I'm removing the Romeo 1(not pro) sight from my early model XCarry and re-installng the plate with integrated rear iron sight.
Any idea what the torque value is for the screws on that iron sight plate?

My Forward Controls Design adapter plate on my M17 uses the sight plate screws to hold the plate on and they are spec'ed to 12.5 in-lb.

I'd say 10 in-lb for the sight plate along with blue loctite should be good enough.

I can’t be the only guy who has never used a torque wrench to mount optics right? Snug, then a little bit more, not too much though. That’s my technique, never lost a screw or an optic. I’m like the Amish of optics mounting.

Sig recommends 30 in/lbs for the sight, so I imagine you can't go wrong with the same spec.

quote:

Originally posted by Flash-LB:
Sig recommends 30 in/lbs for the sight, so I imagine you can't go wrong with the same spec.

No way, the screws are too small for that and will strip or round out. 30 in/lb is for optic to slide from the top, not the rear sight plate from the bottom.

The real issue is finding torque wrenches which go low enough, in inch pounds. The tiny inch pound wrenches - like at Brownells - run from $50 - 100. The last auto in lb wrench I bought ran me over $45 for a one time use. It wont go under 50, but that handles intake bolts, etc. 50 in lbs = 4 foot pounds.

I broke two Craftsman 1/2 drive torque wrenches and wound up tossing them, no warranty. The latest was one I picked up at a flea market for $12, I've never seen inch pound wrenches sold second hand - but I have heard of folks using them to torque lug nuts to 125 FOOT POUNDS and laughing about it. That would be 1,500 INCH pounds.

Those tiny RMR screws and the torque values, stripping them (it's already an issue), having them come off the slide shooting, and no other way to secure them better means I'm standing aside and just watching for now. Show me a slide with an integral flush picatinny rail and I might get interested.

Them quick change knobs/levers will have to go, tho.

quote:

Originally posted by pedropcola:
I can’t be the only guy who has never used a torque wrench to mount optics right? Snug, then a little bit more, not too much though. That’s my technique, never lost a screw or an optic. I’m like the Amish of optics mounting.

I use a Proto Professional 6-36 in/lb torque limiting driver for most of my firearms fasteners. Also have 3 adjustable torque wrenches for the bigger stuff.

Right tools for the job. The goal is consistency and repeatability. No stripped bolts, and none loosening up under use. But then teaching people around the world how to tighten bolts on engines so they don't fail is part of my day job...

All kidding aside I don’t see the issue. I’ve mounted DP, DP Pro, SRO, RMR multiple times, and multiple 507k’s. That is just pistol optics.

Seriously, snug them down and go a little bit more. Use quality driver bits that fit. Use your head.

I’ve never stripped any screw this way or had an optic come loose. The only screws I’ve ever had issues with were screws that the manufacturer installed. Probably using the very torque values we are discussing.

Until proven otherwise I put this in the category of overthinking a simple issue.

quote:

Originally posted by pedropcola:
All kidding aside I don’t see the issue. I’ve mounted DP, DP Pro, SRO, RMR multiple times, and multiple 507k’s. That is just pistol optics.

Seriously, snug them down and go a little bit more. Use quality driver bits that fit. Use your head.

I’ve never stripped any screw this way or had an optic come loose. The only screws I’ve ever had issues with were screws that the manufacturer installed. Probably using the very torque values we are discussing.

Until proven otherwise I put this in the category of overthinking a simple issue.

Yep. This isn't building an engine.

Yea that’s great. This isn’t an engine though so your expertise is somewhat muddled in this instance. It’s a screw holding on an optic. Are you seriously saying you can’t snug it down without stripping it or it coming loose unless you have a torque wrench? I call bullshit.

This is right up there with the grease paranoia that Sig owners fret over. Nobody else who makes aluminum framed firearms fret over rail wear like Sig owners. We even have the “chart”.

Lubricate your guns, use your head and quality drivers when installing screws. You can manufacture entire guns in a cave, this isn’t sending a man to Mars, you guys are way overthinking this.

Do you really want to profess ignorance as superior?'

There is is a shit ton of engineering work that goes into specifying the appropriate bolt size, length, and torque for bolted joints. When you get into tensile clamp load specs that need ultrasonic measurement it gets even more complicated. Technically, torque is 80-90% friction and only an indicator of joint stability. Tensile clamp load is the gold standard for things that absolutely cannot fail, ever.

