I want to accuratly measure the locations of my Metroarms slide lugs to help me try to achieve full lug contact for my new Kart barrel.
I have the original Metroarms barrel that I never intend to use so I deciced to modify the barrel so that I can use an actual barrel to take slide lug measurements.
First I sanded off barrel lugs 2 and 3. Then I sanded down the hood behind lug 1 to the same level as the barrel. I left a .160 wide "fake" lug width as shown here:
Then I choose a Colt barrel bushing to hold the barrel tool in the slide because Colt bushings use a narrow bushing width that is less prone to barrel spring.
Then I installed the barrel, bushing and used the Kart barrel alignment tool from their Easy-fit kit to hold the barrel in position.
I am able to increment the barrel between slide lugs now with confidence. I had great measurement repeatability using my digital calipers.
Here is the barrel locked into slide lug 3.
I am able to increment the barrel between slide lugs now with confidence. I had great measurement repeatability using my digital calipers.
Here is the barrel locked into slide lug 3.
Now I need to decide the best tool to uses to measure each lug location more accurately than my +/-.001 calipers.
I may decide to use the barrel extension for the measurements.
Great idea you've got there!
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I may decide to use the barrel extension for the measurements.
Here's something to consider. You're wanting to find the distance from the breechface to each of the lugs in the slide. But measurements from the muzzle to the slide nose would mean you'd need 2 additional measurements (B & D) to get the distance you want, or A (for lug #2) here:
If you cut off the barrel hood and got the chamber face perpendicular to the bore axis, I think your accuracy would improve simply because you'd only need to take and add 2 measurements (E & F).
P.S.: How do you like your Versa-Vise? I always wanted one.
I am only trying to measure the distances between slide lugs not back to the hood. The hood fitting step is last using the Kart Easy-fit method. Hood length should be easy with the Kart (cross fingers).
I zeroed my measurement at the front of lug 1 then measured how much my barrel-tool-fixture-thing moved to the front of lug 2. This should eliminate most measurement stack-ups (only one meas ± plus another meas ±). When I receive my new Kart barrel I will use the same approach to measure the distances between the barrel lugs. Hopefully they will measure .323 because this is the distance I measured between both lug 1-2 and lug 2-3 of my slide.
PS I luv that vise... it spins... it clamps... it's easy...
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I am only trying to measure the distances between slide lugs not back to
the hood.
Oh! In that case measurements from the muzzle will do just fine.
As far as a measurement tool, I don't know what kind of calipers you have but if it's equipped with a depth measuring rod/bar, separate depth bases are available for calipers to provide a better "footing" http://www.thefind.com/cars/info-caliper-depth-base . A depth micrometer has a similar base and an inexpensive one with 0.001" graduations can usually be interpolated to the nearest 0.0002".
I use optical equipment for the measurements you are looking for but the alternate method I would choose would be using the Cerrosafe alloys. Brownell's and other machining supply houses have this stuff. Take a look at the link below and see if this would be a benefit to you:
The only reason to need the breechface to first lug dimension is to be able to cut the hood to within a thousandths or so of that dimension.
The other two are taken off the first lug wall. From the first lug wall to the second, the distance is .324 +/- .001 inch. From the first to the third is .649 +/- .001 inch.
On the barrel, measure from the hood face to the first lug to bet the baseline. Then from the hood to the second lug. Then from the hood to the third.
For the slide, measure from the first wall to the second, then from the first to the third. A height gauge is the most accurate method if specialty measuring tools aren't available.
Why first to third?
To eliminate a stackup?
Hello and thank you for the idea... I have use different mold compounds in my carreer but they where only used when we couldn't directly measure geometery. I can directly measure my slide with my tool. Also, I have used vistion system (edge detection) systems before too but this technology could only be used on the barrel and I don't have a Visions system at home.
That's the nice thing about doing work like this, there are a lot of different ways that provide good results. I will be interested in how your finished job turns out.
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Why first to third?
Because you want to know where 2 and 3 are in relation to 1. The distance from the breechface is unimportant as long as the slide and barrel lugs are in position to touch when the barrel is fully forward in the slide. The distance from breechface to the 1st lug is unimportant as long as the hood has enough material to allow you to fit it.
