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Member postings for S.D.L.

Here is a list of all the postings S.D.L. has made in our forums. Click on a thread name to jump to the thread.

Thread: polishing in the lathe
07/08/2015 08:30:09

Posted by Bandersnatch on 06/08/2015 23:12:04:

Russell, Martin &Neil

I wasn't commenting, per-se, on whether the practice is safe or unsafe.

Rather that the HSE people used the fact that the Council had used this practice for years (without an apparent problem) as evidence that the Council was at fault for not detecting the problem.

Just seems pretty illogical to me .... or actually that they were trying to twist (not very successfully) the facts to fit a pre-determined conclusion.

Seems fairley obvious to me that the LEA assuming it's a LEA school haven't reviewed the H&S guidance on machines or they would have stopped using strips of emery years ago. Conclusion of HSE looks spot on. They have all the numbers to know the most dangerous activities based on hard evidence and give guidance on that. Talk to a real H&S expert and it's common sense, normally the issue is some jobs worth who uses H&S to get their way or who see danger in getting out of bed.

Steve

Thread: Lathe design not keeping up
29/06/2015 21:58:33

Posted by John Stevenson on 29/06/2015 14:08:02:

Good point Steve.

You have now got me thinking. I assumed [ yes we all know the saying ] it was Whit as this machine also has a load of 3/16" on it but checking as not familiar with numbered unified threads there is a #10 at 0.190 x 24 which is only a couple of thou up on 3/13" whit.

So far I haven't found any fine threads on this machine but I'm working at casting level which is ideal for course threads.

A quick check on some non cleaned up holes with a 1/4" whit and 1/4" UNC cap screw and both go in with the same fit. I know they shouldn't because of pitch angle but most screws are very loose on tolerance.

I need to find some fine threads to see the difference. However any extra bolts going into cleaned up tapped holes will be 1/4" whit as I have boxes and boxes of these but only a very few UNC's wink

Tapped holes on the DRO brackets will be metric as the rest of the DRO's are all metric.

[ EDIT ]

Found a large course grub screw that sets the end float on the start / stop shaft 1/2 x 13 so it is a UNC machine. Thanks Steve

Edited By John Stevenson on 29/06/2015 15:55:57

Just checked my Manual all 1/4 & 5/16 screws are UNC

The number ones are all 10-24

guess yours will be similar

Steve

29/06/2015 12:11:12
Posted by John Stevenson on 29/06/2015 01:14:58:

Ran a 1/4" whit tap thru most of mine to clear the crud out.

Just a note for some who may not be aware, some UK Colchesters are UNC/UNF so there is for example 5 choices for some tapped holes.

ie assuming it looks 6mm or 1/4" it could be 1/4BSW 1/4BSF, 1/4UNC 1/4UNF or M6.

My MkII student is UNC/UNF other than the bits that I have added that are metric.

Steve

Thread: Any ideas what these are?
05/06/2015 15:52:25
Posted by colin hawes on 02/06/2015 16:28:45:

I don't think there is any advantage at all in using Stellite for lathe tools as HSS is more than adequate for most work and carbide is best for cast iron. I use silver steel for small boring bars. Colin

Eccentric Engineering the makers of the diamond tool holders seem to think that class of material has its merits in model engineering as they have just started selling a similar material. see link below

**LINK**

Steve

Thread: My little engine (continued)
05/06/2015 15:45:42
Posted by Gary on 05/06/2015 14:45:28:

Hi Roy

I wish I could, but the Crankpin that the bearing fits is assembled and pinned between the Webs on the Crankshaft. If I had thought earlier I could maybe have made sure I had a bit of 'left over' Crankpin to use for this test fitting - I didn't recognise at the time though!

Something I'll watch out for in the future for sure - I do have some internal bore gauges so I hope I can manage..

Cheers.

Garry

Put your 3 jay back on.

Measure the shaft with your best micrometer.

