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Member postings for Andy Pugh

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

Thread: Unused Vertex BSO divided.
24/03/2019 13:00:51

A very old thread, know, but I was doing a bit of research prior to flogging my own stepper-converted BS0 on that eBay and found this thread.

It is possible to re-engineer the worm to add thrust bearings, I did so on mine.

https://www.youtube.com/watch?v=GnvAibVVajI

I used a pair of double-row angular contact bearings preloaded by a nut. They actually work as single-row in this arrangement, but the double ones are available with a very thin section and rubber seals. I did also end up having to make a new eccentric flange, but that was to mount the motor.

Thread: Are Stevenson's ER Blocks Useful
06/12/2018 19:15:51
Posted by John Haine on 06/12/2018 19:09:13:
Actually you can hold square material in an er collet by catching the corners in the slits. Not for heavy loads since you can't insert the material right through the collet but useful for grinding tools for example.

I wonder whether the collets would still work if you were to wire spark-erode a square hole into one?

04/12/2018 19:21:46

Posted by Martin Connelly on 04/12/2018 18:33:26:

 

Andy, if you want something that goes beyond the square and hex blocks consider the Stevenson's 5C indexing head with ER32 adaptor and nut as sold by Ketan.

 

If I want to accurately index I have this:

https://bodgesoc.blogspot.com/2017/05/harmonic.html

And a D1-4 5C collet chuck. (Or I could hold the ER32 block in a 3-jaw or 4-jaw chuck)

Edited By Andy Pugh on 04/12/2018 19:22:03

04/12/2018 15:17:20

I only just found this thread (looking for octagonal blocks, as it happens).

As this seems to be a compilation thread, here is a link to another way to use the blocks

https://www.model-engineer.co.uk/forums/postings.asp?th=131421

Not for work-holding at all, but to use a coaxial indicator as an edge-finder.

Edited By Andy Pugh on 04/12/2018 15:17:44

Thread: An alternative to parting-off
09/11/2018 14:57:14

For centre-height settting, these are pretty and make good christmas presents:

https://www.machine-dro.co.uk/edge-technology-speedy-lathe-gauge.html

 

 

Edited By Andy Pugh on 09/11/2018 14:57:39

Thread: Cutting a keyway without a broach
09/11/2018 12:50:33
Posted by Farmboy on 09/11/2018 11:33:43:Now, this is probably a silly question but, in my ignorance, I am wondering if/why a key really needs to be square

They don't. Tangential keys, used in pairs, are (or were) sometimes used:

**LINK**

Of more relevance here, you suggest cylindrical keys. These work well, but why limit yourself to plain cylinders? threaded keys into tapped holes half-and-half drilled can work very well and are very secure.

There were a couple of examples on my Harrison milling machine.

09/11/2018 10:11:31

I haven't seen a mention yet of a hand-slotting attachment for this task.

One is mentioned and shown in a photo here:

**LINK**

(That forum, especially the pre-ww2 section, has a number of fascinating 12" to the foot models being built.

Thread: Harrison Milling Machine Zaxis gib strips
09/11/2018 01:51:45

I finally got round to taking a photo.

The front face of the knee has 3 counterbored and threaded holes on each side.

Into each hole is threaded a tubular screw, with clearance through the middle for a 5/16 UNC cap-head screw.

Sitting in the counterbore in the knee there is a widget which is itself counterbored for the screw head and which has a pair of prongs that engage in slots in the tubular screw.

To tighten the gib you loosen the cap screw then, using a special tool, rotate the "widget" which backs out the tubular screw a fraction. Yo can then re-tighten the cap screw which clamps everything up tight, including locking the "widget" in the counterbore.

Special tool:

Not-very-technical drawing. No design work here, needs clearances and tolerances sorting out.

Thread: Cutting a keyway without a broach
09/11/2018 01:31:30

With a CNC it becomes quite easy. 

Edited By Andy Pugh on 09/11/2018 01:32:28

Thread: An alternative to parting-off
09/11/2018 01:27:54

I hadn't realised that this thread had prompted such discussion. (I don't seem to get notifications)

Anyway, as it turns out I am 100% serious about this, and I used the attachment this very evening to finish the cut through some 4" Meehanite bar.

I am sure that it is possible to part much bigger stuff but it does get proportionately more difficult as the tool extension gets greater. I have done some big stuff, but it only takes a moment of inattention or for one of the metal nautiluses to get wedged and you are looking around for another parting tool blade.

My current parting-off tool is an insert-type which takes 2mm tips, but it isn't the blade type, it is one of the more solid ones from P H Horn. **LINK** It does a lovely job, but only goes so deep. I machined a blank Multifix block from Create Tool to match the T-shaped interface.

As for the suggestion of taking the work to the saw rather than the inverse: The three-jaw chuck makes a much better job of holding short round stock than the bandsaw base does.

