This is a discussion on Knurling question within the Gunsmithing forums, part of the M14 M1A Forum category; Newbie question. After poking around the forum, I was considering knurling my GI profile barrel to tighten up op rod guide fit. Friend has a ...

Newbie question. After poking around the forum, I was considering knurling my GI profile barrel to tighten up op rod guide fit. Friend has a hand knurler but only with diagonal (diamond) knurl wheels. Is that usable or do only straight/spline cuts work? Or is JB Weld without any knurling satisfactory?

Note that to do knurling right, you want to match pitch. Knurling wheels have a certain pitch, you can put on a set of calipers, measure the diameter, then multiply by 3.1416 (Pi) to get the circumference. You then count the number of knurls around the perimeter to determine the pitch of the knurl (let's say hypothetically that you determine it is 0.050" per tooth). Ideally, if you are going to knurl, you want your part circumference to be an integer multiple of 0.050, so when the knurling wheel does one complete revolution of the part, the teeth overlap with the indentation made on the previous revolution.

So if your part is 1.5" in diameter, it will have a circumference of 4.712". That is not an even multiple of 0.050. However rounding down, 4.700 circumference would be, at 94 teeth per revolution, and would require a 1.496" diameter (4.7/Pi). So when you start knurling, you would run the knurling wheel 0.002" deep (0.004" of diameter), and the teeth would phase correctly. Of course 4.65 circumference would work too, with a 1.48" diameter, so run the teeth 0.01 deep.

On your hand knurler, it will have a knob on a threaded shaft driving the knurling wheel. Get a pitch gage, and measure the thread pitch. Now you know how many thou pre revolution the drive is. Let's say it is a 28 pitch thread. So your pitch is 1/28 or 0.036 per revolution. In the above example, wanting to go 0.01 deep would therefore require just under 1/4 turn beyond where the wheel starts to leave marks.

Note that to do knurling right, you want to match pitch. Knurling wheels have a certain pitch, you can put on a set of calipers, measure the diameter, then multiply by 3.1416 (Pi) to get the circumference. You then count the number of knurls around the perimeter to determine the pitch of the knurl (let's say hypothetically that you determine it is 0.050" per tooth). Ideally, if you are going to knurl, you want your part circumference to be an integer multiple of 0.050, so when the knurling wheel does one complete revolution of the part, the teeth overlap with the indentation made on the previous revolution.

So if your part is 1.5" in diameter, it will have a circumference of 4.712". That is not an even multiple of 0.050. However rounding down, 4.700 circumference would be, at 94 teeth per revolution, and would require a 1.496" diameter (4.7/Pi). So when you start knurling, you would run the knurling wheel 0.002" deep (0.004" of diameter), and the teeth would phase correctly. Of course 4.65 circumference would work too, with a 1.48" diameter, so run the teeth 0.01 deep.

On your hand knurler, it will have a knob on a threaded shaft driving the knurling wheel. Get a pitch gage, and measure the thread pitch. Now you know how many thou pre revolution the drive is. Let's say it is a 28 pitch thread. So your pitch is 1/28 or 0.036 per revolution. In the above example, wanting to go 0.01 deep would therefore require just under 1/4 turn beyond where the wheel starts to leave marks.

I'd have to go with JBWeld before I do math for an oprod guide. jBW would be setting up already.

Used JB weld on mine and it works well. If you have the tools, which I don't, then by all means knurl. A lot of people on this forum sing praises to Tonyben and rightly so. He recommends using JB weld if knurling isn't an option. That's good enough for me.

I recently asked the same question as the OP. Here's how I did it, and it worked like a charm! What I decided to do was to knurl the inside of the operating rod guide instead of the barrel itself. I mainly did this because I figured if I screwed something up in the modification process, it would be cheaply and easily replaceable. I did not have a knurling tool, so I went out and bought an automatic center punch. This worked well. I applied several punches to the inside of the operating rod guide, on both sides, all the way around. The raising of the metal was tight enough that I had to very carefully maneuver the guide over the upper band stop on the barrel. I had to drive the operating rod guide into it's spot with a rubber mallet. It is now very tight and not going to move anywhere.

The knurling pattern is irrelevant. Your simply wanting to displace metal, to create a larger effective diameter. Knurl it, call it good. You don't need a great diamond patten to do what you desire.

The last one I did I just drilled and tapped the pin holes. Using opposing set screws, align the guide and lick down
pour Locktite 292 on the assembled unit. Shot that rifle in local matches a few years ago, the guide stayed intact.

I'm dumber than dirt when it comes to math ,ya dont need no dern fancy mafemtics to knurl a barrel.

And yer speeling aint too good neether....

I recently bought a GWLA receiver and a Wolfe Modified Medium Weight barrel. I had my local gunsmith buddy install the barrel for me and this build went together very well. I'm very impressed with the receiver and barrel !!!
Head space was a bit tight with a NOS TRW bolt, but a very lightly used TRW bolt I got from Jersey Devil fit perfect.

Now, for the minor problem, I too have a loose op rod guide. I think I will go with the JB Weld method. And since it will be basically a permanent installation, it is not really an issue as the op rod guide is specially made to fit this barrel, and was included with the barrel. So when it is time to replace the barrel,the op rod guide will stay on that barrel.

This build was not in my plans as I have been trying to thin the herd a bit, and sold one of my LRB rifles with all major parts by TRW, and here I am... Thinning the herd is just an exercise in futility...