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Member postings for Jon Gibbs

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

Thread: Which is the best parting tool ?
24/06/2014 09:50:52

Hi Brian,

I'd suggest avoiding the cheap brazed tip versions as others have said. In my experience these are too wide and hard to use. So, I've gone down the HSS route and have a similar rear toolpost version to Ian T's but in HSS and I have both thin and thick parting blades for it to cater for small and big parting jobs...

**LINK**

HTH

Jon

Thread: Bench Grinder
19/06/2014 14:11:53

Hi Andy,

These are the spark guards and should really be set to run 1/16th" from the wheel to catch the sparks and debris as Ian says.

HTH

Jon

Thread: EN3B Machinability
12/06/2014 08:26:37

Hi Colin,

Thank you for the reassurance - phew! I have to admit I got a bit carried away and bought rather a lot.

It certainly seems a bit tougher than EN1A but seems to machine ok.

Many thanks

Jon

11/06/2014 14:57:55

This is a very dumb question....

I have just bought some EN3B bar for general machining rather than the EN1A I have been using.

I'm using HSS tooling.

Am I going to regret buying it or notice little or no difference?

Any thoughts gratefully received - thanks

Jon

Thread: Dickson parting blade holder problem
10/06/2014 16:23:27

Hi Scott,

You could try to make an adaptor similar to the one I ended up with here...

**LINK**

HTH

Jon

Thread: Advice for novice early ML7 owner please
10/06/2014 14:32:39

Hi Hopper - thanks for the thought.

I've had some good experience with a piece of rag stretched over the end of the oil can spout.

I'm not sure where I read the tip but it seems that the pressure of the oil behind the rag seems to force it into a bulge to push the ball in while allowing the oil to pass through at the same time. It also does a good job at sealing things and preventing oil being wasted.

Jon

Thread: myford change gear spacer
10/06/2014 14:11:17

This is very interesting as it is a Super 7-only spacer.

The ML7 which uses the same gears and studs doesn't benefit from the spacer - the edges of the gears do occassionally rub together.

So, Rod's observation that it isn't terribly important seems fairly accurate.

Jon

Thread: ArcEuro Model 100 QCTP on a Myford ML7?
30/05/2014 17:18:59
Hi Ketan,
Ahhh, that settles it then!

Thanks very much for saving me the trouble and thanks to all for the replies.

Looks as if it'll have to be the Dickson QCTP then.

Jon
30/05/2014 11:18:54

Thanks for the suggestions.

Based on Clive's description I sketched this out - obviously not to scale. Would this work do you think?

I know that the Myford/Dickson QCTP and clones of it are always an option but does seem that it is compromised by the height of the standard 7/16" stud, isn't it?

Has anyone tried this before me?

Many thanks

Jon

Edited By Jon Gibbs on 30/05/2014 11:21:21

30/05/2014 09:52:07

Thanks Brian,

Sorry, I should have said that I know how the original 7/16 bolt is fixed and I would be aiming to reproduce the flange and pin with any new solution.

The problem I see is that the ArcEuro version requires a longer threaded bar to allow for the piston handle on top. I'm pretty sure that the original 7/16 bolt would be too short.

I have looked for other variants with a 7/16 hole and they seem to be of the Myford QCTP pattern which looks noticably cruder to me than the Arc version which seems closer to the Aloris?

Nick,

Thanks for the suggestion. I'm not sure I follow how the delrin bush can come into contact with the pin on the underside of the topslide casting. What am I missing please?

Many thanks

Jon

Edited By Jon Gibbs on 30/05/2014 09:52:54

30/05/2014 08:52:49

Has anyone fitted one of these to their Myfords who might have some advice before I splash-out please?

It looks as if "all" I need to do is to replace the Myford's 7/16 BSF toolpost bolt with an M14x1.25 one, but I am a bit reluctant to enlarge the hole in the top-slide to 14mm. Am I being too precious?

Is there a satisfactory way to keep the hole at 7/16 so that it can be returned to original and yet have a sturdy enough M14 thread above?

I thought about a shouldered stud coming through the topslide 7/16 hole with say a M8 threaded section which would screw into the M14 rod but obviously it'd need to be locked in some way to prevent it coming undone and would that ever be satisfactory really?

