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hoffman
12-07-2004, 09:47 PM
Went to the shop for a smoke and before I knew it I was doing something. I got the QCTP mounted and did some turning and threading. Nothing in particular just putting the machine, and myself, through the paces. My post came with a knurler so I figured I'd knurl with it. Cheap, dull chicom wheels which make chinese ratchet knurls... Anyway I figured I'd fool with a scissors type that I got off the bay. Real sturdy cast iron deal with sharp wheels. Couldn't get it to track right. I figure it's gotta be the centering but all I could get was a double track no matter what I tried. Any suggestions?
I like my lathe...

------------------
Hoffman in Warner Robins Ga

JCHannum
12-07-2004, 10:05 PM
Knurls are like gears. They will cut evenly to a specific diameter. There are some fancy formulas some use to determine the proper diameter for a given pitch, or you can take a light cut and try again until a good profile is obtained. The genterline of the knurls should coincide with the centerline of the work, but eyeballing us usually sufficient.

vinito
12-08-2004, 12:01 AM
Made a lot of knurled parts at the last job. The place had a pretty seat-of-the-pants approach to knurling. If the print called out "medium knurl", we'd dig through the tool drawer and pick one out, hold it up to the light and make like we knew what we were doing, then experiment with the speed and feed until we got a consistently clean knurl.

The following factors were considered (by trial and error):
Rate of "plunging" into the material - sometimes creeping in, sometimes getting to full depth within one revolution of the stock.
RPM
Dwell - sometimes pulling out right at one full revolution of the material, sometimes dwelling for a couple seconds before feeding along the material.
"Depth of Cut" - pushing really hard or just hard enough.
We rapidly pulled the knurl away when finished if we were thinking straight that day.

Different guys had their favorite methods ranging from about 100 RPM with no dwell to slamming in at 3000 RPM and pulling away eventually (both extremes are, well, extreme). Basically you might be able to experiment with some of these factors until you get something purdy. Try different pitches of knurls too (we'd even try that if nothing else worked http://bbs.homeshopmachinist.net//wink.gif)

Allan Waterfall
12-08-2004, 04:46 AM
I've just knurled a piece of 1.75" OD steel bar.

I set the scissor knurls approx verticaly centred over the piece and centred horizontally.Put about 1/3 of the wheel width on the end of the bar and tightened the nut until I got a good knurl.Using plenty of cutting oil I then hand traversed at about 90 rpm.

I don't know if this is the correct way,but it worked.

Allan

Guero
12-08-2004, 07:49 AM
I've come to the conclusion that knurling might be more art than science. A couple of years ago I made a scissors type knurler per Rudy Kouhoupt's serialized instructions in HSM. I have three pairs of knurling wheels - fine, medium, and course and depending on the diamter of the work piece I'll choose which of the three pair to use. I usually end up doing what JCHannum says - if the first application is goobered up I'll take a fine cut on it and try again with the same wheels, knowing that the wheels will make a nice knurl at some point (without seriously reducing the diameter).

Randy
12-08-2004, 03:11 PM
<font face="Verdana, Arial" size="2">Originally posted by hoffman:
...I figure it's gotta be the centering but all I could get was a double track no matter what I tried. Any suggestions?

</font>

Centering isn't a big deal. Just eyeball it. Being a little off center won't affect how the knurls track, it will just put a little bit of side pressure on the workpiece, so centering is really important only for slender workpieces.

Are both knurls double tracking? If so, try starting more agressively (i.e. more pinching force.) You want to start by pressing the knurls deeply on the first turn of the workpiece, so there's a deep pattern for the knurls to drop into on the second turn. Then they will continue to track properly. If only one knurl is double tracking, they might be mismatched by a few thou. Measure them and stone the larger one down to match the smaller. That's what cured my double tracking problem.

Here's a fairly exhaustive thread which may give you some other useful suggestions: http://bbs.homeshopmachinist.net//Forum1/HTML/003139.html

jwaggs
12-08-2004, 03:54 PM
There was a recent thread on Practical Machinist about knurling (Nov 3rd). There is a relationship between the diameter of the work and the knurl wheels. If the diameter of the work is a multiple (or close) to the diameter of the knurls, knurling will work without overlapping. Otherwise the knurling overlaps and looks bad.

Lew Hartswick
12-08-2004, 06:58 PM
I've been "investigating" the field of knurling
at school lately. What I did is use the
coarsest knurls we had ( in a "bump" type ) to
be able to see the effect of diameter of work
to knurl. Turns out it's very repeatable and
perfectly locical. :-) They track right for
every increase in circumfrence equal to the
pitch of the knurl. The one I have developed
the info on is about .070" and the range of
diameters that will track is about +/- .004"
When I get all the points I want for this one
I am going to do it for the sizors type we
have with a medium knurl. It should make it
a lot easier for the students to get results
first time.
...lew...

Yankee1
12-08-2004, 08:29 PM
Hi
My knurls are 3/4" diameter and have 52 teeth. 52 divided into .750= .014" so the diameter of the stock I am knurling has to
a multiple of.014". Of course stock 3/4"
which is the same diameter of the knurls
comes out perfect.

vinito
12-09-2004, 12:30 AM
That's close, but we know what you meant. It will actually be more closely tied to circumference. C for 3/4" = 2.356". Divide that by 52 and you find your circumferences need to be a multiple of .0453".

