has anyone come up with another way to secure a Kadee coupler to the pilot?

The pre-drilled holes are for the 2 outer side holes. There are still 2 other holes down the middle in each Kadee that you can use. Just drill a new hole in the pilot using those holes. That should work.

Hi Jeff,

There's only two areas, just below the pilot coupler port(opening), one at each corner; I'm confused about what you're proposing? Besides the two cast iron cylinders containing the threaded coupler holes, on each corner, there's no metal that I can see; there's a 5/16th drop(with no metal in that area) to the pilot base containing the pilot mounting holes(the holes that are used to secure the pilot to the locomotive chassis).

Rick

I see what you are saying- I was thinking you were drilling out a pilot, but you're right the pilots do have those 2 cylinders. Sorry about that-- not sure how to approach that one..

Rick,

If you have some small-tipped tools, like dental tools filed off to a point, it is sometimes possible to insert them in between the cutting "teeth" of the tap (holding the tools almost like chopsticks) and by wiggling them around you may be able to back the broken off piece out.  Even a pair of sharp-pointed tweezers might do it.  Be sure to squirt some oil into the hole, it may help loosen it up.

If nothing else, can you add a metal shim to the surface (super glue?) and tap holes in the shim?

I assume that you are referring to a steam locomotive here, and the front pilot coupler is the part in question? 

Regardless, you can try something. 

Taps are fluted.  Get yourself a VERY fine tool to use as a punch, and then a light tack hammer.  With the work secured well so it doesn't move (take the pilot off if a steal loco, clamp it in a vice with a cloth GENTLY so that you don't break or scratch anything), and slowly tap around counter-clockwise until you get enough out to grab on to.  You will tap counter-clockwise.

You are correct, taps are too hard to drill.  The way a lot of production shops handle broken taps (these are far bigger than we deal with) is to EDM out the center of the tap with an EDM tool well undersize of the hole, but big enough to burn out the solid part of the tap and then the tap portion between the flutes stays behind and can be removed.  If it is important to get the tap out, you should be able to find a tool and die shop that can get it out for you. 

If this is a diesel locomotive, Jeff is correct, you have three holes on a Kadee coupler pocket.  Keep one of the outside holes, drill and tap a new hole for the center hole, leave the broken tap in place. 

Regards,

Jerry

Hi guys,

Jerry, it's a MTH scale wheels GP35.

I think the tap is really lodged in there; that probably why it broke off... as I was trying to back it out.

Bob, would you care to elaborate a little more about your metal shim suggestion?

The die-cast cylinders could be ground off and a metal, or even ABS, filler piece could be glued in place; then two holes could be drilled... What kind of glue would you use, to cement an alloy(steel, iron, aluminum...) filler piece, to the die-cast pilot; would a different glue be required, if the filler piece was ABS?

Rick

The MTH diesels are pre-tapped with metric sized screws.  There are usually screws in the bag with the snow plough.  If the metric screws did not come with the unit, I suggest contacting MTH and let them know.  

As far as the broken tap, where you trying to tap for 2-56 screw? If the tap broke flat you may be able to remove the whole pilot and use a fine dremel wheel to cut a slot into the tap bit and use a flat head screw driver to back it out. 

Mike,

Yes, the screws came with the locomotive, in a small clear bag.

My dealer's closed on Mondays; I think he told me, the other day, that the screws are 2-56; the tap he sent me a while back should be a match.

I found the handheld pin vise, that holds the bits... including the tap, to be quite ineffective. The tap frequently just rotated, inside the vises collar. I never used a lubricating agent, because I thought I was just refreshing the original threading.

Good suggestion re: creating a slot; but, I think the tap is locked in too tight. Probably, just bend the small screwdrivers blade.

I think creating a flat surface(by completely removing the screw hole cylinders) and attaching a 5/16th deep filler, that's wide enough to comfortably house the two screw holes, should work...

There must be glues able to adequately secure the filler piece.

Rick

Rick,

I didn't know if a shim was needed to get the height of the coupler correct or not.

I found out the hard way that lubricant is ALWAYS a good idea, even on plastic, when tapping holes.  It helps clean the debris out of the hole as well as help in cutting the threads.  I've had to torque down the collar with a pair of pliers to keep the tap from turning.

Hey, don't feel bad about breaking a #2 tap, the machine shop I worked in back in the early 70s had a machinist that busted a 6" drill bit once   It sounded like a cannon going off.  Feed and speed is the key!

You might consider taking the engine to a professional machinist and ask him/her to remove the tap.

Just a thought.

Ed

Thanks for sharing your knowledge and opinions, guys. I've learned some things from your input.

Ed, this might sound like a dumb question, but, what do you look under(heading) when you're trying to find an appropriate professional...?

Rick

Something else to try

Since you still have one good mounting post, I would clean the threads on that, then cut off the post with the broken tap, leaving as much of the post as possible. Then build that area back up with a two part metal epoxy putty, I think JB Weld makes some, or go to a store that supplies machinist. make it much bigger than the original. Then drill a new hole and tap it using the one good post as a guide

Clem 

Clem,

I was mulling over something like you suggested, earlier today.

I just got off the phone with my friends dad, he's a retired machinist... I'll be bringing the damaged piece(pilot...) over to his house, tomorrow. He's offered to have a look...

I'll let you guys know how it turns out.

Thanks a lot lads for all your help...

Rick

The last time I broke a tap (2-56) while threading a hole I sought the advise of the tap manufacturer, and here is what they told me: Use some fine music wire that will fit into the flutes of the tap, and lubricate the hole with something like WD-40. Try to back the tap out gently by using all the music wire in a bundle. It took about 10 minutes of fiddling and rocking gently, but it worked for me.

Thank you, John.

