As far as I can tell, after about 2 hours of searching, Kuhnhausen does not list National Match slide dimensions. I thought that was where I got them. Does anyone know where these might be found? I could just use barrel dimensions, but they do not account for hood to breech face gap.
I entered NM barrel dimensions on a page and slide on another some time ago. But they do not match for some reason!
Slide lug dimensions are:
The second lug wall should be located at .324 inch from the first. The third lug wall should be located .649 inch from the first. Tolerances are... IIRC... +/- .002 inch.
NM Slide Blueprint is available in our Technical Issues section via the link "M1911 Full Blueprints (Courtesty CNC Gunsmithing)", on page 51 (PDF page 53).
First to second lug wall works out to 0.324 +/- 0.004 inch.
First to third lug wall works out to 0.652 +/- 0.004 inch.
The later distance is 0.004" more than twice the first, and the USGI slide blueprint yields the same slight disparity. I think this is done to favor engagement at lugs 1 & 2 - as apposed to at lugs 1 & 3. Sounds good to me, anyway.
The only NM barrel blueprint in this collection is for the NM barrel assembly (barrel and bushing) and it does not contain any lug dimensions.
I suspect you are going to hand fit the barrel to the slide, so ultimately what ever you have is what you are going to use. Are you milling up an NM slide or trying to check one prior to fitting it up?
Oops!
Correct the tolerances given in Post #4 to +/- 0.004 inch. Tolerance stacking, doncha know!
I've got a slide on order and wanted specs to compare when it gets here. The Kart NM barrel that is going in it is within .002 on all lugs. And it will be fitted anyway, so this is kind of redundant...
Thanks for the (various ) numbers. The relationships of the lugs *were* in Kuhnhausen, but not the hood. I'm just jumping the gun.
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The relationships of the lugs *were* in Kuhnhausen, but not the hood.
A hood length of 0.181 - 0.003 inch for the "414" NM barrel was given in an article in the April 1963 American Rifleman. The notch (?) for the hood in the slide is 0.159 - 0.003 for both the USGI and NM slides.
I knew if I kept diggin' I'd find it somewhere... and it turned out to be here, of all places... in the tech section.
Cut/Paste exerpt from Wil Scheumann's tutorial.
----------------------------------------------------------------- Checking the radial lug spacing in the slide. ----------------------------------------------------------------- On page 95 of the Kuhnhausen book Jerry describes a technique for using Cerrosafe (obtainable from Brownells) to measure the radial lug bearing surface spacing. Another, and more direct way, to measure the slide radial lug bearing surface spacing is to use a height gauge. Place the slide muzzle end down on the measuring table. Insert the gauge into the interior of the slide, going in between the slide rails, and determine the height of the first radial lug bearing surface (just at the front of the ejection port). Then move the indicator down and measure the height of the second and third radial lug bearing surfaces. The important dimensions are (1) the difference between the heights of the first and second lugs and (2) the difference in height between the first and third lugs. These should be 0.324 inch and 0.649 inch respectively. If they are not, the spacing of the barrel radial lug bearing surfaces must be cut to match the measured slide radial lug bearing surface spacing. This process is described in the Kuhnhausen book on page 124.After measuring probably something in excess of 500 or so slides over the years, I've found this to be pretty much par, and measuring the lug spacing on a quality barrel will reflect that.
Oh for a decent height gauge! Guess I'll just keep using the lug measuring tool based on the one posted here. It does beat eyeballin'.
Not so fast there, David. After I finish correcting all my math errors, it'll probably Tuner doing the changing on me! Should be done checking soon.
Oops, Part Two!
My apologies for the math errors is Post #4, now all corrected.
Both of the distances (0.324 and 0.649 inch) given in Post #14 are within the specs derived from the newest available US Army blueprints, so I guess all's well in 1911 Land.
Tried to get the lug spacings based on an old 1928 blueprint to see if there might be any significant difference, but couldn't make out the numbers.
BTW, the basic dimensions for the USGI (not NM) slide lug wall separations are the same as the NM slide, but the USGI tolerance is +/- 0.009 inch.
Please remember the dimensions I've posted are not for any specific 1911 or group of 1911's. They're just based on the US Army blueprints, and those blueprints may or may not reflect how the slides actually got made at the slide factory. Tuner, Schuemann & Kuenhausen are the ones who know how they got made.
