1911 slide rails with surface grinder. Feel??

Hi guys,

Anybody else ever done their 1911 rails with a surface grinder? (I had one. I had time. Etc.)
The reason I ask: I *know* I'm within .0005" in terms of side-to-side fit, and it does indeed slide very nicely, but it feels almost too smooth, if that makes any sense. It slides much easier than equivalent lapped slides do, even lapped or milled slides that are a little looser. (about a thou, instead of half thou.) I thought I'd overshot somehow, but I checked the fit a couple of different ways, and side to side, I'm within about .0005". I've got about .001" clearance vertically, against the bottom face of the slide, also ground in.

Huh???

Puzzled,
Brian


PS--> Next question: Has anybody ever thought to carve/engrave oil grooves into their slide rails? I started out as a jeweler, I've got the powered engraver and microscope to do it... I use Brian Enos' slide grease (to great effect) and I've started wondering if it'd be worth the bother to put oil grooves into the slide rails. Opinions?
(the same kind of grooves you see on scraped machine guide surfaces. Just a whole lot smaller.)

Ever fired a handgun???? Or watched a high speed camera, showing a 1911 frame visibly flexing during firing??? Very visible on Glocks...

This video does not show it well, but notice bullet is out of bore, before slide even begins to move rearward enough to begin unlocking... Pistol Shot Recorded at 73, Frames Per Second - YouTube

I have also seen high speed xrays of 1911, showing the same thing...

Plenty of copper/brass shavings, powder residue/sludge. Slide grease........

Where in your finely fitted slide, do these byproducts of firing go??? Unlike a machine tool, a limited amount of power in operating cycle..

Sure you can build a 1911 slide and rail combo, fitted to less than a 10th..

You won't win any matches with it, if it won't reliably function...

You CAN build an automotive gas engine, with pistons fitted with less than a 10th clearance too... Most chose not to.

"Only firearms that function well are interesting.." Alan

abarnsley said:

Ever fired a handgun???? Or watched a high speed camera, showing a 1911 frame visibly flexing during firing??? Very visible on Glocks...

This video does not show it well, but notice bullet is out of bore, before slide even begins to move rearward enough to begin unlocking... Pistol Shot Recorded at 73, Frames Per Second - YouTube

I have also seen high speed xrays of 1911, showing the same thing...

Plenty of copper/brass shavings, powder residue/sludge. Slide grease........

Where in your finely fitted slide, do these byproducts of firing go??? Unlike a machine tool, a limited amount of power in operating cycle..

Sure you can build a 1911 slide and rail combo, fitted to less than a 10th..

You won't win any matches with it, if it won't reliably function...

You CAN build an automotive gas engine, with pistons fitted with less than a 10th clearance too... Most chose not to.

"Only firearms that function well are interesting.." Alan

Click to expand...

It'll function just fine. Several of my other 1911's are probably a smidge tighter. It's just that this one seems suspiciously smooth for as tight as it is.

The point of getting it that tight hasn't got anything to do with the frame moving (or not) during firing, the point is to control where the barrel and slide come to rest relative to each other at lockup, after the recoil cycle.
That way the barrel's pointed at the same place, relative to the sights on the slide, every time. (and the tail of the cartridge is in the same spot, with the same tension, and the firing pin smacks the primer in the same place. Etc.)

The other thing to remember is that most of the black crap you get from gunpowder residue is....carbon. As in graphite.

Part of the reason for going to the trouble of clocking the frame in on the surface grinder was that the frame rails were surprisingly out of true for a brand new, never been built, CNC'd frame. It's actually an STI 2011, which has the rails split into two blocks, front and rear. The slide is an STI blank as well. The two rail blocks on the frame were each tapered a few tenths, and skewed a few tenths as well, depending on how you want to think about it. Which is why I pulled out the grinder to straighten them out. The two rail blocks were about a thou (or so) out from being coplanar with each other, in the side-to-side axis. Pretty damned good vertically, which was handy.
The idea with the STI frames is that (as new) the rails are a smidge oversized, so you can fit them yourself, as tight as you like. This one was over in terms of the width of the top rail, but had (and has) plenty of clearance in terms of the side-to-side of the groove, as well as the width of the groove. I ended up having to take .003" off the bottom face of the slide rails to get them to settle in, and then just about .0007" per side on the frame rails to get them to the right width for the groove in the slide. But there's more clearance than I'd like in terms of the width of the lower groove in the slide. As much as a thou or two. Plenty of room for all sorts of crap to squeegie out of the way, especially with the central gap between the two rail blocks.

