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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: What did you do today (2015)
25/06/2015 09:30:28
Posted by Nicholas Farr on 24/06/2015 21:39:40:
Posted by JasonB on 24/06/2015 19:53:20:

3 points of contact so could not hold brush and paint pot, thats HSE for you

Hi, guide lines for working at heights can be found at **LINK** this is of course aimed at anyone being employed, or employing others. When working at home for yourself, you don't have to follow these guide lines, but it would be very prudent to do so, because ignoring these guidelines can lead to an accident that may cause a serious disability for the rest of your life or end it completely.

Not sure whether you've seen this but it's good viewing.

**LINK**

I agree with the sentiment of the post but Fred D wouldn't have got very far following those HSE guidelines

Jon

08/06/2015 18:52:41

I think it's also easier and cheaper to arrange for adjustment of the bearings that way.

A simple shaft on which the bearing runs can be moved in and out of a housing to adjust the tracking.

My side bearings are on eccentrics. So rotating the eccentrics shifts them left and right and the housing allows them to have a bit of movement in and out but I've simplified things quite a bit by deciding to restrict it to 1/2" blades.

08/06/2015 16:53:02

Finally got around to replacing the lower guides on my Electra Beckum 18" wood bandsaw.

It has bearing guides on the top which are visible but underneath it had nasty steel rubbing blocks.

I'm quite tempted to replace the top guides too now as in their design the blade rubs on the sides of the bearings rather than the edges which ends up scoring them if the bearings stops - not very good IMHO.

Jon

Thread: grinding a masonry drill for steel
03/06/2015 09:05:39

I've had some success with spear point tile drills if this helps.

The other option is to try something like the Bosch Multi-construction drill bits but these aren't as sharp from my experience.

In both cases high drilling pressures are needed.

Jon

Thread: Threading and threading
20/05/2015 09:54:35
Posted by Clive Foster on 19/05/2015 17:46:36:

Although the ceoss slide parallel to the bed set-up for threading works pretty well its a major PIA getting things set up specially for threading. Especially on a small machine where there isn't room to leave the topslide permanently at 90°. Actually its a bit crowded on pretty much any home shop capable lathe. A technique I only use for ACME and similar feed screw/nut threads which have to be cut for minimal clearance.

I can agree with that although on the Myford ML7 there is a pretty annoying design flaw in that the topslide is not free to rotate completely - You have to choose the quadrant by positioning the Tee-nuts to either left or right of the cross slide slots.

So, to save keep mucking about taking the topslide off and on I tend to keep my topslide mostly at 6 degrees from parallel to the lathe bed to give a bit of clearance with the tailstock but also to allow a roughly 10:1 ratio for top-slide versus cross-slide movement. If I find myself wanting to take 0.001" off the diameter, moving the topslide in 0.005" has the effect of advancing the tool in about 0.0005".

This is another trick from Harold Hall - See bottom of this page... **LINK**

It's probably of no help to you, but I HTH someone.

Jon

Thread: Best method of boring a bearing housing
20/05/2015 08:38:39

Thanks very much Jason - Brilliant.

Even I ought to be able to follow that.

Jon smiley

20/05/2015 08:00:06

Sorry, another dumb question coming up....blush

Having made the boring bar, what grind for the 6mm HSS round toolbit to cut steel please?

The toolbit is stuck out at right angles to the bore.

Many thanks in anticipation

Jon

Thread: Threading and threading
19/05/2015 13:37:47

There is an easy but not universally appreciated way and that's to keep the topslide at 90 degrees to the cross-slide (parallel to the lathe bed) and to advance the topslide each time by half the advance on the cross-slide.

That works out as being at tan^-1(0.5) = 26.565 degrees and so works well for both Whitworth and metric thread forms.

It means that the thread depth is the direct reading on the cross-slide and also allows a thread to be widened more easily once full depth is achieved by just advancing the topslide.

Martin Cleave's book **LINK** lists this as METHOD 3 in Section 8 and is the method he said he usually adopted.

HTH

Jon

Thread: Best method of boring a bearing housing
19/05/2015 11:09:00

Thanks Jason. I went through the same thought process when I read Neil's suggestion smiley

I suppose that also means that the collet chuck might also be ok in practice

...especially if the bar in both cases has a shoulder that means it can't be forced back into the jaws.

