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Member postings for Roger Woollett

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

Thread: Resistance Soldering question
09/10/2019 15:25:10
Tim,I am sorry as you can see this is not my area of expertise. How does calling it soldering versus hard soldering or silver soldering create confusion?

The term "soldering" covers a range of filler alloys. "Soft soldering" usually means using a lead or tin based alloy with small quantities of other metals to change the melting point. Temperatures around 200 - 350 degrees Centigrade are common and heat can be applied by a flame or soldering iron.

Fillers that melt above 450 degrees C are strictly brazing alloys although the terms "hard" or "silver" sldering are often used. Model engineers tend to use silver solders thart melt from 630 degrees C and upwards. Silversmiths use a different range of silver based alloys described as "easy" ,"medium" or "hard" with melting points above 700 degrees C. These can be used on items that will be hallmarked. Most people will use a flame for these temperatures.

I hope this explains the confusion.

Thread: Silent compressor problem
25/09/2019 10:19:11

I have had this problem with a Bambi compressor. I decided the motor was only suitable for a quite low duty cycle. I had been using too much air and it got very hot.

Because of this the rubber diaphragm in the regulator failed. The first time this happened I got a replacement from Bambi. When that failed I found that it is a standard item. Machine Mart had them but I found one a lot cheaper on eBay.

Thread: Annealing Chinese Machine Tooling?
16/09/2019 12:03:27

I think the Cowells uses the short end of the taper. I agree with Hopper - buy one to try. If I am right then you should be able to put the short end directly into the headstock and turn the unwanted large end down to suit your needs. If it is hardened you might be able to use a carbide tool.

Thread: Help choosing a Chinese lathe please
01/09/2019 09:47:35

Since distance between centres is important to you remember that the quoted distance is with the chuck removed and plain centres in head and tail stocks. The maximum size of workpiece you can realistically turn may be a lot less.

As has been said Arc Euro have an excellent reputation. Their range is smaller than many of their competitors but seems to be carefully chosen.

Thread: Piston Rings
23/08/2019 18:16:43

Possibly from Direct Plastics

Direct Plastics

Not used them for a while but happy when I did.

Thread: Should I begin with mild steel on lathe?
15/08/2019 10:27:00

If you are aiming to machine silver steel then mild steel would be fine to practice on.

Do buy free cutting mild steel from a reputable supplier (there are many who supply model engineers). With a small lathe like the Sherline it is important to use a sharp tool.

When you come to silver steel halve your speed.

Thread: Help needed north London Enfield
09/08/2019 14:46:35

I may be able to help - I have sent a PM.

If you do decide to make them for youself the most difficult part is setting the top slide to the correct angle. Once you have done this make several so you have some spares.

Thread: Hardening a form tool made from Gauge Plate
15/06/2019 09:23:03

As has been said you need to get it hot enough but not too hot. Use a dim light and aim for a carrot colour. Soak times are to get the material hard right through but for a cutting tool it is only the outer millimetre or so that really maters. If the core is still tough as supplied so much the better. I wait maybe a minute after I have got it to carrot colour.

Oil is correct for gauge plate but I am afraid I just use warm water. Keep the water bath close to the hearth so the part does not cool on the way. Plunge straight in and stir to get rid of any surface bubbles.

Clean up and temper by colur or in the oven. I use a flame and quench as soon as the cutting edge gets to light straw.

Having tempered use a stone to get the cutting edge sharp again.

Finally when you use the tool go easy. If the cutting edge goes above the temper temperature it will blunt very quickly.

Thread: How to machine Acetal
14/06/2019 17:50:20

I have machined Acetal from time to time. I use a HSS - keep it sharp with plenty of rake. I usually use quite high speeds - the same as I would use for brass. This gives a nice finish.

Thread: A kitchen table workshop. Tool grinding problems
28/05/2019 15:10:06

If you keep them sharp you do not need a wheel. Get some diamond laps like these

Diamond laps

I have a similar size lathe and find all I need is a quick rub with the finest grade to keep tools sharp.