Then you have to wonder if it's actually the diameter of the material, or the diameter that your knurl end up while it's into the material, or is it the average of the two or a percent of the "depth of cut", and what does the tracking do as you are feeding in (before you are to full depth), and is it the chord rather than the circumference, ad infinitum. I'm sure there has been a treatise done somewhere about knurling that tries to nail it down to a formula, but how much calculus comes easy for you? Fortunately, knurling is usually pretty forgiving and problems are less common than successes.

I think Guero is right - knurling is more an art than a science. Or in my case, more "fiddling around until it works" than art. My evidence is that one day you'll get a CNC lathe working consistently for a whole run, then the next time the job comes up, with a new batch of material and a knurl with the same spec's, the old way fails and you have to fiddle with it again before it works the way you want it to. I think the key is to isolate the factors and adjust one or two while leaving others unchanged. A little harder to do manually, but (at least in my experience) most times it just works OK the first time. Makes me wonder why some jobs cause problems every time while others are cake. :P

Yankee1
12-09-2004, 02:45 AM
Seems like I forgot to say .750X Pi=Cir / 52= amount per tooth on knurl.
Thank you Vinito

Joel
12-09-2004, 04:54 AM
Take a look here:

http://www.myrolypoly.com/users/Flashlights/Knurl_Tutorial.htm

A knurl diameter calculator:

http://www.myrolypoly.com/users/Taig/knurl_calc.php

kap pullen
12-09-2004, 08:23 AM
I've heard the theory on dia. vs tracking.

It may or not be true.

Frequently in the real (commercial shop) world, the drawing gives start diameters and finish knurl diameters that have to be adheared to.

I have knurled tapered belt pulleys on the 2 degree taper with no real problem.

I go in hard and fast, on the edge, as mentioned and have had no real problem with tracking.

I set the knurl with a little clearance behind the cutting/forming corners. Without this, it is hard to get full depth with the knurl.

I have knurled box machine pull rolls that are 5" dia by 100" long.

The inspectors for Ward Machine used magnifying glassed to assure the knurls went to a point and were clean.
The tolerance end to end was about .005"

You need plenty of coolant to flush out, and cool, the knurls for a clean sharp knurl.

We used soluable oil with a spout on each knurl. We made a huge scissors knurling tool for those parts. I ran about 120 rpm at .022"/rev feed.

Sometimes I leave the stock long so the start area can be turned away to make a nice looking job.

Good luck.

kap


[This message has been edited by kap pullen (edited 12-09-2004).]

Fred White
12-09-2004, 08:41 AM
&gt;&gt;I've come to the conclusion that knurling might be more art than science.

NO, IT'S WITCH CRAFT!!!!!!!!!!!!!!!!

ztarum
12-09-2004, 05:49 PM
I don't think the diameter matters at all. I've knurled a number a shafts and never had to adjust the diameter to make the knurl track. Here is how I do it with my scissors knurler.
1. Center the knurls.
2. Begin to tighten down while rocking the shaft back and forth (do not turn the shaft all the way around).
3. Continue to rock and tighten until the knurl looks deep enough.
4. Set the lathe is backgear.
5. Set the feed for 0.015".
6. Engage the clutch.
7. Now start the spindle.
10. Oil liberally as the tool moves along.

These directions are more less taken directly from the sheet that came with my Eagle Rock knurler. The only thing I added was to use back gear. I found that without coolant I was generating to much heat and ruining the knurlers "axles" if I tried to knurl in direct drive.
Also, the feed is key. The first time I accidentally seleceted 0.0015" and it was a disaster.
Give it a try. If I can do it, anyone can.

Z

CCWKen
12-09-2004, 07:09 PM
Oh boy, here we go again. http://bbs.homeshopmachinist.net//frown.gif

Some people will never learn. Keep doing your hit and miss method. Cram it in. Who cares any way? Even a blind squirrel finds a nut once in a while.

I have a pie. I'll cut it in eight pieces and give you half and I'll keep six pieces. That's about what your logic sounds like. http://bbs.homeshopmachinist.net//frown.gif

I can't believe some of you even use a mic. Close must be good enough for YOUR work.

Michael Az
12-09-2004, 07:22 PM
CCWKen, just go ahead and tell us how you feel. Well, what I can't understand is how a good knurl can be accomplished without doing the right diameter thing. It just stands to reason, if the diameter isn't right then when you make a revolution, the knurl tooth can't be in the right place. I wonder if the fellows that aren't doing the formula aren't just reshaping the part every revolution.
Michael

CCWKen
12-09-2004, 07:30 PM
Yep. You can tell who doesn't do the calcs. They're the ones flushing chips off the stock and buying lots of knurls. http://bbs.homeshopmachinist.net//biggrin.gif

vinito
12-09-2004, 07:47 PM
After all, all machining boils down to spinning knobs until the dial reads the right number. If it doesn't do what you thought it should, it's nobody's fault but the machine.
http://bbs.homeshopmachinist.net//rolleyes.gif

(p.s. Sarcasm, BTW. If it was that easy we'd call it "tiddly winks" and we wouldn't have the term "Master Machinist".)

[This message has been edited by vinito (edited 12-09-2004).]

ztarum
12-09-2004, 09:27 PM
Scoff if you will. I think the key to the whole thing is to engage the feed cluch so that feeding begins immediately upon turning on the machine. When this is done I have found that the diameter doesn't matter.

