HTS Bolts

[John CParticipant @johnc47954]

I needed a couple of holding down bolts and thought I would turn down the heads of HTS bolts to fit the T slolts, and then part off to length.  Turning the heads was no problem (nice and thin, so they go before the cross slide – thanks Meyrick) but the parting off was a different matter.  I assume that the shafts are hardened but the heads are soft, although I thought that an indexed carbide tool should still be able to cut the shafts.

 

I decided to anneal the shafts and had them to red heat for a few minutes each. The ‘1 hour per inch of diameter’ rule definitely applies, as they were still very hard!  One thought I had was the effect on me of the zinc coating burning off, but a quick look on t’interweb indicated that my fears of poisoning were groundless.

 

So they’ve been in the woodburner stove all night – I shall see what the results are later.

 

Any thoughts or points on machining HTS bolts?

 

Thanks,

John

[John CParticipant @johnc47954]

[KWILParticipant @kwil]

It is not clear whether you intend to shape the heads to fit the T slots? Why use HTS for this job? 

I have previously use HTS bolts to provide spindle material for a Quorn and Quick Step Mill, turning it with normal idexable insert tooling without undue difficulty.

Edited By KWIL on 31/12/2009 10:32:42

[John CParticipant @johnc47954]

I used HTS because they happened to be on the shelf!  The bolt heads, once thinned, fitted the T slots although with less bearing surface than a non-hexagonal head would have. 

Edited By John Corden on 31/12/2009 10:49:58

[KWILParticipant @kwil]

I am very careful about what I use in the T slot, I prefer the proper t-nuts because I have seen the damage done by others to the underside of the  “T”  by too small a bearing area.

[John CParticipant @johnc47954]

Yes – very good point.  A future project is to make a stock of T nuts and T bars. Perhaps I should do that sooner rather than later!

John

[CirclipParticipant @circlip]

8.8 HTS bolts are ideal for making crank shafts and the like for our toy engines, but as Kwil has stated, not a good idea for tee bolt conversion. If left un-annealed, you stand a good chance of breaking the lips of the tee-slot off and if annealed, why didn’t you use M/S??

 

  Made some Tee-nuts for mine using a tough square section bar the A/F size slightly GREATER than the slot max width and turned a spigot of a diameter equal to the min slot width. Drill and tap to suit and use studs. For same sized bolts I turn the spigot to whatever length required and thread the end. You can then file the heads to a smooth fit on the width.

 

  The Head should Always fill the tee slot.

 

  Regards  Ian

[Alan Worland 1Participant @alanworland1]

I use similar ‘T’ nuts to Circlip and use long bolts where I can, the bolt is wound through the T nut until the bolt end touches the base of the slot, jacking the nut up which secures it in place and thus stops it/them moving around – which I find they always do at the wrong moment!

[KWILParticipant @kwil]

I know a lathe supplier who observed to me, if people use non OEM T-nuts, I end up selling them a new T slotted …..  The moral being, they must fit properly and be of the right size, Circlips got it right .

 

The use of a nut + washer to pull up the T-nut squarely is perhaps a better way of ensuring that the undersides remain in place and the T-nut+bolt combination does not slide about

[david pilkington 1Participant @davidpilkington1]

Tee Nuts should NEVER have thro hol;es, as there will be a risk of breaking the CI tee slot in the bed, if the nut on the bolt becomes bound or tight and the tightening is then in the tee nut.and so jacking it back up and breaking the bed of the machine

[Alan Worland 1Participant @alanworland1]

Good point, but I think a bit of common sense helps? I have never had probs

[CirclipParticipant @circlip]

DP1, “Studs” have a plain part between the threads, so you can only screw into the head as far as the thread will let you, – make em shorter and you don’t NEED any common.

 

  Regards  Ian.

[mgjParticipant @mgj]

I agree with Kwil Circlip and others. I think the practice of pushing a bolt through a tee nut to lock on the bottom of a groove is unwise.

 

I bought  – I think they are Zenit items – 12mm threaded teenuts (which are soft). I got 10 for 86p plus vat.

 

I bought a whole load of studding, but even studding is medium tensile. I cut lengths of studding and then screwed them into the tee nuts and ring welded.

 

Any tee nuts I make I make out of soft MS, and as KWIL suggests, I always make them a good size to fil the slot and give max bearing area. Not too tight because they can stick on swarf, but sensibly full.

 

Of course, it doesn’t matter if you are clamping a vice down, because such a joint puts the bed in compression, but one wants to be a bit less than ham fisted if one is not pulling against a flange and the table is in tension.

[Tony Pratt 1Participant @tonypratt1]

Hi John, pushing a bolt through the tee nut is indeed unwise, if the stud is damaged on the threaded portion which your clamping nut is on [a lot are], when you tighten up,the stud will try to jack the tee nut higher in the slot rather than clamping the job.

In many years of commercial machining I can’t recall ever using high tensile studs or bolts. If you are applying enough force on one clamping location to need high tensile studs etc. you will be seriously compromising the tee slot itself. I have always found the more clamps you can apply the better.

 

Happy new  year to you all,

 

Tony

[CirclipParticipant @circlip]

Well Tony on a purely personal note, nowt wrong with using HTS studs cos they don’t stretch and distort like M/S, far more impotant is teaching the uninstructed to clamp PROPERLY. Bolts to the FRONT of the clamp slots, Know what I mean??

 

         Regards  Ian.

