Member postings for Andy Pugh

It wouldn't really be branching-out for me.

http://bodgesoc.blogspot.com/2015/12/Holbrook3.html

and

https://bodgesoc.blogspot.com/2016/01/holbrook5.html

I actually think that a replacement head casting could be line-bored on the lathe itself.

1) Devise a means of mounting a boring bar to the tailstock quill. I have seen 3-jaw chucks for tailstock mounting, and I have an ER collet in bearings for a similar purpose.

2) As well as the head casting, have a cup-shaped casting made that can bolt on the back of the new casting to guide the boring bar. This could be machined on the lathe prior to dismantling it.

3) <handwaving> machine the head to bed mating surface

4) Set up the boring bar true to the bed, adjusting the steady bearing in (2) until a dial indicator travelling on the carriage indicates dead true. You now have an accurate spindle axis, aligned with the tailstock.

5) <more handwaving> somehow drive the boring bar.

6) Use the tailstock to feed the boring bar to machine the bearing bores and registers.

I have started calling it "Darwin" steering, on the basis that it wasn't invented by Ackerman.

There is a special low melting point alloy which would be ideal for this:

https://flowxrgdotcom.files.wordpress.com/2011/07/new-method-of-building-lathes.pdf

The head castings on these machines are very simple, making a whole new head is probably not outside the realms of possibility.

I made a Y-shaped wrench for my three different things (2 squares and a hex)

There is a D1-4 model here based on the ISO standard: http://a360.co/2ot1Hr0 (ignore the extra mounting holes for my 4th axis)

I have created a macro / spreadsheet to create XML files for Fusion 360 threads.

https://github.com/andypugh/FusionThreads

There is a ready-to-use Whitworth XML there (based on mid-tolerance medium threads)

To create your own, Duplicate the Whitworth tab, type in the tread data then run the macro (View->Macros to see it)

It will create an XML file based on the active worksheet in the same directory as the spreadsheet file.

Edited By Andy Pugh on 26/12/2021 18:35:27

A 10B has just appeared on eBay:

https://www.ebay.co.uk/itm/275001782024

Comes free with an overpriced milling machine

Gate and XYZ list D1-4 in the UK. D1-3 seems rarer.

https://spares.xyzmachinetools.com/KeywordSearchResults.asp?searchCategories=0&keyword=D1-4&Submit=Search

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

Looking (unsuccesfully) for a source of D1-3 cams I stumbled upon this thread.

I have been making myself a D1-4 adaptor for my milling machine. I had extra castings made. Due to messing up I have:

1) A D1-3 adaptor that was a fallback when I machined a D1-4 too small. This should be all ready to go, except that it has no cams:

The raw casting was £36 from AJD and I have a few hours of work in it, so I would be hoping to get £75 plus postage for it.

2) A mirror-image D1-4 adaptor. This is what you get when you machine the radial holes 90 degrees out. This probably means that it won't even work with the pins reversed, as the angle between the holes should be 15.6 degrees but is in fact. 14.4 degrees. But you could still hold a chuck down with toe-clamps, and use it simply as a support and/or positioning device.

This can be had free for the price of postage.

Edited By Andy Pugh on 10/05/2021 22:58:47

I was a bit surprised by that. It isn't generally very difficult to get the screws out, and then the inside ends could be finished off neatly on a lathe.
Just remove the jaws and then tap the forks back with a punch. They are often only retained by the backplate.

I have made a Camlock mount. It's a lot of work.

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

If anyone fancies the idea, though, the cams are probably best bought, and were fairly inexpensive here:

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

Though they show out-of-stock at the moment.

This is a _model_engineering_ forum, the whole raison d'etre of which is to "waste" time and money.

And I disagree with the premise. It is frequently useful to be able to have larger diameter sections of parts on the opposite side of the chuck, even if the parts won't fit through the chuck.

And it is relatively easy to make the hole in the middle of a 4-jaw chuck larger, you only need to shorten the screws and bore out the body.

Better to have spanners and no bolts than bolts and no spanners, which was the situation that prompted me to ressurrect this thread.

(The observation that many new whitworth sets do not contain a spanner to fit the old 5/8* head at 1.10" jaw opening. Ironically you might well have a 28mm and that would fit nicely)

It looks like a BS190 spanner, so yes, it will fit an old 5/8"W bolt head. My point was that modern Whitworth spanner sets do not always include the 1.10" AF size.

I haven't yet found a BS1083 table that lists the "new" 11/16"BSF spanner size. I strongly suspect that it doesn't exist and so to deal with BS190 5/8" bolts you need to find a spanner made before 1951.

I don't think that 11/16BSF appears in BS1083 or BS190. None of our sets (King Dick and Britool) seemed to include it. And if you go to the bolt shops they don't have that size (though taps and dies are readily available)

The big-end bolts on the fire engine are actually 11/16 BSF. Amazingly it survived for years with 3/4 BSF nuts on there, the pitch difference and size difference seemed to conspire to torque up and hold OK. When we discovered the error I seem to recall we had some nuts specially made. But the nut AF size matches a spanner so probably isn't 1.10"

To resurrect a zombie thread..

There is one exception. One of the big-head Whitworth heads did not have a BSF equivalent.

http://www.oldengine.org/members/diesel/Tables/WhitAF.htm

The old 5/8 Whit at 1.10 AF had no BSF equivalent.

I have found it _very_ hard to find a 1.10" spanner for our old fire engine. (1916)

For this sort of thing I would[1] look at using a Feather from Adafruit, a lot more capable than an Arduino with floating point and orders of magnitude more memory, but programmable with the Arduino tools and IDE.

I think that you can setup a hardware interrupt on the spindle encoder pulses. Then in the ISR decide whether the workpiece motor needs a pulse or not. I am imagining here that the encoder resolution is high enough that there are more encoder counts per spindle rev than stepper pulses in the work spindle, but a factor of a few.

If that condition is not true then it is harder.

single-start hob, 12 tooth gear, 1024 PPR spindle = 12,000 ISR calls per gear blank revolution.

200 step motor, 4 x microstepping = 800 pulses per rev, so that is fine, one step every 13 encoder edges. It gets better for higher tooth counts.

Basically, in the ISR the code looks at encoder pulses counted so far, compares to step pulses sent so far, and if the ratio is more than the tooth count requested then it toggles the state of the step pulse output. This should be about as low-overhead as it gets.

Other approaches need to set up constant rate step-generators.

[1] Well, I wouldn't. I would (and do) use LinuxCNC for gear hobbing.

It is measuring "Basic Pitch".

I have an excel spreadsheet that does basic gear calculations, and one thing it gives is a "span across N" which can be used to check when the hobbing process has cut deep enough.
I found a reference online that mentioned using the difference between two spans to determine PA, but that only had an equation.

I used my spreadsheet to calculate the numbers for the range of gears shown

However, armed with these phrases, I have actually found a much more extensive table and a more detailed explanation:

**LINK**

Edited By Andy Pugh on 22/06/2020 09:34:26

The measurement should be tangent to the tooth flanks. As long as it isn't wedged deep in the root or teetering on the tip the measurement should be the same.

If you have a gear and need to replace it or match to it (for example to make a missing change gear for your lathe) here is how to do it.

(Most of this isn't new, but I think that the pressure angle table is)

I just found this with Google, after being challenged to find any one other person that can use the phrase "living room lathe". So thanks for making me not wierd.
I might as well post a photo of mine... https://photos.app.goo.gl/U2X3SLH3YBWLkehz8