Author Topic: Clearance Holes  (Read 10353 times)

Offline vcutajar

  • Full Member
  • ****
  • Posts: 2454
  • Marsascala, MALTA
Clearance Holes
« on: January 06, 2014, 05:39:47 PM »
Hi guys

I have another silly question which might be obvious to everybody except myself.  Bear in mind that when I started this hobby I did not have an engineering or machining background.

Today I was drilling the clearance holes in the rear cylinder cover of the Corliss and was thinking of what type of fastening I should use for this model.  Studs or bolts.  I am sort of leaning on using studs but the last time I tried using homemade studs (on the Kiwi) the experience was not positive.  I could not line up the two halves of the Kiwi crankcase with my studs.  When I used threaded rod instead I had no problem at all to line them up.

Which brings me to my question which portrays my level of ignorance.  What should be the clearance hole for a 3mm stud??

I have always assumed it to be 3mm but now I am having doubts about it.

Regards

Vince

Offline peatoluser

  • Full Member
  • ****
  • Posts: 242
  • liverpool UK
Re: Clearance Holes
« Reply #1 on: January 06, 2014, 06:08:19 PM »
I generally use a drill 0.2mm larger than the nominal thread diameter for small sizes, but there's no hard and fast rules about clearance sizes. A cylinder cover with 10 studs might need larger clearance holes just to be able to fit it over them without it binding, whereas a cover with just 4 studs, 0.2mm might be just fine.
interestingly, commercial counter bores , for socket head screws often have a guide dia. 0.5mm bigger than the nominal thread dia. , so clearance hole has to be at least 5.5, 6.5 etc. 

if your studs are binding in the holes and commercial rod isn't, it sounds like the threads are not square with the stud dia.

yours

peter

Offline Jasonb

  • Full Member
  • *****
  • Posts: 6310
  • Surrey, UK
Re: Clearance Holes
« Reply #2 on: January 06, 2014, 06:18:50 PM »
Or more likely the commercial stud is undersize as it often is.

J

Offline Ramon

  • Full Member
  • ****
  • Posts: 1715
  • Suffolk in the UK
Re: Clearance Holes
« Reply #3 on: January 06, 2014, 06:20:15 PM »
Yes, agreed, (edit - with Peter) and you'll probably find Vince that your studding is slightly under 3mm dia too which might be another reason that your studs were binding on the Kiwi.

As Peter says the actual clearance isn't that important unless its a 'fitted' bolt. Anywhere between 0.2 - 0.4 should suffice on most things.

Just in case - If you don't have an accurate means of dividing both parts separately then drill the cover with the clearance hole first and use as a drill jig to spot the holes to a depth such that the lip of the drill takes out approximately one thread - much neater and easier to start the tap. I would still do this if you drill the tapping holes separately - it's always good practice to take out that first 'thread' before tapping and not after  ;)

Regards - Ramon
"I ain't here for the long time but I am here for a good time"
(a very apt phrase - thanks to a well meaning MEM friend)

Offline smfr

  • Full Member
  • ****
  • Posts: 1195
  • San Francisco Bay Area, California
Re: Clearance Holes
« Reply #4 on: January 06, 2014, 06:30:22 PM »
Or you could clamp the parts together and and drill tapping size through the cover into cylinder, then open out the holes in the cylinder cover to clearance size. Don't forget to mark the cylinder cover if necessary so it goes back in the same orientation. Also, don't make the (easy) mistake of drilling clearance size into the cylinder  :hammerbash:

Simon

Offline stevehuckss396

  • Full Member
  • ****
  • Posts: 1355
  • Sterling Heights, MI
    • Steve's Miniature Sparkplugs
Re: Clearance Holes
« Reply #5 on: January 06, 2014, 08:43:57 PM »
Hi guys

I have another silly question which might be obvious to everybody except myself.  Bear in mind that when I started this hobby I did not have an engineering or machining background.

Today I was drilling the clearance holes in the rear cylinder cover of the Corliss and was thinking of what type of fastening I should use for this model.  Studs or bolts.  I am sort of leaning on using studs but the last time I tried using homemade studs (on the Kiwi) the experience was not positive.  I could not line up the two halves of the Kiwi crankcase with my studs.  When I used threaded rod instead I had no problem at all to line them up.

Which brings me to my question which portrays my level of ignorance.  What should be the clearance hole for a 3mm stud??