If slide lug #2 is too far aft or the barrel lug is too far forward, you're fitting the hood to the second lug instead of the first. Ditto for #3. If you fit the hood to #2, and you discover that #2 is holding the mating 1# lugs apart... and you cut #2 to bring #1 into contact... you lose hood to breechface fit, and you increase the headspace.
Niemi. Try 1 of these. I have a couple and love 'em Also have a Versa vise, no difference that I can tell.
http://www.grizzly.com/products/Parrot-Vise-/H3302
This is how I do it... you can measure 100 barrels, and 100 slides, no two are the same. I cut the first barrel lug, as zero reference, and the rest are just a matter of dialing in the numbers to match the slide...
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This is how I do it... you can measure 100 barrels, and 100 slides, no two
are the same. I cut the first barrel lug, as zero reference, and the rest are
just a matter of dialing in the numbers to match the slide...
Hello and thank you for sharing your measurement techniques Jerry.
We have on OK tool department at my work and I have the good fortune to have worked with top notch tool makers before which there is no doubt that you are one.
It looks like you have a very nice lathe... I am green with envy... geese my wife would kill me if I bought that now... I guess I have to wait until my daughter is through college to give it a try.
But on a more serious note: I am looking for a nice digital indicator with +/-.000X accuracy but they don't seem to be very common. +/-.00X is very common though. If I could find a one I would design a clamping fixture that would use similar methods as yours. In the mean time I will keep fiddling with what I got...
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I am looking for a nice digital indicator with +/-.000X accuracy but they
don't seem to be very common.
Here's one for you:
http://www.swissprec.com/CGI/ISSRIT2?PMAKA=20-073-3
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http://www.swissprec.com/CGI/ISSRIT2?PMAKA=20-073-3
Hello and thank you niemi... $445... ouch... I guess I am running with the big dogs now...
Nice setup - simple and easy to do with just the lathe.
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$445.. .ouch.
Maybe they offer a quantity discount if you buy enough of them.
But on the serious side, dial indicators with 0.0001" graduations are lots cheaper...
http://www.swissprec.com/CGI/ISSRIT2?PMAKA=24-303-0
...but they don't have the range you need to get any measurements. No problem with 0.001" graduated dial indicator but you'd have to interpolate to get the fourth digit past the decimal point.
Here's the same Douglas barrel getting its final concentricity pass.
Recall that I measured .323 between lugs?
I can buy an indicator like the one you just found and use 5/16 (.3125 +/-.000?) gage blocks stacked up while holding that .050-travel indicator in place... yeah... I think that may be an easy-inexpensive way to go...
Here's some additional digital ones with 0.0001" or better resolution that are a less pricey than that $450 model I first found:
http://www.swissprec.com/CGI/ISSRIT2?PMAKA=14-798-3 and http://www.swissprec.com/CGI/ISSRIT2?PMAKA=14-798-3
Only reason I showed the SPI ones is I had a sale flyer featuring them, but have no experience with them. Starrett, Mitutoyo and others probably have them too, but I don't think Harbor Freight would.
I'm just trying to add to your decision making misery!
Here is a link to a thread I started about 4 years ago that shows some gunsmithing tools I built:
http://forum.m1911.org/showthread.php?t=12267
The drawings for the slide lug gauge shown in the thread can be found here:
http://www.m1911.org/full_technic.htm under the title "Drawings of gunsmithing tools (in .dwg and .jpg format)"
I am in the process of designing and building a special micrometer to measure the barrel lug to hood distance. I just finished the drawings and am about to start building it. I will post pictures when it is finished.
I found this one that looks REALLY nice and no gage block are required with 1" stroke. Dem-dare a lot of zeros.
