Barrel Hood Fitting Jig

View previous topic View next topic Go down

Barrel Hood Fitting Jig

Post by Dr.Don on Fri Jan 29, 2016 3:30 pm

For me, one of trickiest parts of fitting a new barrel is fitting the hood width correctly.  The width must not only be correct, but the barrel must remain square in the frame at lockup.  I made the jig pictured below in 1989 to help with this process.  It is not original with me.  I built it after seeing one in a picture or diagram somewhere, but I no longer have any idea where I first saw it.


Briefly, the barrel is inserted into the jig and locked in place via two setscrews on the sides of the jig.  The rollers permit one to use a quality, fine cut pillar file to remove stock from both sides of the hood.  Because the line between the axes of the two roller spindles is offset from the barrel bore axis by the same amount that the hood slot is offset from the axis of the barrel bore in slide manufacture, the jig permits removal of the correct amount of material from both sides of the hood.  The roller must be the same diameter as the width of the slide slot.  I made 4 pairs of rollers with diameters varying by .0015-.002 to cover the range of slide slot width from .4365-.4400.  This has been sufficient to use with all of the .45 slides I have had to deal with so far.  The rollers are fully hardened to prevent damage from the filing operation.  The jig body is not hardened and has held up fairly well.  A hardened jig body would no doubt be good, but I did not have the facilities to harden something with that much mass.  In using the jig I typically shoot for a hood width that is about .001 fat, and then finish the fit by hand using a medium India stone.



Although this jig is not my idea/design, I do not recall ever seeing one other than the original that inspired me to build this one.  I am very curious as to whether Jon, Jerry, KC, or some of our other gunsmiths have ever seen or used a jig similar to this.  Based on the way it has worked for me, I’m a little surprised you can’t just order one from Brownells.





Dr.Don

Posts : 346
Join date : 2012-10-31
Location : Cedar Park, TX

Back to top Go down

Re: Barrel Hood Fitting Jig

Post by james r chapman on Fri Jan 29, 2016 4:43 pm

I hope my boss never sees my future projects list....

I'm putting it on it.

james r chapman

Posts : 1596
Join date : 2012-01-31
Age : 67
Location : HELL, Michigan

Back to top Go down

Re: Barrel Hood Fitting Jig

Post by fc60 on Fri Jan 29, 2016 9:38 pm

Greetings,

Would you kindly add a photo illustrating how the "rollers" mount to the jig body.

Cheers,

Dave

fc60

Posts : 91
Join date : 2011-06-11
Location : South Prairie, WA 98385

Back to top Go down

Re: Barrel Hood Fitting Jig

Post by Dr.Don on Sat Jan 30, 2016 12:09 am

fc60,

I don't have such a picture at the moment.  But each roller runs on a spindle made of .250 drill rod which is permanently soldered into the jig body.  The spindle is drilled and tapped for a screw in its end.  Spindle length is controlled to stand a few thousandths taller than the roller to allow some up/down play in the roller.  The roller is turned to size, drilled and reamed to a .250 bore so there is no radial slop on the spindle, cut to length, and hardened.  It is held on the spindle by a screw and washer.  When mounted the roller has a little up/down play on the spindle but no discernible radial play.

I'll see about adding a picture.

Dr.Don

Posts : 346
Join date : 2012-10-31
Location : Cedar Park, TX

Back to top Go down

Re: Barrel Hood Fitting Jig

Post by kc.crawford.7 on Sat Jan 30, 2016 8:26 am

I use the formula that Weigand has on his web site using this work sheet.  http://www.jackweigand.com/1911%20Barrel%20Hood%20Fitting%20Worksheet.html
Then I put the barrel in my mill and make the cuts.

kc.crawford.7

Posts : 280
Join date : 2012-12-09
Location : Maysville, NC

http://www.kcskustomcreations.com

Back to top Go down

Re: Barrel Hood Fitting Jig

Post by Jon Eulette on Sat Jan 30, 2016 12:04 pm

Ok now the wrench in the gears!
The slide lugs are machined off center in the slide ;p)
Very common on older Colts. Now the centerline of the hood isn't aligned with the slide lugs. 
Jon

Jon Eulette

Posts : 1154
Join date : 2013-04-15
Location : Southern Kalifornia

Back to top Go down

Re: Barrel Hood Fitting Jig

Post by Jerry Keefer on Sat Jan 30, 2016 12:41 pm

I have seen fixtures similar to Dr. Don's over the years, but it would be impossible for me to remember who or when they originated.
I too, like KC, use the Weigand formula of knowns and unknowns to compute the cuts. I also spend time truing and squaring up the hood  recess portion of the slide with guage blocks..   This is my rig.. It is an Accupro Truing Block. This allows me to do all the hood cutting and fitting in minutes instead of  hours..