I have always assumed it to be 3mm but now I am having doubts about it.

Regards

Vince


I don't do mm's except the candy coated ones but I typically measure the fastener and go .004 or so bigger on the drill bit.

#0-80 = .060 - 1/16 drill
#2-56 = .086 - .089 0r #43 bit
#4-40 = .112 - .116 or #32 bit

Can't remember the last time I used a #6 or above. I would suspect the alignment on the Die may have been off if the part wouldn't go on the studs. Misaligned tap might have the stud coming out crooked. Did you thread the studs in the lathe with a tailstock holder for the die? If not try one they are easy to make and do a real nice job holding the die straight.
Do not be like the cat who wanted a fish but was afraid to get his paws wet.

Offline vcutajar

  • Full Member
  • ****
  • Posts: 2454
  • Marsascala, MALTA
Re: Clearance Holes
« Reply #6 on: January 06, 2014, 08:54:49 PM »
Thanks for all the replies.

So, as a general rule, if the studs are made from 3mm bar stock, the clearance hole should not be drilled with a 3mm drill but with something wider, like say a 3.2mm.

Vince

Offline Jo

  • Administrator
  • Full Member
  • *****
  • Posts: 12194
  • Hampshire, england.
Re: Clearance Holes
« Reply #7 on: January 06, 2014, 09:19:31 PM »
Vince,

The guys are saying make sure that the holes are accurately lined up first  ;).

As for the size there are great long tables to help engineers get an appropriate clearance for any given diameter of shaft or stud: A 3mm +/-0mm dowel, is not a clearance fit in a 3mm +/-0mm hole. I personally drill them out to the correct size and then use a watchmaker's broach to take a fraction off to give me the clearance fit. If you don't have one of those then having first drilled it to the 3mm, try opening it up with a 3.1mm... a 3.2mm is a big first jump and they could be loose...

As Jason mentioned commercial studding is undersized which is why it fitted: if you started with 3mm bar and cut the thread the chances are that the burrs have raised above the 3mm diameter and that is why it is not fitting. A gentle touch with a needle file will take away those sharp oversized edges.

Jo
Usus est optimum magister

Offline Baron

  • Full Member
  • ****
  • Posts: 137
  • Grumpy Old Git !
Re: Clearance Holes
« Reply #8 on: January 06, 2014, 10:07:10 PM »
Or you could clamp the parts together and and drill tapping size through the cover into cylinder, then open out the holes in the cylinder cover to clearance size. Don't forget to mark the cylinder cover if necessary so it goes back in the same orientation. Also, don't make the (easy) mistake of drilling clearance size into the cylinder  :hammerbash:

Simon

That is the technique I generally use if possible.  It saves having to make a replacement part because you've drilled a hole in the wrong place.  In my case often because I've lost count of the number of dial marks.

Best Regards:  Baron.

I donít regret the things Iíve done, I regret the things I didnít do when I had the chance.

Offline Ramon

  • Full Member
  • ****
  • Posts: 1715
  • Suffolk in the UK
Re: Clearance Holes
« Reply #9 on: January 06, 2014, 11:57:43 PM »
Hi Guys - just like to clarify why I said to drill the clearance holes first - in effect spotting the hole for the tapping drill.

It is always good practice to take out the top thread of any tapped hole. It is much better to do this before tapping as if done afterward  that small countersink, for that's what it is, will follow the thread and go eccentric. Taking out that first thread definitely makes the tapping easier and subsequently aids inserting the bolts later especially if they are in awkward to get at places.

Secondly and probably far more important, if opening out pre drilled tapping holes, particularly on brass or bronze there's a very good possibility that the part will snatch and pull up the drill if this op is carried out on the drill press, which in all probablilty it will be if tackling it this way. It wouldn't be the first time a tapped hole has been ruined in this fashion that's for sure  ;) - yes, you can stone the drill cutting edges but why do that only to have to resharpen.

When spotting through like this if the drill depth stop is set not only will the spotting depth be consistent but the tapping drill will centre nicely too - it can then be drilled to depth without fear of a mishap.

Only passing on a lifetimes habit - that's not to infer anyone else's method is wrong.

Good luck Vince however you go about it.

