pins

[Vinny]

As I mentioned in another thread (loctite) I'm putting two gears together. I've loctited and pressed them together (the loctite showed up early) and I'm at the pinning stage. I have some 1/8" 1018 round that I am/was planning on using for the pins, set it up on the mill (made a pot chuck to hold it in the vise), and drilled a small pilot hole about 0.250" deep. I figured an 1/8" end mill would be good but just to make sure I ran the end mill in about 0.075" and checked the round for fit. Dropped right in. So that's not the right size end mill and it's back to the drill bits. I have number, letter and fractional bits. What size should I be using for these pins?

I've been taking pics throughout this process and will be posting in the Projects forum as soon as I can figure out how to get them off the tablet. So far email hasn't worked, I guess bluetooth is next. Worse comes to worse, thumb drive should work.

[TomG]

Vinny,

There isn't much strength in 1/8" soft steel pins. How big are the gears and how much power are you planning to run through them? Gears are normally keyed to a shaft with Woodruff or square keys if much power is to be transmitted.

Tom

[Vinny]

It's part of the Logan quick change gear box. I bought it with those gears being bad and at first tried plastic gears. They worked for a while then failed. So I got a couple of steel gears. They're a cluster of a 32 and 16 tooth in the A,B,C,D,E set in the lowest torque position (D and E). The pins in the original weren't all that hard either - took a good chuck out of one with one swipe of a cheap file.

[f350ca]

Would a roll pin work? Think they are semi hard. Drill a 1/8th hole and a 1/8 roll pin taps in snug. Next thought is a tapered pin, but then you have to buy the reamer and the pin but they work quite well.

[EdK]

A 1/8" roll pin has a breaking strength of 1800lbs. According to McMaster "Breaking strength is measured as double shear, which is the force required to break a pin into three pieces.".
I would think that should be more than adequate.

Ed

[TomG]

Depends on the size of the shaft and the power through the gears Ed. The shear force on a small diameter shaft might easily reach 1800 pounds. There isn't enough info available to know if that would work or not.

Tom

[Sunset Machine]

One of the littlest gears in the gearbox. Mine's broken too, never found a need for it anyway. Aren't they keyed together on one of those oddball aluminum bushings, the ones with external keys/ears built in? If it's the one I'm thinking of (.0018" feed), there's no serious load on that gear. It's so small there's very meat little to it; any pins will be stronger than those teeth that look a tad undercut already.

Btw, you can drill holes for pins with a tuned up drill bit. Tune it by rounding the cutting tips just like you'd do with a HSS lathe tool bit for the same reason - it improves the surface finish. Drill your hole with the next smaller drill, and then follow it with the tuned up drill. Nice finish and on size, but don't forget the loctite...!

[EdK]

(07-29-2015, 08:48 AM)TomG Wrote: Depends on the size of the shaft and the power through the gears Ed. The shear force on a small diameter shaft might easily reach 1800 pounds. There isn't enough info available to know if that would work or not.

Tom

I figured I'd get called on that. It was just a SWAG on my part. It wasn't the first time nor will it be the last time I was wrong.

Ed

[TomG]

Sounds like they are pretty lightly loaded, so you are probably safe. ;)

Tom

[Vinny]

The pins are in. I drilled #31 which is 0.010" smaller and used the arbor press to push them in after tapering about 0.020" on one end. Pics hopefully tomorrow. Thanks everyone!!!