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Richard P Wilson
08-22-2014, 09:33 AM
I've been cutting a series of 18DP gears of different tooth counts from 24 to 135T, using standard involute cutters I have acquired from a number of different places, secondhand. All is fine except that the teeth on the 26 and 27T gear look very thin compared to the others. I used a No.4 cutter, clearly marked '18DP', and made by Summit, a well known UK brand, who unfortunately, don't seem to be in business any more. All the measurements I have taken, using a gear vernier, on the cutter and the teeth, point to this being a 16DP cutter, but its clearly marked as an 18DP cutter. Anybody else ever come across this problem?

Its not too bad with just being the 26 and 27T gears, they don't take too long to make, when I get another cutter. I'd have been a lot more annoyed if it had happened to the 127 and 135 T gears.

Richard

Paul Alciatore
08-22-2014, 02:41 PM
I guess there is a reason why they are no longer in business.

Optics Curmudgeon
08-22-2014, 09:58 PM
They don't happen to say "bevel" on them, do they? Bevel gear cutters have a narrower profile and require a different technique because of the profile of bevel gear teeth.

Richard P Wilson
08-22-2014, 10:06 PM
No, they don't have 'bevel' on them. Oddly, there isn't much information on them at all. There is the makers name and trade mark on one side, plus 'super high speed steel' and 'Made in England' and on the other side it says '18DP No.4' All my other gear cutters are marked with the number of teeth they are suitable to cut, and usually the depth of cut as well.

justanengineer
08-22-2014, 10:48 PM
You said they were bought second-hand? Off ebay by chance? If so Im not surprised they were mismarked, a lot of ebay items come direct from China today with fake branding on them. Many folks including myself have run into incorrectly marked taps/dies from ebay, I didnt catch it until after I'd re-tapped a vintage cast aluminum oil pan drain and noticed that my "NOS Greenlee" had serious issues.

lynnl
08-23-2014, 09:28 AM
.... the teeth on the 26 and 27T gear look very thin compared to the others.
...............
All the measurements I have taken, using a gear vernier, on the cutter and the teeth, point to this being a 16DP cutter, but its clearly marked as an 18DP cutter.


Richard

Shouldn't 16DP teeth be more robust and thicker than 18DP, rather than thinner?

Jim Hubbell
08-23-2014, 01:34 PM
16dp are more robust than 18dp. When cutting 18dp with 16dp the tooth is cut thinner on each side. Leaving a thinner remains.

lynnl
08-23-2014, 03:27 PM
Oh yeah, that's right; it's the gaps that would be disproportionately large.
I wasn't thinking that through.