Turn a bit of metal to the same diameter and put a 30 deg chamfer on end.

remove metal from chuck and put 4 jaw back on.

Use gauge just made to judge boring, the taper helps.

easier than internal measumrements.

Steve

Thread: Cutting BSPT threads with a die
01/05/2015 14:09:15

Posted by Mick Berrisford on 01/05/2015 12:29:53:

I want to replicate two radiator bypass hose connectors on a Suzuki Kettle I'm restoring in 303 stainless. They're 1/4" and 3/8" BSPT threads and I've never had to do taper threads before.

Do I just turn the bar parallel to the major thread diameters or should I be using the top slide to taper them up to the major diameter before using the die?. I have looked it up and know the sizes but I can't find any reference as to which is the best way to do things. The taper is 1 in 16 which would mean an angle of 1.5 ish degrees so would have to be a good guesstimate if I did it that way.

Edited By Mick Berrisford on 01/05/2015 12:31:46

Do as you suggest turn taper first then cut with BSPT die.

Steve

Thread: Raising the L5
07/04/2015 22:14:22

Get some universal channel 100 or 150 high as required weld up a frame, gusset top to bottom either side of fixings.

Bolt lathe to frame, lift and put machine mounts frame to floor for level ling.

frame probably ends up as two rectangles first one under head stock the 3 prices to side under tail stock

Steve

Thread: Parting Off MEW225
07/02/2015 10:35:45

In a previous job I volunteered to part off some 316 stst M24 bolts that were too long. I was actually designing things but there was no one free to do it and I had a Factory Acceptance Test the next day and knew that the Resident Engineer coming would reject them for too many threads sticking through.

So onto the Colchester Master front Dickinson post add a Sandvick parting tool. Feeding by hand and Bang tip gone. see Mick and get another tip second bolt, bang another tip gone. Mick says lets see what your doing. digs out the rear tool post and fits on with sandvik tool moved to back and up side down. puts it at about 400rpm and cuts with power feed.

I did the rest of the bolts in less time than I did the fist two. Micks view always part under power feed.

Fast forward to nowadays got a Colchester student MkII in the workshop (Garage) so big by Myford standards. It came with original Dickinson T2 quick change post, using a Sandvik parting blade it parted Brass and aluminum under power fine EN was ok some of the time, stainless was always a disaster. I was looking for s rear toolpost but eventually I saw that the tool holders pulled out and twisted when there was a jam and fired back into place. I replaced this with a Chinese version of the Multifix type. I got the money back by putting the Dickinson and holders on e-bay and the Multifix that is half the size of the Dickinson will part 2" 316 StSt as if its butter sat on the front.

My take is many tool posts are not as rigid as we think and power feed is the key with a tool that rolls the chips or swarf so that it is narrower than the groove being cut.

Steve

Thread: More reliable connectors
07/02/2015 10:14:05
Posted by John Shepherd on 07/02/2015 07:28:30:

There's a lot I don't know about crimping but I do know that the crimp and the wire must match and the only tool to use is one of the ratchet types designed for the crimp in use. Otherwise it's a disaster.

A grey area for me is use of crimps on solid wires and the voltage ratings of crimps. Can any one give some sound authorative advice on the subject of crimping please.

We use both bootlace crimps and the RYB eyelets, fork and blade crimps at work on lamp circuits that run at 950V 4A and have a strike voltage up to 2KV. this arrangement passes both UL and CE low voltage directive via independent test house in UK, so that should give some idea. They do insist on the correct ratchet tools that have to do a pull test on a sample every year or 6 months depending on use.

As others have said soldering ends of wires going into clamp terminals is a no no now days however neat it looks.

Best connection is the spring clamps found on many terminals and increasing numbers of components, gets rid of the screws working loose during shipping.

Steve

Thread: HSS
05/01/2015 21:52:56

Put a groove on each side with tool of choice ( offhand grinder, angle grinder dremmel etc) wrap in rag and put in vice with groove out of jaws, hit with big hammer. If doesn't break get bigger hammer.

