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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: slow speed attachment for Unimat SL
18/05/2011 21:08:02
David,
 
Your book speed of 350rpm for 2" (50mm) gives a surface speed of about of about 180 ft/min. Your lowest speed of 900rpm gives a surface speed of about 470fpm. The tables in Machinery's Handbook (admittedly as a guide for production) give a speed of 150fpm for HSS on plain carbon steel but for coated carbide the recommended speeds are between 400 and 800 fpm. You should be able to get away with a sharp coated QC tip, though the swarf could well be coming off blue and smoking, depending on the feed. I appreciate that the your motor power is limited but I reckon it is worth a try.
 
Rod
Thread: Indexable toolholder grinding/milling/shaping
27/04/2011 14:11:58
I tried milling the bottom off a QC tool only this weekend and failed dismally, it was too hard for an HHS endmill - a solid TC endmill would probably have been OK. I've made my own holders from mild steel and they have been fine. If you do this I suggest that you off-set the holding screw hole towards the back corner slightly to ensure the the tip snugs up nicely. I have assumed that the holders are expensive because they are accurately made so that they can be interchanged in CNC machines without losing position - can anyone confirm this?
 
Rod
Thread: Model Engineer Survey
26/04/2011 23:15:59
I completely agree with NJH. A moderator should have stepped in many posts ago.
 
Rod
Thread: Technical and engineering drawing.
22/04/2011 15:16:20
This is a very interesting debate. My particular problem is that I am trying to draw up a simple i.c. engine in what I hope will be an understandable format. Being entirely self taught (my grammar school preferred Latin to TD) it seems to me that the British Standard is as good a place as any to start, I have been guided by Tubal Cain's book and there is a good introduction here http://www.tech.plymouth.ac.uk/dmme/dsgn131/DSGN131_Course_Notes.pdf . However, it seems to me that there is much that is not particularly relevant to model engineering and could be confusing .e.g. tolerances and surface finish - surely these are much better explained to the amateur by text rather than by cryptic symbols. In addition, I think a comment, for example, to mark bolt holes in the cylinder from the cylinder head is more useful that a repeated set of dimensions. David appears not to favour this method but that may exemplify some of the conflict between the Professional and the Amateur. So, perhaps, what we need is some sort of Model Engineering guidelines for drawings, a la Tubal Cain but with recognition of the capabilities (and restrictions) of CAD.
 
Rod
Thread: Myford advice needed!
15/04/2011 13:57:58
Nic,
 
It looks very nice in the picture. Having followed the prices of Myfords on E-Bay recently I would suggest that the price is pretty good. The fact that there are a couple of user made modifications suggest to me that the it has been cherished by a previous owner. I guess the 2 most important areas of potential trouble are play in the spindle and wear on the bed. I can't really advise on the former but with the bed, as a guide, I recently measured the width of the front shear on my S7 and it was 1.5 thou narrower at the headstock end than the tailstock end - and this does not cause me any trouble.
 
I hope it is as good as it looks, the quality of the paint job may give you a guide.
 
good luck,
 
Rod
Thread: TCT LATHE TOOLS
11/04/2011 12:48:11
I've got 'em all! I think Len Mason's "Using The Small Lathe" is the best. By "small" he means up to 3 1/2" Myford size. It has recently been re-published by TEE.
 
Enjoy the journey.
 
Rod
Thread: Tony Jeffree's Grinder letter in MEW175
15/03/2011 22:33:13
I made a Quorn. It took me 260 hours, of which 17 were used to make the ball handles. I was young and single then and made it over about 2 months one summer, using pretty much all my spare time. I kept a diary and enjoyed making it, but never really used it and sold it. Recently I've been toying with the idea of a Worden but I've moved on to indexable tips for the lathe and you can get a lot of new endmills for the price of the kit. Perhaps I should just make a jig for the bench grinder. I've got the drawings for a Tinker somewhere....
Thread: Index of Magazines? Stuart 10V articles?
12/03/2011 20:37:43
As Geoff suggests, there is a MAP publication called "Building a Steam Engine from Castings" by Edgar Westbury . The 10V was the first project I built, made with the aid of this book, it came with the odds and ends with my old Zyto lathe. In the front of the book it states that Exactus was workshop name of Model Engineer staff. Oliver Smith did the construction and Edgar T Westbury was the author. There are several used copies shown on Amazon UK for about £5.
 
