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Member postings for Avon

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

Thread: How to secure a Piston Rod in the Piston
12/06/2020 20:40:46

HI Guys,

I had to use a punch to drive the rod out of the piston. In truth I was surprised that there are two different diameters in the piston and it was that that led me to believe that it had been riveted (ie the end hammered to widen it out to fill the gap).

I think the idea of tapping it is probably the best. I can probably reuse the original piston as well. There's nothing wrong with it fundamentally and my slowly developing lathe skills are probably not yet at that level - that said I could give it a go just as a training exercise!

I'll let you know how I get on.

12/06/2020 17:42:41

I know this should be simple, but I don't know the answer.

The piston rod in the attached photo has sheared at the pin where it is articulated. How to solve that is tomorrow's problem.

Having extracted the pin from the piston I realise that the 3/16" piston rod has been reduced to 1/8" to fit through the hole in the piston. The hole in the other side of the piston is 5/32" so I've assumed that I now need to hammer the piston rod to expand it, rivet like, to secure it in the piston.

What I don't know is how best to secure the piston rod while I hammer it - I don't want to spoil the surface of the piston rod as it needs to be a good fit through the gland housing. Additionally, I don't think I should be trimming the rod to size at this stage as the hammering is then as likely to flare the bottom end as well as the top.

I've also included a drawing of the two parts.

PS. Does anyone know the maker of this model? It has a W on the valve cover.

Grateful for any advice.

photo 12-06-2020, 10 49 26.jpgpiston rod drawing.jpg

Thread: How to strip a Centec 2A Vertical Milling Head
05/06/2020 18:21:29

Finally produced a new drawbar. Turns out the thread on the original was 5/16 BSF (22tpi). So I've turned down a length of 3/8 and threaded it. I've added a length of Hex bar to the top with a 3/8BSF (20tpi) and will also drill and pin it when I can. The 3/8 rod is a firm fit in the quill, but I can turn it fairly easily with fingers so don't think it will cause any problems and should transmit any stout taps without too much flexing.

Its not at all sophisticated, but I think it will suffice and if I need to make another at least I now know how.

Many thanks for all your help and ideas.photo 05-06-2020, 17 08 50.jpg

20/05/2020 15:53:29

Gentlemen,

Firstly, many thanks for all your efforts, information and advice. It has all been useful and the photos of the drawbar arrangement will inform my manufacture of a replacement.

Below is a photo of the thing apart.

In the end I took it to an agricultural repair shop as the chap is frequently called on to renovate/repair machinery that has been hard used and unloved. It transpired that the ring/snugging nut was almost certainly in contact with the rear face of the chuck, so I was unable to gain further clearance between it and the end of the spindle which I is what I'd tried to achieve in the earlier photos. So we turned in as shown in Peak4's photo until it bore against the bottom of the spindle - it took a considerable effort to move the nut and a man sized spanner stopping the spindle moving which was clamped in jaws of a large Colchester lathe. We then tried heating it, but it made no difference. So back in the lathe and with some more enthusiastic hammering on the spanner until it finally came apart.

The snugging nut is a nice clean thread so I'm sure it was just very tight up on the body of the chuck. The drawbar takes a meandering path from one end to the other, no wonder it wasn't very useful. The taper on the chuck seems to be nice and clean, but that in the quill has clearly had swarf and other inappropriate things in it. I'll have to get an MT2 taper reamer to clean it up.

Gents, again thank your for you help - it gave me confidence in what we were doing and a successful outcome.apart.jpg

PS. Why is it so difficult to work out a lefthand thread when we understand a righthand without thought!

20/05/2020 15:53:28

Gentlemen,

Firstly, many thanks for all your efforts, information and advice. It has all been useful and the photos of the drawbar arrangement will inform my manufacture of a replacement.

Below is a photo of the thing apart.

In the end I took it to an agricultural repair shop as the chap is frequently called on to renovate/repair machinery that has been hard used and unloved. It transpired that the ring/snugging nut was almost certainly in contact with the rear face of the chuck, so I was unable to gain further clearance between it and the end of the spindle which I is what I'd tried to achieve in the earlier photos. So we turned in as shown in Peak4's photo until it bore against the bottom of the spindle - it took a considerable effort to move the nut and a man sized spanner stopping the spindle moving which was clamped in jaws of a large Colchester lathe. We then tried heating it, but it made no difference. So back in the lathe and with some more enthusiastic hammering on the spanner until it finally came apart.

