fitting bottom lugs w/a boring bar?

[bigsaxdog]

anybody ever do this? just got a bridgeport, and whilst picking the brain of a non-shooting machinist buddy, this came up. was trying to describe to him fitting the bottom lugs, without a gun to demonstrate. he mentioned a boring bar, and i've seen some real small ones in the MSC catalog, and i got wondering. if you could set up right, this sounds interesting. i hate that brownell's gizmo, breaks easy, and generally cuts like sh#t, so..... anybody?

[wide45]

Pretty hard to break a chain saw file. Cheap to replace if you do.

[bigsaxdog]

yeah, and you could probably lap it in with a handful of dirt and some used motor oil, but that really wasn't the point.......

[Matt Cheely]

What about using a .200" end mill? Why go all the way to the boring bar?

[BrianH]

What about using a .200" end mill? Why go all the way to the boring bar?

Or a 5mm and fit the rest by hand.

[HSMITH]

It would take a week with a boring bar. You end up removing something between 10 and 25 thou, and over a length of 200 thou. Each bore pass with a two tenth step over would have you doing something like 1000 passes. Plus, it is an interrupted cut, and you would never have more than 90* of contact. Boring bar isn't going to work.

I have pin gauged them and then milled the lugs, it works but is a LOT more work than just using the lug cutter from Brownells. Sometimes low tech is good tech.

Then only other way I would like to try it is with a shaped wheel on a surface grinder that would allow me to cut EVERYTHING that needs cutting on the lower lugs in one set up. Pin gauge it, determine how much needs to come off, set it up on the grinder and do it.

[bigsaxdog]

thanx for the ideas, y'all....... i just got this mill, and gotta try some stuff, you dig? i bet everybody's gone thru the mad scientist stage, somewhat. it's how you learn, and my grandpa used to always say "that's why they put erasers on pencils." thought originally of the end mill thing, just don't know if it would be rigid enough for a plunge cut like that. i guess if you could do the brownell's cutter thing w/an endmill with everything chucked and jigged up on the mill, that's interesting...... the boring head seemed interesting, but it's gotta be an awful small set-up, i realize. probably pretty hard to center too, so..... the brownell's cutter is basically the best idea, but....the locating button on the off side of mine sucks, it ain't square, won't cut square, and i had to turn down the knurled part to clear the slide on the last one i did. i'm also thinking of some kind of jig that you could locate the frame, and then have a hole for the cutter to go in on the off side, and drive the cutter w/ the mill. that cutter is also really delicate, i'm on my 3rd now, so i'm just looking for a better way. saw some reamers at MSC that looked kinda interesting..... it was just interesting talking to my non-shooter machinist friend about how we build these, good to get a different perspective. thanx for the help..........

Edited June 3, 2008 by bigsaxdog

[Aircooled6racer]

Hello: You could use a 3/16" carbide 4 flute end mill to cut the lugs. You will have to set the barrel up in the vise to cut the lugs square. Thanks, Eric

[Toolguy]

You could make a v-block fixture for the chamber area of the barrel to nest in with a dowel pin to locate the link pin hole.Then set up the fixture on a small rotary table with the link pin centered on the rotab and a finger clamp to hold the barrel in place during machining. That way you could cut some, take the barrel off

and check it, put it back on and cut some more. It would be a simple repeatable setup. Maybe your machinist friend could help you make the fixture.

[HSMITH]

For better results the barrel needs to be IN the slide and fully locked up, for best results the slide assembly needs to be on the frame. Cut it to fit where it is going to live. Otherwise it is all but impossible to get even load bearing on both lower lugs and maintain dead solid fit.

[jjanglin]

I agree with Howard, I really like to use Weigand barrel fitting fixture and do the fine fitting

using the frame and slide, Its very important to get the top lugs to fit in the slide solid

if you can push the barrel back and forth while holding the barrel up in the lugs you need to

use a black marker and get the barrel in place before fiddleing with the bottom lugs, I also

use a sized brass of the proper caliber and make sure the fireing pin hole is lined up then

fit the bottom lugs take your time and if ya get stumped call someone in the know.

Jim/Pa

Sailors

[Toolguy]

The BEST way is to do it with the gun assembled, as mentioned above. Bigsaxdog had tried that and was looking for alternatives.

Congrats on getting a Bridgeport! You will enjoy it for many years to come.

[HSMITH]

I was just trying to save some of the fiddling I have done that worked, more or less.......

I am all for doing things differently, I do quite a few things differently than what is common, but I have also wasted a lot of time and spent some money on things that just didn't pan out. Some of them though just came out as a better way, so don't be afraid to try something new!