Any advice gratefully accepted.

Jon

Thread: Single point Whitworth Threads
23/05/2014 19:48:31

Thanks Clive. I think I could probably do the widening that way although my old ML7 is so crude it only has fixed dials on the cross-feed and topslide.

...but when I think about it though, the 12 TPI roots only require taking just over 13 thou off the point of the 55 degree point tool. So it's probably not too bad even if I have to regrind it again afterwards for other thread sizes.

So the way to go for this "bodge" would seem to be to take off the 0.1478p from the major diameter and then with a rounded off point tool (taken off by 0.1600p) go in 0.5664p or maybe a smidge further until it fits?

I'll give it a try over the w/e

Thanks again

Jon

23/05/2014 17:43:34

Ady,

...Blimey, That will require me having a few minutes to get my head around in a darkened room! disgust

...but seriously, thanks. I guess I will have to try it and see.

Jon

23/05/2014 15:57:26

Sorry for thinking on-line but taking Ady's original suggestion though, the depth could be cut to a smidge over 0.5664p and then broadened until the thread fits which would be better from a stress point of view wouldn't it?

...but is there a way to do this easily with the top-slide set over at 27 degrees?

Jon

23/05/2014 15:46:52

Here are my thoughts if it makes it any clearer...

Jon

23/05/2014 15:01:51

Thanks for the suggestion Neil.

I will give it some thought and see whether my pocket money will stretch to one.

The problem I see with that approach is that It's only good for external chasing isn't it?

Jon

23/05/2014 14:47:11

Ok, so checking through my Trig again, the idea of making the major diameter smaller by 0.1478p before single point threading then the crests will be spot-on without needing rounding. This is the same as taking off the U value in Table 21 of BS 84:1956.

For the Myford 1 1/8" x 12TPI this means the diameter will be 1.113" instead of 1.125".

This means the thread depth with a perfect 55 degree point would need to be 0.9605p (full height) - 0.16p (height / 6) - 0.0739p = 0.7266p. Anything less than a perfect point will need less depth so I guess cutting until thread fits should mean the flanks are meshing ok.

Does this make sense?

Jon

 

Edited By Jon Gibbs on 23/05/2014 14:49:57

Edited By Jon Gibbs on 23/05/2014 14:52:47

23/05/2014 14:09:01

Hi Ady,

I agree but I'm sort of assuming that the flanks are more important that the crests or roots which is why I'm trying to take the Myford-bod/flat-earther stance here wink.

I suppose I also was under the impression that it's the spindle register that provides the concentricity - is that right?

Jon

23/05/2014 11:50:06

Thanks for all of the replies and suggestions.

I should empahsised that I have made a spindle nose that works ok but I'm just not convinced that the thread flanks are meshing properly as I ended up with well defined crests. So I suppose was looking for a better way.

I think I might have found something here though...

**LINK**

in "Appendix A: Truncated Whitworth form threads with flat crests" gives the flat topped form.

[Incidentally it's quite amusing to see a Chinese company providing a pdf of a British Standard (84:1956) which is labelled as being licensed to South Bank University. BSI will helpfully provide me the same pdf for £204.] smile o

...I'm not sure whether my pedantry in trying to get this better is typical of Myford bods or Flat-earthers wink

but either way I think I can cope.

Jon

23/05/2014 08:47:18

I hope someone can put me out of my misery please.

I have been trying to cut spindle nose threads to match my ML7 which is obviously Whitworth form but I don't have the right form tool to round the creast and roots. What is the best way to single-point thread these - particularly with a simple 55 degree point tool?

Looking at the trig, starting with the nominal diameter the thread depth of 0.64 x p isn't deep enough to cut the correct flanks. It looks as if it should be 0.82 x p and that leaves a flat crest which still won't mate with the female thread roots..

Is this truncated form the way to go? Apparently it was the way the US machinists made parts to fit UK standards in WWII?

If so any guidance as to the outside diameter - obviously less than nominal but by how much? It's obviously slightly bigger than (nom - 0.36 x p) but I'm struggling with the intersection of the flank with the radius'd top.

Any guidance gratefully received - Many thanks

Jon

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