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Author Topic: cutting threads  (Read 9673 times)

bogstandard

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Re: cutting threads
« Reply #25 on: January 30, 2009, 11:41:57 PM »

Daz,

Just to explain a little less technical than Derek has shown, but in a slightly different way.

Imperial threads use TPI (threads per inch), metric threads use pitch (distance from the tip of one thread to the tip of the next), so really, your measuring in TPI is incorrect to the purist, but accurate enough to show you the difference between the two.

I have done a calculation for you and the correct imperial TPI for a metric 0.8mm pitch is 31.725. So that is very close to the 32TPI you said for your tap, I suspect your thread gauge didn't fit exactly, but close enough between friends.

0.8mm = 0.03152".

1.000" / 0.03152" = 31.725888 rec.   

So I am sorry to say, your old die is ready for the dustbin, as it is surely way out of spec or a very old standard not in use today.

Get a new die and you should be on your way.

Hope this has helped with your problem.


John
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derekwarner

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Re: cutting threads
« Reply #26 on: January 31, 2009, 12:37:42 AM »

OK all.......portside II says....
 
"I bought both the tap and die a few years back from a liquidation sale"

But I think he omitted to say one was found in the bottom of a bottle of French wine or Japanese saki..... %%..... [bogstandard & I know these things]....John  has even trained Bandit & Vinnie to .......measure with the digital vernier & distinguish between FROG FREDS & the dosimilar JAP EFERDS things

I do hope the Moderators :police: understand .....the last comments are light hearted ...... {:-{....as I have a French steam engine [JMC3H] & my mother-inlaw goes to the local Chinese take away once a week  O0 %% :o ....Derek

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Derek Warner

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bogstandard

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Re: cutting threads
« Reply #27 on: January 31, 2009, 04:36:19 AM »

Derek and myself go back a long way, so while most people can't understand his convict Aussie ramblings, I do. So I can confirm there is no malice involved at all. Just a few of those weak Austalian beers talking  :} %)

So just to add a little to the post to Daz.

Your thread gauges can come in all sorts of flavours, all geared to the type of threads you are measuring. You should be able to read on the side of the set what they are aimed at, 55 degree Whit & BSF, 60 Degree unified (UNC/UNF), Metric, usually referred to as pitch gauges and can come as both fine and coarse, coarse being the normal ones we use. Plus a multitude of others that can be obtained. So it can be a minefield out there when measuring pitch or TPI. It is like taking a half litre milk bottle to get a pint of milk, very close, but a little bit might get spilled because it just won't quite fit in the bottle.

John
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derekwarner

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Re: cutting threads
« Reply #28 on: January 31, 2009, 05:19:55 AM »

OK all....just to cut the quick......many would use a thread gauge stamped M&W ....what many would not realise  ;D ....this could be a Moore & Warner [bogstandard & derek %% %%] designed gauge...

However I do not understand how any HUMAN could get an M&W ......M5 thread 'leaf' template gauge into an assumed M5 tapping to check or compare >>:-( ....as the height of the template leaf is 8 mm......Derek
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BJ

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Re: cutting threads
« Reply #29 on: January 31, 2009, 04:10:39 PM »

heres on for the enginers out there ,
I have been making my own prop shafts and tubes for a while now mostly in M4 ,but i have made a few in M5 threads that is .
Is there a standard thread as when i cut a thread on the shaft in M5 and run a M5 nut up it i get a bind after about 1 and a half length's of the nut ,this is so bad that i have broken the shaft trying to remove the nut.
I have run a M5 tap through the nut and thats ok , both the tap and die are M5x0.8 .
Any ideas ??
daz

See http://books.google.co.uk/books?id=7R1bDucTHeAC&pg=PA922&lpg=PA922&dq=chart+of+threads+to+bs+3643&source=web&ots=0wEMj7VR7g&sig=C28_j7goYxtTJKnTUO8I1f99m70&hl=en&sa=X&oi=book_result&resnum=3&ct=result#PPA923,M1

This should give you the COARSE and FINE metric thread details for M1 to M36.
M5 standard pitches are 1.25 for coarse and 1.0 for fine threads. They are on page 923 of the book.
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bogstandard

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Re: cutting threads
« Reply #30 on: January 31, 2009, 04:33:53 PM »

BJ,

I think you are looking at the chart for 8mm, which are as you said, for 5mm it is 0.8 and 0.5 respectively.

John
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portside II

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Re: cutting threads
« Reply #31 on: January 31, 2009, 05:46:01 PM »

So what you lot are trying to say is that my die is worn and i should buy a new one and as long as it reads M5 X 0.8 it will cut the same thread as the tap  :-)) .
I just cant see how the die has worn out to cut threads at 28 TPI from 32 TPI , it just dont sound right or is it just me   {:-{ .
daz
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bogstandard

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Re: cutting threads
« Reply #32 on: January 31, 2009, 07:05:30 PM »

Daz,

Quote
it is surely way out of spec or a very old standard not in use today

As your tap measures 32 TPI (or near enough), then that is the correct spec for the tap.

