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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: lefthand acme thread
27/01/2020 19:58:23

Might be worth thinking about making an acetal nut **LINK**


Thread: Black & Decker Band Saw
25/01/2020 22:41:18


Thread: cam gears
24/01/2020 16:10:23

HPC will supply your needs


Matador wants 48DP 10 and 20 crossed helicals


Edited By Roderick Jenkins on 24/01/2020 16:17:57

Thread: Ian S C Back again
21/01/2020 12:12:00

Good to see you back. We've missed your wise words.


Thread: A good toolpost drill design
20/01/2020 10:41:00

A bit more discussion on these Here

20/01/2020 10:19:11

I made mine from a plain shank er11 collet holder, a pair of angular contact bearings and a 200w 240v treadmill motor.


Thread: Black & Decker Band Saw
19/01/2020 20:45:52

These people may be able to help **LINK**. Blade length is 59 1/2 "



Thread: Betelgeuse in Orion
18/01/2020 23:19:34

After 4.2 x 10^15 miles the base of the cone will have a considerable area...


Thread: The Workshop Progress Thread 2020
15/01/2020 23:04:51

MAP ( note the one P ) is readily available. It is mostly propylene and is sold as a substitute for MAPP since it burns a bit hotter than propane but does not have the other desirable properties. Acetylene is probably the stuff to use for these atmospheric engines. Calcium carbide seems to be available so making a simple generator shouldn't be beyond the wit of an engineer.


Thread: magic 127 TOOTH ?
13/01/2020 09:51:01

In the "good old days" an 8tpi imperial lathe was commonly supplied with a set of change wheels - typically 20-65 in 5 teeth steps which would allow the cutting of any desired imperial screw thread. There are 151,200 permutations using any 6 of these 10 gears for drivers or drivens*. Finding a combination of these gears to give the correct pitch for a metric thread needed a systematic approach, hence the use of a 127 gear or the 63/100 ratio. However, in these days of computers we can can look at all those permutations very quickly and pull out a result that is close to the one we require - as in the table below:

basic gear set metric apprx.jpg

The maximum pitch error is 1 micron.

*not really true since a driver combination of 20,30,40 is the same as 30,20,40 but a bigger number always looks impressive wink


Thread: Scaling the Eureka
10/01/2020 17:51:02

The Eureka device obviously creates a lot of interest. I was astounded to see that my video of the device in action has had over 10,000 views surprise



Thread: First Myford question. hopefully not too stupid
09/01/2020 17:35:32

It should be a taper fit, as I found out when I broke mine. Dear old Nobby who used to post here put me right.


Thread: Amolco Mill
03/01/2020 21:48:04
Posted by Chris Vickers on 03/01/2020 19:26:53:

If I just use the cutters in the collets I know I'm likely to get the cutters creeping downwards during use. So what arrangement would originally have been used to hold threaded shank cutters to prevent this?

Also how useful are the collet closing tubes?


I would be inclined to wait and see if I actually had a problem with the Myford collets. Many people are happy with finger collets which are very similar in action to the Myford collets - just pulled instead of pushed. Threaded milling cutters are old technology. Does any body make them now? As far as I am aware carbide cutters are only available in plain shank. Most hobby users are happy with ER collets if you do have problem but remember that any additional chuck will compromise your headroom which is not great on an Amolco.

The collet closing tubes are pretty much essential to allow you to mount the closing nut on the collet.



Thread: Myford super 7B Chuck threads
03/01/2020 08:44:33

Please be aware that the Myford nose thread is not a standard Whitworth thread. A 1 1/8 BSW tap will be 7 tpi not 12. I've bought a backplate from Arc that was fine and cheaper than buying a raw casting.



Thread: Cast Iron Watch Case
03/01/2020 08:27:58

One of the TV auction shows recently had a pocket watch with a blued steel case that went for a nice price because of its rarity.


Thread: DraftSight no longer free
02/01/2020 10:53:16

My 2012 version still works.


Thread: Simple Gearing for Metric Threads on Myford ML7 lathes with gearboxes
01/01/2020 09:17:47






Edited By Roderick Jenkins on 01/01/2020 09:18:35

Thread: Casting with yellow brass
17/12/2019 15:44:47

It's hard too see why yellow brass, which seems to be a straight copper zinc alloy, would create any hazard different from other brasses. The hazard with straight brasses is with the zinc that tends to boil off and any brass foundry will be equipped to deal with this. Other brass alloys can contain lead or arsenic so I suppose these could pose different hazards. Perhaps the original foundry misunderstood the alloy requirement.


Thread: my first lathe.
11/12/2019 23:30:30


Just like this:

hmat toolpost.jpg

It's a bit crude frown



(Both photos grabbed from the web)

11/12/2019 18:31:50

The original Hobbymat mounts the tools directly onto the top slide:


Jaimie's tool post looks like a brave attempt to make a rotating tool post that will allow a selection of tools to be presented at the correct height. If the tools are ground appropriately then I think it will work.  It also has the advantage that the tools can be adjusted to centre height without the use of shims,  just by the projection of the tools


Edited By Roderick Jenkins on 11/12/2019 18:41:22

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