Member postings for Chris Gunn

If you are running a 16mm cutter along the side of your block 10mm deep, each tooth is trying to take a 10mm long cut, even though it may not be a deep cut. When you are face milling each tooth is only taking a cut of a few thou.

This leads to chatter on a hobby machine, however good the set up and the bearings are. Every vertical miller I have had gives a similar result.

Industrial machines have a much better spindle than hobby machines and are much heavier all round.

The marks can be minimised by getting the speed right and taking a very fine cut to finish, but you will still get a ripple.

In the good old days a horizontal miller would have been used to mill the sides of your block, and you would then be back to a few thou a tooth and a good finish. The answer is, if the finish is vital, dont do it, turn the workpiece around and do it with your face mill if possible.

Chris Gunn

Did anyone visit the Midlands ME Exhibition and see the all steel boiler for a steam launch, made without a weld or braze anywhere, it was all bolted construction ? Of course I know it is easier to do this in this type of boiler when one does not have the constraint of trying to fit the boiler into a locomotive chassis. I have just built a welded vertical steel boiler with copper tubes for my Donkey engine, which was very easy to build, mainly because of the layout. I still say that it would be hard to build a small, 3.5 or 5" gauge traditional locomotive boiler in steel, and weld it, and as cost was one of the major factors raised in the original post, would all the new techniques be available to the amateur?

Chris Gunn

Does anyone know if there are any drawings available for a Ruston Steam excavator, either scale or full size?

I would say that maybe the fifth reason against small steel boilers is the difficulty in constructing a 5" loco boiler in steel, welding the boiler in some of the nooks and crannies, and expanding small tubes in a confined space would be just 2 problems, as well as sourcing the materials. I know someone will have done it, but it is not for the inexperienced.

Chris Gunn

Yes I thought he was using an old mike for a G clamp as well. Do you think they are trying to recreate Fred Dibnah after the steeple jack segment last night as well as the format they are using? Is it a bit lightweight?

Chris Gunn

Thank you for the kind words regarding my boiler retubing article. When I was collecting information before I started on my 4" Garrett, I spoke to a gentleman who had repaired a vertical boiler for a boat, and he had the very problem you describe. It was at that point he cut a manhole. I am currently building a 6" Garrett, and have bought a commercial boiler for that, and it too has come without a manhole door, just a dummy ring welded on for a dummy door. I am not sure why the manhole doors are being omitted, it is one less hole to seal, I suppose. I intend to follow all the aftercare recomendations that came with my new boiler, I will mill a clearence in the smokebox door ring as I build it, so I can pull the tubes out, and I will replace the tubes after about 8 years. This is on the basis that they will pull out OK if they are not too bad, and I will not need a manhole.

Chris Gunn

Dusty, I was not referring to your comment at all, which makes complete sense for the initial test, it was just a general bit of advice, which now seems pertinent after reading the later posts. My stop is the genuine Colchester article, and has 2 Allen cap screws, not grub screws holding it to the bed. The cap screws may not be original, but they allow the use of a bigger Allen key than the corresponding grub screws would. If I am sloppy about tightening it, then one soon knows about it when the chuck jaws destroy the tip of the tool. I always have a test run, with the tool well away from harm, before I get cracking. I wonder if the stops mentioned above are genuine Colchester parts, and why the design has only one locking screw?

Chris Gunn

I am undecided at the moment whether to repair the old or replace it. If I repair the old one, it can go straight back in, if I get a replacement, I am led to believe from the Practical machinist web site, that I will need to scrape the new one in. At the moment I have made 2 temporary plates, one at each end of the gib, and I have the old gib held between 2 adjustable pinching screws, one each end. I have been using it today to edge the spectacle plates for my 6" Garret, and everything seems OK, although I have not taken any big cuts likely to cause chatter, and finish is not an issue either. The gib itself seemed in good shape apart from the broken end, so I am leaning towards the repair, which seems less hassle than scraping a new one in. Thanks again for the input, and I would welcome comment on the scraping in issue.

Chris Gunn.

My vote would be for a Colchester Bantam, but be prepared for a 3 phase machine, do not be put off by this as there are several solutions, the ease of use outweighs this. If you want a 1 phase machine I would go for a Boxford which are plentiful and easily available in 1 phase. Harrison next, and then Myford would be next in my list, and oriental ones last of all.

Chris Gunn

Pictures now uploaded, under Bridgeport jammed knee

CG

My Bantam is the same, and the stop is indeed very handy. My tip would be to ensure the 2 clamp screws are both tightened securely, otherwise it may slip. When I tighten mine, first then second screw, the first can always be tightened a little more, as the "C" section clamp must spring a touch after the second screw has been tightened, loosening the first screw a touch as well. Just get in a routine of doing a double tighten of everything, and you should be OK. If you are doing a job with a long feed, you can walk away and do something else, while keeping an ear and an eye on the lathe, until you hear the clunk to let you know the feed has tripped. I am sure you will be happy with the Bantam, it is far superior in lot of ways to many lathes available to the model maker.

Chris Gunn

I will take pics of gib when I get it out, I also have pics of the set up and other bits, I will check how to do an album, and post them all at once.

