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Post by pkastagehand on Feb 1, 2011 12:09:14 GMT -5
I've made a couple practice pieces too! Maybe more than I realize. We'll see if everything I've done works when I get more parts in place!
keep on keeping on....
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Post by phutcheson on Feb 1, 2011 14:04:38 GMT -5
Greg,
Nice work ...
Just the other day I noticed the Reverse Stand covering part of a mounting hole. At first I though I had made an error in my drawings ... nope, not this time. I also thought about shaving a bit off the stand ... probably will follow your lead.
Pat H.
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Post by kenrinc on Mar 11, 2011 18:38:02 GMT -5
Greg how did you drill the holes in the link blocks? Kozo shows a process that is frowned upon; installing one link that has been drilled and then use that hole to drill across to the other link bracket. You should never drill holes "across open air". You will never get two holes straight that way. One option is to clamp some scrap in between them or to drill them off the yoke. Curious if you did it his way and how it came out.
Ken
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Post by GregMiller on Mar 12, 2011 8:45:06 GMT -5
Hi Ken, I had to refer back to my pictures to jog my memory, but it appears that I drilled the holes pretty early in the process so that I could use them to aid in locating, as shown here: LinkBracket - Quartered by gregrycm, on Flickr If you start at this picture and go forward, you can see the steps that I took. This method does require careful placement of the mounting holes. Kozo's method would be more forgiving if mounting holes were not perfect. I found that I had a couple of thousands of wiggle room as provided by the matching holes in the yolk plates. When I attached the Link Brackets, I ran a length of drill rod through the link bracket holes for alignment, then tightened the brackets to the plate. I then reamed the holes with a hand turned reamer held in a small drill chuck. This method worked for me. The trunnions(?) fit well and rock on the pins nicely.... and I don't recall any resulting practice pieces Greg
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Post by kenrinc on Mar 13, 2011 3:59:50 GMT -5
Thanks Greg, that may be what he intended but I took one look at the sketch and said, no way those two holes are going to line up if drilled the way he shows.
Not sure if your to valve gear yet. The combination lever. He fabricates this entire thing and never mentions or shows when he drills the holes! Very difficult to layout the holes once the lever is milled to shape so I'm trying to figure out how/when he put the holes in. I was going to put them in earlier as its easier to do the layout when the lever is still a square bar.
Thanks again
Ken
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Post by kvom on Mar 13, 2011 14:44:33 GMT -5
For the combination lever, I'd mill the blank to a .400x.400 bar (1.5 scale), find the center line, and drill the three holes before any other milling.
Same for the link bracket; mill an oblong bar and drill (tap) all holes based on centerlines. I would do the same for almost any part that's curved and would be difficult to drill once milling is done.
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Post by kenrinc on Mar 14, 2011 11:40:46 GMT -5
Thanks. Yeah I just did the layout and everything after sawing from the blank. Of course the drawings show the bar being squared after the holes were drilled ....
A "gotcha" for when you get there (also check the errata 1st page for another issue). The distance shown on the drawing from the top of the bar to the bottom of the forked section is .4125 but what he shows on the blank to the right is .4375. He insinuates (never mentions) to saw to the depth of the notch which would be 7/16. Not sure it even matters yet but thought I'd bring it up.
Ken-
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Post by pkastagehand on Mar 14, 2011 15:58:03 GMT -5
I can't remember how I did mine but often for that sort of thing I clamp parts one at a time in the mill vise, use edge finders to get set up zero x and y, then use the dials (DRO if you've got it) to move to where the hole should be. I then use a stop pin to reference the items location in the vise and do multiples without changing any settings.
This of course assumes the parts you're putting the holes in are close enough in size & shape that referencing from the outside edges that way doesn't allow some error to creep in. The tapped mounting holes for example could be off between pieces if they were done first.
Errors don't add up; they multiply. And sometimes it is exponential. <grin>
Paul
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Post by kenrinc on Mar 15, 2011 12:46:18 GMT -5
Paul,
What's a stop pin? That threw me...
I've almost finished the combination levers and I see where one of the errors is on the drawing. It may just be the one error. It's the distance from the bottom hole to the milled center section edge. It says 5/32 on the drawing but look at the two holes at the top. They are spaced 5/32 but that distance is physically not even close to the 5/32 dimension at the bottom. I think he meant 7/32 or something similar just eyeballing it.
Ken-
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Post by kvom on Mar 15, 2011 17:26:48 GMT -5
As long as it clears the crosshead it's good. However, since the opposite side dimension is .12 and 5/32 is .156, I believe 7/32 is likely the correct value.
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Post by kenrinc on Mar 16, 2011 11:37:41 GMT -5
Correct. I actually just eyeballed that part as I knew it was only there to clear the guides. The distance between the link hole at the bottom and the yoke hole at the lower top seems to be correct as that dimension is shown again on preceding pages, confirming it.
Sorry for hijacking this thread. Greg you gotta post some more work and get this thread back on track!!
NOTE: I just layed out the combination rod holes and the drawing is wrong. The distance between the two top holes is not 5/32 or it is and the 1-25/32 dimension is incorrect. For me, in 1.5" scale the dimension between the bottom hole and the lower top hole is 3.562. That puts the hole out roughly .062.
Ken
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Post by GregMiller on Mar 18, 2011 9:55:06 GMT -5
Ken,
I am not worried about the Hijacking, I am just happy to see some activity on the forum. We'll see how this weekend goes in the shop, Spring is getting here faster than I anticipated. I expected to get more accomplished this winter than I did.
Greg
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Post by kenrinc on Mar 18, 2011 10:29:35 GMT -5
Word. I'm so busy trying to come up with time to work on mine that being able to document the build is tough. That's why it seems quiet on the group. Everyone is working!
Ken
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Post by pkastagehand on Mar 18, 2011 15:40:56 GMT -5
Paul, What's a stop pin? That threw me... Ken- For doing duplicates. Any kind of pin, bar, etc that can be held rigid in, near or on the edge of the vise. A part is registered against it left or right. Zero everything out and mill the feature or features. Then remove the part and put in a second part that needs same feature or features machined. The pin stops the parts always in the same place. The back face/jaw of the vise references the other edge and parallels or the bottom of the vise registers the height of the part. Does that make sense? Hard without a picture. Paul
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Post by GregMiller on Mar 20, 2011 19:06:47 GMT -5
Made pretty good progress on the Throttle Assembly over the weekend. Throttle Assy 2 by gregrycm, on Flickr Found some slight issues with plans. The plans call for 5/64 drill in the trunnion holes, but these should be 0.086 for a #2 clearance. Also, my 3-jaw chuck would not hold the trunnion for the final bore and thread, so I reverted to the 4-jaw chuck. Greg
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