HTS Bolts

[Nigel McBurney 1Participant @nigelmcburney1]

hi  I assume that you were attempting to part off a threaded portion of the bolt shank,well a ht bolt will have some heat treatment plus probable work hardening from rolling the thread,best advice is cut it off with a hacksaw,then just face it in the lathe,why ruin a good parting blade or expensive tip and its quicker.the factory where I worked as an apprentice only used tee nuts ,thee eigths and half inch whitworth.and had a large assortment of bolts so the correct length could be selected ,and we were instructed to make sure the bolts  did not bottom out in the tee slot,there were no tee bolts,also studs were only used on special purpose fixtures,I understood that the reason was someone had had an accident caused by long stud projecting well out above a clamp,so the boss preferred bolts and in such matters his workshop practice was good.Too prevent overtightening only short series spanners were allowed in your toolkit.None of our machines or equipment had a damaged slot,but after I left my first job I have seen a lot of damage to tee slots and machine tables,particularly in trade shops.

[Tony Pratt 1Participant @tonypratt1]

Ok, I’m going where angels fear to tread.There is no absolute right number of clamps, 3 could be ok or you might need any number, some long jobs or irregular shapes require large quantities of clamps to prevent movement.

The only time a job will not be distorted by clamping is when the underside is fully supported either by its lying flat on the table or if so required shims or jacks are used to take up any irregularities, therefore when clamping commences the clamps are acting on a fully supported surface. If these precautions are not observed there is always a risk of distortion irrespective of how many clamps are used.

 

Tony

 

[John CParticipant @johnc47954]

Nigel,

I wish I had cut the bolt with a hacksaw!  I have since discovered that I must have chipped the edge of my indexed parting tool, on the threads as you suggested, so this whole escapade has cost far more than a set of tee nuts and studs!  Hey ho – what price experience…….

John

[CirclipParticipant @circlip]

Bl**dy Carbides AGAIN, why have most forgotten how to use a Hacksaw?? Have turned bits up to 75 (3″)mm dia. in the lathe and by cutting a bit and rotating the chuck by hand manage to get through the bar with a straight cut and “Wasting” about a 1/16 0r 3/32 of an inch (1.5 to 2.3mm) of material.

 

 Cover the bed with a piece of wood to stop the saw hitting it and splash a bit of coolant in the slot while cutting.

 

  YES, I have both a bandsaw AND an industrial (Q & S) hacksaw but whats wrong with execising yer arms??

 

  Regards  Ian.

[mgjParticipant @mgj]

Ian  – you can’t blame carbides for that. You’ll knock the tip off HSS trying to part HT bolts like that. All it has to do is lift at then end of the cut, and thats it. Tip gone. Tailstock suport, and the right grade of carbide is the answer.

 

BTW I love your idea about hacksawing. I think its excellent. Hacksaws are much better – mine is about 350 watts I think, with a rigid industrial blade, . 

 

But I agree – in this case I’d have just hacksawed them off and used the abrasive linisher to square up the cut and bevel the edge.

Edited By meyrick griffith-jones on 02/01/2010 15:42:17

[CirclipParticipant @circlip]

Not actually blaming the things Meyrick, it’s just that it’s an automatic thought to use it RATHER than a basic hand tool.

 

  I remember listening to a “Woodworker” explaining that he’d delayed assembling a dolls house cos he was waiting for the electric screwdriver to RE-CHARGE, and sadly he wasn’t joking.

 

  Regards  Ian

Edited By Circlip on 02/01/2010 19:35:48

[ANDY CAWLEYParticipant @andycawley24921]

Sorry to be pedantic about this but the elastic stretch of steel bolts regardless of their tensile will be the same. Non elastic stretch or permanent deformation will just occur soo ner in a lower tensile bolt.

 

Also every time I use my ancient Bridgeport I curse the chap who, in the past, just used ordinary sized hex bolt heads in the tee slots and made a real dogs breakfast of the said slots.