The DC electric, transducer controlled production systems we use to ensure we meet the spec every time without fail are very expensive. But I can show you the correlation to defects between these systems, and less capable systems.

And I also know and have been involved with what happens with service people apply "gudentite" approaches without following the specs. It is not pretty, and leads to a lot more defects, warranty cost, and customer dissatisfaction.

Do what you want. I follow the specs with the appropriate tools.

Couldn't tell you what Sig specifies. Most plate and optic manufacturers are between 10 and 15 inch-pounds for screws. The exceptions are clamp bar screws on optics like the 509T, MPS, and ACRO.

I personally use a Wheeler Fat Wrench for my optic installations.

Proper screw prep is critical. Clean and degrease and use appropriate thread locker correctly. Tighter on the screws is not always better. Witness marks are your friend.

And do you really want to gild a lilly?

You literally have one guy quoting Sig specs and another guy saying oh no that’s way too much. So which is it? While you pontificate the issue I will install your sight, not strip the screw, and it won’t come off.

You are confusing reality with techno theatrics. All the gunsmiths of yore that we would pay huge money to own their work or even recreate their work did it without 90% of the bullshit some of you think is necessary.

This forum has guys who will yell to the rafters, “the owners manual says…..”. Of course what the manual says is don’t use reloads. Don’t store your gun loaded. They also over spring the shit out of your guns. They do it for liability and reliability. People who respring their guns to logical, reliable levels get told that if that was ok the engineers would have shipped it that way. All bullshit. Just like this. (Even Beretta finally acknowledged the mainspring was too much on civilian guns, 92X’s now all ship with D springs which is merely a lower lb spring. People have been doing it for years. But, but, the manual, tech, specs, sputter….). Use your brain and your experience. Gudentite. Oh brother.

If you want a torque wrench to install your RMR by all means go for it. Don’t disparage not using one though. If you are even mildly handy around guns you don’t need a torque wrench to correctly install a Deltapoint.

You know that huge range specified for a AR barrel nut torque? Do you know why it’s so huge?

Not rocket science. Not professing ignorance as superior. Pointing out that confusing specificity with accuracy is common among people who write tech manuals or sell products. If you are so worried then take a paint pen and make an index mark. If it moves one iota then go run to your torque wrench.

There are applications that require this level of accuracy. Mounting an optics plate ain’t one of them.


I also find it telling that you think specs for “DC electric, transducer controlled production systems” is somehow relevant to tightening a screw. You really think so? Is tightening an optics plate need the same level of accuracy as a component for the Mars Rover? I’ll answer. Nope.

Thanks guys for sharing your knowledge

Burris recommends 12.5 inch pounds on my Fast Fire III.

quote:

Originally posted by wingwlkr:
Thanks guys for sharing your knowledge

I'm picturing you doing this:

quote:

Originally posted by pedropcola:
If you want a torque wrench to install your RMR by all means go for it. Don’t disparage not using one though. If you are even mildly handy around guns you don’t need a torque wrench to correctly install a Deltapoint.

You know that huge range specified for a AR barrel nut torque? Do you know why it’s so huge?

Not rocket science. Not professing ignorance as superior. Pointing out that confusing specificity with accuracy is common among people who write tech manuals or sell products. If you are so worried then take a paint pen and make an index mark. If it moves one iota then go run to your torque wrench.

There are applications that require this level of accuracy. Mounting an optics plate ain’t one of them.

I also find it telling that you think specs for “DC electric, transducer controlled production systems” is somehow relevant to tightening a screw. You really think so? Is tightening an optics plate need the same level of accuracy as a component for the Mars Rover? I’ll answer. Nope.

Nice to see luddites tell experts they are wrong. I don't build mars rovers. I oversee corporate build specs for high volume commercial products for automotive customers that expect lower than 250 PPM quality levels. That means 250 defects per million products shipped.

If there is a spec, follow it, with the appropriate tools. Period. If you choose to go "gudentight" or "farmer tight" on your own, good luck with that.

BOTTOM LINE:

Sig sight plate from underneath will be fine with 10 in-lb and blue loctite.

Bottom line your area of expertise doesn’t make you an oracle on tightening screws on optics plates. Quit pretending it does.

You read it in a manual and now you consider it gospel regardless of applicability.

quote:

Originally posted by pedropcola:
Bottom line your area of expertise doesn’t make you an oracle on tightening screws on optics plates. Quit pretending it does.

