00-90 tap and Metal car floors

[C855B]

I am having a really tough time getting tapped 00-90 holes in metal car floors (concor, roundhouse). ...

... You really, really, have to follow the lubricate / quarter turn / remove / clean   (lather, rinse, repeat) or you'll get the tap stuck for sure.

A-yup. Con-Cor floors absolutely vexed me in the late 1960s when the first Kadee couplers hit the market. I must have broken at least one tap on every car until it finally registered in my young-but-stubborn head that the lead alloy was too soft to simply run the threads through. The lube/ 1/4 turn /remove/clean became my mantra. Also, using a #60 or #59 as a tap drill (instead of the "spec" #62) seemed to help without having any strip-out issues. YMMV.

[Lemosteam]

This is ESPECIALLY true with a thread forming tap.

[woodone]

SLOW & STEADY. use a pin vise and don’t over tighten on the tap. Use cutting oil! Use very light pressure and only turn tap 1/8 turn at a time. Clean tap and tapped part often. SOME taps are not as good has others, get the best ones you can buy- I would stay away from thread forming taps- you are tapping into a casting of unknow quality- SLOW AND STEADY !
The reason I say don’t over tighten the tap- if the tap hangs up the tap will slip in the vise- this will take a bit of a fine touch.

[nkalanaga]

I buy the ones from Walthers, at the local hobby shop.  I also use a #63 bit, a little larger, and ordinary loco gear oil for lube.  Haven't broken one in years (watch me break it the next time!), and that one was on a cheap pot-metal casting, which probably had hard and soft spots in it.  In harder metals, with brass screws, a #62 bit will leave enough for threading.

I think MT's tap was originally intended for plastic car floors, back in the early days of N scale.  A thread-forming tap would work fine for that.   

[peteski]

I think MT's tap was originally intended for plastic car floors, back in the early days of N scale.  A thread-forming tap would work fine for that.

As I understand, even the earliers Kadee Micro Trains N scale cars used diecast underframes.  That way they didn't have to add steel weights - the underframe was heavy enough.

My solution for taps slipping in a pin vise was to grind the tap's end into square shape (just like on the larger taps).  I used a Dremel tool to do that.  Since most pin vises have 4-jaws, they grip the square shaped tap end very well.

The ones with ends ground square are the two in the middle. Then the tap on the bottom is a thread cutting tap, while the other three are thread forming.  I also cut the end of the third tap from the bottom to use it for blind holes.  And, as others have mentioned, I use one or two sizes larger drill bit in metal when I use the thread forming taps.



I keep my 00-90 hardware organized in a plastic box.

[freedj]

That is a nice collection of 00-90 hardware peteski!

I really reefed down on my pinvise last night, opened up the hole with one size larger drill, used sewing machine oil,  backed out as soon as I felt any resistance and successfully tapped another floor without a stuck tap! 

I was also considering picking up some 00-90 nuts and gluing them in boxcars so i could use clearance holes in the metal floors to simplify that part of the process.  It also seems like the through hole in the 1016 coupler boxes could accept threads or be drilled out, so maybe the easier solution is to drill a through hole in the floor and tap the coupler box.  Then I would just need the right length 00-90 screw.

Now on to my first world problem.  I don't want to cut off the coupler from the MT trucks and I don't have a supply of c55 compatible crap trucks to harvest.  Hopefully the "great train show" that is in town this weekend will have something that works for cheap!

[nkalanaga]

Peteski:  Yes, MT's cars always had metal floors.  But they were selling couplers, and taps, before they made N scale cars.  Other than Con-Cor and MRC, most cars had plastic floors.  And, as C855B said, the CC floors were a pain to tap.

In fact, for years I didn't bother.  I drilled the hole, jammed a piece of wood through it, and glued the coupler on with Seal-All, a contact cement and gas tank repair.  Not intended for model building, but it will work.  I even managed to truck-mount 1025s (MT-5 back then) on Con-Cor passenger cars, by cutting out the middle of the Rapido pocket, and gluing the MT box into the end of  the truck.  Ugly, but it worked, before they made, or I found, T-shank MTs.