13" Single Tumbler Gear Box Taper Pin Size

Hoping someone can confirm what I have tried to ascertain.

I have a 13" with the single tumbler quick change gearbox. I am in the process of refurbishing the lathe.

I struggled to get the gearbox disassembled. On the code shaft, there is a taper pin that holds a nut on one side of the shaft. I tried for 3 days to get that pin out. I resorted to drilling it out. I was fortunate enough that my drill ran nearly perfectly down the center of the pin. I was able to use a screw extractor get it free.

Unfortunately, it also broke in half and is a little buggered up.

Can anyone, with certainty (I can guess, too) if the size of that pin matches this:

McMaster-Carr

1.25" in length, 0.156 large end, 0.13 small end, rate of taper 1/4" per 12"

It's what I was able to measure with my calipers. But the ends were filed flush before I was able to get it out.

And would I want stainless or carbon steel?

Thanks in advance.

I've not been through my gearbox, but - all taper pins taper 1/4 per foot. Here's a hint, buy really long ones, fit them in the hole, and cut off what isn't needed. I usually tap them in, mark, then pull them back out and cut them. This keeps me from having to keep lots of sizes on hand.
This way you can measure "close enough" to know that the big end is bigger than your hole, and the pin will be long enough to go all the way through.
Carbon steel will be fine, that's what you drilled out.
You can use drill bits to gauge the size of the hole. The pin you give dimensions for is real close to 5/32" on the big end.

I learned something about taper pins. OK. That makes so much sense.

I hate that McMaster makes me buy 25 pins when I only need one. This one is 3" long.

The struggle bus has been taking me for a ride this last week or so. I've got another taper pin that I am likely going to have to extract the hard way.

I'm disassembling the apron, and the last thing I need to do is take out the taper pin that holds the rack pinion gear on its corresponding shaft. I've been trying to soak it in penetrating oil and even use a fair amount of heat, but it won't budge. I'm smacking it with a brass punch as to not deform the pin, but I'm lost on what else to try. The screw extractor did the trick on the little one, maybe it will work here, too.

The parts diagram at Vintage Machinery says it's part number 168x514, which according to the commercially available hardware list, it's supposed to be a #4, 1-3/4". That length seems right, but when I look at McMaster for a #4 in that length, it says it's 0.25 on the big end and 0.214 on the small end.

I snuck my calipers in there as best I could, and I am getting around 0.273 and 0.264, which doesn't compute to 1/4" per foot, so I don't know what to think. Now, these might not be Starrett calipers, but there is no way they are that far off. I tried getting a small steel rule into that space, but there's not enough room. I am wondering if the original taper pin had been replaced. This #5 seems to be a better option (0.247 to 0.289).

Sure, they're $15 or less for a package of 25, but I don't need 25. LOL!

You can buy individual taper pins, just need the size, and google around. Taper pins can be sized by knowing large end, and approximate length. You can also google taper pin size charts, and reamer sizes.

Taper pin chart:



If you have a wrecked hole. Or by chance need to drill a new hole for a taper pin. you would drill the hole to the size of the small side of pin. Then use a reamer by hand to get the taper. It cuts very easy by hand with a reamer, need 5 or 10 minutes.

Reamer size chart:



I think you probably have a #5, but if its a question, buy a 5 pin and reamer.

Sometimes the pins are stuck due to shaft slightly twisting in the gear, coupling, whatever. If yours broke in half, I'd say a fair chance of that. Shop around ebay and such you can probably get that reamer for $15 or so.

Keep in mind that though sized, the pins and reamers come longer than what you need. Generally people ream to get the pin to fit in hole, exactly where along that length can vary, thats why your large end is not exactly matching a chart. After hammering the pin in, you chop off the excess on either end.

Individual taper pins:
https://www.mscdirect.com/browse/tn/Fasteners/Taper-Pins?searchterm=Taper+Pins&navid=4287883861

Your question is irrelevant. All US taper pins use a 1/4" per foot taper. You should have a set of taper reamers from #07 to a #5. The hole is wrecked, so ream larger until is isn't. Then use a long replacement pin and trim to size. That's how it is done.

you can probably get a single taper pin at an ACE hardware.

thing about taper pins is what Rudd and steve-l alluded to...theres really only ONE taper pin....its infinate in length and is 1/4"/ft taper....numbered taper pins are just sections out of that single taper pin.

as such when a taper pin hole is reamed the depth of that hole determines how big it will be.

so you do as he said and buy long ones and cut them to suit.

iwananew10K said:

you can probably get a single taper pin at an ACE hardware.

thing about taper pins is what Rudd and steve-l alluded to...theres really only ONE taper pin....its infinate in length and is 1/4"/ft taper....numbered taper pins are just sections out of that single taper pin.

as such when a taper pin hole is reamed the depth of that hole determines how big it will be.

so you do as he said and buy long ones and cut them to suit.

Click to expand...

Correct......better said, Thank you!

Thanks for all of this!

I am a bit new at this, but I am a quick study. I have been putting off my order at McMaster to maximize shipping efficiency. I'll look at MSC today for the pins and take a trip up to Ace Hardware today.

And do a quick hunt for a set of reamers. And maybe another tool box. The three stacked units I have are full of other general tools.

Ace Hardware had the taper pins I need, I hope. Still have to test fit them. But I am optimistic.



But they didn't have ready made dowel pins. And being ignorant on this, is there anything special about a 1/8" pin that's different than a length of 1/8" steel rod, cut to length?

I'm no expert, but I imagine dowel pins have been precision rolled or ground in much the same way as a taper pin for an accurate interference fit. A piece of 1/8" wire is going to have a bit of tolerance to it. It might be too tight to fit - or it might be like a hotdog down a hallway.

I ended up getting a few dowel pins today. I bought some tooling from a local machinist that was retiring from the trade and he tossed in a handful of pins for me to use.

I much appreciate the help I have been given thus far.

Dowel pins are ground to a tight tolerance and usually hardened, too.

As for your taper pin not matching what the "book" says, it's possibly that someone already went down this path and had to enlarge the taper hole for a larger pin.

texasgunsmith said:

Sometimes the pins are stuck due to shaft slightly twisting in the gear, coupling, whatever. If yours broke in half, I'd say a fair chance of that.

Click to expand...

Got the rack pinion gear out. Yay! I used a method suggested by someone else to drill a small hole in the center and use a screw extractor. That worked for a different pin. I thought I had it here, but alas, no such luck.

The shaft had twisted and broke the pin into three pieces. yay.



I tried to do the ole screw extractor method to get the third piece out of the hole, but that was a no go. I don't have a mill (yet), but I do have a drill press. I'm going to get some brash sheet stock to clamp this in the drill vice. And get a center finder for the drill press and drill out the hole with a smaller bit and see if I can't get the rest of it out with minimal wrecking of the existing hole. I have reamers on the way #0, #4 and a #5. Might have to add a #6.

If you get in a jam, where either the gear/coupling or shaft hole are too wrecked. Rotate one or both both parts 90 degrees and drill and ream a new hole.

I'm going to try and relieve the existing pin and see if I can't get it to push out. I have a #4 and a #5 reamer on the way as well if I need to make a new hole.

Success! I put it in a drill vice with some aluminum flat bar to protect it and drilled a 1/8" hole through the pin, relieved it was a countersing, and was able to take a 3/8" punch and tap it out.

And the Ace Hardware #4 pin should fit just nicely. I will still use the reamer on it to make sure it's clean. Thanks all for the info and the advice.