I noticed on the previous thread that someone mentioned making the holes for the trunion in the receiver. What is your method for making the holes in the reciever ie. measuring, template, combination, etc. This may be helpful to new builders and keep them from screwing up a perfectly good receiver. Jack :lamo:
Best way to properly drill trunion holes
1 - 12 of 12 Posts
Joined
·
7,801 Posts
Talking about the holes on a Hesse/Vulcan receiver? Those are already drilled, but are not correct for most of the kits out there. I (carefully) egg-shaped the holes with the side of a drill bit to re-align them to the holes in the trunion. This was on a screw build so it wasn't as important as on a rivet build, but it won't be pretty if someone loosens the loctite & looks at the holes 
For the BIY receiver, I used the trunion itself as a guide, and measured w/ my digital caliper to get the correct location for the front-most hole. I used a centering punch to start the hole The front (& lower) holes use the 11/64" size, and for the center holes 5/32" size worked perfect.
Using this first hole as a guide, I measured side-side, used the centering punch, and a drill press to slowly drill the holes. I started with a small bit, like a #48 or something, and worked up in gradual steps. If I detected the holes were walking off-center I un-chucked the receiver from the clamp, put it in my vise & egg-shaped the hole to re-align it, using the drill bit literally as a round file... this worked surprisingly well for the job. De-burr and you should be ready.
hth,
- Jerry
For the BIY receiver, I used the trunion itself as a guide, and measured w/ my digital caliper to get the correct location for the front-most hole. I used a centering punch to start the hole The front (& lower) holes use the 11/64" size, and for the center holes 5/32" size worked perfect.
Using this first hole as a guide, I measured side-side, used the centering punch, and a drill press to slowly drill the holes. I started with a small bit, like a #48 or something, and worked up in gradual steps. If I detected the holes were walking off-center I un-chucked the receiver from the clamp, put it in my vise & egg-shaped the hole to re-align it, using the drill bit literally as a round file... this worked surprisingly well for the job. De-burr and you should be ready.
hth,
- Jerry
Joined
·
12,811 Posts
My Dad and I came up with a way to do this that might help.
This for users of drill presses only.
Clamp your trunion in vise or fixture that will allow you to slide the BIY receiver on and off on the trunion.
With the receiver off of the trunion line up your drill press to center on the trunion hole. Use a smaller bit, so you will have some play if you do screw up.
Slide the receiver back on the truion and bring the bit down on the sheet metal to make an indent. At this point you could drill and take a chance on the bit not walking on you. The smart thing to do is center punch on the mark that your drill bit made and then drill.
It sounds a little time consuming, but I think it will give you and very exact location everytime and you need to be careful how you clamp everything up for it to stay nice and steady.
Make sure to have some sort of jig to jold your receiver in the same place and inline with your trunion too!
I haven't built yet, but this is the way I am going to do my ACE build.
This for users of drill presses only.
Clamp your trunion in vise or fixture that will allow you to slide the BIY receiver on and off on the trunion.
With the receiver off of the trunion line up your drill press to center on the trunion hole. Use a smaller bit, so you will have some play if you do screw up.
Slide the receiver back on the truion and bring the bit down on the sheet metal to make an indent. At this point you could drill and take a chance on the bit not walking on you. The smart thing to do is center punch on the mark that your drill bit made and then drill.
It sounds a little time consuming, but I think it will give you and very exact location everytime and you need to be careful how you clamp everything up for it to stay nice and steady.
Make sure to have some sort of jig to jold your receiver in the same place and inline with your trunion too!
I haven't built yet, but this is the way I am going to do my ACE build.
hcpookie said:
Jerry, how bad are Vulcan receivers? I have always used Ohio Ordnance Works receivers and had to drill my own holes quite similar to the way I do my Ace bent mentals. Recently I purchased some Vulcans with some friends (still waiting on Joeken for delivery to our FFL).
7.62x54R, sounds like a neat idea, espically if you could make slight adjustments for different kit trunions. I like the idea of using a fabricated (sounds like Paulie Jr.) jig. You may want to go to the AR 15 threads here as the moderator has what looks like a drilling jig on his web site.
Thanks for the advise guys anyone else have any other ideas?
Jack
Joined
·
7,158 Posts
So far I have had good experience with hesse/vulcan receivers. THe hesse receiver I had was used with a brand new trunion from global trades, so where the holes were for the front trunions, lined up great (seeing I had to drill the trunion). The polish trunion (at least that is what I think it is, could potentially be a romanian), was put into a vulcan receiver today and lined up great. The AMD63 build that is also being worked on (I have to many incomplete projects), seems to line up with a vulcan receiver with no problems. Either I have gotten extra lucky with the vulcan/hesse receivers, or .... What kits have others had problems with getting to line up?
Joined
·
7,801 Posts
Agreed, these would be great builders if the holes are correct from the start.
I think most of the time the complaints were from all of the Bulgarian AK-74 kits that came in just over a year ago, and have since all but vanished. This was the case for mine, the Bulgy trunion didn't align.
Since K-Var sells mainly Bulgarian parts, it most likely made problems for a number of build-ups other than the '74 kits.
I think most of the time the complaints were from all of the Bulgarian AK-74 kits that came in just over a year ago, and have since all but vanished. This was the case for mine, the Bulgy trunion didn't align.
Since K-Var sells mainly Bulgarian parts, it most likely made problems for a number of build-ups other than the '74 kits.
Joined
·
7,801 Posts
I saw something interesting the other day... it was a C-Clamp that was filed to make a "center punch" and had a guide pin on the other part. It was used like a C-Clamp normally would be used, and the guide pin slid into the trunion holes from the inside, and the screw part drove down the "center punch" part that was sharpened to allow more precise hole placement. Kind of a jig in reverse idea, using the trunion as the jig.
Looked really low-tech, but I'm sure it would work.
Looked really low-tech, but I'm sure it would work.
Joined
·
7,801 Posts
Update - found the post!
http://www.akfiles.com/forums/showthread.php?t=1394
Let me see if I can upload a pic of this jig...
http://www.akfiles.com/forums/showthread.php?t=1394
Let me see if I can upload a pic of this jig...
Attachments
Joined
·
7,801 Posts
I like! Your "jig" looks very effective.
You could probably take one of those vise grips and just dremel the end to a point, couldn't you?
I'm thinking about getting a small C-Clamp and dremeling down the "foot" - the end of the worm screw - into a point, then drill or ream a hole into the "C" side, the cast side, to allow a transfer punch to go through the body of the C-Clamp and use this as a "mini-jig", not unlike those "super jigs" for the AR-15s. You'd need two - one for the 4mm and one for the 4.5mm, aka 5/32" & 11/64".
You know where I'm going with this - I'd like to see a super jig for the AK, but it would have to be 2 parts, one parts only for the trunion like I just described, and the other part using the trunion holes as the index for the rest of the holes.
You could probably take one of those vise grips and just dremel the end to a point, couldn't you?
I'm thinking about getting a small C-Clamp and dremeling down the "foot" - the end of the worm screw - into a point, then drill or ream a hole into the "C" side, the cast side, to allow a transfer punch to go through the body of the C-Clamp and use this as a "mini-jig", not unlike those "super jigs" for the AR-15s. You'd need two - one for the 4mm and one for the 4.5mm, aka 5/32" & 11/64".
You know where I'm going with this - I'd like to see a super jig for the AK, but it would have to be 2 parts, one parts only for the trunion like I just described, and the other part using the trunion holes as the index for the rest of the holes.
1 - 12 of 12 Posts
