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knurling....

Janger

Janger

(John)
Administrator
Vendor
Knurling tools....newbie questions...

https://www.busybeetools.com/products/knurling-tool-holder-5-16in-x3-4in-x4-1-2in.html
basic...

https://www.busybeetools.com/products/knurling-tool-no-6.html
Multi head....

https://www.busybeetools.com/products/adj-knurling-tool-holder-no-9800.html
https://www.kbctools.ca/products/WO...LS @@26 KNURLS/KNURLING TOOLHOLDERS/1043.aspx
pinch type...

I see there are better versions on thomas skinner.
http://www.thomasskinner.com/default.aspx?page=item+detail&itemcode=KAR-180177
$448!

I have a 14x40 lathe.

I see there are also BXA or AXA tool holders with Knurling built in to one end.
https://www.kbctools.ca/products/WO...LS @@26 KNURLS/KNURLING TOOLHOLDERS/1043.aspx


I'd like diamond and straight horizontal patterns.

No idea what to get...
 
Bofobo

Bofobo

M,Mizera(BOFOBO)
My cheap china special, bump type seemes to do the job even on my bench top. Got it from busy bee and dont do enough knurling to justify bigger or better, when it ain't broke...!
 
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PeterT

Ultra Member
Premium Member
The push in style can be a bit hard on slender work pieces and/or softer metal because of the force applied (meaning you can warp the work). Although that's how I was taught on my SAIT plumb bob & center punch :) My thinking - its probably not that great for your lathe components. The tailstock center maybe not too bad, but regardless of a bigger 14x40 lathe, all that bump or in-feed force is concentrated on a very few thread surfaces of lead screw & nut. I don't have a number but I cant imagine ordinary or even heavy cutting forces to be anywhere that high. I don't relish the thought of prematurely wearing out the 'precision stuff' so I much prefer the scissor style.

One thing to watch out for on the scissors as they can have wheel axles that need to be pressed out. I find that to be a PITA actually & a bit of manufacturers cop out. Also some systems intend the pins to come out only one way so beware of a used ones where someone may have gotten rammy. I think EagleRocks are still like this http://www.eaglerockonline.com/

I bought this (Heavy Duty Adjustable Straddle Holder) NIB on ebay for decent price. Haven't used it a ton but works very well. Their knurl wheels are excellent & they offer many flavours.
https://accu-trak.com/holders_straddle.html

The KBC might be the same thing as Busy Bee = offshore clone of Eagle Rock. Busy Bee quality varies. They have some semi decent stuff & also some real bad stuff. I haven't used their scissors but have tried the knurling wheels & they were not the best. If you want to save $ & were a gambling man, consider buying the knock-off scissors after you are satisfied the action & quality is ok. Remove the stock axles, drill/tap for a set screw & make axles from hardened/ground drill blank with a slight flat/recess to retain them. Alternatively, there are lots of plans out there if you are game to make a knurler from scratch. I think the main features are good quality wheels with minimal play & tight scissor assembly that holds up under traversing feed.

A big part of knurling success is turning stock to specific diameter/tolerance specific to the knurl pitch. Without considering this, its amazingly easy to get crap results regardless of the tool. Think of it as roughly 2 gears (knurl wheel & stock) except one gear is deforming to a certain degree. Anyway, the hills & valleys need to line up around the circumference. Somewhere in my files I made a spreadsheet. But the calculation & correction factors are pretty simple & you can find them online.
 
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Janger

Janger

(John)
Administrator
Vendor
PeterT said:
Looks like I got the info off the accu-trak website when I made the spreadsheet. If some of you math savvy types want to check its correct, please let me know. I actually haven't knurled anything from it since my guess-and-oh-sh*t phase of knurling life
https://accu-trak.com/technicalinfo/blank_diameter_selection.html
Click to expand...

Great stuff guys thanks.

Peter - care to upload your spreadsheet?

Are knurls from China (eg the B.B. ones etc. ) Metric ? Do you need to turn your stock to a metric equivalent for those knurls? The one time I tried this on my old lathe I just got a mess of overlapping diamonds.
 
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PeterT

Ultra Member
Premium Member
I tried uploading my spreadsheet but looks like site doesn't allow that format. If you give me your email or can suggest another method, happy to provide. If you spot any boo-boos let me know so I don't goof my own pieces next time :)

You have to check the specs provided on knurl wheels, they do make both metric & imperial. I would guess a similar calculation but I haven't done that.
If t says TPI (threads per inch) or DP (diametric pitch) then Imperial. Metric... assume something like a mod#
https://accu-trak.com/knurls_stock_with_images.html
https://accu-trak.com/knurls_cuttype.html

I cant say on BB for certain, they list the holder as nominal Imp.
 
