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| "A Beginners Engine" From Model Engineer. |
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| ParCan:
Did all the tiny bits after lunch. There is something strangely sadistic about making 1/4" square steel blocks and putting a hole in em ! All the Piston valve connection bits made. Crosshead slides made. Valve rod guide made. The Boss will probably stop work over the weekend. I now have the 4 Pillars to make, the 2 Bearing stands and the Base. I think that's about it. The whole thing feels free as it stands. We will see what happens when I start to bolt it down. |
| ParCan:
--- Quote from: NickG on August 09, 2013, 10:01:55 AM ---I had trouble with the crank too i may have to re-make. The trouble was i had to turn down to 8mm and the 8mm end mill gave me a good fit on the bearings didnt on the webs for some reason! --- End quote --- I have 8mm Stainless rod and an 8mm reamer. Also 6 mm Silver Steel crank pin and a 6mm reamer. Why they came out so loose I have no idea. What I have here and now Is imperfect as far as I'm concerned, but it should work. |
| sbwhart:
--- Quote from: ParCan on August 09, 2013, 11:24:47 AM --- --- Quote from: NickG on August 09, 2013, 10:01:55 AM ---I had trouble with the crank too i may have to re-make. The trouble was i had to turn down to 8mm and the 8mm end mill gave me a good fit on the bearings didnt on the webs for some reason! --- End quote --- I have 8mm Stainless rod and an 8mm reamer. Also 6 mm Silver Steel crank pin and a 6mm reamer. Why they came out so loose I have no idea. What I have here and now Is imperfect as far as I'm concerned, but it should work. --- End quote --- Are you using machine reamers or hand reamers: Machine remers are parallel along their length Hand reamers are tapered at the start and usually have a square on the end for a tap wrench. If you put them through under power held in the tail stop in a chuck the chances are they cut over size due to misalignment best to drill out under size to within say .3mm ish then put the reamer through by had so that it cuts true, if using a machine reamer they are best put through with a floating holder or push it through on a carrier with a running centre, like this. that way it will cut true size. Stew |
| ParCan:
I have seen this done before and used this method for the Valve Body which I did on the lathe.. I did the crank webs on the mill. 8mm ER 25 Colette. Used an 8mm dia Centre drill to locate. Then through with a 7.5mm a few times. Then through at around 100 rpm with the Machine reamer. Same process but 6mm all round for the other end. I thought I'd at least get them to be a tight fit... Reality is they are a sliding fit at best. |
| NickG:
They should be a nice sliding fit when reamed which is about ideal for loctite. My 1/4" crankpin was like that. |
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