The lower lugs are tapped into zero on the surface plate.

Both sides of the hood can be cut very accurately without removing or testing the fit..One of the joys of a surface grinder.

The barrel is set up on a guage block and the end of the hood is cut. The guage blocks allow barrel removal and return to zero to get that exact Jo Block fit.. The hood length does not require the barrel lugs to be on zero axis..


Last edited by Jerry Keefer on Sat Jan 30, 2016 12:45 pm; edited 1 time in total (Reason for editing : spelling)

Jerry Keefer

Posts : 999
Join date : 2012-01-02
Location : Maidens, VA

Back to top Go down

Re: Barrel Hood Fitting Jig

Post by Ghillieman on Sat Jan 30, 2016 12:52 pm

This is great stuff!

Ghillieman

Posts : 260
Join date : 2012-02-15
Location : TEXAS

Back to top Go down

Re: Barrel Hood Fitting Jig

Post by james r chapman on Sat Jan 30, 2016 1:59 pm

Jon makes a good point. The sides are not equidistant from bore centerline. The fixture would work if you switched bushings for each side.

james r chapman

Posts : 1596
Join date : 2012-01-31
Age : 67
Location : HELL, Michigan

Back to top Go down

Re: Barrel Hood Fitting Jig

Post by jglenn21 on Sat Jan 30, 2016 2:07 pm

Think the roller pins are offset from the bore centerline

jglenn21

Posts : 549
Join date : 2015-04-07
Age : 68
Location : monroe , ga

Back to top Go down

Re: Barrel Hood Fitting Jig

Post by jglenn21 on Sat Jan 30, 2016 2:11 pm

I too use the Weigand formula as I have a mill. He has a great u tube video on the process

jglenn21

Posts : 549
Join date : 2015-04-07
Age : 68
Location : monroe , ga

Back to top Go down

Re: Barrel Hood Fitting Jig

Post by Dr.Don on Sat Jan 30, 2016 5:11 pm

Jon,

Yes the hood is not centered on the bore axis.  But the roller spindles are offset from the bore axis by the same amount.  So you can indeed cut both sides of the hood by just flipping the file over to the other side.  Of course you have to have the correct OD rollers in place.

As for the slide lugs being off-center, I don't know how you would correct for that without altering the hood cutout in the slide. Am I missing something?

Dr.Don

Posts : 346
Join date : 2012-10-31
Location : Cedar Park, TX

Back to top Go down

Re: Barrel Hood Fitting Jig

Post by Jon Eulette on Sat Jan 30, 2016 5:47 pm

No you didn't miss anything, I just couldn't resist stating that if the slide lugs are off center because they were miscut that you're perfectly centered hood isn't going to be perfectly centered for those lugs. So when you start fitting the upper lugs it will push the barrel off center. On a typical new Caspian slide you won't have this problem, but on an old Colt slides in the last year I have fit three barrels and the slide lugs were crooked. I knew this up front so I had to compensate with the barrel hood and the upper lugs to reach a happy medium. if you go purely by the Weigand method it doesn't accommodate for that. So that's where old fashioned gunsmithing comes into play, because even though the upper lugs are oversized for example on a Kart barrel there isn't always enough meat to remove from one side to accommodate for the off center slide lug. I've worked on slides that pushed barrel off center enough that the slide wouldn't go on frame because the barrel lugs couldn't pass into the frame slot. Unfortunately many shooters cannot afford a new Caspian built pistol, so their old Colt becomes their match pistol. That's reality. And for the record Jerry Keefer is my hero! I can only dream of having his knowledge and his machine shop.
Jon

Jon Eulette

Posts : 1154
Join date : 2013-04-15
Location : Southern Kalifornia

Back to top Go down

Re: Barrel Hood Fitting Jig

Post by Dr.Don on Sat Jan 30, 2016 6:46 pm

Jon,

Thanks for elaborating on this.  I had thought about it after your comment.  My tentative conclusion was that the Weigand formula was not going to address that problem either, and that old fashioned hand fitting with spotting blue and files might be the only way to get there.

And yeah, Jerry's setup and knowledge are really something!

Dr.Don

Posts : 346
Join date : 2012-10-31
Location : Cedar Park, TX

Back to top Go down

Re: Barrel Hood Fitting Jig

Post by Sponsored content Today at 10:20 pm


Sponsored content


Back to top Go down

View previous topic View next topic Back to top


 
Permissions in this forum:
You cannot reply to topics in this forum