Back in the day...
The slide lug slots were cut with a gang tool... probably on a horizontal mill... with all cutters arranged on a common shaft. Think of a cluster gear in a transmision. Nowadays, they're most likely cut with a single cutter that's advanced from one to the next, or possibly with each one cut on a different mill, by a different operator. The locations are dependent on the skill and care of the machinists, and whoever did the setup on the machines.
Gang mills are expensive to make.
I figured that most would be cut on CNC mills today. Again, we are back to programmed specs. Specs or setup are shabby whichever it is. It is kind of hard to excuse it seems to me. A thou or two is not right, but most of us have seen way worse than that. Are there any cuts that are deemed critical?
Height gauge ...
Either you have a *very* steady set of hands or you fixture a way to hold the slide perpendicular to the table. Not a measurement I would want to make by hand and then go argue with the shop about weather they had done it right or not. Not to a +/- 0.002" tolerance.
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I figured that most would be cut on CNC mills today. Again, we are back to
programmed specs.
Assuming:
That they're going by the correct specs.
That they have the correct prints.
That they even have prints.
That they can read blueprints.
That they haven't adopted the "Close enough for gub'mint work" approach.
That the CNC operator is diligent in checking his work.
That the fixtures don't slip and that the operator catches it when they do.
That the CNC operator keeps an eye on tool wear and quality from the time his shift starts until it ends.
See where I'm goin' with this? CNC machinery is a boon to mass production... but it's still not smart enough to allow the operators to push a button and take a nap.
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Either you have a *very* steady set of hands or you fixture a way to hold
the slide perpendicular to the table.
Also known as a machinist's V-block... ground and lapped square to within +/- .0005 inch... and a surface plate. Since the measurements aren't taken off any external reference point, the slide doesn't even have to touch the plate. All that's needed is a precise distance from lug #1 to lug #2, and from lug #1 to lug #3.
Good point, I'm used to stuff where it is a height measure and indeed the slide would have to touch the plate.
Bob, presently I'm using a variation of a fixture posted here on the forum.
It requries a bit of a "touch" to get consistent measurements, but it works.
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Height gauge...
Either you have a *very* steady set of hands or you fixture a way to hold the slide perpendicular to the table. Not a measurement I would want to make by hand and then go argue with the shop about weather they had done it right or not. Not to a +/- 0.002" tolerance.
Nice picture of the fixture. Did you make that one or buy it?
Bob, I made this one. It was "interesting". I clamped the end pieces together, drilled then reamed the holes. After silver soldering them into one end, the sliding fit was almost perfect! In lapping the rods to the other end, so that the light springs would expand it smoothly, I let the rod assembly pop off and hit the floor! Of course alignment was no longer "nearly perfect". So I added the little thumb screw to one leg to avoid that in the future and started realigning things. I finally got it where it is not sticky and doesn't try to cant, but it was a bit of an ordeal. I could have paid for a couple of height gauges with the time I spent. But...
I don't expect to get final fit measurements from it. When I play with it enough, it will give close to .001"+ accuracy. It is more like using calipers than a mike. You need to use a "gentle touch" to get an accurate reading.
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...I'm using a variation of a fixture posted here on the forum.
That sure looks like a much better way than my rinky-dink method:
The washer's made to fit and it's thickness is just added to the caliper measurement taken from the top of the slide. Caliper ID nib length precludes measuring lugs 2 & 3.
[Height gauge . . . .sigh]
Will yours do all 3 lugs?
I keep wondering if there's a way to attack a poor defenseless $12 Chinese micrometer and turn it into a dedicated lug measurement tool. You could even ruin one or two and still not spend a lot of money on the project.
This tool is made to measure from the breech face to each lug. That is why I was seeking those measurements. And I can compile them from what you told me. The biggest trick of using the tool is getting it very flat to the breech and keeping it that way while sliding it into the depth of the lug cut and releasing it. So I measure each lug to the breech face with the tool. It is barely long enough to reach lug 3.
Bob, I've thought of that too. The shop even has a few imported micrometers that we have little investment in. You figure it out, and I will try it to back you up. ;-)
More or less what I'm thinking about:
Glue a block to the open end of the micrometer. The block goes against the breach face. Maybe do something "cute" with a magnet. Come up with something like a disk that glues to the moving part of the mic. That's going to fit up against the lug.
