and duly offered up to the new die and with a prayer to Mr Whitworth, a thread was cut which joy of joys was perfect first time. Encouraged I turned it round and did the other end with the same success. I was so taken aback at the apparent ease that I did wonder why the last attempt was so abysmal, partly my technique which has undoubtedly benefited from the advice here but also I think the die especially was just plain faulty. Certainly Herr Volkel's products seem to work as you would expect and whilst perhaps more expensive than alternatives worth it for the lack of drama. Decent clean threads and not bent.

This all ties in with my oversize facemill thread to produce this, a fixed toolpost for a Multifix aa. It's not been without it's stresses but ultimately a nicely finished end result that works, can't say fairer than that.

Happy Christmas to you

Martin

 

Edited By Martin Shaw 1 on 20/12/2022 15:43:42

[Michael GilliganParticipant @michaelgilligan61133]

What an excellent result, Martin

… must have boosted your self-esteem enormously.

MichaelG.

[Tony Pratt 1Participant @tonypratt1]

Good job, decent tools make all the difference!

Tony

[JasonBModerator @jasonb]

Thanks for the update martin, good to know my suggestion of Volkel worked out for you (and the facemill too)

[jimmy bParticipant @jimmyb]

The quality remains long after the price is forgotten.

Jim

[File HandleParticipant @filehandle]

Most of my (tap) die holders are old ones that I have aquired secondhand, they are much better than any I have bought new. Years ago I used a water pipe thread cutter (a bit like a Coventry diehead). this had 3 pins that you forced in to centre the pipe (and lock in place). It was heavy being turned by a 2' /3' handle. I have often wondered why noone makes a die holder with a similar guide. This would be 40 years ago now (at least), I think it was an old piece of kit then. It took a bit of setting up, but did a good job.

[Author]

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