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Post by terrier060 on Jul 21, 2019 14:26:33 GMT
You certainly can vary the parameters widely and use formulae, and some of the time that will work out just fine. The problem is that there's a huge variation in the difficulty of cutting different materials, and you're not always using a new razor sharp cutter. Some setups are much moor rigid than other, so the amount of force you dare apply can be very different too. Then there's the ever present problem of chatter which is made worse by higher spindle speeds. In my opinion it's a waste of time calculating these things once you get a feel for what it ought to look and sound like when it's happy. At best they are a starting point, but they can lead you into trouble if you stick closely to them in the mistaken belief that they must be nearly right. Sometimes you just have to go very slowly indeed, and with very light cuts to get the job done. Formulae are great for industrial mass production, but are of limited value in the home workshop in my opinion. See apology above Roger! Yes I notice that I can use the same 6mm cutter in my larger Myford machine and hand-feeding must be frighteningly fast, but it cuts beautifully and silently. At a guess I would say the feed was 0.1in/min or greater with 20thou cut and I know the speed was 1600rmp. It is a much heavier machine though, though not quite as large as your Denford.
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Post by terrier060 on Jul 21, 2019 21:22:13 GMT
I had a go at cutting the slots with the 1mm cutter and all was going well until the third one- the cutter broke. I was using cutting oil and I think this may have been a mistake as the chips clogged the cutter. Last time I used it I cut dry. It is a shame as it was doing a good job, but now I have to go to all the trouble of fixing them to my indexing attachment, or rotary table. There are two pairs here mounted together. They have slightly different radii at the two levers I make are different. As they are mounted now would be about right for most 7.25in gauge engines. Just shows how over-scale most are! Racks ready for cutting slots by ed cloutman, on Flickr Reversing lever by ed cloutman, on Flickr
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Post by Roger on Jul 21, 2019 22:03:40 GMT
I had a go at cutting the slots with the 1mm cutter and all was going well until the third one- the cutter broke. I was using cutting oil and I think this may have been a mistake as the chips clogged the cutter. Last time I used it I cut dry. It is a shame as it was doing a good job, but now I have to go to all the trouble of fixing them to my indexing attachment, or rotary table. There are two pairs here mounted together. They have slightly different radii at the two levers I make are different. As they are mounted now would be about right for most 7.25in gauge engines. Just shows how over-scale most are! Racks ready for cutting slots by ed cloutman, on Flickr Reversing lever by ed cloutman, on Flickr Hi Ed, Why couldn't you just fit a new cutter and do those again while it was set up? Even now, you only need to mount them on two pins on a piece of plate and you can set them up again on the Tormach. It sounds like there might have been too much material being removed in one cut so that it filled the flutes. Lots of shallow cuts is one way to avoid this issue.
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Post by David on Jul 21, 2019 22:05:41 GMT
This is the page I used to figure drill feed and speed. Perhaps there are less variables in drilling, it always being the same operation. smithy.com/machining-reference/drilling/page/22Edited to say that reversing level looks excellent. You must have posted at the same time I did as I didn't see your post. I agree the oil is worth a thought as I've noticed it clogging flutes too. I only cut dry now and blow or vacuum the chips away occasionally if I have time.
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Post by terrier060 on Jul 22, 2019 9:21:57 GMT
Hi Roger. Yes could do that - I love the fact that I can draw the work large and watch it being cut out so accurately, but with this one I am not clever enough to get Fusion to cut the way I want it to. Also it ends up with curved bottoms to the slots. I think it far quicker in the long run to use a slitting saw or a Thornton clock wheel teeth cutter, of which I have lots. Thanks David. I will put that with all my other precious tables. One other great thing about CNC is that it is so easy to make scale nuts and bolts. I know one can buy 6BA bolts with 7BA heads etc, but not 8BA nuts with 9BA threads which look much better and to scale. I produced the following CAD drawing which I find very useful (for 7.25in gauge scale 1:7.7931, but easily converted). Nut sizes by ed cloutman, on Flickr
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Post by Roger on Jul 22, 2019 9:51:50 GMT
You don't have to use those huge 1mm cutters , you can use 0.5mm to get the bottom of the slot almost square that only needs a stroke of the file to finish it. Another option is to drill the corners at say 0.5mm diameter before you mill the slots when you need a sharp corner.