Regards - Ramon
"I ain't here for the long time but I am here for a good time"
(a very apt phrase - thanks to a well meaning MEM friend)

Offline Tin Falcon

  • Full Member
  • ****
  • Posts: 425
  • Down Jersey USA
Re: Clearance Holes
« Reply #10 on: January 07, 2014, 12:44:39 AM »

Offline Hugh Currin

  • Full Member
  • ****
  • Posts: 472
  • Klamath Falls, Oregon, USA
    • www.currin.us
Re: Clearance Holes
« Reply #11 on: January 07, 2014, 12:59:03 AM »
Crew:

Let me then ask a really stupid question. If nothing else it will prove Vince's "silly question" is a brilliant inquiry. I also hope it doesn't draw the thread off into a black hole. Please forgive me if my question is too stupid. With this preface:

What is the purpose of a threaded stud, and what do they look like? Are they fully threaded or, by definition, do they have an un-threaded portion in the middle? Are they more akin to a bolt or a shoulder bolt? i.e. Do they mainly hold two parts together or do they locate the parts?

If they simply hold two parts together, like a bolt, the clearance should be like a bolt? That's a fairly "loose" fit and there are tables for clearance holes. I think there are specs for close and free fits, but both leave some wiggle room. (Google "bolt clearance holes").

But if they act as shoulder bolts for location, like locating pins, the clearance is much tighter and dependant on the use. I don't think this is valid unless a counter bore is made into the threaded hole part, so the un-threaded portion of the stud extends partially into this counter bore. This would accurately locate the stud. Then, if the clearance hole in the second part is also a "good" fit to the un-threaded portion of the stud accurate location can be achieved. For this condition I'd think the tolerances for all the parts, and hole locations for a bolt pattern, need to be know to run numbers. I think this is what Jo was eluding to. For our use, I'd think the start small and increase till it fits is best.

So, please inform a beginner. What does a "threaded stud" look like. And are they for accurate location or just hold things together like a bolt?

Thank you for your patience.

Hugh
Hugh

Offline tel

  • Administrator
  • Full Member
  • *****
  • Posts: 1657
  • Bathurst District, NSW, Oz.
Re: Clearance Holes
« Reply #12 on: January 07, 2014, 06:54:21 AM »
If a stud wasn't threaded it would be a dowel.
The older I get, the better I was.
Lacerta es reptiles quisnam mos non exsisto accuso nusquam

Offline Ramon

  • Full Member
  • ****
  • Posts: 1715
  • Suffolk in the UK
Re: Clearance Holes
« Reply #13 on: January 07, 2014, 08:17:20 AM »
Hi Hugh,

A stud is a length of rod usually of standard diameter threaded at both ends with right hand threads. Usually one end - the end that goes into the casting - is threaded shorter than than the other end. I don't actually know what the defined  technical reason is over using them instead of bolts but obviously once fitted and nutted up a lock nut can be used if required. Covers on full-size engines are usually fitted with studs and not bolts.

Threaded rod is not an acceptable way (full size) of getting round the problem and is frowned upon. It can be used in a model particularly for very small sizes when holding material for studs for threading becomes difficult.

Unless a stud is 'fitted' ie the diameter accurately fits the hole for purpose of alignment then their sole purpose is that of a fastener. Clearance holes are usually the norm, end covers usually having a register to ensure alignment.

Here's a pic of some made for a steam chest - incidentally the bolt holding the cover is temporary


Hope that helps you understand a bit more - I'm sure others can add to it.

Regards - Ramon
"I ain't here for the long time but I am here for a good time"
(a very apt phrase - thanks to a well meaning MEM friend)

Offline Farmboy

  • Full Member
  • ****
  • Posts: 117
  • England
Re: Clearance Holes
« Reply #14 on: January 07, 2014, 09:46:53 AM »
In my experience, on older full-size machinery, studs were often coarse threaded (Whitworth/UNC) on the end screwed into the casting but fine (BSF/UNF) where the nut screws on. I always assumed this was the reason for their preference over bolts; fine threads not being generally used in castings.

I don't recall ever seeing a stud used for precise location, which is the job of a dowel.

Mike.

P.S. And it is much easier to locate the cylinder head on studs before fitting the nuts instead of wrestling with half a hundredweight of cast iron while trying to line up bolt holes  ;)
« Last Edit: January 07, 2014, 09:59:01 AM by Farmboy »

Offline Ramon

  • Full Member
  • ****
  • Posts: 1715
  • Suffolk in the UK
Re: Clearance Holes
« Reply #15 on: January 07, 2014, 11:25:22 AM »
Hugh
Mike is quite right here - I'm afraid I've mislead you.

