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| Bogstandard:
Much rarer to find are serial taps, where they get larger on the main cutting thread the less taper they have on the end. Arc Euro are the only cheaper, but fairly good brand that do these types of taps. It makes cutting an almost or full contact thread easier in harder materials, as you are not trying to go to full thread depth from the very beginning. Each subsequent tap of the three sizes cuts the thread a little deeper, just like you should do when using a die. http://www.arceurotrade.co.uk/Catalogue/Cutting-Tools/Taps But for cutting stainless, I have yet to come across any better than these. http://www.tapdie.com/ Bogs |
| Stilldrillin:
Haven't achieved a lot, this past week or so. But, I'm pretty pleased with end quality..... :thumbup: I planned long and hard, how to seal between displacer and cylinder. :scratch: Eventually, I decided to follow the previous pattern, with a threaded tube...... First, I needed the top deck fixing in alignment with the rest of the engine. Referenced the exhaust pipe..... Then aligned the deck to it, and held with a through bolt/ clamp. I then spot drilled the 6 hole pcd, through the deck. Drilled & tapped all ok, after replacing the plug tap for a better quality one. ::) Found a nice piece of stainless bar. Drilled through 4.5mm. Then turned the o/d to a nice sliding fit in the brass repair tube...... Used the blank to align the casting tube hole...... Plunged it all the way in. Then aligned in X to a snug fit against the angle plate. (No gap, as is shown here)...... Aligned in Y direction, and tightened to the angle plate. Leaving the assembly vertically in line with the m/c spindle. Made a 5mm bore drill bush, and dropped it down to rest on the cast iron displacer sleeve...... Drilled through 5mm. Fished out the bush, then opened out to 6mm...... Nice crisp hole...... In the new section...... As before, aligned in X, then Y, using a piece of 6mm bar in the drill chuck and snug in the hole...... Perfect alignment for tapping, M7 x .75....... Threaded the tube, and tapped M6 in 'tother end...... After all my worries over alignment of several components, and threads. It screws smoothly into place, between finger & thumb!! :ddb: :ddb: Thinking how I it previously had a screwdriver slot, and wanting something neater looking....... I realised I could insert and extract, with a locknut in the speed control threads! :thumbup: Just a bit pleased..... :D Hope the euphoria lasts...... Can't see much being done next week! ::) David D |
| NickG:
Not surprised, it's looking a top quality job - well done :thumbup: |
| madjackghengis:
--- Quote from: Stilldrillin on January 25, 2011, 03:59:04 PM ---Well..... With the amount of cast iron dust I'm producing, I should have called this posting. "Getting down n dirty with Mrs Robinson". :D The saga continues. Fitted the skirt and displacer tube together..... Just a little mismatched! :scratch: The crescent, is the end of the displacer tube....... No wonder I couldn't get the hot cap properly centralised! :bang: :bang: Bored the mouth of the skirt concentric to the displacer bore...... That's the new, glued in place, repair section I'm gripping on..... Great stuff, that high temp slidelock Dean! Thank you!. :thumbup: Drilled and started tapping, the 6off, 6BA threads holding the deck casting to the repair section. The (new) plug tap feels very stiff to turn..... :doh: Job stopped. Quality tap ordered, before anything goes snap....... I hate that sickening/sinking feeling! :( David D --- End quote --- I was just thinking, "with the amount of cast iron dust I'm creating", maybe you should be collecting it, and then put it all in a little dam and with an oxy-acetalene torch, melt it down into a new foot. By the way, that fix on the air tube, sealing out the water looks like it should do a fine job and make that engine run. Just a thought :lol: :poke: mad jack |
| sbwhart:
Give that man a coconut:- :thumbup: :clap: :clap: :clap: :clap: Looking real nice Dave. Ther's a nice pic in latest issue of model engineer of a robson hot air engine that was made in 1900 and used for turning roasting Coffee. Ther's also a nice picture of a three cylinder radial engine on the front cover :D :D :D :D Stew |
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