Indian Rear Drum

[rms337]

In teardown, I discovered that my rear drum had a boogered lug bolt hole that had been tapped to a larger thread (see pics of bolt below - right side is original). Even the bolt had a different taper on the head than the original. Is it possible to helicoil this to get back to original size? Or if I take it to a machine shop, should I ask for something in particular?

IMG_9612.jpegIMG_9611.jpegIMG_9613.jpeg

Also, I have a complete set of original Indian lugs. Are there any concerns with using them or should I replace with new to be safe? Not concerned with originality when it comes being safe. I already know my hubs are good and are not all wallowed out due to prior loosening.

Thanks in advance!

[Jerry Wieland]

Yes I have helicoiled many things although not an Indian brake drum. I do not know what the Indian thread pitch would be but most of the time their threads are common standard.

Jerry

[tfburke3]

your rear drum should have studs,not those front drum bolts.
The studs are coarse thread into the drum,fine for the nuts,
Check out Jerrygreerisndian site to seeparts breakdown.
Personally I would order a new drum.I believe the last one I got was from Starklite for a price that is probably not much more than paying a machinist to repair
Also check that the wheel hub holes are round and not oversized.
Tom

[rms337]

Actually, Greers shows what I have - Lug bolts. This is a '41 Four.

Click here to go to Greers page on the rear assembly.

[tfburke3]

I should have noticed the drum was earlier.
If the hole is not bigger than the 3/8 helicoil drill size you should be able to helicoil.
Tom

[rms337]

Thanks, Tom. These are the first Indian drums I have worked with. I have yet to fully disassemble them to inspect them. Are there spec for these drums like you have for car drums? Can you get them turned in the same fashion as car drums? I guess what I am asking is how to tell when it is time to replace them?

[ryan]

You can only use helicoils that have the same O.D. pitch as the I.D. thread that you are repairing, example: 1/4"-20 thread to be repaired has to be drilled out for a 1/2"-20 tap. So coarse helicoil tap with coarse thread to be repared and fine thread helicoil with fine thread hole to be repaired, the thread pitch(count) have to match. etc.

Now you can fix the thread with a staked thread insert if you have enough wall thickness, but I doubt you do.
One thing to mention is the setup time on a vertical mill to pick up the correct location if a mill is needed, not sure if you can do it on a drill press or not. Anyway, bolt circles take either a rotary table, a scientific calculator or a computer with some sort of cad software to find the bolt hole locations. Good luck!

[tfburke3]

Thanks, Tom. These are the first Indian drums I have worked with. I have yet to fully disassemble them to inspect them. Are their spec for these drums like you have for car drums? Can you get them turned in the same fashion as car drums? I guess what I am asking is how to tell when it is time to replace them?

I have no info on your original drum id. or the max allowable id.
My late plunger Stark Repro is on the shelf and the id. measures 6.795.
An old early plunger drum like yours measures 6.825 and has probably been cut.
The more the drums are oversize the more problems with shoe fit and cam/lever action.
Funny when I looked at the early plunger drum it has similar lug hole issues as yours.
Tom

[rms337]

Between these last couple of replies, it appears I may be better off just buying a new drum. I'll see what it looks like once I disassemble. Thanks!