Give it a try. I'm not making this up.

For a non-feeding knurl, the diameter seems to be more important. I don't know why for sure. I think that probably the knurling wheel can slip more easily when feeding, making it easier to track on the grooves formed by the previous wheel.

JCHannum
12-09-2004, 09:59 PM
There is nothing wrong with the cut & try method if all you are making a pull knob. No sense beating yourself over the head when you can have it done in the time it takes to find and sharpen the pencil. If precision is required as Kap discusses, the calculations are required.

I felt guilty about cut & try until I talked to Rudy Kouhoupt at the NAMES show. He had just published the article for his scissors knurling tool and was demonstrating it. I asked how he got such clean knurls, and he said, if they are not right, just skin a little off and try again. I figure if it was good enough for Rudy, It's good enough for me.

CCWKen
12-09-2004, 10:20 PM
That's called trial and error. Mostly error. No need for a pencil either. Take two seconds to look at a chart and get it right the first time every time.

All I gotta say is you "Master Machinists" flushing and cutting away poor methods better never say another word about my Chinese tools. Obviously, you're out of touch. http://bbs.homeshopmachinist.net//biggrin.gif

vinito
12-09-2004, 10:46 PM
"If precision is required ... calculations are required."

If there's anybody here that's done alot of knurling, and the calculations get you there the first time, every time (like it should if that was all it took), then I'm all ears. I think there's more truth in the statement, "There is nothing wrong with the cut & try method". I'm willing to accept a new idea, especially if a little math can get you good knurls from the first part and on. I'm not a master machinist, but I've done enough knurling that I know from experience that a simple pitch per diameter equation by itself doesn't result in success. Indeed, sometimes the knurl that is a perfect fit in theory still double-tracks. What happens can likely be explained in an equation, but there are many variables complicating the matter, including the hardness of the material. It might not be quite as difficult as describing what shape a cloud will have 200 miles away, but there's an element of chaos here.

Note that I'm not saying relating the knurl's pitch to the diameter is a bad idea. But I am saying that that alone will not gurantee success. At best, it gets you thinking about what you're doing (also not a bad idea). If there's some math one can do to help make perfect knurls every time, I'd be into that for sure.

Test: What diameter do you consider for picking the "perfect" pitch? Is it the diameter of the un-knurled material, the minor diameter at the depth of the finished knurl, the raised diameter of the knurled material?

Lucky for us, the knurl has a tendancy to "find itself" once it gets going. Indeed that's likely the reason it turns out OK more often than not.

May knurtheos, god of displaced metals, smile upon you.

[This message has been edited by vinito (edited 12-09-2004).]

BillH
12-09-2004, 10:51 PM
I dont know what all the bitching is about, for the first time in my life,the other day, I took the knurling tool that came with my Phase II toolpost and decided to try it, eyeballed the center, had 300 something rpm, applied some cutting oil, and fed it into the workpiece. IT worked, cool, one more thing I can do on my lathe now.
Now I am getting ready to do some threading for the first time. I enjoy much more from learning by doing, then learning by reading and over analysing.

kap pullen
12-09-2004, 11:15 PM
Calculations are for panty wastes.

Just ram that knurl to that $200. or $500. piece of material and turn on the coolant, and the feed.

Haven't eaten one yet in thirty five years.

If precision is required, calculations are required...bull.

I'll have it done before most guys are done calculating.

What you have on the floor at the end of the day is what counts keeping the wife and kids fed.

Calculations don't make you anything.

kap

PS;

"Course I'm not running a sissy South Bend Lathe.

[This message has been edited by kap pullen (edited 12-09-2004).]

vinito
12-09-2004, 11:27 PM
"Arrrr! Damn the torpedoes. Full speed ahead. Git 'er done!"

That's more like it. Well said, Kap.

I've been pretty cranky today so I been holding back so's I don't say anything I'll want to edit out tomorrow. Now I can rest easy. Thanks.
http://bbs.homeshopmachinist.net//biggrin.gif

J Tiers
12-09-2004, 11:32 PM
What I think is that yer both right....

BUT

I think straight knurls ARE indeed like gears. I HAVE done the cut and try, and it didn't work. BUT with the calculation, it worked great. That's with straight knurls, which is all I have right now. I like them better, looks-wise.

BUT, I can see the point on "ram it in" also, IF you are talking about diamond knurls. Because, if you get the feed right, I suspect the knurls can accommodate some slippage or other adjustment so as to come out right, by following the previous cuts.

I'd bet that if you feed in slow, on the other hand, it will screw up, cut over itself, whatever. Not enough guidance.

But if you feed so as to get a nice deep knurl right away, the wheel might well follow, because its easier than cutting over itself IF THE KNURL IS DEEP ENOUGH to start with.

Makes sense to me, and sure explains the various opinions, if it's right.....

BTW, the "little sissy" South bends and Logans won't feed that hard with old-fashioned knurls. Not if you want to have them last very long.

hoffman
12-10-2004, 12:05 AM
Knurling is obviously too difficult to accomplish in my little backyard shop. I was a fool to even consider pulling off such a complicated machining process...
I'll just leave my knobs smooth and use pliers.
Anyone need a scissors type knurling tool? (I think you need to know a LOT of calculus and trigonometry to get it to work.)