[mgjParticipant @mgj]

Elastic stretch of all steel bolts will be the same (to yield)

 

Well now there is a thought – that Youngs Modulus is identical for all steels! I agree that it doesn’t differ by much, (in the sense of this post anyway, which leaves out the spring steels etc) but for sure, the strain for a given level of stress DOES differ according to the alloy.

 

It can even differ according to the heat treatment given to the same alloy?

 

There are many sorts of bolts- stainless, of varying grades, mild, HT etc, and they all behave slightly differently don’t they?

 

Though you can of course always use an approximation if you don’t want to be pedantic

 

 

Edited By mgj on 03/02/2011 20:36:02

Edited By mgj on 03/02/2011 20:38:35

[Jeff DaymanParticipant @jeffdayman43397]

We seem to be getting rather academic and well away from the original poster’s enquiry. Surprised no one just said ‘give up the HTS, get some off the shelf allthread rod for clamp studs, cut it to length and chamfer the ends, use proper size T nuts ONLY, and have a happy life’.

 

JD

 

(or continue with the metallurgy theory banter and not make anything)

[Gray62Participant @gray62]

I think we are all getting too bogged down with the theory of metallurgy. I have, for many years, made Tee nuts out of MS and used common all thread rod with off the shelf nuts. I have never had a vice or fixture move or lose registration. I use an ndustrial turret mill (Ajax AJT4) and have never experienced any issues wiith movement.

If registration is an issue, then as I have done with my precision vice, set it up as required, then machine a registration keyway and add an alignment bar to the underside of the vice, that way you will ensure correct and accurate registration each time the vice is fitted to the table. Using this method, my precision vice is within 0001″ every time

 

[mgjParticipant @mgj]

Well if I might just defend my self. See posts on 1/1/10 where the issue of stretch against HT or mild was specifically addressed.

 

Metallurgical theory – not really. Its actually very basic strengths of materials, which every engineer has to know about. In the same way that women when discussing lingerie ask what colour it is, when it comes to materials, engineers want to know UTS, yield and Youngs modulus of Elasticity or E.

 

Is it of use to the model engineer, in the conext of this post, and others? Depends on your point of view

 

If you’l pardon the Freudian slip, with my milling hold down tackle I have deliberately used HT kit more recently, but I have sized my nuts in mild so they will strip before studs, tee nuts and table are damaged.

 

Just recently I made the point to ChrisH that that some driving crankpins on a model of Metre Maid were safe as houses. An approximation since I ignored any bending moment, but good enough. Then I did the caclulation for the mild conrod and coupling rod bolts specified in the drawings. You get about 7ton tensile in that, for a yield of about 12 tons. safe – well yes, until you add in in the preload geneated by the nut. and of course its a cycling or reversing load. So those are a scrapbin job – just for insurance.

 

 

Or on my traction engine. Ordering springs for the safety valves. If you can do the maths without taking shoes and socks off , its pretty easy to end up with the right length of spring, at the right rate, so it fits the turret and works first time. (I had other problems, but spring rates which is the common issue, were not amongst them)

 

Or the great front and rear toolpost parting off argument, when its very obvious why parting tools jam, and the cure very simple. (Though I have carbide tipped parting blades, I use Eclipse left and right hand ground blades much more often and since Chris Stevens got me to took at the problem properly, It has simply been solved))

 

So yes, strengths of materials and the associated mechanics or resolution of forces and vectors, affects us as engineers every day of our lives, consciously or otherwise, and sometimes by omission, when something breaks which could easily have been avoided.

 

At the end of the day, materials and mechanics are what engineering is about -, don’t knock it till you have tried it, because a calculator saves a hell of a lot of grief.

 

 

 

 

Edited By mgj on 04/02/2011 01:55:11

[Jeff DaymanParticipant @jeffdayman43397]

OK, you do the math, I’ll do the plain mild steel studs and get on making models.

 

note: I tried to use a calculator once on a clamping problem, but it stopped working when I drilled the stud hole through it. Never bothered since.