Jon

19/05/2015 09:54:38

Hi Malc,

Brilliant! - thank you. I think a few quid on an M10 threaded blank end arbor machined to a 60 degree point would be just as good - perhaps even with a short length of rod poking out to catch the drive dog?

I have an ER32 collet chuck but it also screws onto the spindle nose sad

Bob, no problem. 

Thanks again folks

Jon

 

Edited By Jon Gibbs on 19/05/2015 09:57:52

19/05/2015 08:36:19

Thanks very much to everyone - I really appreciate all of the replies.

I just realized that although my lathe will go in reverse the catch-plate for the boring bar will be wanting to unscrew from the nose in reverse which makes Frank and Nigel's suggestions perhaps the best for me.

At least I feel that it's within my limited capabilities - My welding is certainly not up to John S's suggestion, although I can see that it would work.

Is there a way to get around the catch-plate unscrewing?

The chucks on my woodlathe achieve this with set-screws onto the spindle nose which is ok for wood tolerances but clearly a no-no.

Jon

18/05/2015 19:02:48

Hi Jason,

Thanks very much. When you say " turn end for end and go straight in with a single 1.5mm cut for the opposite side" am I turning the boring bar end for end?

Les, my lathe does have reverse thanks.

Jon

18/05/2015 17:18:14

Thanks very much Jason.

The 25mm was just a rough guess to highlight the need for the shells to rest on something and could obviously be quite a bit bigger as you say.

Many thanks again

Jon

18/05/2015 16:52:33

Hi Bob,

Thanks for the suggestion.

I think I should have been a bit more specific. I think that I need the bearings to sit firmly in the bar with the ends bored like this...

I think that to maintain alignment, the 35mm holes need to be a snug fit for the bearing shells when they're bored and when the bearings are installed they sit slightly proud of the bar.

Unless anyone has a better idea?

Many thanks

Jon

Edited By Jon Gibbs on 18/05/2015 16:53:55

18/05/2015 16:08:26

I have ordered some 15x35x11.8 taper roller bearings to make one of these things...

based around a length of 45mm square bar but I have realized that, while I know how to cut the bearing housings on the boring bar holder, I will need to cut four housings in the ends of a 200mm 45mm square bar on my old Myford ML7. I'm not bothering with the intermediate holes.

What's the best way of doing this?

I currently don't have a boring head - do I need one or is there a cheap and cheerful way of managing without?

Any guidance gratefully received

Many thanks

Jon

Thread: Engineneering-homemade
15/05/2015 15:45:19

Hi Clive,

In theory since kinetic energy is 1/2 m v^2 and mass and volume are proportional, it's better to increase the velocity than the volume by the same factor.

...but I suppose that assumes that the turbine extracting the power has the same efficiency across the range of variables. 

Jon

Edited By Jon Gibbs on 15/05/2015 15:48:17

15/05/2015 13:51:42

Sorry Ian, of course not.

We're just sore because many of us don't have a stream we could use and are on water meters that cost an arm and a leg since water privatization - I guess that's where Jason B's question originally came from.

Jon

14/05/2015 13:57:20

Hi Ian,

You may be right that it's more efficient. Interestingly it's 56% efficient if my maths is right.

60 l/sec will mean 216000 l/hr which is obviously 216000 kg of water which would have potential energy of roughly 6.48 MJ if at 3m.

That will generate about 1kWhr if their claims are accurate but the water has potential energy of 6.48 MJ = 1.80kWhr.

This means that 1kWhr of electricity would cost £278 - Even less fun wink

Jon

Edited By Jon Gibbs on 14/05/2015 14:00:31

Edited By Jon Gibbs on 14/05/2015 14:01:11

Edited By Jon Gibbs on 14/05/2015 14:04:42

14/05/2015 08:50:40
Posted by Neil Wyatt on 13/05/2015 18:52:24:

> buy your electricity from the grid.

Where's the fun in that?

Neil

I didn't say it was fun - just cheaper. I couldn't resist Jason's challenge I'm afraid.

I think I could have fun spending the other £155.87 per kWhr on something else though wink

14/05/2015 08:42:25
Posted by Michael Gilligan on 13/05/2015 20:29:21:
Posted by Faruk Ribic on 13/05/2015 20:06:19:

... I am not sure what turbine with 'backshot' is.

.

I think it's the one also known as BreastShot ... see here.

MichaelG.

This is "Backshot"...

It's described in the Wikipedia page I linked to here **LINK**

Jon

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