Thread: Stainless Steel Metric Fasteners
21/04/2019 15:58:36

Sorry I am a bit late but I have used these people a couple of times and have had good service.

Accu

They have a wide range of stainless fastners.

Thread: Unique engineering training courses offered by SMEE
19/12/2018 15:47:28

A quick note to say the the Part I course starts on February 9th. This course covers setting up a workshop and the tools and machines you might want to use.

We will be at the Alexandra Palace Exhibition (18 - 20 January) so if you are interested (or just want a chat) please visit our stand.

Thread: Lathe bearing oiler wicks/felt
18/08/2018 15:00:46

I have a rather more recent Cowells. As Tom says the oil does come out and can be sprayed around. The worst bit is it can get on the headstock drive belt.

I do not have to top up every time I use the lathe but have found that if the level goes down too fast it is worth checking the headstock bearings. These can be tightened using the pinch bolts. You only need to adjust them by a tiny amount.

Thread: M3 blind thread in ali about 4mm thick. How?
14/06/2018 17:34:34

Following the helicoil idea - drill out to say 4mm. Use a 4mm end mill or make a D bit to get a flat bottom to the hole. Then make a plug tapped through at the original M2.5 and loctite in place.

Thread: Hello from London
31/05/2018 14:19:42

Just to add to Bazyles comment re SMEE. Our general meetings are on Saturday afternoons (usually the first in the month) and we are near Loughborogh Junction station which is on the Thameslink line. Also accessible by bus or car - no restrictions on Saturday..

There is a meeting this Saturday if you are free - you are welcome to attend as a guest. Just turn up and make it known you are a guest and we will be happy to show you round.

More details on **LINK**

Thread: hardening/tempering a bit of steel
02/01/2018 14:16:43

The first thing you need to check is that you are using a suitable steel. It must have a high enough carbon content, silver steel (drill rod in some countries) is the normal choice although there are others. Mild steel does not have enough carbon and will not through harden although it may be possible to harden the surface (called case hardening)..

Stage one is to heat to red heat and then quench (usually in water or brine). This fixes the atoms in the steel into a very hard but brittle state. Your torch will need to be powerful enough to get the countersink red hot.

The second stage is to gently heat the part to get the right compromise between hadness and brittleness. This usually entails getting the surface to a nice clean shiny state and watching the colour as you gently heat the part. In this case I suggest a straw colour would be right. Once the colour is there quench to stop it overheating.

Metalurgist will go into much greater detail but this might help get you started.

Sorry for the repeated info Clive beat me to it.

Edited By Roger Woollett on 02/01/2018 14:19:32

Thread: Arduino &c for dinosaurs
01/08/2017 10:27:29

I think I can shed some light on the programming aspect. The Arduino IDE tries to make programming easier for beginners but can be confusing if you have some experience.

The language used is often said to be C but is in fact C++ . A sketch is essentially a source code file. When you compile the IDE generates a header file so you do not have to provide prototypes for functions. There is a main function but it is in the library - it just calls setup and then loop repeatedly.

Let me know if I can help with other confusions.

Thread: 3D Printer Test Piece
03/07/2017 17:11:03

I did this on a Prusa built from a Thames Valley RepRap Group kit. It has the screwed rod frame and was demonstrated on the SMEE stand at Guildford last weekend. Just used my standard settings for PLA.

p1000547.jpg

Thread: Cross drilling
19/06/2017 16:17:08

A method I have used involves a custom V block.

Clamp a bit if MDF to the mill table and use the tip of a centre drill (or something else that produces an approximate V groove) to cut a V groove across the MDF. Lock the table so the groove is directly under the mill axis. Now clamp the round bar into the groove and drill in the normal way. I have done this with 1mm rod and a 0.5 mm drill successfully.

Thread: Grandfather Clock
11/06/2017 09:45:32

Certainly oil the pallets/escape wheel teeth. Just put the tip of a small screwdriver into the oil and transfer the droplet of oil to the pallet face.

Also put a drop of oil on the pendulum where it passes through the crutch. If the pendulum is very loose in the crutch it might be possible to squeeze the crutch slightly. There should just be the slightest play.

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