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Member postings for Brian Wood

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

Thread: Myford Super 7 Metric thread cutting gears
26/11/2019 17:38:50

Hello Simon,

I ran a few calculations this afternoon based on a combo of 17/31 instead of your 16/29.

The results were rather disappointing and erred unacceptably on the low side so I suggest you stick with what you have worked out

I think the reason is that the error moves to the minus side of the equation for 16/29 which is 0.5517

whereas 17/31 = 0.5484.The 'true' value is of course 16.5/30 which is 0.55 but now the error in minus has more influence hence giving low results. Check it out yourself, I think you will find I am right. I also now have a full table of ratios for the gearbox that you and Jester both have which might be useful to you. I can't send it by PM, my server screws all those attempts up but I can of course by email

Mine is wood_y(at)btinternet(dot)com

Best wishes Brian

26/11/2019 16:20:09


I don't envy you with your house move, we are still recovering from the move to our present address 20 years ago!

No, seriously, it was tiring to say the least and my workshop contents took most of the day to shift into the big shed in which they now live. The house content was by comparison mere child's play.

I hope it goes well for you when that day dawns.

Best wishes Brian

26/11/2019 09:24:33

Hello again Simon and Jesper,

Until Simon had difficulties in trying to apply the information in my book, I had not appreciated that the earlier gearboxes were constructed as they are. It is only fitting therefore that Simon's work, so well supported as it was by John Stevenson, should take centre stage on the solutions he had made, tested and tabulated. He has done a first class job.

I would though just like to add a note of caution if machining thread pitches that are coarser than 0.125 inches [8 tpi]. The gearing in the Myford gearbox is only 10 mm wide, I am quoting here from memory but they are narrow, and the smallest tooth count gear within is 16 T of which there are three. The strain on teeth in that size, when pushing the gearbox hard, is very likely to bend soft teeth. This was I think the reason behind Myford switching to hardened components from gearbox Serial Number 2501 onwards while at the same time improving the design to carry the leadscrew through to reduction gearing on the change wheel side and dump the 12/30 gearing to replace it with 24/30 instead

And finally, as a little bit of mischief maybe, my fag packet calculations suggest another variant to solve the 16.5 tooth dilemma. A very similar degree of error as 16/29 is found for 17/31 and I wonder if 31 teeth could be cut into a blank sized for 30 equally well. The teeth will be a trifle narrower than the 29T version but that might be an advantage. I don't know if Simon would like to explore that as an alternative, it might be an interesting experiment.

Regards Brian

Thread: Tapping a nylon hole.
25/11/2019 14:36:12


Nylon is notoriously difficult to thread successfully with things like taps and dies. It tends to expand when a tap is run into it and shrink with a die, only to return to 'size' when the pressure is off. It is fibrous in nature which is why that is difficult. It will mould with heat but the conditions need to be well controlled

I also would avoid any kind of abrasive treatment to recover your situation, it will only become embedded and then wear whatever is threaded into it later like an everlasting abrasive lap.

I suggest you replace it with Delrin which is much more forgiving rather than flog on with a hopeless situation.

Regards Brian.

Thread: Myford Super 7 Metric thread cutting gears
24/11/2019 17:54:10

Hello Roderick,

Jesper and Simon both have the early gearbox. It has a small outrigger housing on the carriage side of the gearbox with a pair of 18 T gears insideto make the leadscrew turn in a logical direction. I don't think your gearbox is of this pattern and therefore your table is valid for the later gearboxes

Simon and John Stevenson worked out the fiddle gearing needed to get the early gearboxes to work, but as we have seen, the table installed in Jesper's lathe is not matched to the gearbox that is fitted to his lathe; in which case your table will not help him either I'm afraid.

This is yet another combination of conditions brought about by incorrect matching of parts, possibly brought about by fitting the early gearbox to a bare lathe without appreciating the subtleties involved. .

If Jesper could test his lathe using Simon's table, that should work. Whether he has the gears to do it I don't know

Regards Brian

24/11/2019 10:53:38

Simon and Jesper,

Simon and I had a lot of correspondence on this topic some time ago and the trouble he had applying my book methods to his lathe with the early gearbox. You will recognise one by the small additional housing on the carriage side into which the leadscrew goes.

I can't add anything useful to what Simon says so read the story that he has given you links to, it will get you past the difficulties you are having and into the promised land! The results you will get will still be approximations, but they are more than close enough for the sort of work we do. Lambton is quite correct in saying that true values need a final change wheel of 127 teeth in the chain but it is a wheel of very nearly 6.5 inches in diameter. The lathe needs raising blocks to get it clear of the bench, or positioning so that it can run in fresh air over the end of the bench.

Never mind the cost of buying it either!