------------------
Hoffman in Warner Robins Ga

[This message has been edited by hoffman (edited 12-10-2004).]

skeeter
12-10-2004, 12:24 AM
Hey Mr. Hoffman,

What brand is it and how much do you want for it?

I am interested.

e-mail skeeter@tiagris.com

hoffman
12-10-2004, 12:40 AM
Ummmm, Errrr...
I was KIDDING...

------------------
Hoffman in Warner Robins Ga

Allan Waterfall
12-10-2004, 04:55 AM
Perhaps I'm missing something here.....

I would have thought that if a given size of knurl will only work on specific diameters,then you would need specially made knurls for any diameters that do not meet the requirements of the knurls you have.

I only have one set of straight knurls in a home made scissors tool.

Allan

J Tiers
12-10-2004, 08:54 AM
<font face="Verdana, Arial" size="2">Originally posted by Allan Waterfall:
Perhaps I'm missing something here.....

I would have thought that if a given size of knurl will only work on specific diameters,then you would need specially made knurls for any diameters that do not meet the requirements of the knurls you have.

I only have one set of straight knurls in a home made scissors tool.

Allan</font>


All you need is for the number of knurl ridges to roll around the part and end up in a knurled groove again when the part has made one turn.

A small amount of thought shows that this happens at diameters separated by 1/pi the pitch of the knurl. So on the one hand there are a lot of diameters that work

On the other hand, if you get close to one, the knurl will probably slip in, you don't need it right to the nearest micron.

And, the depth of knurl will affect the efffective work diameter, so a little shallower or deeper and you could be right on the money.

Far schmarter shop folks than I have told me that straight ARE gears, but diamond can be fudged.

John Stevenson
12-10-2004, 11:52 AM
Utter drivel and a load of old $hittte.

That formulae setup was dreamt up by some armchair wizard who had nothing better to do with his time.

First off the theory is all wrong to start.
All this crap about D x pi / P = Nc is wrong because a knurl wheel is a gear and gears are made to mate on their Pitch Circle Diameters not the OD or the root so if you are using the wrong formulae how can you get a correct job.

I'll prove this two ways - first theory based on D x Pi etc.
Lets take a 2" bar and a knurl that has teeth measured 30 thou apart.

So 2" x Pi = 2 x 3.1416 = 6.2832"
Now divide 6.2832 by 0.030" [ the pitch of the knurl ] and we get 209.44 teeth.
Perfect we now have a doubled up knurl [ big fanfare etc ] but we havent taken into account the DEPTH of the knurl. You do need a depth don't you ?? it's not just etched on the bloody surface, so we will say that this 30 thou pitch knurl has a depth of 15 thou, that's on radius so it's a total depth of 30 thou on diameter.

So lets do the figures again using the root of the knurl, because that's where the OD of the knurl wheel will finish up.
2" - 0.030" [ the depth ] x 3.1416 [ pi ]
= 1.970 x 3.1416 = 6.1889
Now divide this by 0.030" [ the pitch ] and we get 206.30 teeth

So we have 206.30 teeth at the root but 209.44 on the OD
Three teeth difference, which proves the formulae is crap because at some point as you wind in you go from 209.44 to 206.30 teeth.
Metal is plastic and will 'flow', if you only had to go once round you would get errors but knurling is a continious rotating process and it levels out any differences, hence the three theoretical teeth.

Second method - practical.
Practical for anyone not fully understanding the word is defined by one having to get up off ones arse and go out into the workshop and get ones hand mucky.

Practical - a usefull word to remember.

OK first off this is a knurl test bar to prove the formulae is just an old wives tale.

http://homepage.ntlworld.com/stevenson.engineers/lsteve/files/knurltest1.jpg

This is just a steel bar about 1" in diameter with a skim taken off it to clean up.
Then just using the dials I have stepped this in 5 thou steps [ diameter ] so the start end is 25 thou thou smaller than the chuck end.

I have no idea what the diameters are and the steps are only roughly 5 thou steps. The idea is I don't need to know because it's not relevant.

Now starting at the small end we do a straight knurl and run up to the chuck, under power, same setting.

http://homepage.ntlworld.com/stevenson.engineers/lsteve/files/knurltest2.jpg

This is the finished job. You can see the steps.
You can also see that even though there are 6 different diameters of God knows what size all the knurls have come out good.

Now if thar formulae old wives tale was correct at least some would have come out cack handed but they haven't because going back to the theory buster the difference between ONE tooth is only 1/3 of the depth so at some point infeeding tou have to hit that and once you do the flow of the knurl will guarantee that it carries on.

Now can I get back and get some bloody work done ??

John S.

Evan
12-10-2004, 12:04 PM
He he... I had no idea knurling was a religion.

BillH
12-10-2004, 12:09 PM
Kap, Hey now, Sissy South bend?
Find a better 9" lathe for the average home shop guy. Theres a reason they are popular as they are.

John Stevenson
12-10-2004, 12:15 PM
<font face="Verdana, Arial" size="2">Originally posted by Evan:
He he... I had no idea knurling was a religion.</font>


It's not Evan, it's just that some people want to make it one for nothing better to do and propogate old wives tales.
Gordon Bennett !! a spreadsheet for a knurl - whatever next ?

I spoke to Allen Waterfall on the phone at dinnertime and he told me about this thread.
Ignore the date on the pics, it's my daughters camera, I did that test bar about 1/2 hour ago.
It took longer to type that bloody reply than do the test bar.