[Flexmoney]

Anybody else seeing problems with their cutters?

[HSMITH]

I just filed a flat on the bushing so it would clear the slide, and I have used a couple cutters up. The little crank tool for turning the cutter sucks, I don't use it but that is about all I will say about that. The .195" cutter is about 3.5 thou too small. All in all I think it is a really mediocre get up at best, but it is the best at this time....

[bigsaxdog]

the above is really my point......the brownell's thing works, but i'm just wondering if there's a way to improve it. it's just a very delicate piece, real easy to break off the teeth, plus that locating button thing is junk! the last one cut the lugs pretty crooked, actually changed the POI adjusting them, so....... just looked as mine yesterday after i started this thread, and if you could make some kinda jig where the cutter could be in the mill collet, and the end of the cutter located in a hole in a base plate/jig, with the frame locked up in between, then do the slide like you do in a vise, that sounds interesting. i'm pretty new to the machining thing, and i don't know the possibilities of all the cutters available. there's alot of precision reamers in sizes that would work. i also got a tool-post grinder cheap from a guy going out of business. dreaming of making one with a ground nose that would fit in a jig hole. don't know if one of those straight flute jobs would cut like a brownell's cutter, though. that's the good thing about the brownell's gizmo, it does cut, just way to delicate/$$$. what's the weigand jig about?.......thanx for all the input, i always wanted to start this thread. everything else about building these guns is pretty basic in the set-up, it just always seemed to me that cutting the bottom lugs is the big voodoo......

[z40acp]

It would be nice if Brownells offered a .197" or .198" cutter. By the time you polish the ramp with a .195" you still have .002" to .003" left unless you are using one of the cheaper slide locks that are only .196".

[Carlos]

There are certainly better machinists & gunsmiths posting here (like Brian H.) but I will simply add:

bigsaxdog: you are right to try to improve on what we have currently.

-focus on fitting with the barrel and slide in place.

-problem with endmills and boring bars is they risk enlarging the hole in the frame (which the Wilson tool avoids doing).

-a higher precision version of the Wilson tool would be a good start, for example, one that takes radial forces out of the equation by ditching the little crank handle and perhaps indexing the set up in the mill and driving through the mill head

-see if you can locate a maker of very small "shell mills" that use a solid center shank, with the mill "shell" attached to the outside.

[L9X25]

-a higher precision version of the Wilson tool would be a good start, for example, one that takes radial forces out of the equation by ditching the little crank handle and perhaps indexing the set up in the mill and driving through the mill head

I am lazy and use a low speed cordless drill to spin the cutter.

That speeds the process and removes the forces you describe.

[bigsaxdog]

thanx for all the ideas! definitely more than one way to skin a cat.......started looking at the MSC catalog, some interesting stuff. the shell mill thing looks pretty good, of course they don't have any around -.200. there's also some piloted counter-bores that might have some possibilities, but again not the size. maybe get somebody to re-grind to the .199 size, gotta look into that. leo, hunter said he had some guy re-grind/sharpen his end-mills, maybe try to talk to him. the thing that gets me is why brownell's had M A Ford grind that cutter w/the .131 pin size on the end, have to use the button thing. why not .200 on each side, would center better, clamp something to block the off-side. whatever.....i'm on the trail, keep y'all posted, thanx again......

[ExtremeShot]

thanx for the ideas, y'all....... i just got this mill, and gotta try some stuff, you dig? i bet everybody's gone thru the mad scientist stage, somewhat. it's how you learn, and my grandpa used to always say "that's why they put erasers on pencils." thought originally of the end mill thing, just don't know if it would be rigid enough for a plunge cut like that. i guess if you could do the brownell's cutter thing w/an endmill with everything chucked and jigged up on the mill, that's interesting...... the boring head seemed interesting, but it's gotta be an awful small set-up, i realize. probably pretty hard to center too, so..... the brownell's cutter is basically the best idea, but....the locating button on the off side of mine sucks, it ain't square, won't cut square, and i had to turn down the knurled part to clear the slide on the last one i did. i'm also thinking of some kind of jig that you could locate the frame, and then have a hole for the cutter to go in on the off side, and drive the cutter w/ the mill. that cutter is also really delicate, i'm on my 3rd now, so i'm just looking for a better way. saw some reamers at MSC that looked kinda interesting..... it was just interesting talking to my non-shooter machinist friend about how we build these, good to get a different perspective. thanx for the help..........

If the locating button isn't square and you needed to turn it down to fit, maybe you have it on the wrong side?? As I recall, I originally had the same problems until I figured out the cutter needed to be on the left side of the gun with the locator button on the right side.

Darren