Though it could be - I was trying to convey the opposite to reasonable clearance holes - It is very unlikely a stud would ever be fitted to ensure alignment, dowels, as Mike said, would of course be used.

Bolts on the other hand can be 'fitted' for location purposes - I have a few somewhere with precisely ground shanks which were used on press tools.

Ramon
"I ain't here for the long time but I am here for a good time"
(a very apt phrase - thanks to a well meaning MEM friend)

Offline sshire

  • Full Member
  • *****
  • Posts: 3043
    • LS Editions
Re: Clearance Holes
« Reply #16 on: January 07, 2014, 11:54:54 AM »
Other than historical accuracy, why would threaded rod be "frowned upon?"
Will the stud police show up with a search warrant?
"Sir, keep your hands where we can see them and remove that cylinder head."
Best,
Stan

Offline steamer

  • Global Moderator
  • Full Member
  • *****
  • Posts: 10100
  • Central Massachusetts, USA
Re: Clearance Holes
« Reply #17 on: January 07, 2014, 01:11:08 PM »
Other than historical accuracy, why would threaded rod be "frowned upon?"
Will the stud police show up with a search warrant?
"Sir, keep your hands where we can see them and remove that cylinder head."

 :lolb:

Now that's funny!.

Dave
"Mister M'Andrew, don't you think steam spoils romance at sea?"
Damned ijjit!

Offline steamer

  • Global Moderator
  • Full Member
  • *****
  • Posts: 10100
  • Central Massachusetts, USA
Re: Clearance Holes
« Reply #18 on: January 07, 2014, 01:28:36 PM »
Studs are often used on large parts as its easier to align the part and Hold it in place when placed over stud....imagine if you will the vertical steam chest cover weighs say 300 pounds....or about 150 kilograms  8)....it would be much easier to hang it on the studs and get a nut on than to try to fight the weight hanging on a chain fall while you try to start a bolt.  Or....a 600 pound cylinder head cover that's off....just a little bit...and you can't get the bolt to start....your not moving the head with your hand, you have to get a pinch bar.. to move it.    So a set of studs removes the problem.

So in real life the fit would be pretty loose.   and there would be lifting eyes on the part....

Dave
"Mister M'Andrew, don't you think steam spoils romance at sea?"
Damned ijjit!

Offline peatoluser

  • Full Member
  • ****
  • Posts: 242
  • liverpool UK
Re: Clearance Holes
« Reply #19 on: January 07, 2014, 04:31:19 PM »


...not forgetting that they are really useful to hang the gasket on while you sling up thesteam chest!


peter

Offline sshire

  • Full Member
  • *****
  • Posts: 3043
    • LS Editions
Re: Clearance Holes
« Reply #20 on: January 07, 2014, 04:32:30 PM »
Thanks, Dave
I can see the issue with a "real" part weighing hundreds of pounds. With our tiny engines, I can't see any issue with threaded rod.
My philosophy is:
1. Machine everything to appropriate tolerances.
2. Finish where it's visible. I'm not of a mind to highly polish the bottom of a part that attaches to, let's say, the base.

So, if the visible part (after assembly) of a stud or threaded rod is only the thread, I don't see myself making a stud when I've got every size fully threaded studs from 2-56 thru 10-32. All 1.5" long. All from McMaster. At a few bucks per hundred studs.
Of course, everyone knows what's right for them.
A good thing to know would be, when is a stud necessary for correct operation of a model engine? This would be a valuable addition to stuff I've learned.
Best,
Stan

Offline steamer

  • Global Moderator
  • Full Member
  • *****
  • Posts: 10100
  • Central Massachusetts, USA
Re: Clearance Holes
« Reply #21 on: January 07, 2014, 04:38:28 PM »
That's the beauty of this hobby Stan....You get to be the President and Chief Engineer  of your own Engine building company.....What the boss says....go's!

 :cheers:
"Mister M'Andrew, don't you think steam spoils romance at sea?"
Damned ijjit!

