Springfield 1911 sear to hammer hole position

[Greg528iT]

Today while discussing trigger jobs, the position of the sear and hammer hole was discussed. It was noted that my Springfield is a bit long as well as Rail Driver's.

What is your springfield's center dimension?
It's easy to measure a dial caliper will do. Measure the closest to points of the pin holes add half the .110 pin and half the .157 pin. The Nominal dimension between the holes is .434".
(measured dim) + .055 + .078 - .434 = ??

My 2010 Springer
.025" long
My 1990s Springer
.023" long
My 1980s Springer
.024" long
Rail Driver's Springer
.022" long

I'm suspecting that Springfield increased this dimension, not a sloppy machine.
The further apart the sear and hammer the more the sear nose dives into hammer hooks making a stiffer pull.

 

[Rail Driver]

Today while discussing trigger jobs, the position of the sear and hammer hole was discussed. It was noted that my Springfield is a bit long as well as Rail Driver's.

What is your springfield's center dimension?
It's easy to measure a dial caliper will do. Measure the closest to points of the pin holes add half the .110 pin and half the .157 pin. The Nominal dimension between the holes is .434".
(measured dim) + .055 + .078 - .434 = ??

My 2010 Springer
.025" long
My 1990s Springer
.023" long
My 1980s Springer
.024" long
Rail Driver's Springer
.022" long

I'm suspecting that Springfield increased this dimension, not a sloppy machine.
The further apart the sear and hammer the more the sear nose dives into hammer hooks making a stiffer pull.

Just to add to this thread, my RIA is a bit long as well, but not nearly as much as the springer, at .013 long. The trigger on my RIA is bone stock, as is the trigger on my springer (not sure the year/model... it's a Micro Compact .45ACP The previous owner changed at least the sights and grip safety, but the internals are stock - if anyone can help on that I'd appreciate it), and the springfield is noticeably stiffer than the RIA. The RIA has been fired ~250 rds, and the round count on the springfield is around the same.

 

[1911Tuner]

I have a Thompson Auto Ordnance 1911A1 made in New York State prior to the Kahr take over that is dead on all Browning design specs.

You should play the lottery. Like the man said: "I'd rather be lucky than good."

More than a very minor variation in the location of those holes...called a +/- tolerance in engineerspeak...changes the geometry of the involved parts. The hammer hook and sear angles may "agree" perfectly in one pistol, and be all wrong on the next with a given hammer/sear set. This is why top pistolsmiths get big bucks for their trigger jobs.

Cutting the release angle cures that real quick.

No, it won't.

 

[1911Tuner]

. The Para Ordnance company recommended cure for a heavy pull was 5 or 6 strokes on a Arkansas wet stone to deepen the release angle of the sear.

And that works well assuming that the hammer hooks sit flat on the sear primary angle. If the angles "agree." If they don't, all bets are off. Angles that are in agreement are more critical when the hooks are short and square. Not so much when the hooks are ordnance spec length and undersquare.

The purpose of the breakaway angle is to reduce the surface contact area between the sear primary angle and the hooks, and to reduce or eliminate hammer lift...overcocking...as the sear rolls out of the hooks. Using one to lighten trigger pull can be a slippery slope, especially with .018-.020 square hooks.

 

[JohnBT]

"Glock seems to be the only one to really master that option! "

I didn't know Glock made drop-in parts for the 1911. Dang, when did they start that?

:banghead:

 

[1911Tuner]

The hammer hooks MUST be trued up perfectly square on a good milling machine before any "hammer to sear" fitting can be done. It is the baseline reference point to start out at.

'Zat right?

You do understand that those hammer hooks are undersquare for a reason, and that cutting them dead square and shortening them to .020 inch is essentially taking them out of spec. Right?

And when the hammer hooks are short and square, the sear primary angle had boy howdy better be in agreement or you're courting disaster.

And that stoning a heavy breakaway angle on the sear only brings that disaster closer.

And this is why I emphatically state that when somebody promises you a drop-in 2-pound trigger job...you might get lucky and you might not...but it's probably wise not to count on it.

