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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: Myford ML7 Quick change tool post
25/01/2015 07:46:15

Hi Bill,

They sell through ebay and their service is excellent.

**LINK**

HTH

Jon

Thread: ml7 headstock end play
12/01/2015 16:23:18

Hi Robin,

Have you joined the Myfordlathes yahoo group?

This file... **LINK**

may be of interest.

HTH

Jon

Thread: Vertical Shear Lathe Tooling
11/01/2015 16:34:57

Hi Geoff,

Yes it works for facing cuts too, although the cut at the very centre, perhaps unsurprisingly, isn't very efficient.

Jon

09/01/2015 17:49:56

Hi Geoff, Ian,

No problem. Hope it proves useful.

Jon

Thread: ER Collet with low TIR? Advice required
09/01/2015 08:24:14

Hi Kevin,

I bought the collets, nut and spanner from Arc and made my own ER32 collet chuck using Harold Hall's brilliant instructions. I also made an ER20 collet chuck too as I had the collets already. **LINK**

I learned a lot from doing it myself and the results were pretty good too.

Jon

Thread: Vertical Shear Lathe Tooling
08/01/2015 20:27:45

Inspired by the idea of the shear boring bar I tried grinding a single facet (approx 60 degrees) on a 1/4" round toolbit and setting it at an angle into the end of a square (7/16" ) boring bar (approx 15 degrees).

To bore the hole in the boring bar I mounted it in the QCTP on centre height but at 15 degrees to the lathe bed and drilled using a Jacob's chuck in the headstock.

This results in a cutting geometry a bit like the idea above with the conic section.

When mounting the toolbit you need to rotate it in the holder so that looking from above you have an ellipse slightly angled back from the cutting axis. This puts a slightly positive rake on the cutting edge but the angled facet on the toolbit still results in a shear cutting face against the inside of the bore.

Here's the toolbit mounted in the boring bar seen from above - note the ellipse.

and here's the side view to show the shearing angle...

And here's a piece of 1" EN3B bored to roughly 5/8" (~3 thou per rev - lowest feed on my old ML7)

...and here it is after boring out the outside half with a few passes of the shear boring bar (same feed rate)...

Sorry that these photos don't really show it very well but it does seem noticably better IMHO.

Here's a view showing it being refined and some of the long thin hairy chips...

Jon

Edited By Jon Gibbs on 08/01/2015 20:32:29

Edited By Jon Gibbs on 08/01/2015 20:33:38

Edited By Jon Gibbs on 08/01/2015 20:38:14

Edited By Jon Gibbs on 08/01/2015 20:51:40

07/01/2015 14:15:30

I found a description of a boring bar variant here **LINK**

The only problem is that the "business end" is effectivel a conical section machined from HSS round bar.

...have to find an easy grind that'll mimic the cutting action.

Jon

07/01/2015 08:40:58
Posted by Bogstandard2 on 07/01/2015 08:29:16:

With regards to the pseudo TC from the US, I class most of his work as plagiarism, and as for STEALING our Tom's name, I won't comment.

Truth is they both stole it...

"Genesis 4:22 says that Tubal-cain was the "forger of all instruments of bronze and iron" (ESV) or an "instructer of every artificer in brass and iron" (KJV). Although this may mean he was a metalsmith, a comparison with verses 20 and 21 suggests that he may have been the very first artificer in brass and iron. T. C. Mitchell suggests that he "discovered the possibilities of cold forging nativecopper and meteoric iron."[4] Tubal-cain has even been described as the first chemist.[5]" - source Wikipedia.

Don't we all pass on things we think are good ideas? - I know I do. This thread is a case in point.

I realize it will not be new to some people but will I stop doing it - No.

Jon

06/01/2015 18:02:52
Posted by chris stephens on 06/01/2015 17:30:08:

Edit, on further thought, from my limited experience of Americans they seem not to grow out of childhood, and its fantasies, till the undertaker comes a-calling and reality finally kicks in. Got to love them all the same, as I'm waiting my second childhood, still being in the first.cheeky

Sorry Chris, have to take issue with that generalization about Americans. 'Fraid to say your experience is clearly limited on perhaps more than one issue.

I appreciate him taking the time to share his experience even if you do find his approach dogmatic.

Jon

06/01/2015 11:18:03

That's interesting - I'm pretty familiar with shear scraping and shear cutting in woodturning which has pretty much the same action.

Have you seen anything similar for boring bars or for facing?