If it is correct in what you have measured, 28 TPI for the die, then the die is definitely incorrect. Not worn, but the wrong spec for a 5mm coarse die. It should have the same TPI as the tap.

5mm is one die I don't buy in bulk, otherwise I would have sent you one.


Without actually physically checking it myself, and if all that you have told us and has been checked and reported correctly, then that is about the most anyone can do for you.

You can get a very good quality one from here, and I would suggest you buy a matching tap at the same time to put your mind at rest. Then you would be guaranteed to have a matching pair, that will last you a long time.

http://www.tapdie.com/html/metric__dies.html

John


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derekwarner

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Re: cutting threads
« Reply #33 on: February 01, 2009, 12:05:07 AM »

Goodness....all of this talk of TPI for metric threads make my head hurt  {:-{ {:-{ {:-{

You don't have a 32 TPI or a 28 TPI die nut..... as these would produce

25.4 divided by 32 [TPI] = 0.793 mm pitch
25.4 divided by 28 [TPI] = 0.907 mm pitch

So..... from the words of experience by 'bogstandard'.....[translated to OZ].....

1) don't throw them boith over the balcony just yet
2) console yourself with a small glass [or two] of good Australian wine
3) consider your options/plans & lets start with the tap

4) OK....set your vernier calliper [with or without a TV screen] between two thread points [crests of the thread form]....
5) if you use the TV screen version please set it to the METRIC nomination
6) if you see a numeral 0.8.........you now know you have an M5 x 0.8 pitch threadform
7) if you see a numeral 0.5.........you now know you have an M5 x 0.5 pitch threadform

Please re-read point 5) ....if you don't follow the directions......you will see numbers of 0.031496062 or 0.019685039....which are small bits of inches ["] & only confuse everyone further

8) repeat step 2).....

The only acceptable method of determining the pitch of your M5 die nut is to cut a thread on a section of 5.0 mm diameter bar stock......brass would be very good as it does not require any cutting agent...or coolant

9) ....repeat steps 4) 5) 6) & 7)

10) repeat step 2) or 8)

So now you have the clear physical evidence of what the die nut & the tap produce

11) repeat step 10)

Telephone or call at your local engineering supplier & ask the costs for an M5 x ? pitch die nut in HSS

12) repeat step 11) as the cost will be expensive.....

13) remember you are intending to cut stainless steel material  material with say 620 MPa strength so HSS is the only real option

14) in OZ...we have a product called TREFELEX ....like a green slime....the best cutting agent for carbon & stainless steel grades...[for drilling & tapping purposes]

Derek {-)  :-))




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Derek Warner

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Illawarra Live Steamers Co-op
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www.ils.org.au

BJ

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Re: cutting threads
« Reply #34 on: February 01, 2009, 03:28:53 PM »

BJ,

I think you are looking at the chart for 8mm, which are as you said, for 5mm it is 0.8 and 0.5 respectively.

John

Ta, John.  Thanks for the reminder.    Must make an appointment at Specsavers
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bogstandard

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Re: cutting threads
« Reply #35 on: February 01, 2009, 04:05:15 PM »

Not to worry BJ, you ought to see some of the montrous threads I make, when I don't set the change gears up on the lathe correctly.

I know it is off topic, but the columns on this engine in the pic were threaded on my old lathe.

Haven't tried threading with the new lathe yet, so I expect a bit of trouble in that department eventually.

If you never make mistakes, you would have to take up walking on water as a tourist attraction instead.

John
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portside II

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Re: cutting threads
« Reply #36 on: February 01, 2009, 05:05:28 PM »

Thank you Derek, and as you pointed out its metric so how come it's possible that a die can wear out that much that it cuts a thread that far out , a thread pitch of 0.907 and 0.793 are when looking at clearly different , amd maybe it would be better to replace both of them as either dont cut the pitch marked on them .
Lets try another set and should be ok   O0 .
daz
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Bee

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Re: cutting threads
« Reply #37 on: February 02, 2009, 12:38:38 AM »

There is some strange stuff on this thread!
Although 0.5 and 0.8 are the common pitches for 5mm dia
0.9 is a VALID metric thread pitch for 5mm dia
As are 0.75 and 1. 0 they are just not the common ones.
Taps and dies for ALL the above are available commercially.

So you just happen to have a non matched set, not a worn one.  :}
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DARLEK1

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Re: cutting threads
« Reply #38 on: February 02, 2009, 12:53:00 AM »

Hi chaps, going back to the intitial post of the "I get a bind in two deapths of the die nut" type of thing, has working the die nut up and down the newly cut thread been done?

 When working with stainless steel, it has to be worked more than normal mild steel or any other softer metals, this also depends on the grade of the stainless steel, there are a few.

 If you need to check anything out regarding cutting metals and threads etc, there is an engineering book available caled a Zeuss table I think. I have got one in my work shop and it gives all known threads, types of steel, hardnesses and what dies, taps to use for what ever application. There are a few others on the market in the engineering world also.

 I hope this helps.

 Paul...
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