You read it in a manual and now you consider it gospel regardless of applicability.

Dude, what is your problem? Asshole often?

I said clearly, 10 in-lbs with blue loctite (or red if you are overly worried about fly off) is fine for an M17/M18 commercial style iron sight plate. This is within the normal torque range for an SAE grade 7 or 8 carbon steel 4-40 capscrew with a 3/32" socket head. I don't know exactly what grade Sig uses, but again 10 in-lb is going to be fine. Again, we are talking about the small screws that fasten the sight plate from underneath, not the screws that hold a top mount optic in place. Big difference.

This is not published in any Sig manual that I have seen. Adapter plates from FCD and Bobro spec 12 in-lbs on the same screws, but that is intended to retain a plate holding an optic, not just iron sights, so they go on the high side.

This is how engineering works - bolted joints need enough clamp load to keep the joint together under load and prevent bolt back off. Clamp load is a function of elastic bolt elongation when fully tightened in the joint, and is only approximated by torque (most torque goes to friction not clamp load). Too little load, it backs off and breaks due to fretting, too high load and it can break due to fatigue loading.

The size of the bolt or what it is fastening doesn't change the physics. Almost all bolted joint failures in practice are due to under or over loading, so getting it right every time is essential to quality. I've had very very expensive machinery fail and take days to repair at very high cost (repair parts and lost production) because the technician thought "tight enough" was OK. I've flown around the world on short notice to fix problems when shit flys apart at an important customer because someone didn't hold the right specs in production. And I've gotten pulled into $M's of warranty cost because some techs in a country known for cutting corners thought non-reusable threaded parts could be reused while also ignoring the tightening specs. Yep, "tight enough" led to catastrophic field failures, and the design guys trying to solve the problem were spinning their wheels until I got involved. I happened to have spec'd all the tools on that production line and worked with the original design guys on implementing their specs - except one of them got his tolerances wrong.

Most non-critical bolted joints have pretty good margin on clamp load, and standard bolts have acceptable torque ranges where the combination of clamp load and friction keep them in place. In this case the loctite is doing a lot of the work for you so the torque is less critical - hence my 10 in-lb recommendation.

But sure, do it all by "feel" and tell me how that works out. Might be OK most of the time. But it might not. But I know for a fact over the last 25 years of doing this kind of work that increasing accuracy and precision in tightening bolted joints has a direct correlation to quality and service life of the product. And the products I am responsible for affect almost every single person in this country, no less those on this website.

ADDING:

When it comes to parts fastened to a reciprocating semi-automatic slide, you had better get the joint right if you don't want the thing to fly off and hit you in the face. This is not the same thing as putting a scope on a rifle. In many cases the size of the bolt and available torque range before stripping is insufficient to keep the thing in place without loctite. And even then it had better be tight enough to avoid fretting and bolt failure.

A top mount Sig R1 Pro is spec'ed at 28-30 in-lbs on each M4 x 0.7 screw, which feels a whole lot higher than you think it should be, and is twice as high as the 15 in-lb spec Holosun uses. Sig recommends frequent checking to make sure the screws are not backing off. Trijicon is around 12-15 in-lb as well IIRC. Leupold DPP is 25 in-lb.

This message has been edited. Last edited by: Lefty Sig,

quote:

Originally posted by Tirod:
The real issue is finding torque wrenches which go low enough, in inch pounds. The tiny inch pound wrenches - like at Brownells - run from $50 - 100. The last auto in lb wrench I bought ran me over $45 for a one time use. It wont go under 50, but that handles intake bolts, etc. 50 in lbs = 4 foot pounds.

Screwdrivers, have a Klein, 2-36 in lbs
Home Depot sells one under the Husky brand (8-40 in lbs).
A lot of gun owners use the Wheeler Fat Wrench (10-65 in lbs).
Wiha, Wera, Gearwrench, Vortex, Klein, Proto, Kraftform, etc... just search for torque screwdrivers.

quote:

Originally posted by Tirod:
I have heard of folks using them to torque lug nuts to 125 FOOT POUNDS and laughing about it. That would be 1,500 INCH pounds.

Klein, 200-1200 in lbs. So several lugs up to 100 ft lbs could be done.
That's not what I use it for as I have several in the 30-250 ft lbs for this purpose. They are also longer, allowing for greater leverage.