Just in case it hasn't occurred to you yet...this ain't exactly my first trip to the circus. I've been at this 1911 thing since the mid 60s. I'd be afraid to estimate how many trigger jobs I've seen go sideways without warning over the years. Exciting stuff, but it does tend to frighten the spectators and enrage the ROs.

And finally...because any information posted here that is potentially or probably dangerous, I'd be derelict in my duties if I failed to include a disclaimer and a warning...the same as we'd do if somebody posted dangerous data on the reloading forum. The forum owners can be sued for such things without those actions.

So, I stand by my statements.

You may very well drop in a 2-pound trigger that functions like a dream...at least for a while...and you may also be setting yourself up for a nightmare.

If you really want a 2-pound trigger, you should probably contract a pistolsmith who specializes in such work. Be prepared to pay through the nose. People who can reliably do that sort of work reliably and safely are small in number. They're expensive and they have long waiting lists.

 

[Greg528iT]

Here are 3 pictures of the hammer sear interface






I've marked them up a bit.. But my point is to show that.. 1) hammer and sear too far apart will trap the sear into the hooks more.
2) that increasing the break away angle too much just buries the sear even more.

 

[Greg528iT]

those hammer hooks are undersquare for a reason

Do you realize the blueprint call for a square hook????

 

[Greg528iT]

One more picture

 

[Greg528iT]

AND by the way, this is ALL GOOD, but it's off track of getting some more Springfield data points.

Who has a Springfield 1911? Can you measure your sear and hammer pins? You don't even need to take your gun apart. If you have a standard single sided thumb safety, the pins are EXPOSED on the other side.

 

[Greg528iT]

Besides my milling machine can cut more that just 90 degree perpendicular angles

Did you custom order or make a slight bevelled cutter to make the undercut? And what angle do you undercut it by?

started hacking at it with a file.

WOW your hourly rate must be cheap
Actually I'd be impressed with a guy who'd hand file new sight dove tails. Even more impressed if they turned out right.

 

[CMC]

As far as the Hammer hooks height the Drawing tolerance for the hammer hooks goes from max of .033 to min of .030 per the drawing.
The height is expressed as the difference between .298 + .000 - .003 and .268 +.000 -.003.
I dont know what drawing you got the .023 from.
Also the angular tolerance I beleive is plus or minus .5 degrees.
I will check the drawing when I get home but I think the hammer is under squared as tuner said.

 

[1911Tuner]

Do you realize the blueprint call for a square hook????

Whose blueprint?

The ones I've seen call for 89 degrees.

increasing the chamfer further buries the sear

That depends on the geometry of the breakaway angle. If it's correctly done, the sear shouldn't move any further into the hammer.
It should only reduce the width of the primary. Its purpose is to reduce surface area and reduce or eliminate hammer lift.

CMC...Original print specs for the hammer hooks are .030 +/-.003 inch.
I've never encountered any that were at the high end, but several that were mid-spec to low end, running from .027-.030 inch.

Anyway...the disclaimer stands. Be very careful when playing with those engagement surfaces and angles. They're tiny enough even when left alone.

As the old saying goes:

"There are two kinds of people who tinker with a watch. A watchmaker and a fool."

Carry on!

 

[Greg528iT]

The ones I've seen call for 89 degrees.

OK true the only ones I've seen that are original are at best illegible at best.
Nice to know that they made them use a tapered mill or probably a file.

CMC. Yes. it is per drawing .030. But given given conversations here and a descriptions by 1911Tuner that, .023" is a conservative minimum hook height. Notice on the 1st drawing, I indicate .020 and .030 heights.

Rail... I too would NOT stand for anyone "hacking" on something of mine. I assumed, he was either ummm joking.. or at least extremely exagerating. GAWD I hope so.

Anyway...the disclaimer stands. Be very careful when playing with those engagement surfaces and angles. They're tiny enough even when left alone.

and as stated SO many times.. Hammer and Sear were NOT changed.
On my other post. I show an picture of the actual sear and how it is (short of small break angle) dimensionally correct

 

[brickeyee]

The hole tolerances are +0.002 and +0.0015, but I cannot read the 3 place tolerance for the hole locations measured from the slide stop hole center (X) or the thumb safety hole center (Y).