I was just wondering if anybody'd noticed that grinding the rails made a difference in the way they feel.

Regards,
Brian


PS--> Does *ANYBODY* have any clue just exactly what Browning was smoking that caused him to taper the top of the 1911 slide? It's less than .2 degrees. (.026" in 8.5") Not enough to see, or do anything for you weight or strength wise, just enough to keep you from using the top of the slide as a reference surface for grinding the rails. It's like he was trying to make life hard for the machinists just 'cause. I knew about it already, so other than annoying me while I spent an extra half hour dialing the slide in, it didn't cause me any trouble. I just want to ask "WHY???"

Alberic said:

PS--> Does *ANYBODY* have any clue just exactly what Browning was smoking that caused him to taper the top of the 1911 slide? It's less than .2 degrees. (.026" in 8.5") Not enough to see, or do anything for you weight or strength wise, just enough to keep you from using the top of the slide as a reference surface for grinding the rails. It's like he was trying to make life hard for the machinists just 'cause. I knew about it already, so other than annoying me while I spent an extra half hour dialing the slide in, it didn't cause me any trouble. I just want to ask "WHY???"

Click to expand...

Can't say I know for sure, but I suspect it was to ease production - draft for a forging operation or something of the like. I know I 'discovered' it on my own about 20 years ago when I first tried to flat-top a slide...

BTW - I've had much better luck with Ballistol than Slide Glide.

GsT

Don't dwell too much on the slide to frame fit or make it too tight . Every top bullseye / national match armorer I every talked to said that the accuracy gain from it is not that much , and in fact can cause problems if too tight.
According to them all the accuracy is from the barrel and bushing fitting.

Alberic said:

The point of getting it that tight hasn't got anything to do with the frame moving (or not) during firing, the point is to control where the barrel and slide come to rest relative to each other at lockup, after the recoil cycle.
That way the barrel's pointed at the same place, relative to the sights on the slide, every time. (and the tail of the cartridge is in the same spot, with the same tension, and the firing pin smacks the primer in the same place. Etc.)

Click to expand...

Not on ole slabsides it ain't. All you've accomplished is to align the SIGHTS with the frame each go. Barrel is at the mercy of the cylindrical bushing and wotever it has picked up. That has to be loose enough to allow a characteristic Browning link to TILT the barrel, and from very early-on.

OTHER designers who've dealt with that have done one or both of two things:

Petter style plate-cam instead of link to allow a measure of dead-straight movement BEFORE tilting to unlock or just prior to re-lock.

Hemi or cone, at the pointy-end to improve locating consistency, clean, Vee-block function that self-clears to work well, even dirty.

A 1911 can deliver more accuracy than it has any RIGHT to do, but there are limits, even so.

Bill

Monarchist said:

Not on ole slabsides it ain't. All you've accomplished is to align the SIGHTS with the frame each go. Barrel is at the mercy of the cylindrical bushing and wotever it has picked up. That has to be loose enough to allow a characteristic Browning link to TILT the barrel, and from very early-on.

OTHER designers who've dealt with that have done one or both of two things:

Petter style plate-cam instead of link to allow a measure of dead-straight movement BEFORE tilting to unlock or just prior to re-lock.

Hemi or cone, at the pointy-end to improve locating consistency, clean, Vee-block function that self-clears to work well, even dirty.

A 1911 can deliver more accuracy than it has any RIGHT to do, but there are limits, even so.

Bill

Click to expand...

Yeah, that too. I've had pretty good luck with the Kart NM barrels that come with their own 'ground to match' oversized bushings.
I picked up a 5C expanding collet, machined it to fit the inside, and then used that to cut the bushing to a few thou over on the lathe, and then ground it from there. I got a a tighter fit, and a much easier turning feeling on the one that I ground, versus some that I've just done with a lathe. (even a 10EE) That's part of what got me wondering if grinding just doesn't give a smoother feel, even when tighter. (I just ended up with a surface grinder. I've never had one before, so grinders are new to me.)