That's not going to work because there's no place for the "handle" of the micrometer.
Next up would be something like you have already with a micrometer where the screw is. You still have the springs and second rod. More complicated, but it might work.
I'd like something as positive as the first one, but that has some chance of working like the second one.
Still thinking on it...
If an inexpensive slide caliper could be found whose separate top-mounted ID nibs extended about 0.7" above the top surface of the slide (including any locking knobs, dial housing or electronics package housing), the breech face- to-lug 1, 2 & 3 measurements could be taken directly.
Don't know, however, if there is such an animal. My Mitutoyo caliper's nibs are about 0.1" too short - even if the locking knobs were removed. My Washington Tools catalog has 16 pages of slide calipers and none look like they'd do the trick - without modification.
There's some long-jawed calipers (with combined OD/ID jaws) but it looks like the jaws would need to be relieved to get the ID face far enough up on the breech face. And, they're kind of pricey! Like getting close to a cheap height gauge!
There's a set of slide caliper jaw attachments for measuring internal grooves, but it looks like it would be difficult to insure the measurement was perpendicular to the breech face with them.
Anybody ever try covering the ejection port and making a Cerrosafe casting from the breech face to lug #3? And succeed in getting it out without deforming it?
Or how about a... oh, never mind - it's getting late.
I haven't tried Serosafe all the way to the breech face. That is a good idea. Remember though that that stuff is fairly time/temperature sensative. It has a shrinkage of something like 1%, though I really don't remember the numbers offhand. Serosafe is onhand for chamber casts, so maybe I ought to just give it a shot. But you still have to deal with the slope of the breech face besides the ID struggles. Then there is getting it released from the cavities where it doesn't belong...
Someone should just come up with a caliper with longer ID jaws... for us.
You have the idea for a new tool specifically for the 1911 market. Make one, patent it and see if someplace like Brownell's will carry it.
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But you still have to deal with the slope of the breech face...
Well, there goes that hair-brained idea down the drain!
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You have the idea for a new tool specifically for the 1911 market. Make
one, patent it and see if someplace like Brownell's will carry it.
Cripes! One thing at a time, Ma'am. I'm still working on an ejector with a remotely controlled, infinitely adjustable nose!!
Ok, we'll give ya a week to have it designed, patented and in production. Okay
Actually, the slope of the breech is simple I think... With the tool square, it simply sits flush to the breech before adjusting it to fit the space. Doesn't the barrel sit at approximately the same angle when breeched up?
No patents here either! They are for someone willing to go to court and possibly a lot. Just ain't worth the hassle to me.
I wonder just how good the $39 height gauges actually are?
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Actually, the slope of the breech is simple I think... With the tool
square, it simply sits flush to the breech before adjusting it to fit the
space. Doesn't the barrel sit at approximately the same angle when breeched
up?
Your fixture would, I'm sure, give the proper distance - 90 deg to the breech face.
I thought you were referring to trying to get a measurement off of the Cerrosafe casting that was 90° to the breech face. That, I think, would be nearly impossible. So, forget the Cerrosafe idea.
And yes, the barrel would/should be at about the same angle (0 deg 52') as the breech face when in battery.
Another slide lug measurement possibility might be the use of a depth micrometer fitted with accessory groove measuring rods. These rods have a little disc on the end (like a disc micrometer), but the reference surface would have to be the nose of the slide - which is probably not parallel to the breech face.
And to think I passed up a 50% off sale on Starrett vernier height gauges a few months ago. [sigh]
I think that if you clamped everything down solid and did a series of measurements, you could do it with a depth micrometer. You would just have to measure the depth to the breach as part of the same set. You would have to have a pretty solid setup though.
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I wonder just how good the $39 height gauges actually are?
No foolin'? A $39 height gauge? Where? Harbor Freight? Height Gauges 'R Us?
Grizzly has one on their web site.
http://www.grizzly.com/catalog/2008/Main/683
I know nothing about it other than what I can see. It looks like a height gauge and it says its a height gauge. The price seems a little bit "go good to be true".
A $39 Happy Panda height gauge plus a Formica countertop sink cutout scrap for a surface plate - and you'd be all set!
That would even be lots cheaper than one of these things for a depth mike!
But, the math shows the error in taking these measurements perpendicular to the breech face or parallel to the slide axis only amounts to 0.0002" for lug #3.