Offline steamer

  • Global Moderator
  • Full Member
  • *****
  • Posts: 10100
  • Central Massachusetts, USA
Re: Clearance Holes
« Reply #22 on: January 07, 2014, 04:47:02 PM »
Jason might be able to answer this better than I, but think scale, multiply that scale to get full size and weight...now how would you want to mount it?

Well....that might make sense.    The other is ....like with Jo's build...she's trying to replicate all the details of the original....so she's using studs

The other thing to consider, you probably go thru far less material making a stud and a nut than you would if you made a bolt.   Back when you needed to MAKE all the fasteners for your engine...that might be a serious thing to consider.......

Dave
"Mister M'Andrew, don't you think steam spoils romance at sea?"
Damned ijjit!

Online mklotz

  • Full Member
  • ****
  • Posts: 2387
  • LA, CA, USA
    • SOFTWARE FOR PEOPLE WHO BUILD THINGS!
Re: Clearance Holes
« Reply #23 on: January 07, 2014, 04:58:51 PM »
Stan, you think anality (yeah, I created that word) about studs is something.  Ask the Brits about "thread counter" judges who deduct points during judging for having the "wrong" number of threads showing above the nut.
---
Regards, Marv


Home Shop Freeware
http://www.myvirtualnetwork.com/mklotz

Offline steamer

  • Global Moderator
  • Full Member
  • *****
  • Posts: 10100
  • Central Massachusetts, USA
Re: Clearance Holes
« Reply #24 on: January 07, 2014, 05:04:09 PM »
Nice word Marv!....I like it!

Dave
"Mister M'Andrew, don't you think steam spoils romance at sea?"
Damned ijjit!

Offline sshire

  • Full Member
  • *****
  • Posts: 3043
    • LS Editions
Re: Clearance Holes
« Reply #25 on: January 07, 2014, 08:28:17 PM »
 Marv
"Anality" has now been officially added to the MEM lexicon.

I get what Jo is doing. In many cases she is making as close to a perfect, small scale reproduction of existing engines. Much (if not all) of what Elmer designed never existed as a working, full scale engine.

I, on the other hand, am just hoping that the damn thing runs. Thread counters be damned! I didn't know that they went to such lengths to exercise their anality.

 

Best,
Stan

Offline Jo

  • Administrator
  • Full Member
  • *****
  • Posts: 12194
  • Hampshire, england.
Re: Clearance Holes
« Reply #26 on: January 07, 2014, 08:29:10 PM »
I've bored people on studs before so I won't repeat it  :disagree:

If you are building a model engine and all you want is a fixing you might as well use cap heads... but some of us look for something a little more realistic in our models.

I hate it when you buy a bolt and it is threaded the entire length of its shank. Where did these people come from? A bolt should only be threaded for 2 1/2 times the diameter of the bolt, the plain part of the shank is there for a good reason  :ThumbsUp:

As Farmboy mentioned studs can be threaded to not only take account of the material of the main item in which it is attaching but have a different thread on the other end to allow for fine torque adjustment. Now a good stud is screwed into the metal for a distance of 1 1/4 to 1 1/2 time the diameter, whilst the tapping hole should always be drilled to a distance of at least twice that of the diameter of the thread.

Don't forget that the distance of studs from the edge of the metal should never be less than 5/8 D much better greater than 3/4 D.

As for the dreaded 1 1/2 threads sticking out well that is there for good reason: it is all to do with the lead needed for the thread cutting, the first bit of thread is not to full depth. An if you are a manufacture the last thing you want to do is waste metal on fastenings by leaving the threads over length. It adds to the cost of manufacture and the weight of the final item and on the sorts of things I work on every gram counts  ;)

And of course there is that little problem about lock nuts: should the thin nut be on the top or the bottom :lolb:

Jo

« Last Edit: January 07, 2014, 08:32:55 PM by Jo »
Usus est optimum magister

Offline Jasonb

  • Full Member
  • *****
  • Posts: 6310
  • Surrey, UK
Re: Clearance Holes
« Reply #27 on: January 07, 2014, 08:37:35 PM »


I hate it when you buy a bolt and it is threaded the entire length of its shank. Where did these people come from? A bolt should only be threaded for 2 1/2 times the diameter of the bolt, the plain part of the shank is there for a good reason  :ThumbsUp:

In that case you have bought a screw not a bolt, most of the ME suppliers sell hex head screws thats why they are fully threaded, I think most people buy the screws and cut them to the length required which if it were a bolt may remove too much thread.