Rod
 
Thread: Heavy Metal
09/03/2011 23:27:48
Not sure where to put this request but as it's for an i.c. engine then I guess this is as good as anywhere. Some years ago I bought some 1/4" dia. heavy metal (tungsten alloy) for use as crankshaft balance weights. It came form either Crewe or Whiston, I can't remember which. Does anybody know of a current source for small quantities?
 
cheers,
 
Rod
Thread: Boiler Insulation
03/03/2011 12:18:51
Ceramic fibre insulation sheet is available in various thicknesses. Google should find commercial suppliers. Blackgates list it on their website but I don't have a current catalogue to see what exactly they stock.
 
Rod
Thread: Mill and lathe motor upgrades
22/02/2011 16:21:43
I've just replaced the motor on my S7 with a package from Transwave which includes a BFM motor (3/4 HP). Much smoother and quieter than before, the old (original) motor started clicking after about 5 minutes - very irritating. I did have an issue with the inverter, the earth leakage on the filter tripped the 30mA RCD on the house supply but an upgrade to an unfiltered jaguar inverter (slightly more expensive) soon sorted this out. Transwave were very pleasant to deal with, the new inverter was sent overnight with instructions to send the original back when everything was satisfactory. Recommended.
 
Rod
Thread: Made me chuckle
22/02/2011 09:00:48
Or, on a bucket of dried mealworms for feeding the wild birds:
 
Not for human consumptiuon....May contain nuts.
 
I tried warning the birds but the woodpecker just laughed.
 
Rod
Thread: MT2 collet slipping
11/02/2011 16:37:20
I once had a problem with a slipping 2MT end mill holder that drove me bonkers until I eventually sorted it out. It turned out that the draw bar was overlong and bottoming on the thread in the 2MT holder rather than tightening against the end of the spindle. The difference was so subtle that there was no obvious gap. Slipping a couple of washers on the draw bar solved the problem.
 
My Sharp Mill has a spindle with a 2MT and a Myford nose thread, the idea being to use the Myford 2MT collets. I've never found this to be terribly satisfactory for holding endmills and I had a 1/2" mill come out in use, destroying the collet in the process. Getting a replacement was very expensive. Like MGJ I much prefer the Arrand type endmill holders with a reamed bore and a set screw . They work very well although they take up more headroom than the Myford arrangement . In my professional capacity I use a small Denford CNC mill and this has ER16 collets that are very secure for holding cutters.
 
I like using the Myford collets in the lathe and tend to buy PGMS these days.
 
If I were starting again I'd go for a set of ER25 collets with suitable chucks for use in the lathe or the mill. Then you have a choice of using imperial or metric cutters.
Thread: Condensation in workshops
10/02/2011 13:21:03
I don't think ventillation helps much unless you are actually generating moisture in the room, like in a bathroom.. I used to work in a laboratory that had 20 changes of air per hour. It was in a substantial building with radiator heating. Eveything rusted like crazy because there was a constant stream of moist air being introduced form outside.
 
In the past I used an oil filled radiator, on a timer, behind the lathe which was on a Myford stand. The timer came on from a couple of hours before dawn and this warmed the lathe so that it was not colder than the air. The really bad days were after a cold snap, when evrything got cold, and then a warm westerly blew in from the Atlantic. Fortunately my current workshop is in the garage adjacent to the house and contains the balanced flue central heating boiler. Not always warm, but always rust free.
Thread: Metric or Imperial, Fractions or Decimals
20/01/2011 12:41:17
Thanks for the input. Decimal inches with a mm option seems to be the way forward. KWIL, joking aside, I will probably offer an option of metric fasteners. There are few in the design but they are all BA.
Does any body have a feel for whether UK customers buy metric of imperial machines these days? If I get the chance I'll ask Warco at Ally Pally this weekend (can I mention that on this forum?).
19/01/2011 21:10:07
Hi guys,
I'm redrawing a small i.c, engine I designed and built a considerable time ago, with a view to possible publication. When I drew it (in DesignCAD 2) I was guided by Tubal Cain's Workshop Practice 13. He advocated Imperial fractions for "rule" measurements and decimal inches to a thou or better where precision was needed. That system seems to me to be based on a method of working that largely involves marking out and centre popping. I tend to use co-ordinate methods on the lathe and mill these days. My new CAD package has the option to dimension with a second unit system, so what should it be: fractions and thous, thous and millimeters, fractions and millimeters or what? And what do the US prefer? I get the impression that fractions are still favoured over there. Advice please.
Rod
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