How do I make a hole SMALLER?

[Truckasaurus44]

OK, I've got a Fantic Broncco that was previously owned by a complete freaking nimrod. The bike is Italian so all the original hardware is metric and the yuts drilled out a bunch of the holes for standard hardware! This included the swing arm mount holes on the frame.

I'm swapping out the butchered swing arm and of course, the 12mm hole has been drilled out to 1/2". Better yet, I found that the "bolt" was actually a 1/2" ALUMINUM ROD that was threaded on both ends. Its not a huge difference (about .7mm), but it creates enough slop that I've got to do something. Here's my options that I can think of:

1) Drill out the new swing arm to 1/2" and just accept that the bolt will be wrong (though I will make sure that its STEEL!)
2) Cut off the mount plates, make proper ones and weld them on....yeah right. Not happening unless I get a laser cutter and alot more time
3) Find a way to shrink the hole. I was thining about making a bushing out of the right thickness sheet metal, tack it in and grind smooth

What do you guys think? I'm leaning toward trying #3 and going to #1 if it doesn't work

 

[wayne]

washers ?

 

[KustomKartKid]

get someone with a lathe to make you a couple of Oilite bushings for the holes that reduce them back to 12mm (might actually have to drill the swing arm hole even larger, say 5/8 so you wind up with a bushing that has some wall thickness)...then tell everybody you did it to improve on the original design

 

[Nick Flores]

I think you're going overboard with lathes and bushings and all that... If you're making a new swingarm just drill it to fit the hardware, save yourself the trouble. If you bore the hole out and put bushings in you're just making more parts to wear out eventually.

 

[KustomKartKid]

I think you're going overboard with lathes and bushings and all that... If you're making a new swingarm just drill it to fit the hardware, save yourself the trouble. If you bore the hole out and put bushings in you're just making more parts to wear out eventually.

uhhh...he's trying to repair the holes on the frame that accept the swing arm. And the idea behind an Oilite bushing is that it won't wear out like a crude steel bolt in a steel hole setup will. Rubbing similar metals (steel bolt/steel frame) together is never a good idea especially under a load. Those bushings are about a 15-20 min job in a lathe even for a rookie....... and he can put back the metric hardware that is correct to the bike, which was his goal to begin with.



.

 

[oldfatguy]

I have a similar problem with the front suspension on my go kart, the 1/2 inch bolts are worn as is the holes in the control arms. I was thinking of making bushings on a lathe from brass water pipe. But drilling them and using a 9/16 or 5/8 bolt would work too. For your minibike the easiest solution would be to drill for a larger bolt, I doubt that anyone will ever notice that it is not the original size plus you will still have the option to have bushings made someday and pressed in

 

[Truckasaurus44]

The bolt shouldn't be spinning in the hole, seeing as the swing arm has bronze bushings to rotate on. I don't think I'd need to used oilite or any low friction material. If anything I want the toughest material I can get to work.

Yeah, making a bushing that has a .35mm wall thickness is going to be really tough. I get the feeling I'm going to be drilling out the swing arm bushings to 1/2" I can always get some new 12mm bushing pressed in if I find a way to fix the frame later down the road

 

[Nick Flores]

uhhh...he's trying to repair the holes on the frame that accept the swing arm. And the idea behind an Oilite bushing is that it won't wear out like a crude steel bolt in a steel hole setup will. Rubbing similar metals (steel bolt/steel frame) together is never a good idea especially under a load. Those bushings are about a 15-20 min job in a lathe even for a rookie....... and he can put back the metric hardware that is correct to the bike, which was his goal to begin with.



.

I suppose it depends on what tooling you have on hand or how much money you have to spend.

If the hardware being original is that important why not sleeve your new swing arm and the butchered holes in the frame? Then you can make it much stronger and utilize whatever combination of hardware/bushing you like.

PS.. My bad for mixing up frame and swingarm...

 

[oldfatguy]

The bolt shouldn't be spinning in the hole, seeing as the swing arm has bronze bushings to rotate on. I don't think I'd need to used oilite or any low friction material. If anything I want the toughest material I can get to work.

Yeah, making a bushing that has a .35mm wall thickness is going to be really tough. I get the feeling I'm going to be drilling out the swing arm bushings to 1/2" I can always get some new 12mm bushing pressed in if I find a way to fix the frame later down the road

I just realised that you are a Jersey guy, I'm all the way up in sussex county near the vernon valley ski area but I do have a small machine shop in my garage with a metal lathe if you need a bushing made.

 

[Donmon]

Weld a metric washer on the inboard side of the tab.

 

[KustomKartKid]

Hmmm...if the new swingarm has good original 12mm bushings in it seems a shame to drill em out. Are the exisiting holes in the frame at least round or are the worn/ragged. If you can drill these two holes to say 5/8 and keep them nice and round and concentric to the original holes, I could make you a couple of flanged steel bushings that would drop in (12 mm i.d x 5/8 o.d. with maybe a 7/8 or 1" x 1/8" flange). They would look like washers with a step in them.... you could insert them on the outside of the frame under the head of the bolt and the lock nut on the other side. You just pay me the shipping on them.
If your not hung up on the metric thing than just do as Nick and FG said and drill the whole deal out for 1/2"...or make it 13mm that way you can still say it's metric... :thumbsup:

 

[rodburner]

Drill the new arm bigger OR weld the mounting bracket holes shut and re-drill to 12mm,if you just have to have a "proper" setup.

 

[KustomKartKid]

re-post

 

[Nick Flores]

..... ...drill the whole deal out for 1/2"...or make it 13mm that way you can still say it's metric... :thumbsup:

Now we're just splitting hairs! :drinkup:

 

[KustomKartKid]

Now we're just splitting hairs! :drinkup:

yeah I was just poking fun

I usually take the opposite tack and try to avoid using metric hardware at any cost :doah: but some folks are really particular about keeping things original and I understand that. I was also trying to suggest solutions that didn't involve any welding, grinding, etc in case the bike still had nice original paint on it......

...lot of good ideas suggested here.

 

[Truckasaurus44]

Hi guys. Thanks for the ideas. I'm not that hung up on originality. This is a "custom" resto anyway because I don't even have close to every part for the bike. Not even an original tank.

I just don't want to keep drilling everything out and play musical bolts if there is a way to keep the bike close enough to original for a full resto later.

I think I'll swap the drilled out bushings into my new swingarm (assuming I can get them out) and keep using a 1/2" bolt for now. This way I'll have a nice set of 12mm bushings for later if I settle on a way to fix the holes.

 

[Tom S.]

Now we're just splitting hairs! :drinkup:

 

[supernova]

Good one Tom!:laugh:

 

[george3]

You dont have to weld the hole all the way. just run a bead on the part that was drilled out. Then reem the hole to size. easy to do. Works great.

 

[fixit]

For a frame repair
Make up some precision washers. Say 40MM od, 12MM id slip fit & about 5mm thich & weld them in place. I'ld sudjest A-2 material & that way when you weld it on it will also heat treat it to some extent.

For a swing arm repair
Press fit bushings, but you have to have some wall thickness. Use O-1 material & you can harden them yourself with a propane torch & a bucket of old motor oil