uuu
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Post by uuu on Jul 12, 2020 14:23:28 GMT
The other thing you have to judge correctly is the depth. If the ports are open so swarf comes out when you break through, that's helpful. You ought to be able to feel the end, but it would be a disaster to go too far and bridge the inlet and exhaust ports.
Wilf
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smallbrother
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Post by smallbrother on Jul 12, 2020 17:19:43 GMT
In 1965, with minimal equipment, I filed the angled flat in the end of the cylinder bore, marked out the line of the drilling on the side of the casting, held it in the bench vice and drilled the passages with my trusty Woolworths hand drill, keeping everything in line, by eye. I didn't know that LBSC advised grinding the drill off centre in case it broke, but with my drill sharpening skills back then, I expect it was off centre anyway. Whatever, it worked. You do wonder if we over complicate some of this process! Did you keep that engine Richard? Pete.
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Post by ettingtonliam on Jul 12, 2020 21:43:16 GMT
No, it got sold to fund my next engine, which in turn got sold to give me the deposit to buy a house (£3000 in 1973! The mortgage was £35 a month and I used to lie awake at nights worrying about whether I could afford it!)
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Post by ettingtonliam on Jul 12, 2020 21:46:20 GMT
The other thing you have to judge correctly is the depth. If the ports are open so swarf comes out when you break through, that's helpful. You ought to be able to feel the end, but it would be a disaster to go too far and bridge the inlet and exhaust ports. Wilf I know the 'proper' way is to make a collar to clamp around the drill for depth, but being lazy I measure the required depth on the drill, then put on a blob of snopake. Drill down till the snopake shows the depth has been reached.
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smallbrother
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Juliet
Jul 13, 2020 7:54:18 GMT
Post by smallbrother on Jul 13, 2020 7:54:18 GMT
No, it got sold to fund my next engine, which in turn got sold to give me the deposit to buy a house (£3000 in 1973! The mortgage was £35 a month and I used to lie awake at nights worrying about whether I could afford it!) In the summer of 1973, before going off to Lanchester Polytechnic (Coventry) to study Civil Engineering, I got myself a summer job at llanwern Steelworks just outside Newport. The pay was 35 quid a week. I thought I was loaded! Pete.
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Post by cplmickey on Jul 13, 2020 7:56:41 GMT
The other thing you have to judge correctly is the depth. If the ports are open so swarf comes out when you break through, that's helpful. You ought to be able to feel the end, but it would be a disaster to go too far and bridge the inlet and exhaust ports. Wilf I know the 'proper' way is to make a collar to clamp around the drill for depth, but being lazy I measure the required depth on the drill, then put on a blob of snopake. Drill down till the snopake shows the depth has been reached. I do a similar thing but using masking tape. Ian
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Juliet
Jul 13, 2020 11:50:39 GMT
Post by ettingtonliam on Jul 13, 2020 11:50:39 GMT
No, it got sold to fund my next engine, which in turn got sold to give me the deposit to buy a house (£3000 in 1973! The mortgage was £35 a month and I used to lie awake at nights worrying about whether I could afford it!) In the summer of 1973, before going off to Lanchester Polytechnic (Coventry) to study Civil Engineering, I got myself a summer job at llanwern Steelworks just outside Newport. The pay was 35 quid a week. I thought I was loaded! Pete. Ah, such days! In 1969 I had a summer job in a local factory stamping out clutch plates for Vauxhall Viva cars on a big power press. Paid peace work, I was getting £25 a week. A fiver went to my mother for my keep, a couple of quid to get a substanial meat and 2 veg type lunch in tghe works canteen a couple of quid for petrol to get to work, beer was about a shilling (OK, 10p) a pint, and I couldn't drink that much in those days, so at least a tenner a week left over after paying for essentials!
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smallbrother
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Juliet
Jul 14, 2020 8:30:31 GMT
Post by smallbrother on Jul 14, 2020 8:30:31 GMT
I am hoping to start the actual ports today. They are 1/8 x 1/2 (steam) and 1/4 x 1/2 (exhaust).
Is it critical to end up with square corners? I have a 1/8 milling cutter which will leave a radius of material. Should I try and remove this?
Pete.
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stevep
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Post by stevep on Jul 14, 2020 9:06:24 GMT
Pete,
It isn't necessary to have square corners, and the recess in the valve probably won't have square corners either.
I wouldn't try to cut a 1/8" port with a 1/8" cutter. Use a 3/32" cutter for the steam ports, and a 3/16" one for the exhaust port, milling both sides, and using a gauge to check when you get to the right size.