Evan
12-10-2004, 12:30 PM
So John, cut some reliefs at the steps and harden it up and you have a knurl broach...

J Tiers
12-10-2004, 01:11 PM
<font face="Verdana, Arial" size="2">Originally posted by John Stevenson:
Utter drivel and a load of old $hittte.

</font>


If its a load of **** then why did my straight knurls LOOK like **** for me until the diameter was got close to the "right" size?

(NOTE: See my idea below before "going off" on me......)

At the "wrong" diameter (where I started, of course), it re-cut, split the tips, made chips fall off, etc, etc, etc. It was ****.

At the "right" diameter, it worked so easily that it was silly. Just went right on and didn't cause the slightest trouble. Made me wonder what the big deal was.


Now, mind, this was on a SMALL DIAMETER, about half or 2/3 of the KNURL TOOL diameter. The difference in diameter between "pitch steps" was quite noticeable.

AT LARGER WORK SIZES, the diameter difference between "steps" would be so small that the knurling depth would eat it up.

Sorry John, Most of the time I find you are universally right.

THIS time I think you are PARTLY right.

At small diameters I believe you have to consider the "steps". At larger diameters, I think it would not pay to worry about it.

John Stevenson
12-10-2004, 01:46 PM
No JT it still applies.
OK so we take your smaller sizes, 3/8" Ok ??

So 0.375 x pi = 1.178" now take into account you want a finer knurl on this for looks so we'll say 20 thou pitch, thats 58.9 teeth

Again taking a depth in this case 10 thou, 20 on diameter we get a root figure of 0.355 x pi = 1.115" or 55.75 so again we have these three transition teeth.

When you start a knurl and get this doubling up it means you haven't reached a diameter that allows a full tooth.

I can see some sense in someone working to a formulae that took the PCD into account and not the OD but the truth is it's not really nessesary.
Think about it, you are working a diameter out based on the od of the knurl [ the pitch ] and the OD of the work but the OD of the knurl then finishes up at the root of the work which isn't in the formulae so you may as well grasp any figure.

Now if you were working to the PCD and only fed into the PCD depth it would be different but NONE of these armchair wonders have come up with that formulae.

With a scissor knurl as someone said you may not have matched knurls, in which case you could be wasting your time.
Often though it's a lack of pressure that allows the two wheels to generate different tracks.
More pressure or back off spin one wheel and retry to see if it follows it's mates track is a good dodge.

John S.

andypullen
12-10-2004, 02:25 PM
<font face="Verdana, Arial" size="2">Originally posted by BillH:
Kap, Hey now, Sissy South bend?
Find a better 9" lathe for the average home shop guy. Theres a reason they are popular as they are.</font>

I have to agree with Kap on this one. I only do knurling on the Monarch or Lodge and Shipley at work. Knurling puts ALOT of pressure on your bearings. The scissors type is easier on the machine, but it still puts alot of force on things. I've had parts come out of the 3 jaw chuck when knurling. I only do that operation with the 4 jaw chuck and a center in the other end. Usually, I'll put Forrest's "grip of death" on the part prior to doing any knurling.

Bill, you're right, the 9" south Bend is a nice machine for a home shop, but it really is wimpy compared to industrial equipment. I have a 14 1/2" SBL and I'm really not happy with it. Give me a Monarch or a LeBlond or a Lodge and Shipley or an American Pacemaker any day.

And, I've run knurls by trial and error for 23 years and haven't scrapped any either. Skip the formulas.

Andy Pullen



[This message has been edited by andypullen (edited 12-10-2004).]

Evan
12-10-2004, 02:43 PM
The SB9 has plain bearings so the side load issue isn't such a biggie. One of these days I do plan on making a scissor knurler though.

DR
12-10-2004, 02:45 PM
Yikes, I hesitate to even get into this quick sand. What is it about knurling that brings out all the varied (wacko) opinions?

Two points,

We do high quality knurls on expensive parts using opposed knurling tools (scissor type and other opposed wheel type) with no reject parts, maybe one or two setup parts to determine knurl depth. We don't look at charts or do any calculations.

There is some validity to the calculating of diameters and pitches and other such nonsense. It has to do with high production knurling with single wheel bump knurl tools where the number of part revolutions to complete the knurl is a factor. This has no relationship to what the average home or low production shop does.

J Tiers
12-10-2004, 04:50 PM
<font face="Verdana, Arial" size="2">Originally posted by John Stevenson:
No JT it still applies.
OK so we take your smaller sizes, 3/8" Ok ??

So 0.375 x pi = 1.178" now take into account you want a finer knurl on this for looks so we'll say 20 thou pitch, thats 58.9 teeth


John S.</font>

Nope, smaller.

I think this was in the 1/4 area, using a SINGLE wheel straight knurl. So no second wheel to mess up the job

I had almost surely less than 58 teeth on the part, more like maybe 30 IIRC. There might have been that many on the KNURL.

The feature was for a grip, it was a small cap, so fine knurls were not desired. Actually a replacement cap for the metal tube/wrench holding a set of small transfer screws.

I'll count up when I get back to the shop. We'll see if I remembered right.

But, as I said, it worked as calculated perfectly, BASED ON THE KNURL PITCH, not the OD.

It didn't work previously, several tries. If the part had been an inch or two, it would probably have worked any old way just as you folks say.

