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Member postings for Roderick Jenkins

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

Thread: Trip to New Zealand
28/08/2019 16:11:43

We really enjoyed the Kauri museum. There is quite a bit of engineering interest

log hauler 3.jpg


Thread: What Did You Do Today 2019
28/08/2019 11:33:51

Hi Martin,

'Twas us. You must have had a very hot and tiring week at the show.

martin perman.jpg

There was a magnificent array of stationary engines being exhibited - all chugging away so thanks to you and all the other exhibitors. It was really nice having a chat with you.


Rod (and Sally)

Thread: Backplate debacle
23/08/2019 20:31:56

As Andrew says. I've been using my 3 jaw like that for the last 30 years.


Thread: Simple table of potential hardness of metals
22/08/2019 14:38:25


Your question is a little too complex for a simple answer because once a tool has been quenched to give its ultimate hardness it is usually tempered to give a compromise between hardness and toughness (resistance to fracture) suitable for the job in hand.

If you are interested in this subject then I strongly recommend Tubal Cain's "Hardening, Tempering and Heat Treatment", No.1 in the Workshop Practice series.

Just as a taster, TC quotes the "as quenched" hardness of silver steel at c.67 Rockwell C and High Speed steel as 65 HRc. Both are pretty brittle in this state. If you really get in to it then you can make Dave Lammas' Hardness tester, castings available from Blackgates!



Thread: TTFN
18/08/2019 13:05:38


Right, now about these Velocette gears...

Thread: Parting problem - Morse taper
17/08/2019 13:44:04

A couple of points if I may:

I think the Sherline lathe headstock is the same as on my Sherline /Denford mill and this will take a full No.1 Morse taper. If using the full length 1MT then you will need a smaller diameter drawbar. Mine is 1/4" and holds an ER11 1MT collet chuck nice and firmly. The drawbar need only be a length of studding with a nut.

My experience of blank end arbors is that they are harder than mild steel but not excessively so. I do not think the shank will be any different from the head and they are sold so that you can modify them to your own requirements.

Hope this helps,


Thread: Velocette
16/08/2019 23:27:08


That's a good looking gear and, frankly, I wonder if for a gear with that many teeth and such a shallow angle one would really be able to tell the difference between one that has been cut straight across at an angle and one that has been cut in the correct helical fashion.


Thread: Heartbroken!
16/08/2019 18:21:38

With respect, you wouldn't need to heat the fabrication up to red heat in order to soften a carbon steel tap. Tools are usually considered to be spoiled if they get to blue, which is about 300C. You've another 300C to play with before the silver solder starts to soften - and that's ignoring any liquation effect which will raise the solder melting temperature even further.



Thread: Velocette
16/08/2019 17:01:47

Whoa... If we really are talking about helical gears then that's a whole different problem.. Helical gears can be cut using form cutters but it takes a bit of fiddling around to produce the necessary lead on the blank.


16/08/2019 15:55:30


Sets of gear cutters only produce the true tooth profile for the number of teeth at the bottom end of the range stamped on the cutter but the system works fine. Bearing this in mind I can see no problem in your original plan, I'm sure the gear will mesh adequately. Since Jason is showing off, here's a pair of 0.8 MOD gears I cut for my Farm Boy last week.


I bought my set of cutters from CTC.



Thread: Boiler testers and material verification
07/08/2019 10:59:12

Can I put forward this argument, based on no specialist knowledge whatsoever:

The boiler testing code in the UK has been put together between the insurers and model clubs. The code does not guarantee that the boiler is intrinsically safe but that it provides a reasonable risk that the insurer is prepared to underwrite. History has shown that the fairly loose requirements for silver soldered copper boilers have provided a reasonable risk for the insurers. If an exploding boiler is not insured then I suspect that all the risk falls on the operator/owner - regardless of any inspection certificate.



Edited By Roderick Jenkins on 07/08/2019 11:26:00

Thread: New Mill - Starter Tooling
28/07/2019 18:03:32
Posted by Ron Laden on 28/07/2019 14:49:04:

Would anyone happen to know the rubber thickness of a bicycle innertube...

I've got a collection of old inner tubes waiting to come in useful. Thicknesses are between .75 and 1mm.



Thread: change wheels
24/07/2019 13:32:33

RDG tools have them as do Home and Workshop Machinery.



Thread: Mystery machine..........
22/07/2019 21:07:44

It looks similar to the "Duplex" design in Ian Bradley's "The Amateurs Workshop"

duplex hacksaw.jpg


Thread: Surplus subjects learnt at school.
19/07/2019 18:48:12

Until the the late sixties you had to have Latin 'o' level if you wanted to go to Oxford or Cambridge. It would have been a pity to constrain your choice if you didn't have it wink


Thread: Crystal Ball Gazing
19/07/2019 09:50:18

Quote from Wikipaedia:

"Proxy measurements can be used to reconstruct the temperature record before the historical period. Quantities such as tree ring widths, coral growth, isotope variations in ice cores, ocean and lake sediments, cave deposits, fossils, ice cores, borehole temperatures, and glacier length records are correlated with climatic fluctuations. From these, proxy temperature reconstructions of the last 2000 years have been performed for the northern hemisphere, and over shorter time scales for the southern hemisphere and tropics."


Edit -  beaten by 1s!

Edited By Roderick Jenkins on 19/07/2019 09:52:02

Thread: Gibraltar Toolpost
19/07/2019 00:00:38
Posted by Mark Rand on 18/07/2019 22:28:24:

The residents of the rock, And the late Tom Walshaw might prefer it if folks referred to the Gibraltar tool post by its correct name. cheeky

Edited By Mark Rand on 18/07/2019 22:28:36


Thread: TTFN
18/07/2019 19:28:56

Well, that's a shame. Please don't be a stranger for too long.


Thread: Gibraltar Toolpost
17/07/2019 12:07:08

The Gibralter Toolpost is also detailed in Tubal Cain's book "Simple Workshop Devices"


Thread: A few newbie questions, sorry
16/07/2019 12:18:14

Question 2,

I think best practise is to have the faces with the bolt holes mating. On 4 jaw (independent) chucks the bolt holes are towards the middle which means that a smaller backplate than the chuck diameter can be used. With the 3 jaw chuck the bolt holes have to be around the periphery to avoid the scroll. The caveat is that this applies to screw on chucks.



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