First ever attempt at knurling...

T

TTD

Registered
Registered
Joined
Mar 28, 2014
Messages
131
Needed to knurl a piece of 6061 aluminum that measured .819” o/d (according to my knurling chart) x 1” long x 21P (medium) for a cocking bolt knob on an airgun project I’m doing. Never knurled a day in my life before, so I was a bit apprehensive on how I was surely about to mess this up. Have watched tons of videos & read lots of articles on the subject, but no hands-on experience…

Now, a smart fellow would chuck up a piece of scrap, turn it down to the correct diameter & make a few practice runs so he would have some clue what to expect, but not me….may as well learn on the fly!

As it turned out, I didn’t have any more 1” round bar left so was forced to turn down a piece of 1” hex to 0.819” o/d x 2” long. Then set up the scissor type knurler so only about ½ of the cutting wheels were actually touching stock at TDC & BDC. Tightened up scissor “snug-but-not-to-tight” & turned chuck by hand to see how badly out of sync the wheels were. To my amazement, they “seemed” to look ok so tightened it some more, had a smoke to calm my nerves & went at it. Ended up making 3 passes (tightening more each time) with lots of A-9 cutting fluid used. Speed was around 50-60 rpm & fed in with hand crank.

Overall, I guess I’m fairly happy with how it turned out to say it was my first time knurling, but still doesn’t look near as clean cut as the many photos I’ve seen here on the forum….there are some sweet looking ones!

(see pics below)
Maybe my wheels are not sharp or hard enough?
Too deep a cut? Not deep enough?
Quit buying Chinese crap? (guess that’s a no-brainer, huh?)
Any ideas on what I should be doing/looking for to fix this???

Just guessing here, and I know inexperience is playing a major role too, but I also think part of my problem could be the cheap (but all I can afford) Chinese equipment I’m using:

Craftex 7x12 mini lathe: http://www.busybeetools.com/products/lathe-mini-7in-x12in-1-2hp-cx-series-csa-cx704.html

Knurling tool: http://www.busybeetools.com/products/knurling-tool-for-mini-lathe.html

Pass #2 of 3
m_Crosman%20MK%20II%20PFT%20Bolt%20Knob%20012_zpsb1quqx1h.jpg


And no, the points on top aren't mashed beyond repair...o_O crappy light casting a weird shadow on work...points really are all there!
m_Crosman%20MK%20II%20PFT%20Bolt%20Knob%20015_zpsjytmlrqj.jpg

m_Crosman%20MK%20II%20PFT%20Bolt%20Knob%20027_zpsyjrej9yw.jpg
 
Last edited:
That looks real good to me, at least better than mine are.
You used cutting fluid but grease might be better.
 
Thanks for the tip! I will try that next time around :)
 
Crisco works well with aluminum. Stores at room temperature and can be applied with an acid brush. Stays in place.
 
  • Like
Reactions: TTD
Mike,
I thought the idea when knurling was to flush the chips away. Won't Crisco make them stick to the work?
 
Knurling is a forming operation not a cutting one. There are no chips.
Pressures are high on the metal and even if the rollers are super hard there is a lot of friction.
 
It is a forming operation but I would not use grease or a thick lubrication.

For harder materials you want to knurl in the least amount of passes as possible. You need lubricant to lube the pins & wheels. Since the forces are extreme with hard materials, the lack of lubricant & too slow of a speed may cause the pins to sieze.

On softer materials, the more passes you do, the more you will get flaking. Using lots of lubrication will help flush the flakes out. If they don't get flushed out they will get embedded in the material & you won't get a clean looking knurl. You can also get flaking with hard materials but you get more chances of work hardening first before lots of flaking with like aluminum.
 
I've never come across flaking when knurling, I must be doing something wrong.
Aren't there different wheels for different materials?
 
You must log in or register to reply here.
Back
Top