# Latest Project Finished...  A Scissor Knurl



## jgedde (Jan 3, 2012)

Here are the fruits of my latest labors in the shop...  This is a scissor knurl.  For those who don't know what the advatages are, they create a knurl without putting stress on the cross slide and headstock bearings.  In addition, it is autiomatically self centering.  It also allows small or long pieces to be knurled without deflection.

All the pieces were handmade by me except for the button head screws, spring, circlips and the knurling wheels.

The goal was to produce a rigid tool with no perceptible slop in the hinges.  This allows one to simply stop a knurl cleanly, although the convex wheels installed into the tool are designed for axial feed to a groove or off the end of the workpiece.

The whole thing, except for the thumbscrew, is made from W1 tool steel...  It all came out of either a 5/8 or 1.25 inch round stock scrap bin piece.  The hinge and wheel pins were hardened and left untempered.  They ended up so hard, a Carbide lathe tool did little more than polish it.  In any event, I tried to break them to test brittleness and they held up.

As a test of the assembled tool and to create the thumbscrew, I installed a simple hex nut onto the threaded piece and knurled the thumbscrew.  Obviously, it works.  More important though it that its performance exceeded my expectations!  _*Why was I using a bump tool for all this time?

*_The wheels installed are 64 DP (diametral pitch), M42 cobalt, TiN coated units from Accu-Trak.  They are expensive, but worth it IMHO.  They'll last a lifetime for an HSM and create supurb knurls.  In any case, these beat the living heck of of the import jobs.  The advantage to the diametral pitch knurls (as opposed to the traditional circular pitch knurls) is that they will simply track on any diameter which is a multiple of 1/64" (other DPs will track in 1/32" increments but are a bit fine for my tastes).  This means no calculations of circular pitch vs workpiece circumference afre required to guarantee tracking.  For those that choose to mash the knurls into tracking, I accept that...  I've done it too...

The knurl pins are held in by a retaining clip design which engages a groove in the pin.  This is in lieu of a circlip.  This idea came from Guy Lautard's Machinist's Bedside Reader book.

Here are the pictures...














I intend to put this tool through it's paces in the next few days.  I will post some closeups of completed knurls on scrap pieces of various materials...

Happy New Year!
John


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## ScrapMetal (Jan 3, 2012)

Very nice.  Something very similar is right at the top of my "to make" list.

Thanks,

-Ron


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## Hawkeye (Jan 3, 2012)

John, that looks really good. I haven't heard of convex knurls before. I'll be on the lookout for a pair for my Camjack Knurler. I can see how they would track nicely on a long knurl. On a short disk, I'm thinking they would give you a tapered knurl, with the center section displaced higher than at the edges. That could be cool.


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## jgedde (Jan 3, 2012)

Hawkeye said:


> John, that looks really good. I haven't heard of convex knurls before. I'll be on the lookout for a pair for my Camjack Knurler. I can see how they would track nicely on a long knurl. On a short disk, I'm thinking they would give you a tapered knurl, with the center section displaced higher than at the edges. That could be cool.



It looks a bit funny at the ends.  In a lot of cases the knurl ends up proud of the shaft to be knurled (i.e. the shaft is turned down) so the tapered portion just gets machined off (like the ends of the knurls on my knurler's thumbscrew).  The point of the convex knurls is that they are easier to feed, are actually designed for axial travel, and give a nicer finish.  The big thing for me is the DP as opposed to CP wheels.  The DP wheels seldom yield a double knurl.

If I ever need to knurl to a shoulder or cannot machine off the ends of the knurl, I would resort to a straight knurling wheel.

I got my knurls here: http://www.accu-trak.com/

John


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## ekrteam (Jan 4, 2012)

Nice job, you can see the pride you have in your work.  Have you knurled any steel with it?


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## lockstocknbarrel (Jan 4, 2012)

Hi John,
Very professional looks almost like my "Shop Brought" tool that I picked up some years ago, this reminds me I should sell the old push on tool. 
Kindest Regards 
Beagles.


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## churchjw (Jan 4, 2012)

GREAT job.  I bought one of these about a year ago and I love it.  Will never go back to the other style knurl.  Now I will have to make one since yours looks miles better than the one I bought.  Bet it works better as well.

Jeff


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## jgedde (Jan 4, 2012)

ekrteam said:


> Nice job, you can see the pride you have in your work. Have you knurled any steel with it?



I'll try some steel tonight and post a photo. 

Pride? Certainly. I was raised with the mindset that anything worth doing is worth doing to the best of your ability. Nonetheless, as a newbie HSM, I am still learning and my abilities get better the more projects I undertake. It is pure joy when something comes out as good or better than I envisioned and I can't help but show it off. 

Surface finish is a bit of an obsession for me. Tooling marks bug me (and they really shouldn't).

Of course, since hindsight is 20-20, I would do a few things differently if I were making another one:  Like the recess for the cap screw holding on the shank.  While it looks nice recessed, it weakens the tool (although that area ins't really a stress point).  A bigger thumbscrew would be nice (I plan on retrofitting this). Also a few things could be simplified...
.
Thanks for the good words!
John


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## jgedde (Jan 4, 2012)

lockstocknbarrel said:


> Hi John,
> Very professional looks almost like my "Shop Brought" tool that I picked up some years ago, this reminds me I should sell the old push on tool.
> Kindest Regards
> Beagles.



My 2 cents is keep the push (bump) tool.  It can do things a scissor knurl cannot do...  Things like large diameters (say a handwheel).  Bump tools can also do single wheel knurls like female diamonds or straight knurls (often used in press fits).  I do have two identical straight knurling wheels so I can straight knurl with the scissor tool even though it's usually a single wheel operation.  I use the straight knurls more often than I'd like to correct press fits gone bad due to oversize reamed holes, or undersize parts.

One time I whipped up a SS ring for my wife and used the bump knurler with only one diamond wheel to yield a sort of rope pattern on it.  The scissor tool wouldn't work here.

Thanks!
John


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## HMF (Jan 4, 2012)

Promoted to an article in the Machine Tooling section.


Nelson


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## 8ntsane (Jan 4, 2012)

John
Nice looking job you have done. The attention to detail,s makes your new knurler
look top notch. I see attention to details through out your build. I know most don.t bother, and you did!

Damn Nice Looking Job

8ntsane


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## jgedde (Jan 4, 2012)

Here are pics of steel and aluminum that were knurled with this tool...

John


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## Rockytime (Jan 6, 2012)

Here are pics of steel and aluminum that were knurled with this tool...


John, the knurls are beautiful. Very nice work.
Les


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## jgedde (Jan 8, 2012)

Oops.  I made a boo boo.  This is reallt a STRADDLE knurl not a SCISSOR knurl...

John


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## Tony Wells (Jan 8, 2012)

I wasn't going to say a word, John. :halo:


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## jgedde (Jan 9, 2012)

Tony Wells said:


> I wasn't going to say a word, John. :halo:



Hehehe.  Thanks!  

I had "Scissor Knurl" on the brain because this project started life as a Ti version of the scisor knurl in the latest issue of HSM.  Obviously, I abandoned Ti and the whole scissor concept and made a Straddle Knurler instead.

John


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## thanvg (Jan 1, 2016)

jgedde said:


> ....  In addition, it is autiomatically self centering.



Hi guys, sorry for resurrecting this ancient post but, if I may, could I comment on the 'self centering' feature? I did not come up with this theoretically, had to try my go on this straddle type tools, easily found out that self-centering is still an issue on this. Thinking about it I understand that, unless there is a pivot in the center of the vertical piece, self-centering cannot be achieved...
What do you say?


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