My friend's dad should have a few tricks up his sleeve, too.

Re: the piano wire method, I'd be surprised if I could work anything into that jammed hole.

Rick

I just spoke to my dealer; he advised me to hold off on doing anything... He will be sending me a new pilot, with a coupler installed.

Rick

 I broke a tap off in a Lionel steel car bottom from a CF hopper if I remember right. It was stuck in there good and wouldn't come out. You can't drill them out as it's tougher than the item your tapping. They can be cracked out in small piece if you could beat on them. Tough with a model.

 I always use more care now and oil the tap and massage it in gently. I don't re-tap the MTH pilots unless just chasing the threads. I've had a few that are not threaded well and resist the M2 screws. I usually buy new metric ones if they aren't in the box.

 You are lucky to get a pilot replaced. Not many have gotten them.

I thought I was refreshing(chasing) the manufacturers threading... I've never tapped before; maybe, I tried tapping in 1969(grade 9 metalwork) I can't remember.

I knew enough to go slow, and back out often, to clear the cuttings...

Even if there's a properly sized hole drilled, there must be some amount of resistance during the cutting process. You never know, it might have been a substandard tap bit?

BTW, I personally think MTH should increase the surface area that house the two coupler screws. Get rid of those cylindrical thread housings and go with a broader, solid surface.

Rick

 Yeap! I was trying to cast pilots and those little cylinders kept getting holes in them from trapped air. I redesigned the mold to make them bigger. I figured plastic would crack easier anyways.

 Were you using a metric 2m tap??? Did it bottom out? was it a cheap one? Did you use oil?

 I ordered several taps to try and two broke right away. I have another that has lasted me for years now. I just wish I would have kept track of which one was which!!

Rick B,  

I've got a couple dozen scale wheel MTH diesels to know the pilot screws are certainly not 2-56.  Not sure what your dealer was thinking.  

I would remove the diecast pilot from the model.  Put some good release lubricant like rust penetrator around the stuck bit, hammer the tap with pin punch to loosen the tap bit,  the reason here is to free the harder tap around the softer diecast hole its stuck it then dremelt a slot on the tap then get a very strong jewelers carbon steel flat screw bit and remove it.  

First, if you got your tap from a hobby store, for, say, four bucks, it was bound to break.  Buy good Greenfield taps.  Two- flute.  Use cutting oil.  Two different cans - green for aluminum, and yellow for most other metals.

Rarely does a broken tap rotate out, but sometimes you can get them.  If you are dealing with a thin piece of metal with a hole drilled through, sometimes you can hammer the tap straight out.  The flutes will broach the hole, but there will be enough metal left to save the hole.

Glad your problem is solved, but next time remember - nothing imported has US threads.  they are all metric sizes.  And Kadee boxes have four holes, only two of which are needed to hold the coupler.

I make brass boxes for MTH Kadee installations.  Only one screw is needed then, because the brass holds the Kadee box.  It also fills the giant hole in the pilot with metal, and makes it look slightly more realistic.

Again, never use hobby store drills or taps.  They are not hardened, they do not cut cleanly, and they will break quickly.

Hi Guys,

I just checked in, here.

All  I know is my dealer picked the tools, because he felt they would be useful...

He's a longtime 2-rail guy.

2-56 is his opinion, re: screw size.

Mike, the tap is buried in there, good; there's nothing sticking out to grab hold of... it's flush with the surface.

I still think - getting rid of the screw towers and expanding the surface area makes sense. Those screw towers are weak looking; I don't know why that design was chosen. Something more substantial, would have been a better choice.

I mentioned to my dealer, about removing the screw towers and expanding the surface area, where the screws mount; and, maybe going with a longer coupler box, so there wouldn't be any hassles drilling in the new mounting holes.

My dealer said, the GP35 was designed for a short box coupler...

I was only going to try to fix the coupler holes problem, because were "men" and being "men" - we should be able to handle something like that.

I'm  a creative guy; and, it was sort of a challenge... There's no need for the weak, fussy way it is now; I'm not impressed with those fragile looking screw towers. I think I could do better.

Rick

Was it the rear coupler? If so, that's correct, but the front pilot can carry a standard 805/740.

Matt, it is the rear pilot. I remember you mentioning the short rear... earlier.

Rick

The MTH standard is metric I haven't come across an imported MTH model using anything other than metric.  For 2 rail modeling, my standard is to use meaty 2-56 screws like your dealer but I have a very strong high carbon drill bit and tap I purchased from microfasteners.com.  Two of the newer PS3.0 dash-8's didn't come with screws in the pilot bag–yea what the heck–so I drilled out the existing hole and tapped it for 2-56 without issue.

You don't have to do any drilling.  Just buy a tap extractor for the size tap.  It's really quite simple to do.  Google "tap extractor"  to see how.

A lot of nice guys donating... on this thread; thanks!

Mike P.,

You and I both know, we shouldn't have to be doing... they should work properly, like our money does.

I'm curious if any of you have ever broken/or fractured the the screw towers, during a hard coupling?

This is a pretty cool thread; informative.

Wild,

I haven't had time yet, to check out your suggestion, re: the tap extractors... I will, though.

Rick

Yeah, me too.  Wouldn't it be wonderful if they make 2-56 and 0-80 tap extractors that just go in there and extract?  Yippee!  While we are at it, maybe some broken drill bit extractors too.

Mike P and I agree on this.  I have had zero problems with MTH scale couplers.  The plastic stalagtites that the floorboards screw into will strip and crack.  A casing of brass tube and some JB Weld cures that in a big hurry.

WM, thanks for the tip.  Did not know about those.

Regards,

Jerry

Bob2,

Not a believer eh?

BTW, what causes the stalagtites to strip and crack... repeated screwing...?

Rick