Does anyone have a source for a jig for locating the holes for grab irons in HO? I am working on a used loco that the prior owner had added wire grabs to, just not very well! They were about .020" wire, and no two of them were in line with the one above or below it, and most weren’t even level. Needless to say, I removed the grabs, filled the holes, and sanded everything smooth, but now there isn’t any kind of a guide to keep my new holes straight and even. I have laid the holes out and carefully drilled them on other projects, but I wasn’t able to keep everything as straight as I wanted, so I thought I would make a jig. I drew out what I wanted to keep everything straight and evenly spaced and took my plans and some drill bits into work for the guy in the toolroom to make for me. I figured it would be easy since the mills back there all have digital readouts and he could keep everything in nice, straight lines. Well, he didn’t. Quite frankly, this jig looks worse than the last one I made, and it was pretty sad! The jig was to have 2 sizes of holes at each location, 1 set for the grab, and another .020" lower for the NBW casting that may or may not be there. The holes should have been in line and perpendicular. The finished product was anything but. Some of the holes would be off by probably .020" or more in 2 directions! When the guy was telling me about it, he said he would be lined up just fine, start drilling a hole, then the drill would walk out of position as he was drilling it. I have never seen a #79 drill bit walk .020" without breaking, let alone drilling the hole.
I don’t know that I buy all of that, but if that’s so, why couldn’t the holes be laser cut? We don’t have that level of technology at work, so I don’t know if a laser could do this. Can they “drill” a #79 and a #77 hole in 1/16" thick steel for a jig? Are there any other suggestions? If anybody knows a source for a jig like this,
I’ve done work like you’re writing about. First, I would most likely make this item from aluminum rather than steel–much easier, and I doubt whether aluminum’s softness would be a problem for your task. Next: When doing precision drilling, one uses an item called a center drill to “spot” the hole. It doesn’t bend sideways as it’s much too rigid. This is a usually a starter hole, though, because it doesn’t do “deep” drilling. Also, center drills don’t come in the wide variety of wire (numbered) drills. Now, it’s possible your machinist didn’t know that center drills are made small enough for #79 bits. Many catalogs only list them down to 00 size, but they are made at least down to 5/0. I believe the 5/0 is smaller than a #79 bit. If it’s not, you can still use it by just “kissing” the work; but it’s a little tricky. Also making it worse for the guy is that you wanted holes drilled close together (I think); this can be a bit of a pain, but it’s usually doable. I would think it would actually turn out better for you if instead of drilling holes for the NBW castings, you cut off the shank and just surface glued the piece next to the wire of the grabiron. The above comments are based on the assumption that you had a REAL machinist who knew he had to use a milling machine (or at least a milling table) instead of a drill press. I should also note that many REAL machinists don’t know that there are miniature tools they can use because they just don’t get anywhere near that tiny in their work. Also, if the guy was using a full size machine, it can be a bit brutish toward such a teeny bit of tooling. He may deserve more sympathy than you think.
OK, I’m gonna suggest something really low tech using really high technology…use a cad/paint program to draw the jig as you want it, then print it on a thin sheet of paper, tape that to the locomotive, and then at each point indent with a fine steel needle, and use that to locate your drill bits.
Else-wise, why can’t you create just one jig (4 holes should be a lot easier than 20 or more) out of whatever material, and slide it along the side walkway of the loco, or the roof, or whatever, using a perpedicular locating tab, aligning it to the right spot via blue painter’s masking tape with the location of the grab iron drawn on it. (meaning post the tape with the mark - marks offset by edge to hole distance - move the jig along the side to this mark, make sure all is straight (clamp if need be), drill holes, and move on to next location).
Thanks for all of the replies, particularly the Walther’s link. I had already searched the 2007 catalog, but either this was a new product, or I just plain missed it. It does look pretty close to what I am after. I don’t check their website very often.
The guy who made the jig for me does know what he is doing, having been a machinist for 9 years before I went to this job, I know the difference between good machinists and bad ones. He’s good, but he readily admitted he doesn’t work in this small stuff. I even had to bring in a chuck to hold these little bits because we don’t use them at work. I didn’t watch him make this jig, as I am in maintenance and have to be out screwing around looking like I’m working, but I was under the impression that he was using one of the Bridgeports we have in the toolroom. Looking closer at the jig, I found some lines that could be scribe marks, so he could have tried to do this on the drill press.
For whatever reason, I can’t seem to get my holes to look right using cheaper, easier, manual methods. I have tried making my own simple jig from .020" and .040" brass, drawings taped and transferred, pencil lines, everything I could think of. But every stinking time I end up with holes that aren’t right. Maybe I’m just being too anal, (wouldn’t be the first time) but if I can get a jig that has everything lined up right, then maybe I can get the results I want. My only thought with using a laser to make the holes is that it would be REALLY difficult for that “drill” to walk off position! I feel like this would also perhaps save buying so many drill bits, maybe if there was a thicker jig, it would help keep me from flexing the bit by changing the angle while drilling. I don’t know, but I do know that I need to do something! What I’m doing now doesn’t make me happy with the results.
I build my jigs out of 1/16 styrene.
Draw gridlines for the exact locations.
“centerpunch” for the holes using a sharp pin.
Follow the pin mark with a real centerpunch. Adjust as necessary.
Drill pilot hole as small as possible after any final adjustment.
Microscopic adjustments can be made as you graduate the hole size.
securely fasten jig to the model and use it to “dimple” the location on the traincar with small drill.
remove jig and finish drilling small holes.
graduate the size of the holes until you get to the proper size.
install grabs with a press fit.
I work with strong light and use magnifiers.
The extra effort to get that jig right is both necessary and worth it.
I will soon be filing off a lot of cast on plastic grab irons from MDC old time box cars and need to make a reliable jig. Up until now I used a jig made from a piece of card stock. Recently, I came across an old MR article on the subject that I am going to try. The jig was made from a piece of brass bent at a 90 degree angle so that it fit against the corner of the box car. The side that butted to the end of the car was drilled and tapped near the top and bottom of the jig to accommodate two adjustment screws. These end screws could then be adjusted in or out to clear rivets and other details cast on the car ends so that the jig could held steady and level against the car ends and accurate holes could be drilled in the side of the car. (Using most of the techniques previously mentioned.)
Saw an article in an old MR mag on this subject. They used brass ladder stock & drilled at the junction of the hand rails & the rungs. I think they drilled one side then slid the ladderstock over & located the edge by putting drill bits in the previously drilled holes against the side of the ladderstock…or something like that. Jerry