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PeterT

Ultra Member
Premium Member
Janger

Janger

(John)
Administrator
Vendor
Good video on knurling theory and technique. Starts out a little dry but I found it clear. I do disagree with him on one point - I think putting the knurl wheels inline with the axis makes sense with the pinch type tools. He also suggests putting a ‘big’ bite into the first pass - I tried that and it worked well this time. See pictures below. I decided ‘big’ meant 1/2 turn on the pinch knob corresponding to 20/1000” depth. EDIT: that’s reduced by a factor of 2 or 3 4 to account for the lever effect.
EDIT 2: no the lever is at the same
Location as the knurls so it is 20 thou.


I remade my millstop adjustment knob. Turned out better.

@Jwest7788 how can we post spreadsheets to the forum?
 

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Jwest7788

Jwest7788

Joshua West
Administrator
Really does look fantastic.

The easiest way I know to submit a spreadsheet off the top of my head is via a google doc, which has cloud sharing stuff.

I’ll look into more forum specific solutions in the morning though and will report back.


Sent from my iPhone using Tapatalk
 
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PeterT

Ultra Member
Premium Member
Janger did my spreadsheet help with the consistency of the knurls or is it still an iffy procedure?

I am no knurling expert that for sure. I don't do it often & still get hit & miss results as the video also demonstrates. My own personal view is its because there are other factors that come into play too even if the setup & dimensions are perfect, materials & tooling can have an effect. Some materials deform well (because that's what knurling is, as opposed to cutting), others don't. Some create shavings mung which the wheels chomp on & progressively messes up an otherwise good pattern unless you can keep it clean & lubricated. The air blast looked good. Some materials like stainless work harden which may self-limit the knurling depth. Might explain why my smaller pitch knurls are OK but coarser size is either incomplete or pattern problems & clamping pressure goes way up.

Some comments specific to the video, maybe you guys have input from your experience. I visualize the interaction of knurl wheel & stock is somewhat like spur gears. I know this is a rough analogy but here goes. In a perfect arrangement the gear teeth are meshing inside one another's OD's. You could say the theoretical pitch diameter is the diameter that each wheel shares. Now if you took this perfect, known gear arrangement & did a test: run the smaller gear (knurl wheel) on top of some blank stock with same OD of large gear, the teeth pattern would not leave a perfect coincident track. No surprise there, the gear teeth are running out of phase around the circumference because the pitch circles don't yet coincide. This can only occur when they are engaged. So I don't think lightly knurling on stock & observing the pattern proves anything. Its only when the knurl wheel is at its target depth does the math work out. That's part of what the (manufacturer) sizing calculation does by factoring the knurl DP (and some correction factors).

But now it gets interesting. With scissor type knurling wheels, you are not in-feeding a set depth amount like cutting stock or threading. You are clamping down, bringing the wheels together as they deform the stock & come to some equilibrium. I guess you could work out the screw pitch of the clamp thread & relate it to degrees of turn, but most do it by feel. Also the material diameter itself is enlarging as the diamonds are being formed. So lets say the perfect feed is 0.030". If you only crank to .020" theoretically tracking should be pretty good but incomplete formed knurls. Now lets say your stock was 0.005" oversize, but you cranked in 0.025" depth. That combination makes 0.030" 'equivalent' & you may have better looking knurls with a slightly off diameter to begin with. That's maybe the one thing going for the plunge-in knurlers - the cross feed is dictating depth vs. more vague partial crank turn on scissor type. So I think its still worth getting the diameter close to ideal & eliminating some degree of problems. If you choose to ignore it, sooner or later you will stumble onto a diameter/knurl combination that is hopelessly out of phase & no amount of cranking will help. Like trying to mesh spur gears with mismatched, incompatible teeth counts.

Well, I've got some knurly knobs to make myself, so we'll see if this 'armchair machining' comes to any fruition! :)

Happy Knurling & Happy New Year!
 
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PeterT

Ultra Member
Premium Member
Finally had to do some traverse knurling myself. This time I turned down the diameter using the formula related to chosen wheel pitch & it came out better than my prior duds. Not perfect, but better. Everything else remained the same, so I think there is merit to proper sizing. This was 12L14 steel.
 

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Janger

Janger

(John)
Administrator
Vendor

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