J

Offline Jo

  • Administrator
  • Full Member
  • *****
  • Posts: 12194
  • Hampshire, england.
Re: Clearance Holes
« Reply #28 on: January 07, 2014, 08:43:14 PM »
I think most people buy the screws and cut them to the length required which if it were a bolt may remove too much thread.

:facepalm2: You might as well use threaded rod  :ShakeHead:

Jo
Usus est optimum magister

Offline Jasonb

  • Full Member
  • *****
  • Posts: 6310
  • Surrey, UK
Re: Clearance Holes
« Reply #29 on: January 07, 2014, 08:51:59 PM »
But that would look wrong where a bolt/screw was needed, plenty of bolts on a traction engine which would look out of place if you had studding with a nut on both ends.

J

Offline Baron

  • Full Member
  • ****
  • Posts: 137
  • Grumpy Old Git !
Re: Clearance Holes
« Reply #30 on: January 07, 2014, 08:55:31 PM »
Hi Guys - just like to clarify why I said to drill the clearance holes first - in effect spotting the hole for the tapping drill.

It is always good practice to take out the top thread of any tapped hole. It is much better to do this before tapping as if done afterward  that small countersink, for that's what it is, will follow the thread and go eccentric. Taking out that first thread definitely makes the tapping easier and subsequently aids inserting the bolts later especially if they are in awkward to get at places.

I countersink before tapping the hole.  I use "Weldon" type countersink tools.

Quote
Secondly and probably far more important, if opening out pre drilled tapping holes, particularly on brass or bronze there's a very good possibility that the part will snatch and pull up the drill if this op is carried out on the drill press, which in all probablilty it will be if tackling it this way. It wouldn't be the first time a tapped hole has been ruined in this fashion that's for sure  ;) - yes, you can stone the drill cutting edges but why do that only to have to resharpen.

I've been caught several times with the drill grabbing the work particularly with larger drills 5mm or so.  Smaller drills tend to break.
A few years ago I had this happen when I was drilling disks made from 6mm aluminium plate.  Someone came into the workshop unexpectedly.  My attention broke for a fraction of a second and I eased the pressure on the drill.  The drill grabbed and the disk pulled out of the jig and spun round catching the first finger on my left hand, neatly slicing the top half of my finger off from the second knuckle right down to the nail.  Fortunately it missed the nail itself.  (Shudder)...

 
Quote
When spotting through like this if the drill depth stop is set not only will the spotting depth be consistent but the tapping drill will centre nicely too - it can then be drilled to depth without fear of a mishap.

Only passing on a lifetimes habit - that's not to infer anyone else's method is wrong.

Good luck Vince however you go about it.

Regards - Ramon

Some good tips.  Its nice to learn others techniques.

 
Best Regards:  Baron.

I donít regret the things Iíve done, I regret the things I didnít do when I had the chance.

Offline tel

  • Administrator
  • Full Member
  • *****
  • Posts: 1657
  • Bathurst District, NSW, Oz.
Re: Clearance Holes
« Reply #31 on: January 07, 2014, 09:01:14 PM »
Quote
the first bit of thread is not to full depth.

Erm, if that was the case the nut wouldn't go on?
The older I get, the better I was.
Lacerta es reptiles quisnam mos non exsisto accuso nusquam

Offline Baron

  • Full Member
  • ****
  • Posts: 137
  • Grumpy Old Git !
Re: Clearance Holes
« Reply #32 on: January 07, 2014, 09:03:40 PM »
I think most people buy the screws and cut them to the length required which if it were a bolt may remove too much thread.

:facepalm2: You might as well use threaded rod  :ShakeHead:

Jo

There is all ways a file !
Best Regards:  Baron.

I donít regret the things Iíve done, I regret the things I didnít do when I had the chance.