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Post by ettingtonliam on Jul 22, 2019 13:57:34 GMT
'Huge 1mm cutters'!!! I get all nervous if I'm going below 1/8", and was definitely scared when I had to use a 2mm cutter to cut my valve ports recently.
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Post by Roger on Jul 22, 2019 14:37:11 GMT
'Huge 1mm cutters'!!! I get all nervous if I'm going below 1/8", and was definitely scared when I had to use a 2mm cutter to cut my valve ports recently. It's very difficult to use 1mm cutters when you're hand feeding because you can't move smoothly and slowly enough. Even power feed is usually way too fast even at the slowest speed. This is where CNC has the edge because the control is very smooth and subtle. You can ask for 2mm/min and get exactly what you ask for. This is the sort of feed you need with say a 50micron (2 thou) cut using a 0.5mm PCB cutter. You can get away with more if you're using an industrial cutter designed for machining metal, but they're prohibitively expensive.
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jma1009
Elder Statesman
Posts: 5,901
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Post by jma1009 on Jul 22, 2019 21:50:59 GMT
I have always filed the reverser quadrants, and filed the slots for the reverser lever catch to suit the valve gear, after a few judicious cuts with a junior file. Never taken me much time to do, and I have always done the reverser stand quadrants in tough stainless out of the same sheet given to me in 1983 out of the scrap bin of 'Argo' works in Ryde IOW.
The Terriers in full size had a notch a few for when well notched up on the reverser quadrant. The fullsize Terrier valve gear was quite good, but I recall the late Ken West (ex-Calbourne driver in BR days) criticising Drivers notching up too far to much when the valve gear started to "kick", and was of the view an old loco should never be notched up too much. This is actually a very good down to earth Driver's view of running on the regulator with short travel valves and without superheat- without knowing that the modern valve gear simulations entirely supported their assessment.
I have only cut notches in the reverser quadrant that equate to my own findings of the miniature valve gear.
Cheers,
Julian
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Post by terrier060 on Jul 23, 2019 8:08:46 GMT
Yes that's very interesting Julian. I believe I heard/read somewhere that unlike Walschaerts' valve gear, Stevensons' runs as well in reverse as forward gear, as regards cut-off?
I have taken my measurements from the full-size locos when I visited the NRM and the Bluebell Railway so it will be interesting to see how it fits the model! It is all scaled down as is the rest of the valve gear.
I did have to do a bit of hack-sawing recently which came as quite of a shock! Got very hot and arms ached after! I have found my eyes are not what they used to be for fine filing or any fine work now for that matter.
It is annoying that I cannot get the reversing quadrant tested until I have the cab installed as it is fitted to it, as is the damper gear. I am loath to put the cabs together as I do not have room to store them. Better as a flat-pack!
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Post by terrier060 on Jul 25, 2019 9:48:03 GMT
I had a long think about the suggestions above and came to the same conclusion as many of you that sub-1mm cutters were not for me so I would do it the trusted way that I know from cutting clock wheels and pinions. So I had an old No2 morse mandrel I made years ago for some job long forgotten, and a piece of 3/8" aluminium plate that I made to form the copper throat plate of the Terriers. By using CAD and F360, I was able to drill the holes accurately to take the racks. Remember they are slightly different on each loco for some reason. I can't remember why, but in my notes I have measured the reversing quadrant on several restored Terriers and maybe they are different? I shall now mount the job on my dividing head and the angles fit in very nicely (4 degrees = 90 divisions in 360 degrees and 2.25 degrees = 160 divisions). Rack Template drawing by ed cloutman, on Flickr Reversing Quadrant by ed cloutman, on Flickr
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Post by Roger on Jul 25, 2019 11:52:52 GMT
I can fully understand your reasoning, but using say 0.5mm cutters is not as hard as you might imagine. After all, I've just machined that Gauge Plate form tool with one. The trick as always is to give the small cutter as easy a time as possible, given that PCB cutters are so long. If you use say 5000RPM, 50 micron cuts and 5mm/min you can cut just about anything. All it takes is time.
