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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: Os Gemini twin glow engine - conrod req'd - no longer made
21/07/2017 17:55:04


it would be easiest if you were to copy the one I have sent to Mick if he wants to go down that route.

21/07/2017 14:26:32

Hi Mick,

the newer rods are dimensionally identical to the original and are made from tougher bronze than the original type so there is no problem with conversion. I have sent you the old one I had and it will be with you tomorrow. I would recommend fitting the newer type, however, if you can't get them then at least you will have a matching pair of older type rods which will be OK.

If I had to replace the rods I would make a new pair from Aluminium Bronze which is much tougher stuff than the old rods bronze that was originally used. A High Tensile Aluminium Alloy would be best but am not sure how it would affect balance/vibration

20/07/2017 23:05:28

Hi Mick,

I've just finished a session in the workshop but took time out to find the con rod. It was a little battered here and there with a bruise on one of the faces of the little end so I ran an adjustable reamer through it to clean that up.

Three are a couple of marks on it but it looks to be OK. I would gently smooth out these marks to prevent them becoming stress raisers.

Contact me via the message board and let me have your address and I will try to get it in the post on Friday, hopefully you will get it by Saturday, unless of course you live in the South Manchester area and you could always drop by and pick it up.

Here is a picture of it before I ran the reamer through the little end.

On the other side of the big end there are two reference marks 180 degrees apart on the face of it in line with the centre line of the con rod.


18/07/2017 17:45:24


I believe I have an old style con rod from a Gemini Twin, they must be a weak point because my engine snapped one and I replaced it with two of the newer style ones. I am away from home until tomorrow but I will check and if it is still where I think it is I will let you have it F.O.C.


Thread: Timken bearing
09/07/2017 21:28:37

If they are Imperial/old bearings try the Vintage Bearing Company. He deals mainly with cars & Motor Cycles but might well be able to help.

Thread: What Did You Do Today (2017)
23/06/2017 19:19:55

Last week in the hot humid weather we had I had occasion to case harden a couple of gudgeon pins for a veteran Triumph motorcycle. I have never had problems with corrosion in my workshop up till this point.

Once the pins had been soaked for a few hours at 900 degrees Celsius I opened the furnace door to remove them from the pot containing the case hardening compound, then I returned them to the furnace to bring them back up to temperature before qrenching them. This was done with the door open at one end of the workshop.

The next day when I went into the workshop I was greeted with all steel and iron surfaces coated in a layer of rust, All of the TTS nooling for the Tormach Mill had rust on the mandrels that are gripped in the spindle were affected. I spent the whole morning carefully removing the rust with very fine wet or dry paper and giving them all a smear of oil.

I found that the closer to the section of the workshop that houses the furnace the worse the rust coating. I can only assume that this has happened as a result of the very high humidity, lack of air circulation (there was not wind whatsoever on the day) and the fumes from the case hardening compound.

Once bitten, Twice Shy I resolved to not having this happen again so yesterday I ordered a 14" industrial extractor fan. It arrived this morning and I chain drilled a hole in the brickwork for it, knocked out the bricks so that I could fit the fan, fitted it and wired it up.

The neighbours aren't going to like it one bit, it's really noisy but boy does it shift some air. You can feel the draught coming through the curtain doors, hopefully from now on when I use the furnace I won't have a future recurrence of the corrosion.

The fumes from the case hardening compound must be very acidic because even some brass pipe fittings on my model aircraft engine turned a copper colour, as though the zinc near the surface had been eaten away leaving them looking more like copper than brass.

23/06/2017 17:29:30

Nice work John, almost makes me want to buy a 3 D printer.

Thread: Countersink
18/06/2017 16:02:57


are the valve cages cylindrical, if so why use a countersink?

Thread: Cylinder steam passage repair ?
08/06/2017 17:49:43

I would have thought that if there is sufficient metal that it could be tapped and a threaded plug fitted or it could be silver soldered but not sure what it would do to the finish.

Thread: What Did You Do Today (2017)
08/06/2017 17:47:12

Today I went to pick up the repaired Ballscrew for the Tormach and while on the way I picked up 3 lengths (3.5m) of .625", .875" & 1.0" EN36 at High Peak Steels.

I noticed that when I got them home each bar end had a different colour painted on it so I hope they are colour coding them for sizes otherwise I have three different grades of metal. No doubt I will find out when I try to case harden it.

07/06/2017 21:10:02

Hi Murray,

I moved from Whitley Bay about 10 years ago but still go back to the North East regularly to either meet old pals or to ride vintage bikes on lovely quiet roads. I now live in Cheadle Hulme.