Offline tel

  • Administrator
  • Full Member
  • *****
  • Posts: 1657
  • Bathurst District, NSW, Oz.
Re: Clearance Holes
« Reply #33 on: January 07, 2014, 09:11:32 PM »
Realistically, you can make a proper stud in not much more time than you need to cut off and clean up a machine screw or bit of studding.
The older I get, the better I was.
Lacerta es reptiles quisnam mos non exsisto accuso nusquam

Offline Tennessee Whiskey

  • Full Member
  • *****
  • Posts: 3743
  • Springfield, Tennessee. USA
Re: Clearance Holes
« Reply #34 on: January 07, 2014, 09:32:18 PM »
Well in redneck terms; it's a bit of rod with threads on both ends and none in the near about middle,  ain't rocket science. :thinking: :old: :lolb:

Whiskey

Offline Hugh Currin

  • Full Member
  • ****
  • Posts: 472
  • Klamath Falls, Oregon, USA
    • www.currin.us
Re: Clearance Holes
« Reply #35 on: January 07, 2014, 09:40:15 PM »
The thread is moving fast, and this now read a little out of date. But I'm gonna post it anyway.

The consensus is studs aren't normally used for precise location. This makes sense to me. So, the clearance holes for a stud should be the same as for a bolt. For a 3mm stud/bolt the clearance holes should thus be 3.15mm (close fit) or 3.3mm (standard fit) [google "clearance holes metric"]. I usually start with a close fit and open it up only if needed.

Why use studs? Already mentioned is the ease of assembly. I had a VW that used bolts to hold the wheels on, a pain even with those "small" tires. Also, battering of the threads may be a reason. The shank of a bolt can't extend down to the threaded hole, or you couldn't tighten it. A stud can be threaded up to the shank, up to the un-threaded portion. Thus, if the bolted-on part is jostled about it won't bung up the threads, just bear on the shank.

Also, critical threaded fasteners are put under significant tension to press the connected parts tightly together. Think of holding a head on an engine, the bolts must hold the head tightly to the cylinder. This leads to torquing the bolt near, or into, yield (permanent deformation). I don't fully understand why, but the "nut" yields before the "bolt" (if similar materials). If a bolt is used, the "nut" is your casting and hard to replace. If a stud is used, the nut is easily replaced. Some machines use studs and specify replacing the nuts upon each reassembly. This is irrelevant unless the tension is carefully controlled (torque wrench).

None of these seem overwhelming reasons for a model engine. I suspect the main reason for studs is in building scale models. And as Marv says, all aspects can be critical. I marvel at some of the beautiful scale builds here, but I doubt I'll ever have that much patience. I love seeing them though.

Thanks for all the great info and insight.

PS. Whiskey, I think they really are used on rockets. We'd have to check with Morton-Thiokol to be sure though. :-)

Hugh
Hugh

Online mklotz

  • Full Member
  • ****
  • Posts: 2387
  • LA, CA, USA
    • SOFTWARE FOR PEOPLE WHO BUILD THINGS!
Re: Clearance Holes
« Reply #36 on: January 07, 2014, 10:17:24 PM »
Marv
"Anality" has now been officially added to the MEM lexicon.

I'm flattered.  Even more so now that your research reveals that anality is a genuine word found in several dictionaries.  I had no idea.

Nevertheless, the success of this word-coining has emboldened me.  Given the opportunities afforded by this forum, I'm sure I can come up with some really stunning additions to the local lexicon.
---
Regards, Marv


Home Shop Freeware
http://www.myvirtualnetwork.com/mklotz

Offline tel

  • Administrator
  • Full Member
  • *****
  • Posts: 1657
  • Bathurst District, NSW, Oz.
Re: Clearance Holes
« Reply #37 on: January 08, 2014, 01:51:54 AM »
Marv
"Anality" has now been officially added to the MEM lexicon.

I'm flattered.  Even more so now that your research reveals that anality is a genuine word found in several dictionaries.  I had no idea.

Nevertheless, the success of this word-coining has emboldened me.  Given the opportunities afforded by this forum, I'm sure I can come up with some really stunning additions to the local lexicon.

Hey Marv, we got a whole country full of 'em here that I would be willing to let you use (for a modest licensing fee, of course)
The older I get, the better I was.
Lacerta es reptiles quisnam mos non exsisto accuso nusquam

Offline peatoluser

  • Full Member
  • ****
  • Posts: 242
  • liverpool UK
Re: Clearance Holes
« Reply #38 on: January 08, 2014, 05:48:20 PM »
I've always believed that  - in full size practice anyway - studs where preferred to bolts in high load situations because when you tightened a bolt you put a twisting load as well as an axial load on the bolt and all this was taken by the threads in the hole and bolt. whereas when a stud is used , the load is purely axial and shared by the threads at both ends. The bit I don't understand is, I believe, that if you reduce the plain part of a stud to the core diameter of the threads it's actually stronger.
I'm no engineer, so if I'm wrong I really would like to be corrected.
personally , I've always thought the biggest factor in tightening a bolt and/or nut is the bloke in overalls with a lump hammer in one hand and flogging spanner in the other, and not the choice of fastener!

