GoinCircles

I have a project I am working on where I will be using a 42/52mm integrated head tube from BPS.

The head tube is aluminum, undersized and needs to be reamed to spec after welding. Unfortunately no bike shops in a several hour drive have reamers this size. While park tool sells some, it’s too much for a one time job.

Considering this is aluminum, I should be able to make something that will work, but I am having an issue with bore depth.

Does anyone have a chart or resource that gives iso standard dimensions for bore depth.

I have been able to fine several repeatable sources listing the OD tolerances for each
(41.95-42.05mm top, 52.05-52.15mm bottom), however information on the depth is sparse and inconsistent.

A cane creek poster list 2.8-3.0mm for the 42mm top, and 7.4-7.5mm for the bottom. A Peter Verdone drawing has 3.2mm for the top. Measuring my 42mm bearing, with compression ring and cover shows this needing about 4.2mm of depth for the dust ring to make contact. Various head set drawing online typically have 3mm but do vary.

Does anyone have a solid resource on this?

FBinNY 

Step one is determining the critical dimensions per the headset specs.

For example, most integrated headsets seat conically, so the critical dimension are the angles of the conical faces, and not the diameters of cylindrical walls.

So, you need ID to clear the steerer, with breathing room. You also need a certain depth for the races to pocket and the top and bottom end caps to have a small gap to the tube.

The point here is that you get the info you need from the headset, then it's a question of access to either the needed tools, and/or a mechanic who can do the job.

Note, the depth dimension is more critical on the bottom, because top cap clearance is easily adjusted with a shim under the cap.

BTW the original logic for this design if for the tube to be factory machined to final spec. and stout enough to be welded without distortion. You might come out ahead if you sought out one of those.

dsaul

Why not use a 44mm head tube? More shops are likely to have the reamers for a 44mm head tube and you can use any size steerer you want on it. For a tapered steerer, you would use an internal top cup and external lower cup.

GoinCircles

So for the most part I have the critical dimensions with the exception of depth. While I was able to get a ball park, sources seem to have a variance of 0.4mm. That is what I am hoping someone can clarify.

The head tube an off the shelf factory machined tube, I still can’t post a link, but it’s 155MM DEDA FIRE LIGHT 46/56 TAPERED HEAD TUBE FOR IS42/52 HEAD SET MTS56E155. The IDs are undersized 1mm.
The top dept is 3mm, I’m seeing tolerances that are 2.8-3.0, and 3.0-3.2mm depending on the sources. The bottom is 7.5m depth, I have sources showing 7.4-7.5mm and 7.5-7.7mm.

Depending on the source that looks more complete, it would appear that I am already at the upper end of the depth tolerances and need more facing, however, another one shows that I need to face and bring them deeper.

I am assuming that despite being standard, there is a level of variance from manufacturer to manufacture that is more than simple tolerance. i’m seeing this on a Facebook page for a gravel bike cone, several people have tried to upgrade the integrated headset bearing, and have found that Hope and other brands don’t sit down as deep.

While I can have the tool made perfectly to the depth of the head set I have on hand, I would rather make it to a more typical standard so I don’t have any issues with future replacements.

The park tool for the 42mm and faces at the same time, but they don’t list the tolerance. I believe the 52mm reamer and facet are separate, meaning you can vary it. There are enough other brands that make these size reamers, but they are still expensive and don’t list their depth.

GoinCircles

That came up with the shops lol. Initially one told me they had the proper size reamers when I purchased the head tube, turned out they don’t.

I would change corse, however currently I have the head tube and head sets, and the pieces mostly fitted, ready to weld. I also have a way to ream it. I just need that depth dimension, I didn’t plan on that being a hold up.

squirtdad

suggest ask same question in Frame builders https://www.bikeforums.net/framebuilders/

FBinNY 

You need to understand that there's no fixed, precise dimension for the depth. Since the bearing is located by the cone, tiny variations will change the stack height. The cutters made for this job are stepped, cutting both the cone and lip of the tube simultaneously, and ensuring that everything is the same with respect to each other. However even so, headsets often need shims to ensure a minimum gap without rubbing.

So, you can proceed by trial and error, cutting to a depth within range, and either filing the lip or using shims to achieve the ideal fit. Worst case, you don't set the cone deep enough and need a second pass.

l

GoinCircles

Thats what I was starting to assume, thank you for confirming that.