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Post by terrier060 on Jul 25, 2019 18:41:36 GMT
It still would take days to cut them all on my machine Roger. I found a 1/16" end mill for my autolock chuck so decided to use that. It is only a HSS cutter but whips through it on my larger machine. I think the extra weight of the machine must help. I am machining it manually with generous applications of cutting oil applied with a brush. I decided against the Thornton cutter, as it required a more complicated setup and needed two passes to get the required width of slot. Machining Rack Setup by ed cloutman, on Flickr
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Post by terrier060 on Jul 25, 2019 19:55:33 GMT
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Post by Deleted on Jul 25, 2019 20:21:42 GMT
That's an excellent piece of model engineering sir...
Pete
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jma1009
Elder Statesman
Posts: 5,901
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Post by jma1009 on Jul 25, 2019 21:20:41 GMT
Hi Ed,
That looks a very good result.
Don Ashton ran the original fullsize Terrier valve gear on his simulator and found it very good, but there are limits to how far you can notch up the fullsize locos with short travel valves and no superheat.
Having watched the late Ken West on the IOWSR (ex-SR and BR fireman and driver, and driver of W24 'Calbourne' in later BR days) drive W8 'Freshwater', he would not go beyond notch 3 or 4. He was very critical of anyone who tried to notch up further, and caused the valve gear to 'kick'.
Cheers,
Julian
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Post by David on Jul 25, 2019 22:08:55 GMT
Very nice.
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Post by terrier060 on Jul 26, 2019 8:18:44 GMT
Thanks all. The lever was a nice neat piece to make. Stroudley was quite artistic in the way he attached the detent to the trigger.
It will be interesting to see how far the model notches up, but I suspect that when I tried it on compressed air it was about the equivalent three notches. Of course it will run slightly differently under the expansion of steam.
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Post by terrier060 on Jul 28, 2019 21:58:49 GMT
These little flange nuts are so easy to make on the Tormach and they look really neat. They are 7BA with 8BA hexagons. They only take two minutes, so you can stand and watch them appearing. It takes a full depth clearing cut with a 2mm cutter. 7BA flange nuts by ed cloutman, on Flickr I did have a major disaster today. I should have stopped working as I must have been tired and made lots of silly mistakes all day. I was in the computer room, and am fairly deaf, but luckily Jan heard this hammering sound and said I had better go and see what it was. I thought at first it was coming from the garden as it sounded just like someone hitting a post in the ground with a sledge hammer. I quickly realised to my horror that that the noise was coming from the workshop and hit the red emergency button immediately. The 2mm cutter had miraculously chuntered its way through the 3/16" thick clamp and was happily making its way down the workpiece until the collet nut started to hit the holding down bolt. Thankfully Jan's sharp ears saved the day and no damage was done except a little of the black anodising on the nut was scraped off and the 2mm cutter broke when I restarted the machine to pull it out using the Z axis. It is quite clearly stated by the manufacturers that these machines should not be left un-attended, but then life would be really dreary if we had to stand by them all the time. The moral is not to get complacent as I did, and keep making regular checks, however inconvenient it may be. Bad day at the office by ed cloutman, on Flickr
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jma1009
Elder Statesman
Posts: 5,901
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Post by jma1009 on Jul 28, 2019 22:18:09 GMT
These are ordinary nuts with a washer behind covered in paint! Seems to be a pic of Stepney. To the best of my knowledge, Brighton never made or used 'flange nuts'. Cheers, Julian
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