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Member postings for Bob Rodgerson

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

Thread: Mass Production
03/09/2018 21:53:51

Posted by Neil Wyatt on 03/09/2018 10:27:02:

If the M6 hole can be made right through so all the machining is done from one end, it would be a one-setting job.


M^ hole must be blind so no easy fix.

03/09/2018 21:52:57
Posted by Andrew Johnston on 03/09/2018 09:09:07:

Bob: Not enough information! What material? What tolerances are needed? If the component is 26mm long with a 17mm recess one end that only leaves 9mm for the M6 thread. If you really want 8.5mm of thread that only leaves a 0.5mm wall thickness. no tap is going to do that. You'll either need to screwcut or thread mill.

In theory any capstan or repetition lathe could do the job, athough the M6 thread is tricky. But I think all would need a second op. And I'm not offering to make them!

Personally I'd change the design to make it easier to manufacture.


Hi Andrew, Material is 316 Stainless, tapped hole is tapping drilled 9.5mm deep and tapped as deep as possible, not sure what you mean by 1mm wall thickness because at this end of the work piece it is 18mm dia. The other end is 18mm O.D X 15mm bore X 16mm or so deep.

I have made the prototype on my manual later and am sure I could do it on my Tormach with the Rapid Turn set up using gang tooling and the lever operated chuck, however I have no desire to stand at the machine manually loading it and then turning the part around to carry out the work on the opposite end.

03/09/2018 08:41:54

I am trying to find out what type of machine would be used to manufacture several thousand simple components from round bar of say 18mm dia with a 15mm Dia X 17mm deep blind bore in one end and an M6 internal blind thread *.5mm deep on the other end, the whole job being no more than 26mm long.

Pre-CNC days, how would this have been done? What modern CNC type machine would be used today?

Obviously the job could be done by programming a simple single spindle CNC machine to carry out the operations on one end of the bar then part off but the components would have to be re-loaded the right way round to carry out the operation of drilling and tapping the hole in the other end. This would be extremely time consuming and would probably take longer than the drilling and tapping operation itself.

Thread: Aluminium eccentric
25/08/2018 09:36:06

"The probem is that small particles of aluminium wear off and oxidise. Aluminium oxide is used to make grinding wheels.


If this is the case, how come most IC engines are running with Aluminium pistons.

I see no problem with using Aluminium alloy for eccentrics, provided eccentric straps are made from case hardened steel. However, the environment beneath a Locomotive boiler is hardly conducive to longevity of nearing surfaces.

Thread: Vertical Boiler Fittings
15/08/2018 21:46:12

I use Wellseal on my Motorcycle all the time. It's really good stuff for getting a good seal on mating surfaces. It doesn't harden and can be cleaned off with methylated spirits.

Thread: Valve guides
04/07/2018 07:47:01

I made and fitted a couple of new guides to my Humber 1929 motorcycle yesterday, the old guides were OK but I have fitted modern valves which are a lot more durable than the original which are prone to drop a head.

Cast iron was the material used originally and is best used in exposed valve gear as it wears less readily when exposed to road grime compared with phosphor bronze.

Thread: Flashing red LED lights
17/06/2018 15:32:09

Halford sell them as bike lights but might be pricey compared to direct from China.

Thread: Aircraft General Discussion
16/06/2018 14:01:41

I flew in helicopters to and from work offshore for 40 Years. I hated them most when I was outbound and only hated them slightly less when I was homeward bound. The one time I was flown off sick, to be honest I couldn't have given a damn if we made it back or not I was in so much pain.

Thread: Motorcycle General Discussion
26/04/2018 09:25:51

Seriously Jim, I contend that anybody who has built a model locomotive or model I.C. engine should be able to make their own cases from solid. It does take skill and more than anything determination and a willingness to accept that if it goes pear shaped you have wasted a lot of money on a large chunk of aluminium.

A bit of research and permission to take a bunch of pictures and measurements at the National Motorcycle Museum was required to provide the basis as well as similar cases from the 350cc Side valve model to copy from. A profile drawing was made and the first process after that was to machine the internal cut out for the flywheels and bearing housings. This was followed by the outside profile and then the contouring of all the various external features, leaving material that couldn't be machined to be finished with the Dremel.

25/04/2018 17:18:58

Hi Ronan,

Triumph cases are very thin in comparison to the BSA parallel twin cases. The beauty of using billet material is that the material is consistent throughout and can be machined with constant thickness and be beefed up where required without affecting the outward appearance too much.

