3-wheel knurling tool?

[Allen Smithee]

In my Stuart S50 thread I mentioned that it was part of a load of miscellaneous stuff I had been passed by an aging friend. There are some curious in the bunch which I probably need to ask questions about. The first one is this knurling tool:



As you can see, it has two wheels fitted (left and right knurls), but on the same side. Should there be a third wheel, or should that be a "blank" roller or something? In the same box there were a few spare knurling wheels, but none of the same size or pattern.

My brain wants to say "DUH???", but is there such a thing as a 2+1 knurling tool? If so how does it work without making an odd pattern?

Incidentally the same box had this which I'm pretty sure is an unfinished Hemmingway "Basic Knurling Tool" (HK1110) with the arms assembled on the wrong sides:



Perhaps that's what the other wheels are for.

AS

[Admiral_dk]

As far as I can see - then there is a hole for an axle for the third wheel opposite the first two .... 

Per

[Allen Smithee]

Yes, I saw that. But I don't understand why this knurl has two wheels on one side. A third wheel would make a strange pattern, but if it was a plan wheel it would surely flatten the knurling? I usually take a skim cut over the surface after knurling to make it less snaggy - is this supposed to have a plain wheel to do the same sort of thing?

AS

[internal_fire]

A third wheel would make a strange pattern
AS

I took a close look at the photo, and it appears that the knurls are straight, not angled. In that case a third (straight) wheel would work just fine.

Gene

[Allen Smithee]

I'll check again later, but I'm pretty sure that the knurls are angled because I remember noting they were an opposing pair.

AS

[dieselpilot]

I believe this is a hand knurl.

[Jasonb]

You would think that if all three wheels are to be used that the top one would sit centrally above the bottom two. As it is it will be unlikely to apply much pressure if you have the bottom two touching as the top one will be over the back of the job and not in an equilateral triangular formation.

Or is it the angle that the arms are at that make it look that way, can we have a photo with the arms parallel or angled out evenly?

If they do line up in a triangle then bottom two may be soft rollers and just the top one to form the knurl hence one of each pattern

[Mcgyver]

I'm doubting its a hand knurling tool because of the square shank, otoh every hand knurling tool I've see does have three wheels....I guess they'd have to.

If the pocket book is too heavy, one can pay Horia a visit:    https://www.horia.ch/en/Products/Knurlingtools/Knurlingtools/Knurling-tool.html

Alternatively, here's a rough and ready DIY version.  The opening screen shows the arrangement of the wheels.  It seems to work well.

<a href="https://www.youtube.com/watch?v=KzB8MGFsaV8" target="_blank">http://www.youtube.com/watch?v=KzB8MGFsaV8</a>

[Allen Smithee]

I'll check it later, but the bottom two are definitely hard knurls not soft rollers.

AS

[Allen Smithee]

I was right and wrong. I was right in that the wheels are definitely hard knurls not soft rollers, but wrong in that they are not opposite-handed:





AS