Andrew
12-10-2004, 05:58 PM
Hey John, have you ever thought of co-starring on Myth Busters? I think you've pretty much busted this myth.

Andrew

gglines
12-10-2004, 06:03 PM
My experimentation agrees with John S. and I have played with knurling quite a bit in my home shop. I use a scissor syle knurler in a South Bend Heavy 10.

I tried experimenting with different diameters with both straight and diamond knurls after reading, "How to Knurl". The book is crap.

The diameter never mattered in my experiments, the knurl is so loose on its pin, I don't see how it could. High knurl pressure gives me a good knurl no matter the material or diameter. YMMV.

George

Yankee1
12-10-2004, 10:19 PM
Hi
I'm thinking if the knurl is not tracking in the groove then maybe we should call it
swaging knurls by rearanging the teeth.
If after one revolution the teeth previously knurled are being recrushed by
being struck in different places swaging would be a proper term I believe.

spope14
12-10-2004, 10:47 PM
OK, here it is, my method for teaching scissor knurls. I can do this right 99% of the time. It is an art, and this method has withstood 12 years of teaching and scrutinization. You have to follow carefully as I flail through this.

I call this my fore - back - fore to tangent method.

1. Set the knurler with the pivot point at aproximate center of the machine / part height.

2. Open the clamping nut way up.

3. Start at the far right end of the part.

4. Set RPM to aprox 190 RPM. many will think this fast, but it works, you will se why later. Set feed to aprox .025 per rev (40 TPI also works), or your fastest feed rate.

4. Close the knurler totally up by hand, not with the nut. The nut should be plenty open.

5. Move the knurler over the part diameter, this "opens" the knurler. Move th knurler using your X axis handle (crossfeed dial handle) by hand, machine stopped. Watch BOTH the bottom an top wheels. Move the knurler until it is open all the way, the wheels at tangent points to the part. GO BEYOND center until the whels stop. I suggest about 1/4 inch beyond center. The knurler wheels are now on the opposite side of the part from the operator. This is the first "Fore" movement. DO NOT CLAMP OR TOUCH THAT KNURLER.

6. Bring the knurler BACK towards you. Watch as both wheels contact the part very slightly, both moving at once at the tangent points. keep going back to you beyond the tangent point, the wheels stop turning. Aprox 1/4 to 1/2 inch beyond the tangent point towards you. DO NOT TOUCH OR CLAMP THAT KNURLER. Your backlash is also the wrong direction at this point. This is the BACK" movement.

7. Now the final "Fore" movement. Move the knurler back to the part, watching the top and bottom wheels carefully. Move in slowly, never moving back towards you - like setting backlash - this is important, for most knurls are ruined by backlash - the #1 problem. One wheel will contact the work, then the next will contact the work. When both move at ONCE, STOP!!!!!!!!

8. Tighten the knurl clamping nut by hand, really tight hand tight.

9. Tighten the nut with your wrench 1/8 to 1/4 turn.

10. Turn on the machine for a few revolutions, check the quality. It may be doubling, but only a "skin" doubling. Clamp in very small increments (1/8 turns) until it gets a good looking but not too deep knurl. YOU MUST HAVE CUTTING FLUID applied liberally at this point to the knurler, or little chips off the metal will run through the wheels and cause issues such as gumming, eating the knurl, or incorret 'set".

11. When you get the knurl looking good, turn on the machine and feed the knurler. you do NOT want a great ammount of pressure on the initial or subsequent knurls, because scissor knurlers tend to "shift" and move laterally due to leverage, and will "dig" or move away. Your last "fore" move prevents backlash issues. Run the part to the end, but do NOT run the knurler off the end or remove the knurler.

12. Add a bit more clamping presure if your knurl is not quite deep enough, check with turning the machine on for a few revolutions. Feed the knurler back to your starting end. Easiest way is to run the spindle in reverse.

Should only take two passes, one to headstock, one back. Sometimes three. Too much pressure early on will cause shifting as mentioned, and also chip buildup.

During knurling, always keep a good ammount of cutting fluid going on the wheels for cooling and chip flushing.

I use a 190 speed and a high feed to help flush out the chips out the back end of the knurler, an to prevent heat build up and "dwelling" issues that also ruin knurls.

Just remember - tangent points, no baklash, move fore (to the part and beyond center), back (to the operator, and beyond center), and fore - back to the part to find the common tangents of the wheels to the part).

actually, only takes about ten seconds or less to do this. a proven method, would love it if I could do a movie, it would be easier.

CCWKen
12-10-2004, 11:48 PM
Geez! My head is going to explode. http://bbs.homeshopmachinist.net//eek.gif
The calcs have nothing to do with the diameter of the knurls. The knurling wheels could be any size and they usually are.

What counts is the pitch of the teeth on the knurls. And for crying out loud, I've never seen a knurling wheel with "58.9" teeth. (Or 66.4 or 38.6 or ....) http://bbs.homeshopmachinist.net//rolleyes.gif

Some of you guys just don't know the difference between a repetitive best guess lucky half-ass sloppy chip flying knurl wearing job and one that can give you a perfect knurl with no chips. It doesn't take rocket math or 12 steps. If you're flooding chips away, you're abusing your tools and getting crappy looking knurls. You just can see it. http://bbs.homeshopmachinist.net//frown.gif

I have 4 different knurls. (Fine, Medium, Course - Diamond and Medium Straight) I use the size knurl that looks the best on the item to be knurled. You slop-jocks that put course knurls on a 1/4" rod deserve what you get. But of course, looks don't mater to you.