Steve

Thread: Latest boiler regs?
05/01/2015 21:47:48

Posted by fizzy on 04/01/2015 20:55:28:

Not looked at the green book in a while but pretty sure there is nothing akin to this in it. Indeed why would there be? So long as the boiler is safe and to spec what you do with the steam is your business...ah, it drives me mad!!

It's not just the boiler being tested under the PSS2000 its a system test. Green book 1.2

Green Book clause. 3.13a states that system is "boiler shell including fittings and pipework"

Fittings are defined in 3.3 and include saftey valves and regulators etc.

In essence the whole system has to satisfy the inspector not just the boiler she'll, at the end of the day it's the inspectors nuts on the line.

Steve

Thread: One for the thinkers?
27/12/2014 19:38:01

Posted by fastjohnrs on 27/12/2014 19:27:31:

If they have the same amount of play I'd imagine they'd knock the same, unless the difference in weight of components has a part to play, be interesting to see what other people think

 

For any class of fit the amount of clearance or interference increases with diameter so what may be sloppy on a small shaft would be proportionally tighter on a bigger shaft.

Steve.

 

Edited By JasonB on 28/12/2014 07:25:30

Thread: Thread Size
24/11/2014 18:31:49

Posted by Jack Foreman 1 on 24/11/2014 09:39:54:

A bit of a shot in the dark.

Can anyone, offhand, tell me the size of the internal drawbar thread in a Clarkson 30INT chuck please? I have to make the drawbar for the mill to secure the chuck.

Thanks
Jack

I have seen M10, 3/8 BSW, 3/8 UNC, M12 and 1/2 BSW, and I expect there was 1/2 UNC as well. I brought some threaded rod back from the U.S. for the UNC one.

Try some bolts or if very carful some Taps to try them.

A lot of auto locks have the size in very feint writing on the side, if tarnished try cleaning up wit a bit of WD40 and fine scotchbrite.

Steve

Thread: Boiler thickness and pressure
24/10/2014 18:36:15
Posted by JasonB on 24/10/2014 15:24:04:

From SDL's posting the temperature is taken account of by a separate allowance and the safety factor remains the same at 8.

J

The martin Evans book that I took this from has good worked examples and certainly the tube thickness is what is in the Northern association guidelines. Note these design guidelines are separate from the testing book. This should not stifle developments but few boiler inspectors are going to have the experience to review FEA but this should not stop people adding blind bushes for fixings of door runners etc

Please spare a thought for your Boiler inspectors, many do a thankless job, at the end of the day its them that has to sign off and pass things. At our club for many years the boiler inspectors thought they were covered by the club insurance, It was only when I raised a question in writing during the review before the last code change that it was made clear that the club needed separate indemnity insurance for the boiler inspectors otherwise there assets are on the line. as you could imagine we took this out promptly. This insurance is shown on the southern fed form but historically the implications had not been understood.

Steve

24/10/2014 13:24:20
Posted by JasonB on 24/10/2014 11:26:54:

SDL would it be possible to put some figure sinto that formula particularly the stress value that you used as that seems to be one of the big variables.

Figures I used are shown below from my spreadsheet based on Martin Evans book which are the same as the Northern Association guidelines I mentioned earlier.The .9 join allowance is what I would allow, drawn tube is 1.

this gives .091" or 2.32mm

 

Steve

Barrel thichkness

Source

Model locomotive and marine boilers

By Martin Evans

ISBN 1 85761 138 1 P28

Where

P Plate thicnes in inches

D OD of Barrel in inches

 
F Factor Of Saftey 8
 
WP Working pressure PSI
 
S Ultimate tensile strength cu 25000 psi cs 60000 posi ss 70000 psi
 
R Riveting allowance single rivet = 0.5 double rivet 0.7 silver solder=0.8
 
C Corrosion allowance cu 0 ss 0 cs 0.5
 
T Temperature allowance <100psi = 0.8 100-150psi = 0.7
 
 
I used as below
 
 
  P =     0.091 "
when D 5.875 " OD      
  8        
  WP 70 PSI      
  S 25000 PSI      
  R 0.9 Joint Factor    
  T 0.8 Temperature Factor    