peter

Offline Admiral_dk

  • Full Member
  • ****
  • Posts: 1244
  • SÝften - Denmark
Re: Clearance Holes
« Reply #39 on: January 08, 2014, 08:59:14 PM »
Ever since my teens, I've hated studs - the thread on the exhaust studs on for instance a Puch mopeds always disappeared after a few years  >:(  :wallbang:  :cussing:

But if you could get them out and put bolts in instead => no more trouble  :cartwheel:  and the same has been the case on many of the motorcycles I've worked on  ;D

That said - I would prefer studs on very heavy equipment ..... as others has stated, it makes it easier to assemble.

Offline tel

  • Administrator
  • Full Member
  • *****
  • Posts: 1657
  • Bathurst District, NSW, Oz.
Re: Clearance Holes
« Reply #40 on: January 08, 2014, 10:50:19 PM »
Quote
Ever since my teens, I've hated studs - the thread on the exhaust studs on for instance a Puch mopeds always disappeared after a few years

 :Lol: Blame the material, not the stud! Make a set out of stainless or bronze and they will last forever and a bit.
The older I get, the better I was.
Lacerta es reptiles quisnam mos non exsisto accuso nusquam

Offline Steam Haulage

  • Full Member
  • ****
  • Posts: 210
  • Notts UK
Re: Clearance Holes
« Reply #41 on: January 09, 2014, 07:59:43 AM »
Whlle we're talking about strength and accuracy as well as reproducing full size practice in a model engine has anybody considered the use of these? http://www.helicoil.com.sg/.

I have worked in a shop where Helicoils are used in aero engines. You will see on the linked site that there is more than a handful of specs. for various applications.

Jerry

Dogs look up to you, cats look down on you, pigs treat you as equal.

Offline Ian S C

  • Full Member
  • ****
  • Posts: 1025
  • Stirling Engine Maker Darfield Canterbury N Z
Re: Clearance Holes
« Reply #42 on: January 09, 2014, 01:03:42 PM »
We used Helicoils mainly on exhaust studs on aircraft engines, mostly Continental IO 470/ IO 520.
One person in NZ had an engine failure because of a Helicoil,  he rethreaded the sparkplug hole with a stainless coil, instead of a bronze one as specified,(single cylinder Robin engine, on an Ultra Light aircraft), cooked the sparkplug through lack of cooling.   Ian S C

Offline Steam Haulage

  • Full Member
  • ****
  • Posts: 210
  • Notts UK
Re: Clearance Holes
« Reply #43 on: January 09, 2014, 01:38:03 PM »
Ah, spark plugs! Helicoils come in StSt and Bronze. (follow the link above.)
Although I didn't specify, (my mistake) the ones I meant were of the Suck-Squeeze-Bang-Blow type. In some of these engines flanges are connected using 91+ studs or some other odd number with an H-C or equivalent in every one. It's quite possible you have been conveyed using them perhaps for several thousand miles.

Jerry
Dogs look up to you, cats look down on you, pigs treat you as equal.

Offline Admiral_dk

  • Full Member
  • ****
  • Posts: 1244
  • SÝften - Denmark
Re: Clearance Holes
« Reply #44 on: January 09, 2014, 04:46:50 PM »
Quote
Blame the material, not the stud! Make a set out of stainless or bronze and they will last forever and a bit.

That's right Tel - I can only whole heartedly agree the that originals where crap and the material was to blame, but stainless might not have worked with the rest (or it might), not all materials work equally well together. But the fact was that we had easy access to cheap bolts that never failed and the studs always did, no matter what brand of bike.
I suspect the one of the main reasons where that we always have our roads covered in salt in wintertime => a stud + nut will be covered inside out in a corrosive solution that destroys them  :hellno: But using a bolt + washer => that almost nothing of the salt-solution would enter the thread in the cylinder = no trouble  :D

I've repaired a number of threads with Helicoils, but I can't see them do studs as a repair - sorry.

Ian - thanks for the warning about stainless Helicoils in sparkplug applications  :o