 

Re strength of materials: You mean people calculate that stuff? I thought jet aircraft designers just got lucky all these years, eyeballing it…..( ie. Hmm, looks strong enough…)

 

JD

[TerrydParticipant @terryd72465]

Hi MGJ,

 

I know from your postings that you like precision and theoretical exercises. So I am surprised at your lack of accuracy in the use of language when you mention a ‘Freudian slip’.

 

A Freudian Slip or Parapraxis is an error of word thought or deed due to repressed (unconscious) thought or wish or conflict. As it is unconscious it cannot be known by the person to whom it refers. i.e. if you think it is a Freudian slip, it cannot be one as you are conscious of it.

 

What you were describing might be called a Paranormasia (or pun) where two meanings can be attached to a word or phrase or two words sounding the same. For example, “your description of Poissons theory sounded rather fishy to me”

 

However as there is obviously a reference to genitalia in your posting it could also be described as a ‘Double Entendre’ but not a Freudian Slip,

 

Best regards

 

Terry

Edited By Terryd on 04/02/2011 08:00:31

[Jeff DaymanParticipant @jeffdayman43397]

Now we are well off the rails. Come on guys, this is a model engineering forum. I’m sure there are theroretical metallurgy forums and English usage forums somewhere else where this stuff can be bandied about, but please not here.

 

The OP just wanted to cut some studs and clamp some stock.

 

JD

[chris stephensParticipant @chrisstephens63393]

Hi Guys,

Since I got a mention, I thought I would chip in, then thought better of it and decided against.

It’s all above my head, I think in Victorian terms, make it look strong enough then add a bit more for luck.

chriStephens

 

PS Terry, when you were using your dictionary to look up the meaning of Freudian Slip, did you miss the page where Pedantry was explained?

[TerrydParticipant @terryd72465]

Hi Jeff.

 

I entirely agree I just thought that mgj would like to be as accurate in his speech as he appears to be in his theory.

 

Like you I’m not sure how much we need to know about UTS at this level of model engineering. I just know that you need to use proper tee nuts with ms bolts and studs. The other important factor is to resist the temptation to overtighten the nuts, Like other have said , I’ve seen gorillas hanging on 12″ lengths of tube on the end of a ring spanner, and even on one occasion a miller using a hide mallet to tighten a clamp. I just had to close my eyes and hold my breath. I too use a short series spanner and never had a problem.

 

I know that at least two clamps must be used on any workpiece never less. any more depends on various factors, e.g. shape, size, depth of cut etc

 

I also know that bolts stretch when tightened and if within the elastic limit , the elastic effect combined with friction is what allows the nut to do it’s job. I always use studs due to the possibility of the bolt bottoming out , reducing the clamping and possibly damaging the tee slot.When making tee slot nuts, do not tap fully all the way through, Use a second tap and leave the last few threads tapered this helps prevent bottoming out bu the studs.As an alternative you ca bruise the bottom couple of threas with a pin punch to prevent bottoming out.

 

Oh yes, just one more thing, I always use the correct height packing and thick washers under the nut/bolt head. Hope that’s On T enough for you Jeff

 

Hi Chris,

 

Of course not, I know the word full well, other useful words I know are ‘imperceptive’ and ‘humourless’, also, a relevant phrase from my book of English Quotations and Phrases is ‘Tongue in Cheek’ . Useful reference to have, you should study it. I like ‘blinkered’ as well, lovely word to roll around the tongue, relevant too.  Did you miss those?

 

Best regards

 

Terry

Edited By Terryd on 05/02/2011 09:08:08

Edited By Terryd on 05/02/2011 09:14:17

[Ian S CParticipant @iansc]

The main reason for 8.8 bolts could be the greater resistance to damage of the threads over a period of time compared to softer botls. The studs in my clamping set appear fairly hard. When I use bolts on the mill, its into propper T nuts, not the head in the slot with a nut on top. Ian S C

[mgjParticipant @mgj]

Judas Iscariot. The lad originally asked about using some bolts of some unspecified material. The advice he was given in general was yes, crack on, but keep bolt/ nut heads thin, so that the head gives before the x/slide/rotary table/milling table.

