Recommendation for hand reaming tool

[Seb_N&BLR]

I recently bought a replacement gearbox and worm+gear set for an IP deluxe chassis that is forming the basis of a shunting loco that I’m building. The supplied nylon gears and two-piece plastic gearbox were very poor quality so I decided to start with better quality arrangement. Dean Goods sell a printed one piece gearbox and various grades of gears (in my case, 40:1 for slowest speed operation!) that are both designed specifically for the IP chassis. Match made in heaven.

Slight problem - despite being supposedly drilled out for a 2mm bore motor shaft, the steel worm gear is actually about 1.85mm bore and doesn’t come close to fitting onto the motor shaft.

I don’t have a lathe (nor planning to get one) and I read online that an adjustable hand-reaming tool might do the job. Can anyone recommend a good quality tool for a reasonable price?

Much obliged
Seb

[philipy]

I'd be more inclined to contact Dean Goods for a worm with the correct bore.

[tom_tom_go]

I agree with Phil.

You have purchased a new product that is not fit for purpose!

[Seb_N&BLR]

That may be the logical choice, but I’d still be interested to know people’s recommendation for a tool? This actually feels like an opportunity to learn a useful skill.

[LNR]

I have adjustable reamers, but have never seen or heard of them for that small diameter. The parts that make up such reamers could not physically be made that small. Smallest I have is either 1/4" or maybe 3/16th'. In Horology (clocks) we use hand reamers that have an extremely slow taper for opening up bushings, it would be possible to use one of these and sets do not cost that much. However I agree with Philip and Tom return it and get one that is correct.
Grant.

[GTB]

That may be the logical choice, but I’d still be interested to know people’s recommendation for a tool? This actually feels like an opportunity to learn a useful skill.

I've bushed and/or opened out gears for model loco mechs over the years, but always in a lathe.

I've got a couple of different size sets of the pivot cutting broaches mentioned by Grant and they work well for opening up holes in brass sheet, or a hole in a plastic part. However they operate more like a scraper than a cutting tool, so you'd be there forever trying to use one in a steel worm that is about 10mm long.

I don't use adjustable reamers, but my usual tool suppliers don't list them in sizes below 1/4” or 6mm.

You can get fixed size hand reamers down to 2mm and they are used in a similar way to a tap when cutting a thread. A 2mm reamer isn't much bigger than a 10BA tap and would be just as fragile when used freehand.

I would guess you could successfully use a hand reamer that small in a tapping fixture. Although by the time you buy or build a fixture, get a small machine vice and then set it up to ream just one worm, getting the manufacturer to replace the faulty part would be looking pretty attractive (and cheaper). Just saying.........

Regards,
Graeme

[Seb_N&BLR]

Just a footnote to this, as a correction to my original statement.

Turns out there is nothing wrong with the worm bore, the motor has a 2.3mm shaft! Now I’m off to get my eyes tested.
(It’s one of those learning experiences I seem to keep having... )

Just to reassure anyone who was doubting the quality of the Dean Goods product.