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| Rob.Wilson:
:clap: :clap: :clap: The dividing head is looking great Matthew , nice job doing the castings :thumbup: Rob |
| mattinker:
Thanks Rob! --- Quote from: PekkaNF on September 29, 2013, 02:25:13 AM ---Would you elaborate a bit of this split cotter design consideration? I'm familiar. with the design and have this same book and read some further info, but haven't used this method yet. Therefore I'm interested to hear reasoning about the material choices you made. Pekka --- End quote --- Pekka, my variation on the cotter is based on an article in the Model Engineer 29th of December 1965, written by Duplex, "Machining spindle locking devices". I don't know if I can provide this information to the group, for copyright reasons, (Moderator, what's group policy?) but I'm sure I can send it to you personally if you want it. I am going to show more about the split cotter soon, but, I am making a split cotter, the locking device show in the book is a single piece cotter which locks from one side. First of all, I'm boring with the cotter in place, when finished, the cotter is cut in half, providing a sleeve at the top and a threaded part at the bottom. I pre-drilled the cotter 5mm, taping the bottom M6 and drilling the top to 6mm, clearance, M6, when screwed together the two halves pinch the shaft instead of pinching from one side, doubling the clamping surface. In this particular case, I used cold rolled for the cotter. I have previously use brass in steel, but I was afraid that Brass in Al might give electrolytic problems. Sneak preview, I was also afraid that the steel would deviate the bore when drilling the "mixture" of metals, last drill, 25mm showed no sign of deviation, I don't think the boring bar will give problems. I'll be back soon with more photos, regards, Matthew [ |
| PekkaNF:
Thank you. It's chrystal clear now. I paged GHT "The Model Engineers Workshop Manual" page 22 description of split cotter. It's rather different. I think I read somewhere comparison of these two different locking mechanisms, but really can't remember right away. Pekka |
| mattinker:
Hi, At this point, I'm about to make modifications to suit the Emco Compact eight flange chuck mount and to allow the use of the three different change gear sets that I have. Instead of a threaded chuck mount, the Emco has an odd size DIN cone three bolt mount. The flange is 80mm in diameter, as I don't have a lump of anything usable of that diameter, I cut a piece of 20mm hot rolled square and then chopped the corners . Setting up in the four jaw on the Colchester. After centre drilling, step drilling. final hole size, 25mm. 45°chamfering for weld I had a suitable length of cold rolled 30mm which I clocked in on the four-jaw on the Colchester. (the bore in the Emco won't take 30mm) I centre drilled both ends and one end I step drilled out to 12mm, tapping size for M14. The last 20mm were left at 12mm and the first 30mm were drilled out to 14mm, clearance for M14 thread. This is the beginning of the interchangeable gear mounting, easier to do before welding on the flange. Reducing the Cold Rolled to 25mm Ø over 20mm. 45° chamfer for weld. Assembled ready to weld. Welded on one side. I was a touch wide and there was a piece of splatter in the centre bore. Welded the other side. De-stressing, the rectangular objects in there are pieces of cold rolled for another project. So, while the shaft cooled, I set up the casting on the cross slide of the Emco, everything lined up nicely using the alignment pins. The cold rolled for the cotter was locked into place with a hold down. Centre drilled. The smallest bit I have that was long enough is 8mm, and only long enough held at the very end of the shank. Step drilling, this is the first time I used this bit that I bought for next to nothing ten years ago! 22mm Finally, 25mm which as you can see only just made it. At 25mm the cotter was beginning to be cut. I hadn't drilled a mixture of steel an Al before and I was afraid of deflection, but there wasn't any that I could find. I forgot to take pictures of setting up the shaft in the four jaw before turning the flange round and re drilling the centre which had been partly filled with weld! Machining the inside weld I left a 45° fillet that will be covered by a spacer. Cleaning up the other end. I have a consistent 29.94mm over the full length of the shaft. Now I can finish boring the casting. To be continued, regards, Matthew |
| vtsteam:
Great sequence mattinker! I really appreciate the photos and seeing how you work. Thank you! :clap: |
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