Drive Dog Set Screw(Best One?)

Hi All,

I know they make different points on alloy set screws IE: cup,flat, oval.

I need set screws for a production run of drive dogs and noticed most are cup point.

I know the cup grooves the shaft when tightened.

Does this weaken that point on the shaft?

Which one do you prefer or is best for drive dog?

Am I being to picky?

Thanks In Advanced

Tim

I usually grind a very small flat under the set screw to both prevent rotation and fix the burr issue. I then put a drop of red Locktite in the hole and tighten the set screw. That makes a permanent assembly. If you need to take it apart it will take a torch. The set screw is a one use item in the assembly so re-tap the hole and repeat the procedure with a new set screw.

Lohring Miller

Use an 8-31 black oxide bolt. Be sure bolt is flat on end. Grind a small flat on shaft. As Lohring said, use red Locktite to set. Cut bolt off at drive dog and finish profiling in a lathe or can be done by hand. I believe the drive dog is better balanced on the shaft this way.

Stu

I grind the bottom of the set screw almost flat, removing most of the pointed ring on the bottom. I've had it flatten out over a short time causing the dog to loosen up on the shaft. I also grind a flat spot onto the shaft big enough so the set screw makes full contact with it. Add lots of red loktite, tighten it up (usually to the point of stripping the set screw), and then grind the top excess setscrew flush with the outside of the drive dog. Like Lohring said, one time use, if it needs to come off, its with a torch and a screw extractor.

I like the idea of using a bolt , i may start doing that in the future.

To aswer your question about the shaft, sure the groove weakens it, but not enough to cause problems from what i've seen. Just dont go deeper than you need to.

Brian

Hi Guys Thanks,

Stu I remember us talking about this before and both of you make great points and ideas.

My thoughts were to provide a set screw that people wouldn't need to modify to buy anything extra.

Brian,Lohring on your thoughts, a flat point would probably be best from a supplied with the drive dog purchase?

Stu your thoughts are, have the option for people that want to take a little effort verses a plug and play.

You definitely can get it tighter with a hex head.

I can have the bolts available for that

I didn't mention that the the drive dogs will be SS and not hardened steel.

If I can get better pricing on the Octura I will still carry those but right now I dont like my pricing on those, so again going out on my own to offer good pricing and keep it USA.

I guess that brings up another issue of which is preferred.

It sounds like petty stuff but want to provide the best I can and what people want.

Thanks

Tim

Tim,

Offset the holes 180 degrees so they can be balanced.

Three holes can be another option. So if the drive dog

Is not balanced what do you think happens to your driveline

and propeller balance?

Just A Thought,

Mark Sholund

DING,DING,DING!!!!! You win the prize on this one, Mark! Been using two set screws 180 degrees apart since day one.

Dick Tyndall

Mark,

Great Idea!!!

I would like to still do 1 set screw for people that like that and have the shaft set up for it.

But can do some 2 Set Screws opposite(180º) is easily doable.

I will raise the price a little, just because of extra time.

In yours and others thoughts on a 2 set screw,

Would you do 2- 8-32 screws or 2- 6-32 screws for (SS 3/8" od for 3/16" shaft) drive dog?

after that will be 7/16"od for 1/4" shafts.

Thanks Guys

Tim

shoboat said:

Tim,

Offset the holes 180 degrees so they can be balanced.
Three holes can be another option. So if the drive dog
Is not balanced what do you think happens to your driveline
and propeller balance?

Just A Thought,

Mark Sholund

Click to expand...

Tim,

Be careful with the design as it is critical between a good piece and a junk part.

As was mentioned. The setscrews do not want a cone shaped tip at all. It is best dead flat as this prevents rotation best as it indexes into the flat ground into the shaft.

Stainless setscrews are soft and worthless for anything you need tight like in the driveline. You can not tighten SS setscrews dependably even with a new quality allen wrench to the tightness they should be.

Don't buy short setscrews that screw in flush as they will have no depth for the allen wrench to properly tighten it. If you want it out of the slipstream then you grind it off when you have it tight.

Do not use two unless they are 180° apart at the same point as the dog ears but you do not really need two for any real reason as the difference in balance is too small at that close to the center of axis. Any meat removed anywhere other than the thickest point dead inline with the ears for a setscrew will allow the collar of the dog to split in two. If you want it to end up perfectly balanced use extra long hardened alloy black oxide steel setscrews, tighten them with liberal dose of red locktite and grind them down flush (without cooking out the locktite, grind slow and use water to cool with) and the piece of the setscrew left in the dog will be solid and not effect the balance at all.

We run full mod twin cylinder 60+cc engines turning huge 3317's in and out of the water with a single setscrew. The dog ears will fail long before the setscrews grip on the shaft does. I have a box of SS and hardened drive dogs with the ears sheared off as proof. Lol. These are with props that dog in properly right to the base of the ears to. Seen people that have ground these terrible angled notches in the prop hubs sometimes that only touch the dog ear at the tip (maybe only one if the notches leading/working edge are that bad or not 180° to the other one) and wonder why they are shearing drive dogs. It folds, bends and cracks it right off.

Thanks Daniel,

Much appreciate the feedback and Is welcome.

All over a drive dog I never thought would be so much discussion.

It seems only one design is out there and trying to see what people that use them say( like yourself and others) verses telling them what they need.

I have never broken a drive dog myself(I have small boats) but that doesn't mean it doesn't happen and I'm sure like what your saying,it happens with the bigger boats.

I'm so glad I asked.

Set screw/s will be alloy steel and Yes you are right, keep inline with the tangs.

Tim

Daniel's Racing said:

Tim,

Be careful with the design as it is critical between a good piece and a junk part.

As was mentioned. The setscrews do not want a cone shaped tip at all. It is best dead flat as this prevents rotation best as it indexes into the flat ground into the shaft.

Stainless setscrews are soft and worthless for anything you need tight like in the driveline. You can not tighten SS setscrews dependably even with a new quality allen wrench to the tightness they should be.

Don't buy short setscrews that screw in flush as they will have no depth for the allen wrench to properly tighten it. If you want it out of the slipstream then you grind it off when you have it tight.

Do not use two unless they are 180° apart at the same point as the dog ears but you not need two for any real reason as the difference in balance is too small at that close to the center of axis. Any meat removed anywhere other than the thickest point dead inline with the ears for a setscrew will allow the collar of the dog to split in two.

We run full mod twin cylinder 60+cc engines turning huge 3317's in and out of the water with a single setscrew. The dog ears will fail long before the setscrews grip on the shaft. I have a box of SS and hardened drive dogs with the ears shears off as proof. Lol. These are with props that dog in properly right to the base of the ears too. People grind these terrible angled notches in the prop hubs sometimes that only touch the dog ear at the tip(maybe only one if the notches leading/working edge are that bad or not 180° to the other one)and wonder why they are shearing drive dogs. It folds, bends and cracks it right off.

Click to expand...