The snugging nut is a nice clean thread so I'm sure it was just very tight up on the body of the chuck. The drawbar takes a meandering path from one end to the other, no wonder it wasn't very useful. The taper on the chuck seems to be nice and clean, but that in the quill has clearly had swarf and other inappropriate things in it. I'll have to get an MT2 taper reamer to clean it up.

Gents, again thank your for you help - it gave me confidence in what we were doing and a successful outcome.apart.jpg

PS. Why is it so difficult to work out a lefthand thread when we understand a righthand without thought!

19/05/2020 17:37:10

Hi Dave, All, I think its well and truly set!

I've heated it (wife didn't notice it in the oven - only 120C) then cooled the chuck in cold water. Clamped it in the vice as show and gave the well fitted spanner some enthusiastic attention. Not the slightest sign of if moving and I checked and thought through multiple times whether I was trying to turn it in the right direction - I'm certain I am!

The spanner is now showing signs of cracking (maybe a bit too much enthusiasm) and tomorrow we're off to a local engineering firm that are experienced in attending to old agricultural machinery and the chap is a bit of a whizz (I'm told and hope).

Maybe that's why my father never seemed to us it very much - I know I can use it setup as it is, but it'd be a shame to refurb the rest of the machine and not get this sorted out.

I'll update the thread when I've made some progress.

in the vice.jpg

Edited By Avon on 19/05/2020 17:37:32

Edited By Avon on 19/05/2020 17:38:16

18/05/2020 19:55:45

Dear All,

The quill is out of the bearings so I've found the taper rollers and oil seal mentioned by Duncan. I think I'm going to try using a bearing puller first (I think I have one somewhere), perhaps supported followed by making up some wedges as mentioned by 'not done it yet'..After that some heat, WD40 and possible a good whack with a mallet - Old Mart doesn't believe that the drawbar would be captive - so an enthusiasic whack might be all thats required.

I'll let you know how I get on!!

Many thanks

18/05/2020 16:47:39

Hi Howard, I've been thinking about the careful use of heat to free things up. My first concern though is the drawbar which I presume will prevent any effective use of wedges - unless I've completely misunderstood the drawbar's function (entirely possible).

To heat it up I was actually thinking of putting it in a bath of boiling water? It'll be hot, but can't get too hot.

Peter

18/05/2020 16:16:06

draw bar head.jpg

18/05/2020 16:14:39

Gentlemen,

Many thanks for the replies. I've now stripped the head down and have the quill together, draw bar and Clarkson S type collet holder in one lump on the bench. Currently I have them in a bottle full of diesel in a vain hope that it'll soften some of the old gunk; even poured some down the quill shaft.

I've tried undoing the damper on the chuck having found a proper spanner to fit the holes - nothing moved, even when I carefully checked the thread direction.

Neither does the draw bar move. With regard to the drawbar does it act in such a way internal to the quill that it will pull any taper fitting up tight or should it be acting on something on the top of the quill shaft? If if acts internally then to use T.B.s suggestion surely I'd have to have unscrewed the drawbar first? Since it doesn't move at all at the moment, I'm considering cutting a slot in the head to act like a screw head.

I'd be grateful for your thoughts. I'll post a pic of the quill head shortly.

17/05/2020 18:59:38

Thanks Duncan, I did wonder whether it the drawbar as you've described it had a better function than simply being there to be whacked! Fully agree with you about not wanting to damage bearings etc as the whole setup currently feels sufficiently tight. Thing I'll continue to strip it down and then probably soak it all in diesel or something similar.

Do you know how the drawbar should be tightened? I can't see any obvious way of doing so - I'll investigate further, but I wonder whether its sheared off as there's method for locking it off.

I'll know much more when I've finished!!