Edited By Circlip on 01/01/2010 00:34:15

[mgjParticipant @mgj]

And only ever 3 clamps – like 3 legged stool as opposed to a 4 legged table. 3 clamps won’t rock.

 

Going back to  the original question – how to machine HT. reasonably slowly, not too much rake, lots of coolant and tailstock support (the latter especially when parting off, because it quite often pops up towards the end of the cut, rahter than dropping off as it should – helpfully that just chips the tip off the tool.

[John CParticipant @johnc47954]

Happy New Year one and all.  Thanks for all the replies!  I must now confess – the only reason I was using HTS was because I picked up the first bolts I came to to off the shelf, and only after the failed cutting attempts did I see they were HTS.  So – I shan’t be doing that again!!

 Incidentally, putting them in the fire all night had the desired effect, but too much so – they had the properities of sticks of lead!  I shan’t be tempering them as the correct option – i.e. do it right in the first place – has now become the quickest and easiest.  Here endeth the lesson.

 

John

[Tony Pratt 1Participant @tonypratt1]

Hi Ian, nothing wrong at all with using HTS bolts, as you say mild steel does tend to stretch a tad ! I know exactly what you mean about clamping correctly, it’s easy to do the wrong thing if not shown the correct way. I have also seen plenty of so called skilled men create some appalling lash ups, but that’s another story.

 

Tony

[Frank DolmanParticipant @frankdolman72357]

       Well, Meyrick I was not surprised by your reply to my question about

   torque on clamp bolts under the ‘table cover’ thread.  It all seemed

   sensible but now we have a couple of contributors saying that MS bolts

   stretch too much!  Even baby 1/4″ bolts would need fair old torque to

   stretch enough to affect their clamping surely?

        Are these contributors perhaps some of the sailors the Admiralty

   found stripping anything under 1/2″ Whit?

[Tony Pratt 1Participant @tonypratt1]

Hi Frank, I don’t believe any one said that MS bolts “stretch too much”. From my old college days I think I am right in saying that any bolt will stretch when put under load, MS more than HTS for the same load, they will return to their original length once the load is removed unless they have been taken past their elastic limit. I await the definitive answer on this one as it’s been a fair few years[too many] since I was an apprentice.

Tony

[Nicholas FarrParticipant @nicholasfarr14254]

All bolts should streach a tad during thier application, all be it by a few microns. This is how they work. You can imagin them as solid springs, but as with springs they all have different tensile strengths. When springs are streched beyond thier design limit, that is thier yield stress, they will not return to the original length. The same is true with bolts. HTS bolts will streach less than soft bolts, but will have a much higher yield stress. I would not recommend any HTS bolt higher 8.8 to be used in T slots as the yield stress of 8.8 bolts and above would probably be above that of the T slot. A grade of 4.6 would probably suffice in most cases, where as soft MS bolts do seem to keep on streaching and the threads distort with continued use. I also agree that using bolt heads in T slots is asking for trouble as well as allowing studs to protrode through T nuts. Nick

[mgjParticipant @mgj]

Don’t matter if you have mild nuts.You’ll strip the thread out of most ordinary nuts long before you get to yield on HT.  Yield on mild is about 12 tons. Yield on hT – depending on the HT, 50-100% more.

 

I always thought the elongation would be about the same before yield, its just the load per unit area (stress) to achieve that elongation is  greater. 

 

ie the elongation (strain) is the same (similar – except in specialist steels) but Poissons Ratio is greater, as is the strain energy? Still I could have it wrong.

 

I think people are confusing distortion after yield with strain before?

Edited By meyrick griffith-jones on 01/01/2010 14:00:35

[Nicholas FarrParticipant @nicholasfarr14254]

Hi Meyrick, your theories may be correct (never could get my head round all of the bolt science) but I have been using nuts and bolts of all sorts of sizes tensile strenths materials etc. in industry for over 40 years and in my experience I have found that softer bolts using the same torque settings as higher tensile bolts streach and thin on thier shanks more before they creep, fracture or become useless. The point I was trying to make is that it is better to use softer bolts on T slots rather than HT bolts. As most people have not had the experianceof the damage HT bolts can do when not used properly and a lot of people use tubes etc. on thier spanners to try and get it tighter. Remember a bolt/stud has to streach within its yield limit to work properly. I believe it has already been said that it is better to use as many claps as possible and practical rather than one or two very or overly tight ones. Nick.

[KWILParticipant @kwil]

Use a CORRECTLY SIZED ring or combination spanner, use your fingers and NOT your hand to tighten, that should be about right. NEVER use a socket and bar, that is staring disaster in the face

[mgjParticipant @mgj]

Agreed Nick – thats what Poissons Ratio says, but once the shank has started to thin etc you are past yield, and springs and elasticity no longer apply.

 

Poissons Ratio  = Stress/strain. 

 

Where stress is load per unit area.

 

Strain is change in dimension by original dimension  (delta L /L)

 

Strain is also Stress/E (Youngs Modulus of elasticity)

 

So yes the HT stuff will be less elastic for a given load, but that is NOT the same as %elongation at yield.

 

I also agree entirely about using softer bolts and fixings for clamps, for the very good reasons you have given. Also cooking mild “slides” before it goes so you get warning when you have loaded all up to near busting and uslessness. HT tends to snap suddenly because % elongation after yield tends to be quite small and yield tends to be closer to UTS, whereas mild is quite long..

 

I have to disagree about clamps. As I have said before  – 3 is the correct number to use, because three will find a level and 3 (depending on exact placing and circumstances) will not distort the work.

[Author]

Posts