Free Bearing Press Drift Generator
Free bearing press drift generator. Sized to your pivot bearing, it clears an extended inner race and presses only on the outer. Order it printed in NZ.
What It Does
A suspension pivot bearing with an extended inner race cannot be pressed with a flat drift. The inner race stands proud of the outer one, so a flat face lands on the inner race first, drives the bearing in through its own balls, and pushes it in crooked. This generator turns a drift that does the opposite: a relief bored deep enough to clear the proud inner race and the seal, a narrow land that touches only the outer race, and a pilot that starts in the bearing bore so the whole thing goes in square. Give it the four numbers off the bearing and the drift is built live in your browser, with nothing uploaded. Designing is free; we print the drift and courier it anywhere in New Zealand.
The Four Numbers
Bore, outside diameter, outer race width and inner race width. The first two are on the bearing's own marking or in any bearing table; the two widths are what separate an ordinary bearing from one that needs this tool. Where the inner race is wider than the outer, the difference split between the two faces is how far it stands proud, and that figure sets how deep the relief has to be. The library covers the bearings that turn up in mountain bike linkages, with the extended inner race ones first: the 6901 SM MAX and 38802 used by Santa Cruz and Trek, the MAX-E series on Pivot and Yeti, and the ordinary 6900 and MR sections behind them.
The Outer Race Inner Diameter
The one measurement that is not a published spec, and the one that matters most. It is how far the flat outer race face reaches inward before the seal starts, and it decides how much metal the drift can push on. The tool estimates it from the bearing's proportions, which is close enough to work with, but a pair of calipers on the actual bearing is better. The estimate is marked as an estimate until you change it. When that figure leaves a contact land narrower than about six tenths of a millimetre, the tool says so: at that point the load is concentrated on almost nothing and the job wants a machined drift rather than a printed one.
Printing It
The file comes out oriented base-down and every feature is self-supporting, so it needs no supports. Print it solid, or with eight or more walls and eighty per cent infill, because the contact land is narrow and carries the whole press load. PLA and PETG will do a handful of pressings before the land starts to creep; ASA, polycarbonate or a filled nylon will live in the toolbox and keep working. Check the pilot fits your bearing bore before you press anything, and ream or drill it out if your printer runs tight.
Using It
Freeze the bearing and warm the link and it will want to go in on its own. Start the pilot into the bearing bore first, then bring the press up until the land touches the outer race. The shoulder behind the nose is a depth stop: it meets the housing face once the bearing is fully home, so you cannot press it too far. Go slowly, and stop if it turns notchy. A bearing that has started crooked gets worse under more load, not better.