Here is a list of all the postings Douglas Johnston has made in our forums. Click on a thread name to jump to the thread.
Thread: Digital Rev-counter |
02/12/2010 10:32:01 |
Hello Owen - I built this tachometer a while ago and it works very well on my lathe. It is possible you may have bought the wrong display unit as I fell foul of this myself. The display units come with different input sensitivities ( 50-300V or 0-5V). I bought the 50- 300V unit and could not get the display to count, just as you found, all digits reading zero.
If this is your problem, both units are essentially the same except for R16 on the printed circuit board which needs to be changed from 47k to2k. It is quite easy to do this with a fine soldering iron. I have a letter in 'scribe a line' in issue 153 relating to this problem. I hope this is of some help.
Doug |
Thread: Where to buy indexable tool tips |
20/08/2010 18:39:49 |
Ebay is a good source for carbide tips, I have picked up quite a few bargains in the past and often make a suitable holder for the tips. If you are familiar with the nomenclature you can tell the size,shape and tip radius before you place a bid.
Douglas |
Thread: chuck myford ml10 |
20/08/2010 18:31:54 |
I often use a 6 inch 4 jaw on my Myford Speed 10 but you have to be careful to ensure the jaws do not protrude much beyond the body or they will hit the bed. For that reason I would buy a 5 inch one for this machine. I like the ones that have the body threaded and do not use a backplate ,since they have less overhang.
Douglas |
Thread: induction heating |
14/08/2010 21:14:18 |
Thanks for these responses to my query about induction heaters. These two sites were new to me and look interesting. The open source plans on the site mentioned by Andy look very promising and I will study them in detail when I find the time. Sourcing the bits might be the biggest problem despite my having quite a large electronic junk box.
Douglas |
14/08/2010 09:04:43 |
For some time I have been looking to make a small induction heating coil for general interest and heat treatment of small items. Despite searching online I have failed to find enough information to make such a device. There are plenty of sites showing them working (eg Utube) but very little in the way of practical help in building one.
Has anybody worked out how to build one or where plans exist. I am sure I am not the only one daft enough to want to build one.
Douglas |
Thread: Belt sander |
08/08/2010 13:08:06 |
I have started to build the belt sander described in ME in Jan / Mar 1995 but there seem to be quite a number of errors in the dimensions given in the drawings. Has anybody built this sander and found all the errors so that I don't fall into any traps that I have not spotted ,or were any corrections printed in later issues.
Doug |
Thread: Humidty |
03/11/2009 09:24:18 |
A couple of years ago I made a cover for my milling machine out of two layers of plastic sheet (cut from a cheap B&Q plastic tarpaulin) with a layer of bubble wrap in between. The whole thing was stuck together with duck tape, and while it is a bit cumbersome it does appear to be effective in keeping the rust at bay over the winter.
Bubble wrap is an excellent insulator and provided it completely covers the machine it should prevent a large temperature difference between the metalwork of the machine and the surrounding air , when the air temperature rises quickly due to morning sun after a cold night. This keeps the metal temperature above the dew point temperature and thus prevents condensation.
Doug |
25/10/2009 11:32:19 |
I have been looking into the idea of using a dehumidifier in my workshop for some time. The best type of unit seems to be the type that uses dessicant (not the simple silica gel filled containers that you need to revive every other day). These units work well down to to very low temperatures, unlike the compressor types.
The units can be run all the time on a humidistat but that can be rather expensive if your workshop is not well sealed to the outside air. The other problem is that of making sure that the temperature of your machinery is kept above the dewpoint of the air in the worshop.
The real problem is found when your machinery is cold (usually overnight) and the morning sun heats the air inside the workshop causing the dew point to rise above the machine temperature, since the metal machinery cannot rise in temperature at the same rate as the air. The result is condensation and the dreaded rust.
A well insulated workshop helps a lot in reducing the rate at which the air temperature changes inside the workshop thus helping to reduce the temperature difference between machinery and air.
I am in the process of designing a system which will switch the dehumidifier on only when there is a danger of condensation forming on metal surfaces so that the cost of running the system can be kept to a minimum.
Regards,
Doug |
Thread: DRO with 65 tooth bullwheel |
09/07/2009 14:35:35 |
My letter in the latest issue of MEW (153) asked about creating 60 pulses from a 65 tooth gear in the lathe. Since writing the letter I have been trying to answer my own question by delving into the internet and using an electronics forum. I have been told about an interesting chip which can be used for this (CD4089BE) and using two of these chips cascaded in the add mode provides the correction needed to a very acceptable degree of accuracy (about 0.1%).I found a supplier of these chips on ebay and am waiting for delivery.
I still feel however there may be a simpler electronic solution so if you can come up with one lets have it. Douglas
|
Thread: plastic containers |
03/07/2009 09:07:28 |
I have just received a set of 5 trays from Allendale (only took 1 day in the post- very quick service). A couple of them were a bit twisted which is not unusual with this type of plastic moulding but they sit flat with the weight of cutters in them. They are not the greatest bargain in the world but will serve the purpose well.
Douglas
|
01/07/2009 22:03:06 |
I have just ordered the allendale trays which look ideal for storing cutters, so thanks for pointing me in their direction David, but I still can't find a supplier of telescopic boxes for other applications.
Douglas
|
30/06/2009 11:06:29 |
Thanks for the reply, these boxes are indeed what I have been looking for but there do not seem to be any suppliers of small quantities of these boxes. All the references seem to be about manufacturers making the boxes or trade suppliers with huge minimum orders. I will keep hunting! |
29/06/2009 19:25:06 |
I have been hunting ebay and google to find a supplier of the two part plastic containers that a lot of new milling cutters etc come in, but I can't find any. Does anybody know of a supplier of empty containers of this type and do these containers have any special name? |
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