You'd probably need a $5,000 height gauge to actually measure that small a difference!
US$39. Hmmm-m-m. How bad could it possibly be? [rhetorical question]
For not a whole lot of money you can get the Happy Panda granite block to go along with the height gauge. Of course shipping the block isn't going to be cheap.
I haven't checked it, but I feel sure that the slide nose is roughly square to the body, not parallel to the breech. Otherwise, you would not need to relieve the bushing to counter barrel springing. Or you would have to relieve it when the barrel was down instead of up. So the depth mike would probably be tricky.
We sell a lot of the cheapest Chinese dial calipers to reloaders. I check almost everyone that we get in. I've yet to find one over 0.001" off at an inch. However, all the ones I've checked have been off over 0.0005". So you can probably count on a thou error plus however much the user may add to that by technique. I still bet that Grizzy would be easier to get consistent measurements than my tool. Remember that you still need a surface plate, but they aren't too expensive.
Here's method I just tried out that'll allow calculating the distance between any two lugs or between any lug and the breech face. All that's needed is a 6" slide caliper with depth rod, an "edge finder" and a wooden handled cleaning swab.
The edge finder is a nice flat washer trimmed to fit into the locking lug recess of the slide, and is held in place for the measurement by a suitable length of wood stick:
Once the edge finder is wedged in place with the stick, measure (along the top interior surface of the slide) the distance from the slide nose to the edge finder at each lug as well as the distance from the slide nose to the breech face.
From these four measurements, any of the other breechface-lug or lug-lug dimensions can be calculated.
The results are no doubt not as good as with a good height gauge or with the nifty fixture shown in David Rose's post, above. But, not having a height gauge or the ability to make DR's fixture this was the best method I could come up with.
Niemi, I suspect that your method should work fine and would probably be repeatable. Repeatability is one of the things that the high end height gauges say that the cheapies don't. I don't remember ever using one, so the deficiencies are likely not readily visible unless you mess with both of them.
However, I have rarely bought a cheap tool that I didn't regret. And every time, I say I won't do it again. At a glance, the differences may not be obvious. But use one of the better ones, and it becomes so quickly. I have some cheap tools that work for specific jobs just fine. I have a feeling that the height gauge is not one of these. [sigh]
The cheap measuring instruments do have their limits. That's why I was trying to start off with a micrometer that was sort of good to 0.0001 , but only count on it for 0.001
Yeah, I would be very happy with a quick, simple, repeatable 0.001". Keep goin' folks. Oh, and "economical" would be nice.
My guess is that other things will keep a measurement from being any better than 0.001. I kind of doubt the slide, breach, and lugs are all "square" to below that level.
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Niemi, I suspect that your method should work fine and would probably be
repeatable.
I think the critical part of this method is the edge finder. One side must be quite flat with a little chamfer to insure a snug fit to the lug wall. And, its diameter should such that it will just wiggle into the recess.
Once wedged securely in place most of the measurement uncertainty is due to the instrument and measuring technique. Because the measurement differences are the one's used, any systematic instrument error is cancelled out. And I use vernier slide calipers becuase they are about 4 times as accurate as either dial or electronic digital calipers.
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However, I have rarely bought a cheap tool that I didn't regret.
Ditto here. Bought a $20 drill press chuck on EBay a few years back. While its runout is pretty good, if its tightened too much loosening it takes superhuman effort with the inevitable chuck key bite! Agonized for months over case neck (tube) micrometers and just ordered a $100 Mitutoyo - life's too short to be taking chances on junk (I tell myself)!
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I have some cheap tools that work for specific jobs just fine. I have a
feeling that the height gauge is not one of these.
Especially one with a dial indicator! DIN accuracy standard is ±0.001" for a 6" one, who knows if a $39 one meets the standard?
Hey. Please explain the statement about a vernier caliper being more accurate than a dial. Curious minds *need* to know! I graduated (up?) to dial indicators with a couple of trades a few years ago. To be honest, I was about needing magnification to read the markings. These two, an old B&S and a Starrett agree to about 1/2 a thou. I bought a new B&S last year. Comparing them to a regulated Starrett 1" mike, they are accurate to better than 1/3 thou with extreme care. The best I can remember reading the interpolation on the vernier, it was tough to get closer than 1/3 of a thou. But that is limited by the user anyway. Caliper jaws will flex without a lot of pressure.
