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View Full Version : Atlas 7B shaper owners? Question about feed screw.



Wirecutter
12-24-2016, 06:40 PM
I've got an Atlas 7B shaper with serial number < 1500. I'd guess it's 1940s vintage. I've had it a while and don't use it much, but for some things, it's the only tool for the job, such as internal keyways. Oh, and it's kind of fun to watch.


So I was using it the other day, and the feed locked up. I shut it down and took it apart. Turns out the feed gear (9-101-20) blew up. I want to thank senior member dp for the following diagram from a previous post here:

http://metalworkingathome.com/images/atlas7bcrossfeed.png

Full post:

http://bbs.homeshopmachinist.net/threads/43458-Atlas-7B-Shaper-Feed-Timing


On my machine, bushing S7-111 and gear 9-101-20 have about a 0.150" hole through them and a pin is driven in to secure them to the S7-29A feed screw. On disassembly, I discovered that this is not the original configuration. I found another pin, now sheared into 3 parts, with 2 parts in the bushing and one in the feed screw. I'm sure it took plenty of force for that to happen, like maybe letting the auto-feed run into the stops.

Anyway, my question is this: Is the pin that secures the bushing supposed to go just in the bushing, or is it supposed to go all the way through the gear? I suspect the former is the original config, and the latter a repair job. The hole through the gear seems innocuous enough, and it's between teeth on a gear with an even number of teeth. I noticed that the "new" hole goes right through the centerline of the screw, unlike the old pin I found.

Anyone out there that knows about the Atlas 7B? I'd love to know why my feed gear disintegrated, but it may be just from weaking from the previous repair job.

Oh, and I've already made another bushing and pin. The bushing fits a Boston Gear replacement part that I found, of all places, on Amazon. I was able to use the shaper to make the bushing, at least. I should really post pictures.

Thanks for any info, folks!

-Mark

Wirecutter
12-24-2016, 07:11 PM
Ok, photos:

On the left is the replacement gear I got from Amazon, on the right is the wrecked original gear.

http://bbs.homeshopmachinist.net/asset.php?fid=712&uid=3942&d=1482624268


I got more than one replacement, just in case. :P On the left, note the thickness of the gear as delivered. Next to that on the right is the same gear, but faced down from .500" to .375" on the lathe. And again to the far right is the original destruction:

http://bbs.homeshopmachinist.net/asset.php?fid=713&uid=3942&d=1482624272


Finally, this is the new gear with the bushing that I made for it. No hole yet for the pin to secure it to the feed screw:

http://bbs.homeshopmachinist.net/asset.php?fid=714&uid=3942&d=1482624282

RGS
12-26-2016, 10:25 PM
On another forum someone else was having issues with there feed. I tried to remove my gear to get a picture of the pin but my gear was stuck on the bushing. I did look at the gear at that time and I could not see the pin in the gear and I looked at that time. It does use the standard 10/12 Atlas Lathe gears and bushing.

I could not see the pictures that you posted in the previous post but would like to see the setup you have to make the bushing for the gears.

Thanks

Wirecutter
12-27-2016, 04:20 PM
I didn't photograph the setup, but I can tell you what I did and attempted...

I first made a mandrel out of a 1/2-13 bolt and nut. Using that, made a disk out of (I think) 4140 steel on the lathe. It was about .950 in diameter and .375 thick, like the old bushing. I bored a .490 hole in the center, which is a tight fit on my purpose-built mandrel. My dividing head will also accept the 5C collet chuck I use on my South Bend 9, so I mounted the dividing head up on the Bridgeport, aligned, and zeroed the Y axis on the centerline of the DH axis. I put a .500 in endmill in the mill and zeroed Z to the DH axis.

Then came the kinda dumb part. I offset the Y axis by half of 3/16" in positive and negative direction and took passes in the X axis to create the two 3/16 "keys" in the bushing. I then realized that this setup was no good for creating the smaller .750 in. diameter for the rest of the bushing. I did use it to "rough out" most of it, but the result was not ready for prime time, as they say.

So, I went back and reassembled as much of the shaper as possible. I have this old indexer from some kind of Hardinge grinder, but have never even seen the machine it came from - it was part of a bulk tool purchase years ago. The indexer happens to line up perfectly with the spacing of the t-slots on the shaper. So I got it all lined up and mounted, and setup on the shaper. I manually operated the indexer in very small increments to cut the .750 in outer diameter of the bushing. Took about an hour, but nearly everything takes longer on a shaper. The resulting bushing has a decent finish and is a firm press fit into the off-the-shelf Boston Gear part that I'd faced down to .375" thick.

I put it all back together last night. I made a tapered pin to tap into the hole for holding the bushing in place on the feed screw. I had to play some games to get the hole lined up, since the original hole in the feed screw wasn't exactly through the center line of the feed screw. I chose not to extend the tapered pin all the way through the gear, instead going with the press fit of the gear to the bushing. I *think*, but do not know for sure, that this was the original configuration of the shaper.

Since I don't know exactly why the original gear exploded, I'm watching it pretty closely. I suspect that the pin going through the feed gear got loose and caused a cascade of failures. The damage was contained to the gear and the pin, but I made a new bushing for good measure.

I've got about an hour of run time on the repair, and it runs fine. The shaper is fun to watch.

-M

Wirecutter
12-30-2016, 12:25 PM
I got my answer. The bushing is a press fit into the gear. (Replacement is a standard Boston Gear part, but has to be faced down from .500" to .375") The retaining pin goes through the bushing, but not the gear. So I guessed correctly.