 

Then someone came up and said IIRC that mild strectched too much -erroneusly, and that was addressed, the explanation being that mild and HT stretch about the same, (in %dimension though the forces required to provoke that stretch will be greater – ie HT is a stiffer spring – surprise surprise) before yield but not breakage, because mild is more ductile, and will stretch after yield.

 

Not that that matters because once the stuff is behaving like toffee, its not actually very useful. and once it has started to strech, stress levels may be very high, because it is thinning, but it still can’t carry any useful load in our sense.

 

Then someone comes back and says pedantically that mild and HT will stretch the same – and that is factually wrong. However we knew that in principle – and the reasons why – over a year ago.

 

 

Do I calcute these things – yes I do, quite often, not because its some amazing exercise to prove that I’m better than anyone else. Its much simpler than that. I don’t like wasting time, or having to repair things because of some dumbarse engineering failure. Most of these calculations are not very difficult, and don’t take very long, and its nice not having to frig about sorting irritating problems. But, like anything else, there comes a point where the best becomes the enemy of the good.

 

At which time its probalby time to stop playing – both with ones kit, or the english language.

Like my little coupling rod bolts – they’ll last a while. At some stage they’ll get changed – sooner rather than later, because they will break sooner rather than later. The arithmetic says so. I prefer to replace a few bolts than cope with bent conrods and dinged gunmtal bearings. And if 5 minutes on a calulator saves me that, I think its 5 minutes well spent.

 

 

 

 

.

Edited By mgj on 05/02/2011 18:06:27

[Nicholas FarrParticipant @nicholasfarr14254]

Hi, just another extract from my college days, which should help understand this streching business, and will back up what mgj is saying somewhat. First is a tensometer graph which I did in my lab work, it shows different carbon content steels streched to breaking point. Stress is shown on the vertical and extension is shown on the horizontal. It can be seen that the higher carbon content steels do extend more before the yield point, allbeit by just a small amount.

 

Proof Stress

 

Mild and medium carbon steels have a definite yield point, followed immidiatly by a plastic stage, during which the material extends considerably. As the carbon content increases, this plastic stage becomes smaller and the steel enters the ductile stage soon after the yield point. In very high carbon steels both the yield point and the plastic stage disappear, and as the stress in the steel is increased it passes directly from the elastic state into the ductile state.

In materials which have a yield point, it is important that the yield stress is known, for if this stress is exceeded, then parts made of the material will have large permanant extensions. This permanant set is often specified at 0.1%, i.e. one thousandth of a gauge length. Thus on a 2″ gauge length, the permanant set would be

 

2″ X 1 over 1000 = 0.002″

 

The stress providing this permanant deformation is discribed as Proof Stress

 

Hope this is of interest to someone.

 

Regards Nick.

[mgjParticipant @mgj]

Bless you Nick – that makes it all crystal clear. Happy days in labs at the College of Knowledge! Should have kept my notes and handout s. One never knows when htey might be useful.

 

Perhaps one should make the point that strength (HT) and hardness generally = more carbon. (as a principle)

 

You are a wiser man than I.

Edited By mgj on 06/02/2011 09:38:55

[Nicholas FarrParticipant @nicholasfarr14254]

Hi mgj, thanks for the compliments. I have found a few more notes on this lab test, and have put a couple more extracts in my Nicks alubum for any one who is interested. The first one shows the object of the test, and the secound one shows a labled graph.

 

You’ll see I only got nine & a half out of ten for this one. Might have lost half a point for not putting the ductile range lable on the graph, or maybe it was just my scruffy writing.

 

Regards Nick.

Edited By Nicholas Farr on 07/02/2011 00:29:20

[Ian S CParticipant @iansc]

Nick, or a tutor who did’nt think anyones perfect, and proberbly never gave 10 out of 10 how ever right you are. Ian S C

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