Broken Set Screws on Main Drive Sprockets

[Eldon]

Less than a year ago I discovered that both set screws had sheared the tips on them on the center drive sprockets on my Max II. After a fairly difficult repair I replaced them , lock-tited them etc. Last night when backing in the garage I could determine that definitely the set screw sheared on the left side allowing the sprocket to slide enough to hit the frame when rotating. At least this time I know what it is right off last time I nearly gave up before identifying the trouble.
It only breaks the set screws when the tracks are on for winter usage . The machine is ten years old,never sheared a set screw until last year . It is actually potentially a major over haul to repair these, last time on this same side I had to pull the axle as the set screw had to be drilled out and re-tapped. I did a complete bearing replacement about 3-4 years ago,this failure has been since that. I'm puzzled in theory there shouldn't be much strain on the set screw side to side but under torque I guess there still would be.
I can't figure what I am doing wrong but would like to move beyond this. Any ideas? Possibly the older hollow axles with bolt-thru on the sprockets or the new desogn with the snap ring retention system would serve better.

[ARGOJIM]

If there is enough room you could use the split locking collars to hold things in place, if the machine gas 3 individual sprockets you may need to put spacers between the sprockets to do initial line up and lock the 3 together.

When you had the machine apart the last time did you notice any play in the splines? It may not be side to side movement but back and forth due to worn splines, this would necessitate the replacement of the worn axle or sprocket. Splined parts are much better than pinned or bolted parts.

[Eldon]

There is about 400 hours on the machine, no detectable wear in the spline, looks good . I never had any trouble with them until changing out the bearings and then not for about three years. It is perplexing because there shouldn't be strain on it sideways but when tracking strain goes every which way.The axle is locked properly and aligned. Its only been nine months since last repair and I have put maybe 20 hours on the tracks since. I'm frustrated but still a 6x6 fan. :-)

[ARGOJIM]

How much movement do the jack shafts have side to side?

[Eldon]

I haven't got up the courage to open it up yet Jim. From here I would say virtually none , but it is a good thought , if it moves or is out of alignment somehow that would definitely put end strain on the set screw under heavy torque. I really appreciate your input.

[msafi65]

check alignment from transmission to jackshaft first. This determines axle alignment. I seldom reinstall a set screw axle in a MAX. I cut the snapring grooves in the axles and install snaprings as needed. The center axles n a II are a bit tight for lock collars ,if you use them try to place the openings on top of a spline as they hold a bit better than in a low spot. good luck with the repairs

[Eldon]

Thanks msafi65 and Argo Jim. I believe it is in alignment but it won't hurt a thing to check further.
I'm wondering also if those set screws could be over-tightened? Whatever changed did so on both sides last winter though I think there may have been a time lag from first one breaking then the other, I didn't even discover it until removing the tracks. When I tear it down soon in the spring perhaps application of a laser alignment might be a good idea.

[msafi65]

The early set screw ones used 1/4 inch set screws and I've seen a lot of them sheared off. I believe the screws are brittle. Later ones used 5/16 inch dog point set screws(same as Argo )and held up better. If yours are 1/4 I would drill and tap for the larger size. Problem solved.

[Eldon]

They are indeed 1/4" , if I can get the old one out in place I'll just replace it but if I have to pull the axle I'll definitely follow your advice. Is there a torque spec on those screws?

[Eldon]

Well I have been on the defective allen screw for the second day now and can still see no daylight. I heated the screw with a big soldering gun to soften the lock-tite and managed to get one turn on the screw before the head stripped. Since I have been trying to drill the set screw out and have a flex shaft for the drill to reach, have new bits but it doesn't appear that whatever the set screw is made out of, can be drilled. When I got the turn on the set screw it loosened on the axle more and slides easily outboard to where it was fouling on the frame but sliding inboard it goes no further than as far as it should to line up. I tried to pull the axle but the sprocket won't slide off. I'm pretty discouraged to make an understatement. The set screw is flat black, is it possible they are undrillable? Only other way to get the sprocket out that I can see is to cut the axle. Any ideas? I'm open to anything.

[liflod]

I've used a diamond tip cutter in a Dremel to get one out. I've also heard that taking a long bar of sorts and a BFH to drive the sprocket and break the tip of the set screw. I tried it, but it didn't work for me. The set screws are very hard and brittle.

[Eldon]

I tried breaking the tip which I think is the broken tip still locking it from sliding inboard. I tried to drill a screw like I think is in the sprocket and it did drill . Removed the jackshaft as a flex shaft drill couldn't get enough pressure on it but with the jackshaft moved even bearing down on the drill doesn't scratch it. I have a dremel but not diamond tip cutters. Went thru this on both sides in August if I ever get it apart I'll probably only be interested in a permanent fix. LOL Enormous job to replace an allen screw.I appreciate your advice very much.

[mike d]

Hi Eldon, I feel your pain. Had to do 2 of them in my daughters max2. I alternated between carbide bits and reverse bits. Very frustrating. I think I damaged my liver. lol Good luck.

[Eldon]

Thanks for the reply Mike. I find comfort in knowing a Max doesn't just pick on me :-). I'll try the carbide bits. I may abuse my liver this evening after todays events. LOL

[phabib]

There are some solid carbide reverse drill/screw remover tools that may work for you. Here is a photo of a set of them from MSC.

Bolt Extractor Sets | MSCDirect.com

I've seen them sold in singles rather than the whole set at hardware stores if you don't feel like dropping $120 on the set. I've never used them but since you had the screw moving before the socket stripped out they seem like they ought to work. I was going to buy one to remove a stuck stud on my transmission but I wound up just drilling it out and putting in a Heli-coil instead.

Of course if you break something like that in what's left of the screw your only option is the hot wrench.