Thread: new gear for Fortis lathe
23/11/2019 14:23:42

Hello ega,

Light cuts and slow speeds with some coolant are the secret, I have made holes through steel with the holesaw arbor held in nothing more that a standard drill chuck. The arbor did have a six sided grip for that purpose


Edit. Frequent chip clearance is needed, especially when the saw teeth have cut into the material and buried the gullets

Edited By Brian Wood on 23/11/2019 14:25:22

22/11/2019 19:55:23

That's neat idea David, I might vary it by using a holesaw to cut off the rim as you suggest rather than flog through the dozens of chain drilled holes. I have made big holes through both steel and cast iron using those.



22/11/2019 17:03:03


These lathes were produced in the 1940s and 50s so I would imagine them to be 14.5 degree pressure angle. Furthermore, they were I believe based on the US Clausing of the 1940s which would almost certainly have been made to that PA.

I think it a fair bet that the 'clone' would be as little changed from original as possible.

I hope that helps

Regards Brian

Thread: Float indicator in water gauge glass
22/11/2019 12:21:46


Could Mick do the same thing by painting a red line down the back? I can't imagine it is much more sophisticated than that.

Regards Brian

22/11/2019 11:17:59


Try fitting a strip of material behind the glass which has closely spaced angled marks on it, like a pattern of chevrons. The contrast needs to be good, yellow on black is satisfactory for viewing at a distance.

The presence of water in the tube in front of it will refract the view of the chevrons to make them look horizontal and it is easy to distinguish the level from this change in view.

It is an old trick used on gauge glasses with ship's steam raising plant so that they can be rapidly assessed visually.

Regards Brian

Thread: New Myford Owner
18/11/2019 12:42:29

Hello Darren,

Welcome to the Forum, you will have plenty to do by the sound of it

Regards Brian

Thread: Mitutoyo DRO Fault
16/11/2019 18:04:09


I am a bit confused in my interpretation of your testing analysis. I am just a simple soul really!

If you take the X channel for example, does that give a different reading [as it should] when the X position is changed? And then, with the X input transferred to Y channel, do you still get another series of results that change as one expects? If so, the scale and reader are both good as well as the display.

Taking the same two tests but now using the Y channel instead. if the scale or reader are faulty then the same fault condition will be seen on either test.

I think you will be able to establish by these means whether a scale or reader are at fault and which one or whether the fault lies in one of the amplifiers in the readout

Spare ;parts like scale and/or readers may still be available from Mitutoyo. The display module too perhaps, but that is likely to be expensive.

Regards Brian

Thread: How do I undo these leadscrew nuts?
15/11/2019 15:50:40

C--C-- Baloo,

No, not really. It is more a case of feeling the degree of resistance to motion that exists in the bearing when the nuts are clamping it, especially the thrust bearing, and reproducing that later when you reset them. Doing that by counting or marking won't be sensitive enough

Too much pressure on a thrust bearing can in time indent the race and the bearing begins to feel 'digital' I can't think of a better description. For that to take place it would have set been so tight as to be stiff to move and clearly unhappy Too far the other way and it is then too slack to take up end play. The happy medium is to achieve no detectable end play along with free rotation of the bearing.

It is all a question of judgement which was why I suggested you felt it's rotation characteristics by hand before you disturb the setting of the two nuts and return to that condition after you have done whatever you are doing.

I hope that helps.

Regards Brian

Thread: What is this Tom Senior colour?
15/11/2019 11:40:24

And me again in reply!

An off white would be just fine---I have no idea what the "official" colour is but that would look OK.

Regards Brian

Thread: How do I undo these leadscrew nuts?
15/11/2019 11:35:41

Yes, they are double nuts, one locks the other and they are used to set the pre-load on the bearing

You can release them with spanners shaped like hook wrenches, but with pins to fit the holes rather than squared off hooks. They are not difficult to make really. Test the pre-load on the bearing, one of which is a thrust bearing, before you release them so that you have a feel for how they were set beforehand.

Before I made such spanners, and you will be surprised at how often they are used on machinery, all in different sizes of course, I used a pair of water pump pliers when I had to move mine in a hurry. Being slim they are about the right size.

Regards Brian

Thread: Boxford metric lead screw fitted to imperial lathe?
11/11/2019 14:51:54

Hello again Cupboard,

How satisfactory to hear at last the full story. I don't think it would have been possible for anyone here to guess at the way the drive was coupled to the leadscrew; no wonder the results were odd and confusing. Thank you for completing the saga

I am reminded of one query we in the forum were able to solve 'remotely'. for a posting some time ago. It all boiled down to him using a change wheel of 54 teeth that had been incorrectly stamped as 45 teeth and only by suggesting he actually counted everything was the truth of that situation found



Thread: What would you call this tool
11/11/2019 14:38:22

Possibly a positioning aid for precision welding


Thread: Workshop series
10/11/2019 18:32:16

I endorse the series too, lots of good information


Thread: Cutting an unlisted thread on colchester student
07/11/2019 08:29:45

Hello Ian,

Thank you for bringing us up to date with the outcome of your experience. It is always gratifying to hear that suggestions have worked, as planned, and that you are pleased with the outcome.

Happy threading

Regards Brian

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