I can see how the rails could add to error, but I haven't seen it happen with good calipers until they go weird with a lot of use or abuse. I traded for a Starrett electronic (very used) caliper that had some electrical problems and got rid of it before really checking it out.
In general 'smithing, I often need close to a thousandths accuracy, but not more than that very often. Part of the problem with my shop made tool is that some error occurs when seating it, and then error stacks when I measure the tool. I know, the error could cancel out, but Murphy lives here! Also, it takes me playing with it for a bit to feel comfortable with the measurements. Bare contact is ideal and seems to be the most accurate. And the slides I've measured with it do not have straight walls on the lugs as Bob said.
Measurin' Dan, have you compared several quality calipers and found the error to be true? I may not need more than a thou, but when things are stacking or surfaces are not quite true, it is nice to have that edge.
Get one, David. It's the easiest way to check lugs. On the last barrel and slide I messed with the first and second lugs on both measured exactly the same. Much joy. The hood was left a little long and I tapped the lugs into engagment. Both were touching. More joy and minor celebration. I fully believe that $450 Mitutoyo is accurate to .001 easily. The EGW tool gets you in the ball park on the hood. I made an attachment to use mine as a depth gauge also.
Was it you that mentioned using one of these a few months ago? Someone posted a pic of one.
There is a myriad of these things out there. I also noticed that for $500 you can get a model that is repeatably accurate to 0.0005" for whatever that might be worth.
I need to find more uses for it to justify that cost. So what else is it good for in 'smithing?
So what do you have? Where did you get it?
A set of calibration blocks are one way to know what your gauges are doing. If it's something like a mic or a caliper, precision dowel pins are another way to check things out. You don't need very many to get a good idea of what's going on. The cost isn't all that great.
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Please explain the statement about a vernier caliper being more accurate
than a dial.
It's just based on this little blurb in the Starret catalog:
Starrett makes/markets all three types of slide calipers, so I figured they have no particular reason to ballyhoo one over the other.
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...have you compared several quality calipers and found the error to be
true?
No I haven't. Even if I had the other two types of calipers, I don't have the standards to calibrate them.
That may just be a Starrett thing. It's unusual to find anybody claiming real accuracy below 0.001 on a caliper. I think I would grab a micrometer if I really wanted to be sure of what I was measuring. It's rare that I care that much...
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That may just be a Starrett thing.
You probably hit the nail on the head with that. Starrett's no doubt referring only to their Model 123 vernier caliper in the catalog blurb. These make other brands I've used or hefted seem flimsy by comparison.
Oddly enough, the only vernier caliper manufacturing standard I could find (JIS B7507) in reference had a +/- 0.05mm/ +/- 0.002" error limit for a 12 inch caliper! That's about what Mitutoyo's accuracy claim is for 12 inchers.
Maybe Starrett just plain makes them better than anybody else! Maybe you do really get what what you pay for - some of the time.
P.S.: Or, maybe it's just advertising hype.
David, I use the one I have, (Mitutoyo Absolute Digimatic PN 570 312-$450 @ Penn Tools), mainly for barrel and slide lug fit. I made an attachment to check depths in the lugs, bowties and other chores. An attachment for finding the center of two drillings is available. There is also available an electronic gizmo available that lights up when the probe touches metal to prevent tilting the gage. The main reason I got this thing is that I never trusted my ability to hold a caliper correctly. Plus the readout holds the mistakes down.
Checked a firing pin stop thickness and the width of a slide with the height gage and a Mitutoyo Absolute Digimatic 8" caliper with identical results. Zero the gage on the vise and then check the height. Zero on the first lug, move down to the second and third. No math. The accuracy of this gage I have is the same as the Mitutoyo venier height gages, according to their web site. A very handy tool to have.
Thank you sir! You know that you are pushing my tool lust button. Shame on you!
Are you simply standing the nose of the slide on the plate or do you hold it in some way to allow for the (slight) angle? I haven't calculated or looked up how much difference that angle would make, so it might not really matter.
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...the math shows the error in taking these measurements perpendicular to the
breech face or parallel to the slide axis only amounts to 0.0002" for lug
#3
That's for lug #3 to the breech face, almost 2 inches.
I square up the slide in a machinest vise. You just can't trust them slides.
Quite true. There is an amazing lot of "out of square" machine work out there.