Shaper cross feed increments

jwmay

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Hello all,

Does anyone see any pros or cons of changing the cross travel lead screw to something a little less random? I’ve got an Ammco 7” shaper and the cross travel leadscrew is 1/2-13. I’m not saying I WANT to do it. But it occurred to me that a 1/2-20 would be a little easier (possible) to cipher on. I don’t think they chose 13 tpi arbitrarily, but I can’t come up with a really good reason why. Probably something to do with the ratchet mechanisms diameter and tooth count. So anyhow, I’m free writing here it seems. What do you say? Any thoughts?
 
That sounds like a really odd pitch for a lead screw, 2 mm pitch is close, sure its not a metric pitch one that someone has installed before you.

Greg
 
I guess I don't understand the need to change the cross feed screw. The feed is currently adjustable from .003" to .018" per stroke. Here's a excerpt from page 2 of publication 27-100, "Delta, Milwaukee, AAMCO 7" Precision Shaper for Metalworking" manual. This is the 1950 version of manual PM-1737.
"The feed is a reversible and adjustable type. One tooth on the ratchet is equal to a cross feed of .003". By adjusting the position of the T bolt S80-16 in the feed adjusting lever S80-3 a feed varying form .003" to .018" can be obtained"

There are several versions of manual PM1737. I have a newer version published by Rockwell that gives a bit different explanation of the adjustments. This later version makes the assumption the operator already has a working knowledge of the machine. It highlights the range and how to read the scale on the rocker arm.

Here's a link to the Rockwell Publication on the Vintage Machinery.Org website:
http://www.vintagemachinery.org/pubs/detail.aspx?id=3662
 
There isn’t any need. But assuming I was cutting a .050 wide by .050 deep slot. Assuming I could even do it once without a dial, how could I get back exactly .050 to my starting point? .050 divided by 13 tpi, which equates to something like .077 revolutions of the handwheel. Versus a 20 tpi leadscrew where .050 becomes exactly one revolution of the hand wheel. Now make it a 1/2” slot. Hmm...6.49 revs of the handwheel on a 13 tpi leadscrew. Well that’s not so bad. I guess the obvious answer is to mount a dial indicator with a mag base. This shaper doesn’t have a graduated dial on the cross feed. Or if it does, the graduations have faded. Anyhow that’s what made me start thinking about it. But truly there’s no “need”. Actually, since you forced me to do the math, it’s not looking like such a problem anymore. Just looking for group input.

On the subject of the manual: It’s funny how they worded the bit about changing feed direction. Stating how to change feed direction, and following it up with a recommendation to ensure the table is feeding during the correct portion of the stroke. As it happens, anytime you change feed direction, you must also change the orientation of the feed eccentric which dictates when the table moves. So they tell you it’s one easy step to change feed direction. But oh by the way, it’ll be feeding on the cut stroke now, so change this other thing too, if you happen to notice. It probably took me 20 minutes to figure out why it was cutting all wonky when it was headed left, but just fine going right. Ha!
 
Here's another version of the PM-1737 manual that came with the machine. This one was printed in 1951.

http://www.lathe.com/catalogs/DeltaMilw7ShaperInstrGS.pdf

I guess I never thought of changing the lead screw, mostly because like you suggested I mount an indicator to the base and just watch the knee progress. When it gets within a few thousandths of my goal I disengage the auto feed and manually feed it to the desired width
 

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Wonder why they didn't put a typical 1/2-10 Acme lead screw on the shaper as you would find on others?
 
Now thats really interesting. I never thought about having to change the orientation of the feed eccentric when you change directions but yes it makes sense. Guess I've been feeding on the out stroke half the time and never noticed. Thanks
Really why 13 but Dave an I were discussing why 8 tpi. My down feed is that so 125 divisions on the dial. Would it be they used more fractions as in 1/8th of an inch when my shaper was built, Possibly 20's or 30's.
Greg
 
Now thats really interesting. I never thought about having to change the orientation of the feed eccentric when you change directions but yes it makes sense. Guess I've been feeding on the out stroke half the time and never noticed. Thanks
Really why 13 but Dave an I were discussing why 8 tpi. My down feed is that so 125 divisions on the dial. Would it be they used more fractions as in 1/8th of an inch when my shaper was built, Possibly 20's or 30's.
Greg

I don't believe there was any "standard" at the time. Somewhere along the line someone in the design department picked 5, 8, 10, 13, or whatever. It got approved, went into production, and is now part of history. I have several machines in the shop with different pitch lead screws. My Sheldon lathe cross feed screw has an 8 pitch. Making one full revolution of the dial .125". The Seneca Falls lathe has a 10 pitch cross feed screw making one full revolution .100", and the AMMCO shaper has a 13 pitch lead screw, making one full revolution .077". The Bridgeport has a 5 pitch lead screw making one full revolution .200"

Now you know why I don't take a beer with me when I go to the shop.
 
My shop built shaper has 1/2 x13 as well. I assumed it was an easy size to tap . I've got a 100 division dial, thank you Grizzly, and a 1/2 x10 acme redi-rod for the new feed when I get back to that project. For the down feed I've got a 50 division dial and 7/16x20 redi-rod.
 
There isn’t any need. But assuming I was cutting a .050 wide by .050 deep slot. Assuming I could even do it once without a dial, how could I get back exactly .050 to my starting point? .050 divided by 13 tpi, which equates to something like .077 revolutions of the handwheel. Versus a 20 tpi leadscrew where .050 becomes exactly one revolution of the hand wheel. Now make it a 1/2” slot. Hmm...6.49 revs of the handwheel on a 13 tpi leadscrew. Well that’s not so bad. I guess the obvious answer is to mount a dial indicator with a mag base. This shaper doesn’t have a graduated dial on the cross feed. Or if it does, the graduations have faded. Anyhow that’s what made me start thinking about it. But truly there’s no “need”. Actually, since you forced me to do the math, it’s not looking like such a problem anymore. Just looking for group input.

On the subject of the manual: It’s funny how they worded the bit about changing feed direction. Stating how to change feed direction, and following it up with a recommendation to ensure the table is feeding during the correct portion of the stroke. As it happens, anytime you change feed direction, you must also change the orientation of the feed eccentric which dictates when the table moves. So they tell you it’s one easy step to change feed direction. But oh by the way, it’ll be feeding on the cut stroke now, so change this other thing too, if you happen to notice. It probably took me 20 minutes to figure out why it was cutting all wonky when it was headed left, but just fine going right. Ha!

This does seem to be a common idea with manual writers. I guess they didn't want to scare anybody off, but like with the Atlas their terminology isn't really clear but through watching YouTube vids and the Rudy K. vid I put 2+2 together. I inadvertently complicated the whole thing when I methodically took everything apart and cleaned it. The manual was very close to worthless about some of the hidden ways things came apart and makes no mention about proper clocking the timing for the gears that run the rotary for the ratchet. Only through watching vids did I get there was this vast timing difference in how the different Atlas would "click" the advance. You would think they would have put timing marks on everything but I guess they didn't think about maintence. It is a very vague and iffy process to change even the advance amount as there are no graduations on the ratchet wheel. So I just feed everything the one direction that is feeding properly right now. I can really get lost in the minutiae of this old tech.
 
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