 

Edited By S.D.L. on 24/10/2014 13:26:06

24/10/2014 10:58:13
Posted by fizzy on 23/10/2014 21:55:00:

Hi Julian. I can assure you that I am far from bonkers! The fact remains that there is a published and accepted formula which if applied to the letter would allow the use of the gauge I referred to. As a scientist I can either accept the formula or reject it. It is either right or wrong and the fact that no one has published a boiler to this specification is completely immaterial to the fact. I have no intention of building said boiler without thorough understanding, but as yet I have not seen a single argument which in any way proves the formula to be wrong. Indeed if we had never departed from accepted standards we would still be building wooden battleships and car bodies would be made of 1/4" steel plate. I openly welcome constructive input and criticism but without supporting evidence it is merely an opinion and they don't stand up to scientific scrutiny. I still fail to understand upon what grounds an inspector could fail the boiler other than he didn't much like the look of it. Why should it be rejected if it satisfies published and well used formula?

Hi Fizzy

The answer that I posted earlier was based on the Martin Evans formula. I have been rooting around in my workshop and found a guidance note titled.NORTHERN ASSOCIATION OF MODEL ENGINEERS BOILER INSPECTORS SEMINAR. Boiler Design Materials Calculations. In this they recoment that the Martin Evans formula of

P=( D*F*W.P)/(T.S.*R*C*T*2) be used

Now if I was a Boiler inspector at a club in the northern federation that is what I would use until the guidelines were changed.

On a different note, I have never used a strength of 1 on welded joint design even with coded welders hence my use of .9. When you were coded did the welds still have to be x rayed on butt welds and dye pen on fillets?

Steve

21/10/2014 13:13:05
Posted by fizzy on 20/10/2014 14:55:04:

Im fast aproaching completing my 71/4 invicta. Now moving to the boiler design phase. Im planning on using copper for this, the thinner the better as far as construction ease goes (TIG Welded) so I put the following for discussion:

ID is 5.625"

Using 3125lb/in (safety factor x8) and 16g tube I can run WP 70psi.

Is 70 psi likely to be enough pressure or will I need to calculate this also?

Can i justify a lower safety factor?

Thanks

Using Martin Evans numbers I get minimum 0.082" wall allowing a .9 factor for the Tig butt weld.

Silver solder lap joint would be 0.8

Steve

Thread: New addition to the family.! ;)
17/10/2014 12:09:41
Posted by magpie on 17/10/2014 11:55:19:

Nick, if the head is nice and square on, leave it where it is and buy a tilting table or a tilting vice. Unless of course you don't mind spending ages traming the head up again every time you tilt it.

Cheers Derek.

Surely the reason for the tapered dowel is to give correct alignment???

Steve

Thread: Clamps,
30/09/2014 10:26:21
Posted by XD 351 on 30/09/2014 02:59:39:

There isn't much in making making them yourself mostly basic metal work with a bit of turning and threading thrown in - a good beginners project maybe?

Ian

That's why I posted asking if anyone can remember what magazine an article has been in. Several members at our club want to make some and although I have 1 clamp to copy I remember an article in one of the magazines but cant remember if it was in ME / MEW / EIM or one of the US magazines Home Shop Machinist or Machinest Workshop.

Steve

29/09/2014 20:14:01

Posted by PeterGee on 19/02/2013 11:27:59:

Here is a photo of one of my own Crab Clams:

Crab Clamp

The preview shows the photo as rather distorted, but the background should help work out the true aspect ratio of the photo... I hope.

Does anyone remember an article in one of the model magazines about making clamps to this design.

Steve

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