25/04/2018 17:16:03

Hi Jeff,

I made a crankshaft up from an original pair of flywheels and had three sets of spiral bevel gears cut for the bottom end cam drive.


25/04/2018 17:16:02

Hi Jeff,

I made a crankshaft up from an original pair of flywheels and had three sets of spiral bevel gears cut for the bottom end cam drive.


25/04/2018 12:04:40

Cause it is Jimmy,

here's one I did earlier. Cut from solid on a round column cheap manual mill and an 8"rotary table. Finished off with a Dremel and lots of elbow grease followed by shot blasting to make it look cast. Everything you see there except the cylinder, cylinder head and cam box are made in the home workshop. It's a 1929 Humber 350 OHC.img_2133.jpg

Thread: The Workshop Progress thread 2018
25/04/2018 10:07:26

I've been meaning to finish two of these off for the last year but I've been busy with lots of other stuff. They are rear hubs for a veteran Triumph motorcycle circa 1911. The body was machined on the Tormach mill using the Rapid Turn Lathe attachment. It struggled with the 2 1/2" diameter material (EN8), but I got there in the end. The profiling was done entirely with a 2mm wide grooving tool. Turning without chatter initially was a problem but as the diameter reduced it became easier.

The ratchet on one end is from a damaged free wheel chain pinion that was used as thread gauge.


Thread: Latest Update of Fusion 360 seems to have omitted the Tormach Slant pro from it's list of Post Processors
19/04/2018 13:50:15

Today I modified a programme for my Rapid Turn lathe attachment and went to produce the G-code from it but noticed that there had been an overnight upgrade. When I went to post process all I could find was Path Pilot, which previously was for the PCNC Miill and there was a processor for the Tormach 150 Slant lathe which was also the one to use for the Rapid Turn.

If I use the Path Pilot option it just keeps coming up as Download failed.

Has anybody else had similar problems ?

Thread: What did you do Today 2018
05/04/2018 16:06:45

Tracy Tool have always provided a good service. I have ben using them since 1980 and can't remember any occasion where the stuff ordered didn't turn up in the next post.

What did I do today, I cleaned and polished my 1959 BSA A-10. I went for a run on it last week and it was filthy with salt mud and general crud from damp roads, I had sprayed it with ACF-50 before I set off so I wasn't worried about the salt causing corrosion. All the muck washed off easily but the one job I hate is cleaning and polishing the Alloy rims and the brake plates, you are almost guaranteed to stub your fingers against a spoke or catch the ends of the split pins in the brake clevis pins.

Thread: Milling ali
03/04/2018 11:15:56


I assume the block is to be machined completely through. If it is I would advise drilling through holes to take out most of the material. The drilled holes will also act as drain holes for coolant and allow cuttings to clear, which is essential for aluminium to avoid cuttings building up on the cutter which will result in the cutter snapping. Take cuts of about 1/8"- 3/16" max with as high a speed as you have. Listen out for any signs of chatter in the form of a high pitched screaming noise and reduce the feed/RPM to get the optimum rates.

Good luck.

Edited By Bob Rodgerson on 03/04/2018 11:16:44

Thread: In-line Diesel Engine Model
21/03/2018 22:40:28

You are on the right track Fred. It would only be possible to do this with a vertical or possibly Vee formation engine.

21/03/2018 15:41:24

I made a 22 cc compression ignition four stroke engine with variable compression ratio controlled by moving the crankshaft up and down. For fuelI used a mix of paraffin with 10% lube oil and about 1-2% easy start. It was successful and flew a model aircraft quite well. It has a lovely sound especially when opening the throttle with a very distinct Diesel Knock. I displayed it in a model at Elvington about 1999, quite a number of people who thought they knew it all told me that my engine needed looking at because you could hear the big end knocking.

it f I'm not saying how I moved the crank shaft up and down but will leave you guessing.

Thread: Problem With Corrosion Of Stainless Steel
10/03/2018 23:51:04

Hi all,

thanks for responding. I have heat treated 10 buttons tonight and will see if this improves their corrosion resistance.,

The same material has been used in the past for this application but nobody can tell us what surface treatment was used ,if any.

I should point out that I am not dealing directly with the power station but with a sub contractor who specified the material. I m trying my best to resolve the problem for him because it has cost him so much money with people being pulled off the job twice while the problem was investigated.

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