CCWKen
12-11-2004, 12:00 AM
Oh man. I could never paint a car for you guys. A "good" paint job to me is when you can read steet signs down the block in the reflections.

Some of you must think a paint job is good if it covers the rust. http://bbs.homeshopmachinist.net//frown.gif

J Tiers
12-11-2004, 12:49 AM
<font face="Verdana, Arial" size="2">Originally posted by CCWKen:
I use the size knurl that looks the best on the item to be knurled. You slop-jocks that put course knurls on a 1/4" rod deserve what you get. But of course, looks don't mater to you.

</font>

Since that is directed at me, I will say NO THEY DID NOT. The knurl was for function, as in gripping a small cap. The final knurling has been quite functional, thank you very much. Looks nice too.

When it didn't knurl right it was non-functional. If that is what I deserve for not meeting YOUR criteria, tough luck, pal.

You ain't me. Your opinion on desirability of a particular knurl visually is of less than no consequence to me when I want function.

John S' opinion counts for something here, as he is addressing factual matters.

Anyhow, it WAS about 3/8, 35 knurled "teeth". The single-wheel knurl has 70 teeth and is 3/4 in OD.

The knurling did NOT go right until the cap was turned down a bit, to what I figured to be a good size based on knurl pitch. I don't remember any of those numbers now.....



[This message has been edited by J Tiers (edited 12-11-2004).]

vinito
12-11-2004, 01:05 AM
"a repetitive best guess lucky half-ass sloppy chip flying knurl wearing job"

ROFLMAO
(and shedding tears)
Man, you're killing me. http://bbs.homeshopmachinist.net//biggrin.gif

CCWKen
12-11-2004, 01:28 AM
No, I wasn't taking aim JT. I just had this vision of chips flying off a small diameter rod with "jammed-in" knurls. Now that you mention it, I've put course knurls on small screws myself. Function does take the front. There's some items that just don't look right with any knurl. It's like wearing brown pants with a green shirt. http://bbs.homeshopmachinist.net//biggrin.gif

By visual preference, I guess I mean that the knurl looks good and clean. Not all chopped up. It IS easy to see, and feel, the difference.

Forgot to mention:
All of my wheels were sold as "3/4 inch" wheels but NONE of them are .750. They all very by as much as .008 between the TPI's. That's what I meant by the wheels can be any size. It's the TPI that matters (pitch).

[This message has been edited by CCWKen (edited 12-11-2004).]

John Stevenson
12-11-2004, 07:32 AM
<font face="Verdana, Arial" size="2">Originally posted by CCWKen:

What counts is the pitch of the teeth on the knurls. And for crying out loud, I've never seen a knurling wheel with "58.9" teeth. (Or 66.4 or 38.6 or ....) </font>

Missed the point. It's not the knurls that have 59.9 teeth but the diameter of the work if you use the formulae stated.


<font face="Verdana, Arial" size="2"> Some of you guys just don't know the difference between a repetitive best guess lucky half-ass sloppy chip flying knurl wearing job and one that can give you a perfect knurl with no chips. It doesn't take rocket math or 12 steps. If you're flooding chips away, you're abusing your tools and getting crappy looking knurls. You just can see it. </font>

No can't see it 'cause we're using flood coolant http://bbs.homeshopmachinist.net//biggrin.gif http://bbs.homeshopmachinist.net//biggrin.gif
No flood cooolant ??
So 99.987643267 % of commercial machines that produce nearly 100 % perfect parts don't need flood coolant ?
Then why the hell do they sell then cased up in big tin boxes with windows in ??


<font face="Verdana, Arial" size="2">I have 4 different knurls. (Fine, Medium, Course - Diamond and Medium Straight) I use the size knurl that looks the best on the item to be knurled. You slop-jocks that put course knurls on a 1/4" rod deserve what you get. But of course, looks don't mater to you.

</font>

Not always relevant, often a drawing calls for a certain size - do you know better?
I do a lot of straight knurls and they have to be to a finished diameter and straight, no wander at all.
These are for electric motor rotor shafts and if you get any spiral on the knurl as it's pressed into the laminated rotor it rotates the laminations and it's scrap.
In my case my OD is determined by the size of the hole in the rotor. I can't alter this to conform to some ear of bat, tongue of newt formulae, it's written in stone.
On top of this I have to get a perfect knurl.
manufactures have been doing this for ages with no problem.
I can replicate this, again no problem so why do we need this armchair knee jerk to a problem that experiance will overcome.

Many people have trouble parting off and getting a taper on their work.
Wheres the formulae for that ?? - Don't exist it's called experiance and what one person does may not work for another.

I have said many times that there is never a defined right and wrong way to do a job, just many different ways.
You do what works for you.

John S.

DR
12-11-2004, 10:17 AM
Regarding cutting fluid use when knurling. FormRol Company where I occasionally buy knurls has repeatedly told me fluid is not needed when knurling. I use a squirt before the knurls hit the workpiece only to lubricate the knurl axles.

If you're washing away chips in the process something's wrong, unless you're using cutting knurls. Normal forming knurls shouldn't make chips.