Chris Gunn

I am more than pleased to report that I have released the knee. I used the method from the Practical machinist, as I mentioned earlier. I made a wedge to go under the knee to hold up the end of the Gib. I made a clamp arrangement to hold it upright. I removed the screws holding the table raising nut, and backed it off 1/8" so the table could drop if it had a mind to. I squirted all the joints with WD40, especially on the gib side. Then I made myself an impact hammer with a 5ft tall bar, that screwed into a tenon in the bed. I put a 8" diameter disc around the shaft on the bed, so this transmitted the impact to the bed. I drilled a 5/32" hole about 12" from the top of the bar, and made pin from a bit of 1/8" rod to go in it. Above the pin I loaded about 28KG of weights, then pulled the pin, and not a lot happened, after 2 or 3 goes. I then set up a medium sized propane torch to warm up the knee casting, and let it play on the casting while I had a good tidy up, maybe 20 to 30 minutes. Then I had another go, and this time I could see from my witness mark that it could have moved a touch, so had anoher go with the impact hammer, and this time there was no doubt, it moved 1/32", and the next time 1/6", I released the table nut some more, and then it went 1/4", and the bottom of the gib was then level with the bottom of the knee, and I found I could wind the table down. I wound it down about 1", and noted that the gib stayed where it was, and the top of the gib is now sticking 1/2" above the table. I stopped at that point, feeling pretty pleased, as I need to secure everything before I remove the gib for inspection.

Once again thanks to all who helped me, especially Andrew Johnston who provided the link to the Practical Machinists site, which was worth reading to the end where I found this method, which worked, without tipping the machine over.

Chris Gunn

 

After my last post, I read the Practical machinists thread right to the end, and there I found the alternative method to release the gib that does not involve tipping the machine on its back, but involves supporting the end of the gib, then backing off the table raising nut, and giving the table a jolt downwards with a sledge hammer. It is then possible for the table to drop 1/4" or so and start releasing the gib. Accordingly today I made the few parts needed to do this, backed off the table raising nut 1/8", and set it so an 1/8" thick packer would just go in, and I marked up the nut, and then had a go, but it did not move a thou. I then broke the head off my sledge, fortunately with out damage to anything. Then I tried warming the knee up a bit with a propane torch, and tried again, and then warmed it some more, and still no joy. However I ran out of time before I could apply more heat, as it did not get it anywhere near hot enough to burn the paint. I will have another go tomorrow when I will have more time.

CG

Thanks for the additional information, reading the Practical machinists link has cheered me up no end. Just to confirm, the drip tray has been removed, it is the cast rim around the base that contains the suds that has curves in all the wrong places.I can confirm there was a bit of stiffness since I had it, as mentioned before, i think it was like it when I bought it, again from Practical machinist, it is obviously a problem with these machines, my tip for the day is remove the wiper cover before buying a used machine and check it. I am going to make a start in the morning, watch this space.

CG

Thanks for the info so far, I will try and answer the points raised, first it is difficult to get a jack of any sort right under the gib, as the base casting is curved, and so are the raised sides of the drip tray, so I cannot easily span the base under the gib. For the same reason it is difficult to get a pry bar under it and get a good purchase on it. The target is only 1/8" by 1" and nicely chamfered as well. The leadscrew is still connected. I like the idea of taking the weight one one side relieveing the pressure, my intention is to get the gib moved up, it looks like it could be up to an inch out of position, and once I can get the table moving on the lead screw, and the gib loose, I can block everything up, lower the table, and make it safe before removing the gib. Thanks again for all your time and trouble. I will keep you posted. Chris Gunn

I just moved my Bridgeport, and after some shuffling about I got it where I wanted it. an hour or two later I went to raise the table, and found it jammed tight. The raising handle and lifting screw seem free enough as far as I can tell. Further investigation revealed that the gib strip was sticking out about 1/2" below the bottom of the knee casting, which I had not noticed before. Can anyone have a quick look to see if theirs is the same? I imagine the gib is not normally this far out. Even further investigation revealed that the top of the gib strip which normally locates on the adjusting screw was broken off, and by the dirt and colour of the break, had been broken for some time. This has then allowed the gib strip to move lower than normal, making the table tight. In fact the knee has always been on the tight side, and has occasionally stayed in an up position when lowering, and then dropped an 1/8th with a bump when lowering. I imagine that when I moved the machine, and jarred it a bit when barring it across the workshop, the knee has dropped a fraction more, and jammed. I tried tapping the gib with a brass drift, but it did not move, and as luck would have it, the knee is well down, so I cannot get a good swing at it. My next move will be to make a steel yoke a pretty close fit around both sides of the dovetail below the table, and a corresponding one to sit on the top of the knee, and put a pair of holes in these so I can pull them together with studs, and push the gib up. I envisage removing the gib completely, and either replacing it or repairing it. The repair I had in mind was to drill a hole for an 8mm stud in the end of the gib, and make a plate to sit over the gib in place of the current wiper with a clearance hole for the stud, which I can use to pull the gib up, and a tapped hole for a second screw to push the gib down. Before I start I would welcome any thoughts/advice/ pifalls to avoid. If anyone has a spare gib I would also be interested. Thanks for looking,

Chris Gunn

I have read through the thread, and up to now no one has commented on the bed design of the Myford. I remember reading a long while ago in the ME that this was felt to be the reason for poor parting off in the Myford. As the bed is of rectangular construction, with no vee sections, it is difficult to get the cross slide rigid and chatter free. Parting off in a front tool post in a lathe with a vee bed surely pushes the cross slide down into the vee, and will tighten things up. When I worked at British Steel in the DRTD, we had aworkshop for small jobs, with Myfords, Boxfords and Kneller round bed lathes, everyone would pick the Knellers first to do a job, the Boxfords second, and would avoid the Myfords apart from doing a bit of polishing. I know this will upset the Myfordfans but thatis how it was.

I have a Bantam, and use front and rear toolposts, and it will part off using the feed with a sharp tool and plenty of suds, something else no one has mentioned. I was always taught to use copious amounts of suds when parting off when I did my apprentiship, ithelps keep everything cool the tool sharp and flushes away the chips.

Chris Gunn