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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.

<< First < Prev 34 35 36 37 38 39 40 41 Next > Last >>
Thread: Taps - What material?
27/04/2012 09:16:42

As a general user of taps I have invariably found the HSS ones to be of better quality and cut better. I am sure there are good quality carbon steel taps out there which perform very well, but I don't seem to see them.

I think the biggest problem people have is slavishly following recommended tapping drill sizes, which often results in excessive force being needed to drive the tap and can lead to breakage. Life is so much easier when one learns to use slightly larger tapping drills when strength is not an issue.

Doug

Thread: How Accurate Are Low Cost Digital Calliper Micrometers?
22/04/2012 14:00:48

Provided the mechanical parts are well made they seem to be fine. I have an expensive Mitutoyo calliper and a couple of cheap Chinese ones and they all give the same reading within a thou. The Mitutoyo one has a smoother action and feels a bit more refined but was ten times the price.

I tend to use the cheap ones for all rough work and keep the expensive one for better work. I have often wondered how the Chinese can make these callipers at the price they do considering the work that goes into making them and with the use of hardened stainless steel for the body.

Doug

Thread: Small Vice Advice
23/02/2012 09:12:40

Thanks Dias,

I see now how it is clamped using the holes along the sides.

Doug

22/02/2012 09:43:01

I like the look of the Arc Euro vice mentioned above but wonder how it is fixed to the milling table.

Doug

Thread: What cutting tools for mini - lathe (HSS or Carbide Tipped ?)
14/02/2012 09:30:54
I think we have to be careful when talking about carbide tools since there are some that are dreadful on small lightweight machines but others that are superb. I use a Myford speed 10 lathe and have used both HSS and carbide and find both have a place. I have found in recent times that I use much more carbide than I used to and this is because of the types I use. You can get some modern types with good positive rake and very sharp edges that can produce wonderful surface finish. Some of these good ones use titanium carbide which seems to give good results at slower speeds.
 
For a complete novice HSS is a good starting point however since it is more forgiving, is cheaper and easily sharpened. The sharp carbide tips can be quite fragile and you have to treat them with care but they are a joy to use. The simple answer is to try all types of cutters and see what works for you.
 
Doug
Thread: Small Power Hacksaw
12/02/2012 15:55:09
Hi wotsit - yes you have a point, perhaps we were both a bit quick to condemn on limited data. I did actually enjoy building the power hacksaw but in my case the results were rather disapointing.
 
Doug
11/02/2012 09:19:02
I think with a lot of Chinese stuff the quality is variable. My 6 by 4 bandsaw was decent quality (perhaps I was lucky ) and with a little adjustment cuts very true and the blades last a long time. A bad experience with one machine should not condemn the whole lot.
 
Doug
10/02/2012 09:58:57
I built a small powered hacksaw some years ago but it simply was not worth the effort involved. Limited capacity and very slow and was soon discarded.
I replaced it with a 6 by 4 bandsaw and never looked back. These bandsaws are so much better for most cutting and are much quicker in use. I replaced the rickety stand with a lower wooden one with wheels so it could be easily tucked under a bench when not in use.
 
I would think very carefully before spending time and money on a power hacksaw.
 
Doug
Thread: More chat about sheds
04/02/2012 10:22:29
When I built my workshop some 6 years ago I used self adhesive polyester roofing felt stuck directly onto wooden roofing planks coated with bitumen damp proof coating. This combination has worked very well and shows no sign of deterioration. The polyester material is much stronger than traditional felt and being stuck down you do not need nails and the wind does not lift the surface. Rather more expensive but well worth it in the long run.
Doug
Thread: Another broken tap thread
29/01/2012 16:11:01
 
Doug
27/01/2012 11:50:58
Robert,
I went out this morning to look for an issue of Engineering in Miniature but the February issue was the only one on the stand. Is the spark eroder article in the December and January issues since I will need to get a back issue/issues.
 
Doug.
Thread: Making a Tool Holder for CCMT 06 tips?
18/01/2012 09:32:12
As has been said they are very easy to make, I have even made holders for screwcutting inserts although they are a bit more tricky with more complex angles.
 
A milling vice with angular base is very convenient to use along with quite a small milling cutter (2.5 to 3mm or even smaller for the tiny inserts)
 
When making the tapped hole I make a punch with a diameter about 5 thou less than the diameter of the hole in the insert, with a shallow point angle. The insert is then placed into the milled pocket in the holder and the punch (held vertically) forces the insert tightly into place while spotting the hole. This proceedure ensures that when the insert is screwed into the holder it is levered tightly into position with no chance of moving when cutting metal.
 
Doug.
Thread: Quality of Engineer's squares
07/01/2012 16:01:55
One thing I would like to see is the use of stainless steel for squares and other similar measuring equipment. I bought a stainless square a couple of years ago which looks like the Warco one mentioned earlier and it is a joy to use since it is very well made and does not need to be oiled to prevent rust.
The problem is the range of stainless items is very limited. The largest square I can find is only 100mm and I would like a larger one. If we can get dirt cheap hardened stainless steel calipers, why can't we get other measuring stuff in this material?
 
Doug.
Thread: Blacking
02/01/2012 09:19:18
I have used rapeseed oil from the supermarket instead of motor oil for a number of years and get very satisfactory results. As mentioned just heat to dull red and plonk into a container of the oil and the steel comes out a deep black colour.
Doug.
Thread: Is 0.1 deg good enough..
20/12/2011 09:20:12
The MEW article seemed to imply that the digital level came with a bubble vial on top and it was not clear to me what was going on between the digital reading and the vial reading. Since the vial sensitivity was greater than the digital sensitivity there did not seem to be any point in having the digital level at all or am I missing something?
Doug.
Thread: Morse Taper Removal
15/12/2011 09:32:07
Most impressive, this looks to be a very good simple idea and the youtube video makes it so clear. As a matter of interest how easy is it to make and post such a video on youtube?
Doug.
 
Thread: Myford / RDG
15/12/2011 09:15:30
I see what you have done more clearly now. I thought you had used one of the lever type grease guns which have a spring loaded plunger coming out of the end which would have been more difficult to adapt.
Doug.
10/12/2011 09:22:45
Thanks Bill,
I've got an old grease gun in the workshop which I will experiment with when the weather gets warmer- it's freezing today
Doug..
09/12/2011 09:08:54
Hi Bill,
I did not know that cannibalism was still legal in Poole. More seriously the problem I have had with oil guns is leaking from the body of the gun which means it needs to be kept in an oilproof container and wiped clean before use. How did you seal the hole in the top of the grease gun where the grease is put in?
Doug.
08/12/2011 09:16:06
Hi Bill,
I am very interested in converting a grease gun for use as an oil gun since they can be picked up quite cheaply. Is the conversion straightforward (any extra information would be welcome).
Doug.
<< First < Prev 34 35 36 37 38 39 40 41 Next > Last >>
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