I have one of the current clamp knurlers from LittleMachineShop. Very similar to many that
can be found on the net. The shaft pins for the rollers are simply installed with snap rings
and they wear fast. Also there is a lot of clearance on the width of the knurl wheel housings.
I replaced the pins (all 4) with shoulder bolts. 1/4" cap screw type worked out perfect.
They seem to be a bit tougher than the pins and you can reduce the side clearance
of the wheels and the arms. This increases the rigidity of the knurling tool. Don't take out
all of that side clearance, leave just enough for a smooth action. You could also make some
shim washers to remove that clearance and continue to use the original snap ring shafts or
still replace the pins with shoulder bolts.
The shoulder bolts are 1" long with the shoulder being about 5/8" long. You need to grind about
3 threads from each bolt to provide as much clearance to your lathe chuck as possible. I also
grind a flat on one side of each bolt. Keeps it from turning when tighting the nut and provides
the needed clearance for the bolt head to fit the knurler's arms.
Buy extra shoulder bolts for replacements when these new ones wear out. I consider them
I would rather the wear was on the "pins" or shoulder bolts than the knurls. Pins and bolts are cheap knurls are not. Just sayin.
I have the same knurler and the same problem! What amazes me the most is the fact that I used the tool 15 times tops (3-4 times on freecutting steel and all the others on brass) and the pins wear out! I thought on making my own pins and then given those for hardening, but its time consuming and pricey! Your solution is by far the best. Unfortunately for me I can't find shoulder bolts (inch sizes) in Greece; only in metric that can't be used in any way, plus that if you want to buy shoulder bolts here you must buy the the whole box (100pc)!!!
Thanks for sharing
Last edited by Dimitris Polychronis; 12-10-2018 at 11:07 AM.
Dimitris Polychronis (12-11-2018)
Thanks for your reply! As for the hardened dowel pins, it might can found (I'm not 100% sure, because we use metric sizes here). For the set screw I'm afraid that might weaken the frame; the thick side at front of the frame is a bit less than 4.70mm (one hand holds the caliper and the other took the picture), so only a 2mm set screw can be put and the questions are: can the frame withstand the pressure? the set screw can clamp securely the pin in its place? Honestly I don't know!
All the best
Dimitris, I agree that there is not much material for a set screw but I think it would hold.
One other method would be to use a hardened dowel or drill blank or shank from an old drill bit.
If you have a dremel type grinder with the small abrasive discs you could cut a groove in each end
of the dowel and use a snap ring or external retaining ring on each end of the dowel. Some method to
prevent rotation of the dowel would prevent wear in the hole in the arms. Loctite or thread locker might
work if the end of the dowel is a close fit to the hole in the arm.
Hope this helps,
Dimitris Polychronis (12-12-2018)
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