SPI Part Number 14-797-5
Electronic Indicators Type: Digimatic Indicator Minimum Measuring Range: 0
In., 0 mm Maximum Measuring Range: 1.000 In., 25 mm Resolution: 0.00005
In./0.001mm
Type: Digimatic Indicator
Maximum Measuring Range (Decimal Inch): 1.0000"
Maximum Measuring Range (mm): 25mm
Resolution: 0.00005In./0.001mm
Stem Diameter (Inch): 3/8
Back Type: Flat and Lug
Battery Type: SR-44
Data Output: Yes
Includes: Certificate of Calibration Traceable to NIST
SPI Part Number: 14-797-5
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I am in the process of designing and building a special micrometer to
measure the barrel lug to hood distance.
Would it be something like this? http://www.swissprec.com/CGI/ISSRIT2?PMAKA=13-535-0 FWIW, the sale flyer I've got says the disc diameter is 0.5", but its reach is only 3.38" - just a bit too short for the #1 lug on a 5" slide.
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height gauge is the most accurate method if specialty measuring tools
aren't available.
A height gage with a test indicator is best even then. I used these routinely as an aerospace machinist.
http://www.qualitymag.com/QUAL/2006...106-meas-p3.jpg
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Would it be something like this?
http://www.swissprec.com/CGI/ISSRIT2?PMAKA=13-535-0 FWIW, the sale flyer I've
got says the disc diameter is 0.5", but its reach is only 3.38" - just a bit
too short for the #1 lug on a 5" slide.
Not exactly. Mine will use a regular 1" micrometer head that I am attaching to one end of a v-block. The barrel will sit in the v-block. There will be a measuring face at the other end that is contoured to fit inside the barrel lug groove to measure the distance from the lug face to the end of the hood.
FWIW, Mitutoyo does make several groove micrometers with sufficient reach to measure the distance from the breechface to the lug faces in the slide. The Starrett 260 isn't long enough. These are the Mitutoyo 146-Series and are available with 1/4 or 1/2" diameter discs and with rotating or non-rotating spindles with reaches in excess of 4".
I think the 1/4" disc model with a 1 to 2" range could get the slide measurements all by itself. The 1/2" disc model would need a gage block on the breechface to obtain clearance for the disc, but with a 1" rectangular gage block on the breechface, the mike with the 0 to1" range would be needed. That mike could then also be used for other (non barrel fitting) measurements on the 1911.
The prices on those Mitutoyos, however, will make Harbor Freight shoppers gasp in horror - expecially the ones with non-rotating spindles!
True Dan and they don't show up on ebay without about $140 starting bid and a reserve on them. Sure like to find one though...
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A height gage with a test indicator is best even then. I used
these routinely as an aerospace machinist.
Dg12 is on the right track here. I like the Brown & Sharpe test indicator that resolutes to the hundredth... achieving equal contact on all three lug shoulders is probably one of the most difficult parts of 1911 building, so, eliminating as much of the human handling factor of manipulating measuring instruments as possible, the better... You can also use your mill with an electronic sensor to get a very accurate measurement between the breechface and the first lug. And you can duplicate the lathe set up on your mill, with the slide upside down in the vise, but accurately cutting the barrel lugs will be the largest challenge.
I am building mine to measure the lug to hood distances on the barrel itself. I have already built a tool to measure the slide lug to breechface distances.
I would like to thank everyone for their input.
I have experience with measurement devices including height gages, CMMs, Visison system, air-gages... et.al...
I'm trying to get the most bang for the home built buck and want a gage that I can use on other projects without having to buy a surface plate too. To me a drop indicator and stand will give the best price, flexibility and accuracy for the project. Together with the modified barrel I hope that I can pull it off. Recall that I will be measuring using a barrel that will oriented in the same way as the actual Kart barrel.
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...they don't show up on ebay without about $140 starting bid and a reserve on
them. Sure like to find one though...
For some reason I'd think a fairly good place to find one might be in a pawn shop in a large city that has a trade school with a machinist's program. But maybe I'm just daydreaming.
I want to report that I was able to get lugs 1&2 in full contact... 2 out of 3 ain't bad. I didn't realize that a good barrel fit would tighten up the slide to frame fit until now.
I shot 100 rounds yesterday and she is a great shooter and now with all tool steel internals she is more durable too... Next step is Melonite.
I would like to thank everyone for their kind words and new ideas.