You are best to call One Stop, they are pretty helpful people, at times a bit gruff but well meaning. I have dealt with them a lot since moving here and they have a good range of the usual stuff EN1A. EN 8, EN 9 & En24T etc. They will also cut steel plate up to 12mm and bend/fold stuff too. Not sure what their range is for deliveries though.

Thread: Piston rings muddled up
07/06/2017 16:34:38


I hope you gave the fuel a spoonful of R-40 to protect the valve gear and to give that nice aroma on top of the sweet smell of freshly mown grass.

Thread: What Did You Do Today (2017)
07/06/2017 16:28:19

Muzzer, not quite Preston but there are plenty of suppliers around Manchester.

One stop Metals at Trafford Park cut to length and deliver. I have just ordered 3 lengths of EN 36 from High Peak Steels in Glossop. They also cut to length and deliver.

06/06/2017 16:27:00

EmGee/Andrew, yes my machine is relatively new but I have suffered some bad crashes whilst negotiating the learning curve to CNC machining.

I first noticed the loss of travel when cutting in a circular path but more so when thread milling external threads, there were distinct marks more or less diametrically opposite each other about 30degrees off the X axis centre line.

I did the standard checks that Tormach recommend using the conversational programming and found that advancing the table .010" then returning it it would only show .007" travel.

The last crash I had completely broke one of the TTS tool holders at the end of the parallel shank and I think that this was the one that did it.

I only hope that with the X axis sorted and the Gibbs adjusted that the Y axis is within spec otherwise I will have to cut a hole in the workshop wall to permit removal of the stepper and also make an inspection cover in the machine stand to allow me to unscrew the ball nut housing because there is no room in the workshop to get any kind of lifting gear into position to lift the table and saddle.

05/06/2017 17:51:03

Recently I had noticed some loss of accuracy of my Tormach Mill and carried out checks for loss of travel. The X-Axis showed a loss of travel of .003".

To import new ball screws for both the X & Y axis would cost about £2k by the time import duties and shipping costs are taken into account so I decided to investigate a cheaper option.

A Google search found a company in Nottingham called Ballscrew Services who seemed to be able to offer a strip down and inspection plus repair and rebuild service. I gave them a call and asked them if they could take a look at the ballscrew for me. They said to send it to them, they would appraise it's condition and let me know what the costs would be. On Thursday afternoon I sent the item off in the post and on Friday at mid day I gave them a call to see if it had arrived and they said it had. The works is shut from Mid Day on Fridays till Monday mornings so I had to wait over the weekend.

Early this afternoon I got a call from them confirming that they had fixed the ballscrew , a condition report had also been sent to my email address. New slightly larger balls had been fitted and preload had been restored.

The cost for this service was £280 plus VAT which is a lot cheaper than importing a new one from the States.

I have no connection with this company other than being a very satisfied customer but thought that anybody that is using a CNC machine might want to know about them.

01/06/2017 13:13:34

I thought that you weren't supposed to import Meat or Dairy goods into the country.

Thread: Who has bought a Tormach mill ?
11/05/2017 09:23:57


I used the same company as Andrew to import my mill. , will find them. They have recently handled the import of a PCNC 1100 for Jeff Whitaker who contacted me and whom I supplied the information required.

He has received his PCNC but has had a few issues with parts of his order not being there and one or two minor technical issues. Most of the problems seem to be down to Tormach changing the warehouse/shipping system, I believe to a new location and the technical issue was down to poor QC of tooling.

In fairness to Tormach, these issues have been dealt with but I am sure they aren't pleased with their performance with this particular order. Hopefully they will have sorted out the QC issues by the time you get your order in.


Thread: The diesel controversy
07/05/2017 17:34:10

Ethanol is horrible stuff. It dissolves older paint like Nitromors used to, rots plastic and draws in water which settles in the bottom of steel tanks and causes untold damage to fuel systems.

Millions of people are starving all over the world and the US farming lobby to grow more and more Petro crops to put the stuff into fuel as an additive.

Russia also grows millions of acres of wheat for the same purpose.

It must cost a fortune to brew and probably generates more greenhouse gasses than would be generated by burning straight mineral petroleum.

Thread: Tormach Flycutter with SEHT Insert
20/04/2017 14:47:42

Paul, I should have answered your question ages ago but I've been a bit busy lately. I am using a Tormach mill and kept the speeds high and feed moderate with a shallow depth of cut about .020" for roughing and .002 for finish cuts. I used coolant too.

I used the tool on some EN24T and found that it cut OK but there was some slight Hammering and it was slower than using a face mill so I reverted to using that for steel.

18/04/2017 21:57:54

I have one of these fly cutters and it does perform well, especially on Aluminium. It produces a finish such that it is almost impossible to see any machine marks.

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