KDP, why not use a roll pin?

[QRTRHRS]

I was running the KDP scenario by my machinist friend and he asked me that. May be a mute point but I said I would ask for opinions.

 

[Joe G.]

What's a roll pin?

 

[JStordahl]

Roll pin? A hollow pin, slotted lengthwise along one edge that is slightly oversize for the hole. Tension fit. I wouldn't use one to replace the threaded set screw for the KDP jig type fix. Seems to me it'd be adding another pin that may or may not walk. I did the washer tab fix, and thanks again for all the info on that Joe G.

 

[GLowe]

I'm thinking a solid pin is much stronger and would prevent the gearcase from moving more than a roll pin which I think is more like spring steel which might allow more movement side to side and up and down? My . 02

 

[Cummins Corvette]

I have thought about that. But any possible movement in the case could make it walk out over time.

 

[Extreme1]

The pin is only to align the parts when assembling, the bolts actually hold it in place.



I think the roll pin would be more succeptable to vibration at certain frequencies than a solid pin and might (although unlikely) walk out of the hole.



BUT, if it did, it wouldn't cause nearly as much damage as the stock pin because it is thin spring steel.

 

[QRTRHRS]

I agree, it would make no sense to risk putting one in. Just wanted some thoughts on it. Wonder if Cummins ever tried it? If it would work, that would be the place it should come from.

 

[illflem]

Extreme1, the KDP is there for more than just assembly. The bolt holes have slop, without the pin the case will shift and cause alignment problems and can take out the injection pump and crank seals/bearings.



As for a roll pin, unless the KDP is most of the way out it is very difficult to remove. Most are in very tight and the hardened dowel pin is almost impossible to get a grip on to pull. Much easier to pound the pin back in and tab or jig fix it. The spring steel on roll pins tends to shear easily also.

 

[Deezul1]

illflem is correct, the dowel pins are for precise location the bolts keep the case from falling off.

 

[dseabaugh]

spring pin ( roll pin)

I have seen instances where spring pins have been used for dowels and they do allow for some movement as you can note wear in the case where the pin goes through. not a good choice. I think a better choice would have been a shouldered bolt (like what your lawn mower wheels run on) where the shoulder could hold alignment and the threads would keep it from backing out when properly torqued. i wonder if some of these pins work out due to sloppy machining. has anyone mic'd any? also wondered if they are machined tight if pheumatic pressure is pushing them out (trapped air in hole when driven in. If that is the case they could elimate that by dropping in pins from dry ice storage into room temp blocks and allow room for gasses to escape and a tighter fit. That's how we used to do axel bearings. axle went into the deep freeze and the bearing collar went on the toaster oven . you could just drop the collar in place, but after both pieces arrived at a uniform temp, it took a torch to get it apart. It is probably like an engineer for a tractor company told me one time. I asked why they designed inherant problems in the tractors we used and he told me that they design them to last forever and then sales tells them to cheapen them up so that they can sell them.

 

[illflem]

Cummins excuse was that just a few of their many manufacturing machines were boring the hole for the pin . 0001" oversized. I have only heard this here, can't vouch for the validity.

 

[dseabaugh]

one ten thousandths over

If their machines weren't making them to specs and their quality control let them out the door then they ought to at least stand behind them all and offer oversize pins.

 

[bighammer]

If I used it in the truck, my wife might choose a deadlier weapon

 

[QRTRHRS]

How this started,

Dowl pins being pretty cheap, I decided to grab one to show my friend. The mechanics I work with are all skilled machinists and happened to be working on a lapping machine. These machines have an outer ring about five feet in diameter and an inner ring about a foot in diameter both with hardened roll pins that stick up maybe 2. 5". The process involves placing thin steel carriers (they look like ring gears) between the rings so they counter rotate as the whole thing turns on the plates.



The steel carriers are say 1/16" thick and wear grooves into the roll pins. Grooves get too deep, the tables are raised to a new surface area on the pins. This goes on until the pins length has been used up.



The pins which happen to be 10mm in diameter are then driven out and replaced.



Anyway, it was just a "what if" question.

 

[edgeman]

First post

Hello from the U. P. (upper peninsula) of Michigan, ive been reading your posts on this KDP thing. pretty scary stuff! the question i have, is the jig fix a perminant fix or am i going to have to go in and tab it later?

 

[illflem]

Welcome to TDR!!! The jig fix is permanent

 

[edgeman]

Illflem,

thanks for the welcome, and the reply. i feel like i have a lot of catching up to do on my truck. oh well, i have to start somewhere.

Edgeman

 

[QRTRHRS]

Edgeman,



If you read the KDP threads, the jig is fast and less involved. The tab is for when you need to replace the crank seal or want to check the bolts as well.

 

[edgeman]

QRTRHRS,

I have noticed the tab fix seems a lot more involved,i just wanted to make sure the jig fix is a permament thing.

 

[JStordahl]

Edgeman: Either way is considered a permanent fix..... just keep that killer pin from walking. I was going to do the jig fix, but got nervous waiting, so I tore off the cover and tabbed it.