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Member postings for Douglas Johnston

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: Grinding your own lathe cutters
18/08/2019 22:57:48

Martin- nice to know that the Chinese ones are worthwhile. If my stock ever runs out I know where to find more without breaking the bank.


18/08/2019 20:14:12

I'm glad to see that polished carbide inserts as sold for aluminium are making more fans amongst hobbyists. I have been using and advocating these inserts for some years but there always seemed to be a distinct prejudice against any carbide for hobby size lathes.

I was lucky enough to buy a whole bunch of these inserts very cheaply on ebay a number of years ago and have become more and more of a fan ever since. The ones I got were top quality branded ones but I notice that you can buy this type of insert very cheaply from China. I don't know if the Chinese ones are any good but they must be worth a punt.

It is the sharp edge and high positive rake that makes all the difference on a small lathe. You can feel them slicing through metal with very little effort and I have found they work very well on all types of metal including hard steel and cast iron. They are also an absolute delight for boring.


Thread: New Milling Machine
13/08/2019 20:04:52

For years I used a mill without a DRO and thought it was fine. I then fitted a decent quality DRO and I was delighted with it. Apart from the instant swap between imperial and metric, the time saving is considerable when finding the centre of work, or returning to an exact location etc. Once you have one there is no going back !


Thread: Black Oxide coating
12/08/2019 08:25:35

It does not need to be used engine oil (which I understand is rather toxic ) but unused oil works fine. I had some unused 5W-30 engine oil which I no longer needed and tried it with good results. Rapeseed oil from the supermarket also works a treat. Best done outside if possible, where the fumes don't stink the house and set off the smoke alarm, as I found to my cost.


Thread: What size milling tool
06/08/2019 08:24:33

Once the end of an endmill has become blunt, a lot of cutting is still possible using the side edges of the cutter. Straightening the edges of plates is a perfect example of this. All you need is some way of holding the plate flat so the edges can be machined. It is also useful to use different parts of the cutter sides to even up the wear.


Thread: Any uses for an old tired lathe bed
04/08/2019 09:06:03
Posted by Pete Rimmer on 03/08/2019 19:52:20:
Posted by David Kenyon 2 on 03/08/2019 19:39:29:
Posted by Pete Rimmer on 03/08/2019 18:45:27:

My first scraping project was a S7 bed. The simple shape makes for a great first project.

That's an idea , I might have a go at scraping it.

Scrapers are easy to make. Buy a sandvik tip and make the rest. Get a 1500-2000 grit flat lap disc off ebay (or get a set of three different grits for about 12 quid) and fix it to your chuck face with double sided tape. Turn lathe at 300-400 rpm and use it to sharpen to 5 degrees negative.

I was hoping to make a scraper and tried the link above but no joy, the link has no mention of making scrapers. Was the wrong link posted?


Thread: Upgrading to fibre optic broadband
31/07/2019 08:40:10

I have been with Virgin media fibre for a number of years and am getting fed up with the expense of it. They seem to put up the price at least once a year and often by at least 10%. The system does work well and is reliable, which makes me loathe to change to a cheaper provider, but I resent the cost which just went up another £3.50 a month a couple of weeks ago.


Thread: Dehumidifier project
30/07/2019 08:49:44
Posted by AdrianR on 20/07/2019 11:50:35:

I just found a new (to me) item that may be of interest for the "under a cover" problem. It is a desiccant dehumidifier. that has to be recharged by plugging it in. £15 for two electriQ MD100

Could also save on the SO buying those disposable dehumidifiers.


I have been using a couple of these units for the past 5 years over the winter months in Scotland. I put one under a polythene cover on my lathe and another under the mill. I try to make the covers provide a reasonable seal at the bottom and find that they last about a week before needing to be recharged overnight. This costs very little to run and seems to work quite well.

As an aside you can get a large quantity of cheap silica gel for making your own units by buying silica gel cat litter.


Thread: DIY magnetic DRO
29/07/2019 22:48:08
Posted by ChrisB on 29/07/2019 21:38:52:
Posted by old mart on 29/07/2019 20:09:30:

Are the guidelines regarding reusing the tape ok with the possibility of it stretching?

Stretching? Didn't quite get how that could happen, maybe we're not referring to the same thing. The magnetic tape I'm using is not a tape pre se, not like a cellulose tape. It is a stainless steel strip with magnetic material bonded onto it with double sided tape applied to the stainless strip (by the manufacturer). I just peel the backing film off the strip and attach it to wherever I require it. If I should need to take it off, I'll slip a blade under the tape and lift it off. Can't think of a way I'd be able to stretch it, I think it would be fine.

