Odd gearcutter question

I've got some gearcutters (or something related) in my collection
which I don't know the purpose of - anyone able to shed any light?
first is like a Brown & Sharpe type gearcutter, but with straight
sides to the teeth instead of involute form. They are marked with the
included angle (45 deg) and what appears to be the width of the flat
tip of the teeth (.015").
Second are a couple of 'hobs', 20mm long & about 49mm OD, but conical
in form. The cutting section, with teeth in a spiral like a hob,
starts at the 49mm dia, reduces to about 43 mm over 16mm axial length.
The angle to the axis is about 15 deg. The teeth are highly
asymmetrical, one flank being almost square to the axis, the other
flank being of the order of 45 deg to the axis. They are marked with,
among other things, what might just conceivably be module sizes, one
of1.221, the other 2.355. Made by Mikron.
Any clues? I can send email pics if anyone has an idea but needs
clarification.
I doubt they could ever be any use to me, if so, I'm open to offers
from anyone who thinks they could use them.
Cheers
Tim

Tim Leech
Dutton Dry-Dock
Traditional & Modern canal craft repairs
Reply to
timleech
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Spline cutter or just a horizontal angled cutter that's very similar in appearance to a B&S cutter.
Ratchet hob? Hobs can be made to perform just about any job. The teeth on film spools and the tags on motorcycle clutch disks are hobbed so you can visualise what the hob must look like.
-- Regards,
John Stevenson Nottingham, England.
Reply to
John Stevenson
Seems likely, though their size (50mm OD, 1/2" bore) plus the fact that they came with my Mikron hobber led me into looking for a gearcutting or related use.
I can see how they could hob a ratchet form, but I'm still mystified by their conical shape. I suppose if they are set 'off centre' they will give a tooth form which might be awkward to achieve with a 'centred' cutter.. Not something that my hobber is designed to do, though these also came with it. They're also a bit big (19mm bore) for my machine.
Thanks Tim
Tim Leech Dutton Dry-Dock
Traditional & Modern canal craft repairs
Reply to
timleech
Tim,
Could the straight sided one be from a Fellows shaper type gear cutter - if so one side will be very slightly concave.
Could the other one be for hobbing bevel gears?
Andrew Mawson Bromley, Kent
Reply to
Andrew Mawson
No, they're dead straight, with 45deg included angle.
It's tempting to think that, because they do look superficially a bit like bevel gears, but for one thing I don't think it's possible to hob bevel gears, plus I can't see any way they could be used to cut an involute tooth form or anything remotely near to it.
My hobber can, in theory, be used to cut (small) bevel gears but it uses a little 2-tooth cutter, with slightly spiral form teeth, I think alternate teeth are supposed to cut opposite sides of the bevel gear tooth, and doesn't actually hob them. I haven't seriously investigated that side of things, partly because I haven't had a need to make any, also I believe it needs a different cutter for *every* size of gear! If anyone *knows* about these things I'd be interested to know a bit more about how it's done.
Cheers Tim
Tim Leech Dutton Dry-Dock
Traditional & Modern canal craft repairs
Reply to
timleech

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