I'm assuming the slightly rounded nose version might help for facing but I've been wondering whether a boring bar which takes round toolbits could be used with the right grind to shear cut the inside of bores?

Jon

06/01/2015 08:56:17

Hi All,

I just watched MrPete222's recent video pair on vertical shear lathe tooling and made a LH and RH pair - brilliant!

If you haven't seen them they're worth a watch **LINK** and **LINK**.

I've been struggling to get a decent finish on EN3B for some time but this really solves most of my woes and for finishing cuts seems hard to beat.

HTH

Jon

Thread: Safety Glasses Side Shields
05/01/2015 15:55:15

Hi Chris,

Have you seen these? **LINK**

£8 + P&P = £10 - a bit cheaper.

HTH

Jon

Thread: Cheap Tools ........ Grrrrrrrr.!!!!!
15/12/2014 16:24:14

Hi Michael,

If you take a look at the Metcalfe experiment conducted here **LINK** you may get a clue to what may have happened.

In short I think it looks very much like a fracture of badly hardened steel.

HTH

Jon

Thread: Wimberley lathe tool holder
08/11/2014 10:54:04

I may be wrong but turn the Wimberley through 90 degrees and it looks as if you've got a presentation that is almost identical to the tangential tools - but perhaps switched from right-hand to left-hand?

Thread: cross slide micrometer wheel
07/11/2014 14:54:26
Posted by Jon Gibbs on 07/11/2014 11:51:11:

I think if you can accurately set the top-slide at 23.19 degrees to the lathe bed then 10 thou on the top slide would result in an advance the inward feed by 0.1mm.

Sine(23.19) = 0.39378 which is almost exactly 10/25.4.

To set this angle precisely it would be necessary to check for a 0.500" advance for a movement of 1.270" advance of the topslide using this set-up.

Just realized that 51.94 degrees would also work and give the 100/127 reduction.

In this case you'd have 0.2mm for each 10 thou advance on the topslide so you'd have to keep multiplying by two but not too hard to do.

...but John S's words of wisdom are still ringing in my ears ... not to mention the expletive laugh

Jon

07/11/2014 11:51:11

A thought occurs, and I don't know whether it would help, when trying to work metric with imperial dials.

I have just used Harold Halls top-slide method of putting on fine cuts using 6 and 0.6 degrees for 10:1 and 100:1 fine feeds but this could be adapted to do the conversion from imperial to metric over short cuts.

I think if you can accurately set the top-slide at 23.19 degrees to the lathe bed then 10 thou on the top slide would result in an advance the inward feed by 0.1mm.

Sine(23.19) = 0.39378 which is almost exactly 10/25.4.

To set this angle precisely it would be necessary to check for a 0.500" advance for a movement of 1.270" advance of the topslide using this set-up. See the Achieving Precise Diameters Section here... .**LINK**

Hope this helps

Jon

06/11/2014 19:51:05

Hi Robin,

My ML7 came with a cheap vertical milling slide with a 12 TPI thread on it and no scale.

I turned a conveniently sized cylindrical collar (1.044" diameter) and made a paper scale with 83.333 1mm divisions around the circumference (= 83.3333 mm).

I glued the scale on with PVA and put some shellac varnish over the top (doesn't cause the type to run) and it does the job but it doesn't get a lot of handling.

Tubalcain2 has made some neat new ones for his Logan lathe recently which may give you some better more robust dials.

Hope this helps

Jon

Thread: How to lock a nut tight on a threaded rod ?
22/09/2014 11:19:00

Interesting figures - I think we can be certain that either's strong enough though...

Rough calculation of surface area for an M5 x 0.8 thread through a 10 mm long connector nut would be in excess of 150 sq mm (pi x diameter x length not including the additional s.a. of the thread). So whether it's 25 N per sq mm (>3750 N) or 37 N per sq mm (>5550 N) I think we can be sure the threaded rod will break before the bond.

Jon

 

Edited By Jon Gibbs on 22/09/2014 11:26:02

19/09/2014 13:33:52

Thanks for the explanation.

Apologies for the naiive questions/comments.

Jon

19/09/2014 12:25:10

I think Ian's comment about the torsion delay over even 14" may be quite serious though. It's quite likely to result in the rod twisting in two at a weak point eventually if there's any real tension in the arrangement.

While the double thread is elegant in one way and ought to be twice as fast, is speed in adjustment really necessary?

Why not fix one end of the rod and use the connector nut as the means to tighten/slacken the whole arrangement and/or change the thread pitch from 0.7 to 1 or 1.2mm to ge tthe speed back?

HTH

Jon

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