17/05/2020 17:05:41

vertical head - top.jpgHi,

I've just started to refurbish my father's old Centec 2A milling machine. I've started with the vertical milling head, which I believe is the MkIII. However, I can't remember seeing it being used so have little first hand knowledge of this machine. Attached (I hope) are two pictures, one shows the bottom of the head and the other the top. The device at the bottom of the quill which has the knurled nut fitted I believe is a cutter holder. However, I can't remove it from the quill, I've tried clamping the body of that part and using a proper spanner in the holes of the larger diameter piece. Nothing moved. I suspect that it has all got siezed with old oil and lack of love. I can't even remove it from the quill, which I presume it fits into via the MT2 taper. The other picture shows the top end of the head (sans gear carrier etc). What appears to be a pin in the top of the shaft wobbles about and I've presumed it might act to disengage anything in the taper, but a few reasonably heavy taps with a hammer didn't appear to achieve anything. I'm loath to give it a good whack unless I'm sure that that is the right thing to do.

I'd be grateful for any advice or guidance on stripping this down. I want to clean out the many years of old grease and gunk, repaint and reinstall.vertical head - bottom.jpg

Thread: Imperial Fasteners
30/12/2019 16:50:57

With regard to the GroupsIO site. I created it when the Yahoo Group was about to expire. I've copied all the old files and photos to it so at least they're still available. There hasn't been much traffic as there are only 5 members. I'm obviously happy to accept new members or to migrate the data to a more appropriate website. Alternatively, it could be expanded to accommodate all S&B owners, but in order to host all the photos that would come at a cost - which is why I just limited it to Model M. That said I suspect many of the old photos don't need to be migrated. One option is to simply allow it to grow as users find useful.

Happy to consider suggestions?

28/12/2019 16:58:28

Just thought i'd share a couple of photos of my newly filed dog pin socket screw - it retains the gear for moving the saddle along the bed. Both the original and the replacement are shown. I heard a similar story to Howard's many years ago - if I remember correctly an expedition to the Duhd Kosi river in Nepal had a problem with a wheel stud - the local mechanic simply filed a replacement which apparently gave good service for the remainder of the exped.

photo 28-12-2019, 14 22 21.jpg

26/12/2019 20:04:41

I did try contacting Bracehand a while ago but didn't get a reply. If they are operating I would happily share the drawings I'm making of the Model M Mk1 on Onshape.

It would have been a wholesale job to convert the lathe to metric and it would have been a surprise (but not impossible) if it had remained metric. My thinking for this is that the S&M was based on a German Boley lathe which I expect was metric, but since this was shortly after WW2 I imagine the enthusiasm for things metric would have been limited.

For info, I've now cleaned the threads that were causing concern and ordered replacement screws - the sizes were 2BA and 4BA.

24/12/2019 21:56:30

Hi Duncan, I thought the Mk 1 was made until 1956, but I cant find where I got that from. Lathes.co.uk could be read to say that it was no longer produced after 1948, but that would assume the Mk1 and Mk2 weren't available together. I simply don't know, but if you have more info I'd be grateful to know. All the best.

24/12/2019 16:24:32

Gentlemen,

Many thanks for the advice - I'm not certain that the screw sizes are 2BA & 4BA. I've now cleaned the threads with the relevant taps and things are looking much better.

The help has been very much appreciated.

Hope you all get suitably useful Christmas presents!

All the best.

Peter

23/12/2019 16:32:52

Gentlemen,

Delighted to have started such an enthusiastic debate smiley!

I have now had a closer look at two screws in particular (thanks Hopper for making me look through other old stuff from my father - a magnifier was found!). The results are as follows:

Baseplate retaining screws: 32tpi with a measured major diameter of 0.1825". The thread gauge actually reads 32G5/32, but 5/32 is too small!

The countersunk screws appear to be 4BA, with what appears to be almost exactly 38tpi and 0.134" max dia.

It is worth remembering that most of these screws/holes are worn so measured sizes are unlikely to match the 'as designed' specs.

Does this help you to help me?

Regards

20/12/2019 19:41:19

thanks John - they look to be a useful source. I'll give them a call when I'm more convinced of the sizes I need.

20/12/2019 19:33:29

Martin, to my shame I do have a tpi thread gauge but the results seem inconclusive! i'm going to spend more time at the bench and carefully assess the tpi and my use of the guage (maybe the ones I have are a bit cheap!).

Bazyle, what a thought - I shall see if I can find any in the loft!!!

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