At the very least the hole centers are going to have tolerance stacking since X and Y are specified separately (modern drawings often use geometric dimensioning and tolerancing to reduce stacking and give hole location tolerances as a single allowed variation from ideal location).

Using a dial caliper to measure hole spacing is also going to introduce error.

Correctly chosen pins are used to match the actual hole size and then pin to pin spacing measured, followed my some arithmetic.

And yes, it matters when we are already down to only a few thousandths of allowable hole size tolerance.

 

[Greg528iT]

I suspect you mis-read the blueprints.
.458" spacing is correct.

I've looked at a couple different pdfs online. I did the trig 2 times.
The 2 drawing I saw said.
2.602" to sear.. 2.973" to the hammer on the X axis
.210" down to sear... .016" up to hammer on the Y axis
thats .371 and .226 for a .4344 hypotenuse
What drawings do you have?

 

[Greg528iT]

Using a dial caliper to measure hole spacing is also going to introduce error.

I agree, but for this exercise we should be close enough.

 

[Greg528iT]

ANYMORE? Springfield owners willing to measure this?

 

[CAWalter]

Faulty print reading. The nominal would be .458", .371"X .268", the .268 comes from the correct reading of the sear to hammer of .252"+.016"=.268". The .210 is the thumb safety hole.

CAW

 

[CAWalter]

Whose blueprint?

The ones I've seen call for 89 degrees.

Whose say 89 degrees? The prints available say 86 degrees.

What's important isn't really the floor to hook face angle, but the hook face relation to the pivot hole. The position desired by the original design puts the hook face if extended toward the pivot center above the hole perimeter by a good measure. If a 90 degree cutter where used the lower half of the hammer would be machined away. The hook face position was very aggressive and resulted in the desired pull weight of 8# minimum. Today's hammers are not nearly as aggressive as a more reasonable pull weight is desired. With the hook face plane between the pivot center and hole perimeter a 90 degree cutter works fine. The hook tips must be in a reasonable timing position relative to the hammer face so the slide can fully cock it.

There do not seem to be any prints available of today's hammers as the design is proprietary to the manufacture.

CAW

 

[CAWalter]

'Zat right?

And when the hammer hooks are short and square, the sear primary angle had boy howdy better be in agreement or you're courting disaster.

And that works well assuming that the hammer hooks sit flat on the sear primary angle.

No, a common misunderstanding. The sear primary should always be cut as per the drawing, the primary face must be 90 degrees to a line from the sear pivot hole to the sear tip. What this means is the area where the hammer hook tips land is higher than the escape edge. This allows for a non-stacking release, and a safe trigger. If the sear face is cut to match the hammer hook faces then the trigger will be safe, but the pull will stack up till break. Altering the hammer hook face angle so the hook plane is directly inline with the hammer pivot center will bring the hook face and sear face in contact, this will work in 3.5# plus pull weights, but is prone to follow at light pull weights.

CAW

 

[Greg528iT]

Whose say 89 degrees? The prints available say 86 degrees.

That's what I am looking for, just for information. All the "blue prints" that appear to be original are to low a resolution to be able to see.

My bible of the 1911 is on order.. being able to find this stuff reliably on the web is to tough.

My sear is per the drawings I can find. (untouched by me) the hammer is at 90 deg, but hooks are a tad short.

CAWalter.. do you have any Springfields to measure the holes on?

 

[CAWalter]

Just detailed an SA TRP full rail Operator, and did an outside plus inside divide by two and got .4575.

CAW

 

[Greg528iT]

THANK YOU CAWalter. That is now the 5th Springfield that measured near that.

My hypothosis that Springfield increased the dimension from the original is continuing.

AND yeah your way of measuring, dividing by two... way easier.

 

[CAWalter]

Increased? The prints when read as they are, show it should be .458", or to take it to the fourth place, .4576, seems to be pretty much as it should be.

CAW