Member postings for Douglas Johnston

I believe that is caused by the closing bracket being used without a space before it.

Doug

Just what I was thinking, I have made quite a number of holders for inserts and have always just used mild steel which works just fine. Sometimes I case harden the end where the insert pocket is but even that is probably not really needed, but it is fun to do. If case hardening I fill the threaded hole for the insert screw with fine chalk powder to prevent the thread from being hardened and thus possibly too brittle.

Doug

Good grief Neil, that is a real horror, these valves should be on display in every garage to warn people to change their cam belt at the right time. I am amazed the engine survived at all.

Doug

I bought some polymorph a few years ago, but have not done much with it apart from playing with it. It might be worth a try for this application and I might give it a try myself. I don't know much about the properties of polymorph but the moulded objects are quite tough and not unlike acetal/delrin and would be easier to mould round a leadscrew since the temperatures involved are much lower.

If you have some polymorph, give it a go James and report back. When I get an odd moment I will try it myself on something smaller to see if it is a runner.

Doug

I don't think coolant would be a problem John. The read head is completely sealed as I remember and I covered the magnetic strip with a thin non magnetic layer of brass shimstock. The only problem I can see is a metal chip getting trapped between the read head and the magnetic strip, but this has never happened to me and is quite unlikely due to the fact that these items are pretty well protected due to their location.

There is never one perfect solution, just choices to be made.

Doug

My solution to a similar problem on a small Myford Speed 10 lathe was to fit a magnetic scale underneath the cross slide (photos in my album ) with the read head mounted at the back. This way there is nothing that gets in the way along the side of the cross slide. I did this a while ago and so far it has proved to be very reliable and convenient.

If this can be done on a very small lathe with very little space to play with ,it would be a doddle on a larger lathe.

Doug

Second thought, it probably is the rubber shield that has hidden the thicker side, making both sides look the same, but that does not solve your problem!

Doug

Are you really sure they are angular contact bearings since they look just like ordinary ball bearings. Any true angular contact bearings I have seen can be identified by the thick/thin ends as shown above, but then again I have not seen that many.

Doug

I use a high quality Sumitomo carbide tipped tool in my flycutter running at about 500rpm at a turning radius of 1.5 to 2" on steel with a depth of cut of about 5 thou and with auto feed and get a superb finish.The cutting tip has positive rake and lasts a long time before a change of edge is needed. The tips I use are triangular so you get 3 edges on each tip.

Doug

You can use tracing paper instead of expensive transparency film since the tracing paper is pretty transparent to UV. Over the years I have tried a few printers for making masks for printed circuit boards with varying success. The best one was an old Epson inkjet which gave very good solid black images. All subsequent printers have not been as good and I have had to resort to printing two images ( one a mirror image ) and aligning them exactly one on top of the other with the printed surfaces touching. With luck the defects in one image are masked by the second layer.

I now use a laser printer and tracing paper, but still have to resort to making two layers to get a decent mask. I think some laser printers are better than others, but you don't know how good a particular machine is until you try it out.

Doug

Floor paint is also excellent for floors made of flooring grade chipboard. I did this some 8 years ago and it is still looking good. It really is tough and sweeps clean very easily, although the Screwfix stuff I used had the most horrid smell during application.

Doug

I have fitted both glass and magnetic scales on different axes of two machines and both types have performed perfectly. I have used two 1 micron resolution magnetic scales so high resolution is available.

The slim physical size of the magnetic scales allowed me to fit one under the cross slide of a Myford Speed 10 lathe and the rock steady 1 micron resolution is a joy to use (photos of this in my album )

I previously had a set up with Chinese scales of the type used in digital callipers and they were a nightmare due to poor stability.

So both types are very good and it really comes down to cost and available space.

Doug

It is always the same with Johnstons, you wait for ages to hear from one then two come along at once.

Doug

John,

I rather feel you want to close down all discussion of the machine from people who don't own one. The point I raised about the grinding elicited a very polite and helpful response from Ketan, which I much appreciated ,and would also be helpful to others who are considering the machine. Surely this is what the forum is all about. I think we should call a truce on this one, life is too short to argue about who has the right to speak.

Doug

The only reason I wanted chrome plated bar was to reduce the chance of corrosion, but perhaps I should heed the warnings and go for the hardened carbon steel which I can get hold of in 1" size from Marchant-Dice. It is cheaper anyway than the chrome plated stuff. Thanks for all the input.

Doug

Thanks Ketan for that information about the grinding wheels, my earlier comment about the appearance of the ground edge was not meant as a criticism of the machine, which I much admire.

Doug

Edited By JasonB on 28/05/2015 13:02:40

The magnification of the image probably makes it look rougher than it really is. It would be interesting to know what the specification of the grinding stone /diamond is and whether there is a choice of grit size.

Doug

Is it just me or does the grinding look a bit rough. The picture on the right shows the cutting edge with quite a serated look.

Doug

That is an interesting observation John, I had thought hydraulic ram rods were a similar spec to linear bearing rails but that may not be the case. I suppose hydraulic rams don't need to be that hard under the chrome plating as there won't be much load on the surface of the rod..

The 1" chrome plated rails I am looking for seem to be much easier to get in America, things seem to be more metric here in the UK.

Doug