sisddwg

I'm trying to fit a Campagnolo N.R. shift lever to a Huret clamp on boss and everything works except that the Campy screw seems to be to large in diameter to fit the Huret boss. Will a proper size tap work on the Huret boss to enable the Campy screw to fit?

Thanks.

onespeedbiker

The Huret uses a French thread on the tension screws, which if I remember right is slightly smaller than a Campy screw; the Campy screw is 5mm. There a person on ebay that modifies these clamps so one can use Campy downtube shifters so I'm sure it can easily be done with a 5mm tap. However, you say it looks like the Huret clamp on bosses will work, but the bosses are made for Huret and Simplex shifters and don't have the flats at the end needed for Campy shifters. Unless your bosses have been modified they will not work. Here is a link to the ebay seller and an explanation of the modifications he does. https://www.ebay.com/itm/DOWNTUBE-SHI...item27ce5f3812

rekmeyata

Damn it, I responded then it got deleted. Let's try it again.

First off it would be easier to switch to Simplex Retro Friction shifters instead, they were the best of the friction shifters.

But if Campy is what you want then next try this. Find an old set of junky Japanese shifters and see if the screw will fit the boss. French did import bosses from Japan and England to put on their bikes which if they did then the Campy screw should fit.

If the Campy screw does not fit then you need to tap the boss out to a M5x.8 thread. But before you tap away check my numbers to make sure their right, someone here may know for sure or and LBS may know. And I think I recall they have to be bottom tapped which is more difficult then a standard tapered tap.

Edit: I just found this, not sure if it's helpful for you but maybe; see: https://search.bikelist.org/getmsg.as...10906.1178.eml

FBinNY 

I don't think it'll work. If I remember correctly the clutch plate system is different. For the levers to work the outer cover must key to the boss so it can't rotate, otherwise the back and forth motion of the lever will work the screw back out.

Otherwise, if you think you can make a go of it, then it's far easier to find the right screw than it is to tap the boss.

sisddwg

Thanks for your response onespeedbiker. The Campy levers don't need a flat, they are round. My only problem is getting the campy tension screw to fit the Huret boss. To clarify, I'm using a single boss clamp on. In fact, I got the clamp on boss from the ebay seller that you listed. I think the tap will solve the problem.

sisddwg

Hmm, that makes sense. Thanks.

onespeedbiker

Maybe I didn't make myself clear. A Huret boss is round from top to bottom. A Campy boss is also round but it has two flats (or is keyed) at the end so you can install the clutch plate and/or outside plate that has a rectangular hole. The purpose of the rectangular holes is so the plates don't turn with the lever. It's the same argument that FBinNY made. The photo on the left has standard Huret bosses (no flats). In the photo on the right the bosses have been modified with flats at the end to work with Campy shifters. If you're careful you can take a file or dremel tool and create the flats for yourself. Otherwise you can return the clamp to the ebay seller and I'm sure he'll be happy do the work for you (including taping the threads to 5mm) for a small fee.

sisddwg

Thanks onespeebiker. That helped a lot!

dddd

You really want a precise, tight fit between the boss with flats and the anti-rotation washer.
Any slop at all will tend to "ratchet" the adjusting screw to a looser setting with each downshift.
I've even seen many brazed-on Campy bosses that didn't have a quite tight-enough fit and resulted in loosening.
I found it surprisingly difficult to deform such loose-fitting washers to more of an interference-fit.