The one thing to be very careful of is that when you get to the 'corner' and the cutter hits the face, it will flex, and make a little dip into the lovely straight port edge that you have just machined. Best to either fit a stop, so you come up to the same place every time, or if you have a DRO, use that. Whatever, make fine cuts towards the end, and take it gently.
The same is true when milling the valve recess.
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Post by gwr14xx on Jul 14, 2020 9:31:06 GMT
Pete, You will get a straighter edge to the ports if you start by roughing them out normally, then, taking a few thou at a time, climb mill them to the finished size. Climb milling needs to be done very gently to prevent the cutter snatching, but will give the ports perfectly radiused corners (if you haven't tried it before, a practice run on a bit of scrap material is advisable).
Regards, Eddie.
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mbrown
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Post by mbrown on Jul 14, 2020 10:20:35 GMT
I had some success by making a dummy portface in steel, with the ports carefully filed out to precise size, case hardening it, and then bolting it to the portface using the steamchest studs. That acted as a guide to the slot drill and (by luck or judgement) the ports came out exactly to size. The mill I had in those days didn't have a DRO or stops on the table. Case hardening might not be absolutely essential as I found that, because I could see the shape of the ports clearly, I could approach the ends (and edges) very carefully indeed.
On a different loco, I made the portface from gunmetal (the casting supplied as the steamchest cover) and cut the ports by drilling and filing before securing it to the cylinder with high temperature Loctite and screws. This is worth keeping up your sleeve just in case you make a dog's breakfast of milling the ports - machine the portface down and fit the new portface separately.
Hope this is helpful.
Malcolm
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Post by ettingtonliam on Jul 14, 2020 10:38:08 GMT
On a different loco, I made the portface from gunmetal (the casting supplied as the steamchest cover) and cut the ports by drilling and filing before securing it to the cylinder with high temperature Loctite and screws. This is worth keeping up your sleeve just in case you make a dog's breakfast of milling the ports - machine the portface down and fit the new portface separately. Hope this is helpful. Malcolm What a good idea! Not unknown in full size practice with elderly traction engines I seem to recall.
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smallbrother
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Juliet
Jul 14, 2020 16:06:29 GMT
Post by smallbrother on Jul 14, 2020 16:06:29 GMT
I have ordered some small slot drills so will get on with something else meanwhile.
Thanks all for the tips.
Pete.
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smallbrother
Elder Statesman
Errors aplenty, progress slow, but progress nonetheless!
Posts: 2,269
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Post by smallbrother on Jul 24, 2020 20:12:17 GMT
Here are the first steam ports. By no means perfect but I think I will make things worse if I fiddle about any more. These were done on my mini-mill. I am sure the results are way better than me using a drill and home-made chisel as suggested by LBSC! Pete.
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Post by ettingtonliam on Jul 24, 2020 20:55:22 GMT
As the Irish saying goes, 'Sure, they'll be grand'
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Post by suctionhose on Jul 25, 2020 1:23:38 GMT
A tip for machining 'pockets' aka ports: always climb mill around the finished dimensions to prevent the cutter pulling into the corners.
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smallbrother
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Errors aplenty, progress slow, but progress nonetheless!
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Juliet
Jul 25, 2020 8:28:46 GMT
Post by smallbrother on Jul 25, 2020 8:28:46 GMT
A tip for machining 'pockets' aka ports: always climb mill around the finished dimensions to prevent the cutter pulling into the corners. There were a couple of jerky moments in the process away from the corners. Not sure if I had the speed wrong or maybe something in the casting. The cuts were about as light as I could sensibly make them. I will get the other one underway and hopefully make a better job with the experience gained. Yes.
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stevep
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Post by stevep on Jul 25, 2020 9:31:48 GMT
Climb milling is an excellent way of avoiding the annoying 'undercut', but because the cutter is pulling the table in the direction you are already traversing, it will tend to 'snatch' and jerk the table, taking up the lost movement in the lead screw.
You can help to avoid this by a) only taking very light cuts, and b) slightly tighten the table lock or gib screws, so the table is harder to move
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Juliet
Jul 26, 2020 9:45:48 GMT
via mobile
Post by suctionhose on Jul 26, 2020 9:45:48 GMT
Good point Steve. When doing these things on hobby size machines it helps to be ambidextrous!
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smallbrother
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Errors aplenty, progress slow, but progress nonetheless!
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Juliet
Jul 26, 2020 10:36:59 GMT
Post by smallbrother on Jul 26, 2020 10:36:59 GMT
Despite light cuts I have broken the two 3/32" slot drills I bought recently. Am about 50% through second cylinder.
Two more on order. I hope I can finish the second cylinder before these 2 break!
Pete.
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