In any case I started installation of the DROs on the mill, should be ready by tomorrow. I threw some iron filings from the bandsaw at the tape and some will stick, but it's very easy to dust it off and none will get under the readhead as there's no gap. Will post some photos of the installation tomorrow.

Some double sided adhesive tape can be very difficult to remove, as I know from bitter experience. Better to make sure it is in the best place from the start.


27/07/2019 08:52:49

I installed a magnetic scale under the cross slide of my Myford Speed 10 lathe a few years ago (a few pictures in my album ) and it has proved to be very nice and reliable. I covered the magnetic strip with a thin strip of non magnetic copper alloy to protect it and that has worked fine.

The whole scale being under the slide keeps it out of harms way and does not clutter up the right hand side of the carriage. I have the read head stuck out at the back of the carriage with an alloy plate to cover and protect it from swarf. All in all it is more work to install it this way but the benefits are really worthwhile.


Thread: TTFN
19/07/2019 20:26:04

From one Johnston to another, I am very glad to hear that you intend to return. I think we all need a sabbatical now and again.

All the best, Doug

Thread: Engineers blue alternatives
19/07/2019 20:05:41

Thanks for the useful replies, a new thread would have been a good idea to separate the Sharpie type markers from the stuff for scraping. I have been spreading the blue I have with an applicator I found on the end of my hand and it seems to be OK if a bit messy, so I will check out a roller to stop leaving blue fingerprints everywhere.


Thread: Milling Problems
17/07/2019 19:25:54

That shiny surface looks like you have hit a hard surface on the casting, which can rapidly blunt even carbide cutters. Too shallow a cut is the problem, you need to get under the very hard surface layer and into softer iron. I ruined a carbide cutter the other day with the same problem. By increasing the depth of cut all was well with another sharp cutter.


Thread: Engineers blue alternatives
17/07/2019 08:53:50

Thanks for that information Gordon. I had a look on the Amazon site and easily found rollers but could not find the water based colour you mentioned. Could you give me any more information about what to search for on the Amazon site. I am looking on the Amazon-UK site by the way.


16/07/2019 17:43:30

Thanks for that Pete, I should probably have started a new topic rather than stick my question on the end of an old topic. My question about rollers got swamped by the previous discussion. I will see if any local arty shop has rollers I can look at otherwise it will have to be pot luck on fleabay.


16/07/2019 11:04:46

I have been trying out some scraping lately and saw on youtube that some people use a roller on the surface plate to spread the blue indicator over the surface. I was thinking about trying that but can't find any reference for the type of roller needed. There seem to be hard rubber rollers and soft rubber ones and probably ones in between. Is there a scraping mastermind out there that can recommend a suitable type of roller?


Thread: Best instructions
06/07/2019 08:49:36

I was using my Haynes manual recently and tried to follow the instructions for removing the rear bumper of my Fiesta. Try as I might I could not complete the task, the last instruction just did not work. I must have spent an hour trying to complete that final instruction and then went for a break. On the off chance there might be something on youtube I fired up the computer and had a look. Bingo, there it was in great detail showing the subtle move needed for that final instruction. Back to the car and I had the bumper off in two minutes.


Thread: How to machine Acetal
14/06/2019 20:00:11

The sharp polished carbide tips as sold for aluminium are what I use and they work a treat giving a very nice finish. They don't seem fussy about speed or feed rates. In fact I now use these inserts for most of my cutting from plastic to aluminium to mild steel and stainless steel, they are just superb tips especially on smaller lightweight lathes.


Thread: Ballscrews?
30/05/2019 08:46:14
Posted by Bear G 1 on 29/05/2019 22:28:45:

Please don't post in my threads again, your opinion is utterly worthless to me.

For a person with only 9 posts you sure like making a good impression with members here.


Thread: Buying a Reel of Bandsaw Blade
27/05/2019 19:57:28

Silver soldered blades work every bit as well as welded ones, I have been doing it for years and have never had a joint fail. Just a decent scarf joint as mentioned above does the trick. I overlap the scarf joint and place a very small piece of silver solder between the ends and flux the joint.  With everything in a simple jig to keep things in line I use two of the tiny butane torches ( the kind poncy chefs use in the kitchen ) above and below the joint and wait a few seconds until the solder fills the joint.


Edited By Douglas Johnston on 27/05/2019 19:59:22

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