Regards,
Brian

The ultimate solution to the 1911 bushing problem is the Briley spherical bushing. Free movement in swivel with very small radial clearance. It works so well S&W used the same principle on the Mod 52.

RWO

It works so well S&W used the same principle on the Mod 52.

The .38 Special one or the 9mm one?

Alberic said:

Hi guys,

Anybody else ever done their 1911 rails with a surface grinder? (I had one. I had time. Etc.)
The reason I ask: I *know* I'm within .0005" in terms of side-to-side fit, and it does indeed slide very nicely, but it feels almost too smooth, if that makes any sense. It slides much easier than equivalent lapped slides do, even lapped or milled slides that are a little looser. (about a thou, instead of half thou.) I thought I'd overshot somehow, but I checked the fit a couple of different ways, and side to side, I'm within about .0005". I've got about .001" clearance vertically, against the bottom face of the slide, also ground in.

Huh???

Puzzled,
Brian


PS--> Next question: Has anybody ever thought to carve/engrave oil grooves into their slide rails? I started out as a jeweler, I've got the powered engraver and microscope to do it... I use Brian Enos' slide grease (to great effect) and I've started wondering if it'd be worth the bother to put oil grooves into the slide rails. Opinions?
(the same kind of grooves you see on scraped machine guide surfaces. Just a whole lot smaller.)

Click to expand...

I stumbled across this page on a Google search for some kind of validation. I don't know if anyone is still on here 5 years later but maybe. .0005 was about the tolerances for QC felt windage and elevation at STI with light oil. We used surface grinders to do all the slide to frame fits back in the day. Started with a .250 wheel and cut them down to .050 on surface grinder, if I remember, to fit inside frame rails. Did thousands of 1911s and 2011s over several years this way. No better way to get a very smooth and straight, tight fit.

I may be wrong but I think JMB was the first pistol designer to understand that slop is only needed after the bullet is moving downrange, no one cares how loose everything is halfway into recoil, but having everything come back together tight is where the accuracy is, as the OP said;

"The point of getting it that tight hasn't got anything to do with the frame moving (or not) during firing, the point is to control where the barrel and slide come to rest relative to each other at lockup, after the recoil cycle.
That way the barrel's pointed at the same place, relative to the sights on the slide, every time. (and the tail of the cartridge is in the same spot, with the same tension, and the firing pin smacks the primer in the same place. Etc.)"

The whole fuss about a tight slide to frame fit came about from testing for accuracy in a Ransom rest, like a revolver was tested. This effectively moved the sights to the frame. This fit also became important with the older optics setup on a frame mount. With iron sights or optics mounted on the slide, the only thing that is important for accuracy is the barrel slide fit at the moment of ignition. We proved this year ago with iron sighted M1911NM pistols that would not shoot to standard out of the Ransom rest winning matches in the hands of a good shooter. At work we are still required to test for accuracy out of a Ransom rest, but are working on a better test method, especially for the plastic framed pistols.

partsproduction said:

I may be wrong but I think JMB was the first pistol designer to understand that slop is only needed after the bullet is moving downrange, no one cares how loose everything is halfway into recoil, but having everything come back together tight is where the accuracy is, as the OP said;

"The point of getting it that tight hasn't got anything to do with the frame moving (or not) during firing, the point is to control where the barrel and slide come to rest relative to each other at lockup, after the recoil cycle.
That way the barrel's pointed at the same place, relative to the sights on the slide, every time. (and the tail of the cartridge is in the same spot, with the same tension, and the firing pin smacks the primer in the same place. Etc.)"

Click to expand...

Yes, lockup is all that matters. Too much bearing surface area can be a bad thing. I know on some 1911s we would have to cut the dust cover to match bottom of slide rail on frame. It would give you like 8" or something of rail that the slide is riding on bottom? Like a forever pistol there, try to wear it out, Lol. If you notice on the modern combat pistols they only have small sections of rail on front and back. Lots of places for dirt to go and get out of the way in the middle.