Thread: Where to learn Gear Hobbing?
03/11/2018 12:11:25

You can make a differential with only spur gears, the Dennis Patent Overhead Worm Drive differential is such a device:

The first picture here shows one.

https://en.wikipedia.org/wiki/Differential_(mechanical_device)

The spur gear design makes it possible to put a pair of diffs inside another diff, for four co-axial outputs:

https://photos.app.goo.gl/BKPQMLMt94ACWR4e9

Edited By Andy Pugh on 03/11/2018 12:12:00

Thread: An alternative to parting-off
02/11/2018 21:34:34

It isn't easy to part-off material on the lathe much over 2" dia in my experience.

I think I have thought of an alternative having noticed that Aldi are selling a handheld bandsaw for £150 (identical model available on eBay for £220...)

The bandsaw comes with a vice and table as an accessory, and my lathe has a T-slot at the back for a taper-turning attachment.

A bit of cutting, welding and machining later:

Thread: Where to learn Gear Hobbing?
02/11/2018 16:08:14

Whilst the Ivan Law book doesn't describe hobbing in any detail it is probably a good starting point.

https://www.amazon.co.uk/Gears-Gear-Cutting-Home-Machinists/dp/1565239172/

Hobbing is, in essence, very simple. The gear blank needs to go round at 1/n the speed of the hob, and the hob has to cut the teeth to the correct depth.

The speed division is pretty trivial nowadays, with cheap steppers and encoders readily available.

You can even do it on a milling machine if you have an encoder on the spindle.

The only other wrinkle is that the angle of the hob to the blank is not 90 degrees. The required angle is marked on the hob, but not all machines make it easy to set.

The video above uses a tilting head. My current setup uses a Harrison Milling machine where the table swings.

Thread: Harrison Milling Machine Zaxis gib strips
02/11/2018 15:58:58

I only just saw this. I will try to remember to take one of mine apart to photograph it.

Fundamentally there is a hollow tube with an external thread that the allen bolt pulls the rear keeper strip up against.

But there is the complication of a seat for the allen screw head.

Thread: helical lathe prototype - choice of components
11/09/2018 12:18:03

If you have already decided to use an Arduino then I am too late

(LinuxCNC won't run on an Arduino, and does the same job in the system as the code on your Arduino)

Thread: Holbrook Lathe Conversion
11/09/2018 11:31:48

I have converted a Holbrook Minor lathe to CNC. (as a partner to my CNC-converted Harrision milling machine).

I attempted to do the conversion as I imagined Holbrook themselves might have done it, and also in such a way that the lathe could be returned to manual operation if anyone wanted to (But that is no longer likely, as I have given away all the removed parts). It became largely an exercise in pattern-making.

I documented the process in this series of blog posts.

http://bodgesoc.blogspot.com/2015/08/holbrook1.html

Edited By Andy Pugh on 11/09/2018 11:32:50

Thread: Tom senior conversion
11/09/2018 11:27:51

I have converted a few manual machines to CNC (Chinese multi-machine, Harrison Miller, Holbrook Minor lathe).

On the Chinese Machine and the Harrison I went to some lengths to retain manual operation.

(A coupling for a handle on the Y axis, the option to un-clamp the screws and rotate them with handles on the X and D, both of which used rotating-nut on the ballscrews). On the Holbrook lathe I didn't bother, having noticed that I had _never_ felt the requirement to use the other machines in manual mode.

Thread: helical lathe prototype - choice of components
11/09/2018 11:17:58

Am I too late to suggest LinuxCNC? (I should admit that I am a developer, but as it is free and open-source I derive no benefit from expanding the user base).

Another developer, Dewey Garrett makes beautiful things using a home-built ornamental lathe controlled by LinuxCNC. You can see his machine in the video at the bottom of this page:

http://www.deweygarrett.com/

 

 

Edited By Andy Pugh on 11/09/2018 11:18:32

Thread: Ideal amateur lathe spindle nose?
11/09/2018 11:02:44

FWIW I recently made a camlock nose for the 4th axis of my milling machine, to match the one on my lathe.

http://bodgesoc.blogspot.com/2017/05/harmonic.html

I think that boring the holes in the right places would be something of a challenge in most home workshops. In fact I think that I would have struggled to make a complete spindle with integral nose. Boring the axial holes with the full length of the spindle behind the face would exceed the capacity of my mill in vertical mode. I might have been able to do it in horizontal mode.

Some significant trouble can be saved by buying the actual cams rather than making them.

These are quite inexpensive:

http://www.gatemachinery.com/product/cam-d1-4

 

Edited By Andy Pugh on 11/09/2018 11:03:38

Thread: Setting a Machine Vice Parallel on the Mill
11/09/2018 10:51:23

Another idea that I have seen in that internet.

Get a piece of ground material, ideally the same thickness as the T-slots, but not necessarily.

Cut a big inverted U-shape out of it so that the horizontal section can be gripped in the vice and the legs reach out round the vice and into the T slots.

Grip this fixture in the vice, push back against the T-slots, tighten the clamps, remove.

 

This aligns to the T slots, not to the travel axis. For real accuracy the DTI in the spindle is the only way.

Edited By Andy Pugh on 11/09/2018 10:51:50

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