John Stevenson
12-11-2004, 01:36 PM
Fluid IS NEEDED.
Knurling is a forming process and as such requires a lot of pressure to be applied to the work.
Hence the posts on using lightweight lathes for this process.

Because pressure is needed to form the knurl into the parent metal heat is generated.
This shouldn't come as a suprise to anyone.

Attempting to knurl anything but the smallest length without some form of fluid to lubricate the pins and keep the wheels cool will result in disaster.
If a wheel picks up on it's pin it will shave the knurl off.
It far more common than a lot of people think. I have bought many knurling tools in job lots where they have been siezed solid or show past examples of it.

OK flood coolant is possible extreme unless you are setup for it but the wheels do need something to lubricate them and keep cool.
If you are setup for flood coolant, tray and pump etc then it's easier to use this than an oil can or brush.

DR has stated that ordinary knurling doesn't produce chips, true it shouldn't as it's a forming process but the very action of running the knurl and work together will produce some amount of chips.

Image two gears running together, if geometrically correct they will run with minimum clearance due to thir design which is based on an Involute profile.

Now imagine the work and hardened knurl wheel running together. This will have straight sides at about a 60 degree angle as there will be interfearance as it rolls into and out of the work.
This action because it is not of an involute profile will rub and create chips to some extent.
The courser and deeper the knurl, the more chips are generated and this is why it's recommened to wash away to stop them getting roled back into the work.

John S.

[This message has been edited by John Stevenson (edited 12-11-2004).]

Shuswap Pat
12-11-2004, 09:05 PM
Knurling - If all else fails- push like hell! Slow speed, lots of feed, lots of cutting oil! This is for "Push Knurling".

We use a 'Cut Knurl Tool' for (relativly)large diameter feed rolls - 8" - 16" Dia. Even with these we don't have to calculate the diamter. Once it makes a revolution or two the cutter will find the 'Pitch Line' and cut a good pattern.

Pat

spope14
12-11-2004, 09:56 PM
Nobody ever asked HOFFMAN what type of knurler he has. Aloris makes a tool called a scissor knurl that really is not, and it is hell to center and set right. I am using "Eagle rocks", but also have an old J&L shop type thing. I also saw a scissor knurler that was only a crazy adaptation. I mention this because if it is not a true scissor knurler, then methods will vary widely.


I stand by my post. Little chips develop whn knurling soft steels, resulphurized steels, brass, and aluminum. Cutting fluid is a must to flush out these little chips (better described as flakes) or they gum up a bit. The cutting fluid also makes a better "press" in the part due to less presure over an un fluided surface as cutting fluids are used for three reasons : heat reduction, lubricating cutting edges and machined surfaces during the cutting action, and chip flushing. Knurling is no exception.

The length of the post was not to explode ones head (then again, maybe so), but to be detailed for a new person.

Machining is an "Art". There are many ways to do a single thing, and that is what I love most about this stuff. I do not let the varied opinions get to me, and actually look forward to reading the many ways things can be done, and sharing when possible my methods. This is what makes us better.



[This message has been edited by spope14 (edited 12-11-2004).]

Thrud
12-11-2004, 10:04 PM
John S

Many moons ago we had this discussion (again...) and I posted the PCD formulae for knurls - I won't do it again - they can be looked up in "The Handbook for Metalworking Industry" or "Machinery's Handbook".

Guys - do some searches on past posts first - there is a tonne of information on the BBS http://bbs.homeshopmachinist.net//biggrin.gif

Merry Christmas! http://bbs.homeshopmachinist.net//smile.gif

Thrud
12-11-2004, 10:17 PM
DR:
Your supplier is misinformed.

John is 100% correct in saying coolant or more accurately a high pressure lubricant/cutting fluid is required for proper operation. The metal DOES flake sometimes and metal is removed from the process and that **** DOES interfere with the rollers operation AND they can seize up and ruin the work. And tremendous heat is generated in the forming operation as John has stated - you are work-hardening the metal.

I prefer cutter type knurls - less stress on the lathe and much faster. Downside is cost - ouch!

DR
12-12-2004, 10:42 AM
Thrud,

A search of a couple knurl manufacturers sites gave good info on knurling. Formrol and Accutrac (sp), I believe were ones I visited.

Their mention of cutting fluid/coolant was to lubricate the knurl axles. They make no mention of it having anything to do with the forming process.

As I said in my previous post regarding this, we program a squirt of fluid onto the knurl head prior to engaging the work. This has proven to be satisfactory in our part runs where the part totals may in the thousands. Materials are brass, 316SS, mild steel and aluminum. Aluminum is the material that gives us the most headaches, flaking is the major problem with this material.

With all our knurling, the best results are by being aggressive, high feed rate, form the knurl fast in a single pass and get the tool off the work rapidly. Never allow the knurl to be in contact with the work for more revolutions than is absolutely needed to get the job done. I don't recall ever feeling the knurl temps mid-run to see if they were heating up. I have to assume they aren't doing more than mild warming on long runs since the squirt of liquid we give doesn't cause a burst of steam as it hits the knurls.

As far as this subject goes, I know what works for us in our production work. It may not work for others, but it's worked well for us.

CCWKen
12-12-2004, 10:25 PM
And... I'll keep doing what works well for me. http://bbs.homeshopmachinist.net//biggrin.gif

Merry Christmas to all and to all a good night.

J Tiers
12-12-2004, 11:09 PM
<font face="Verdana, Arial" size="2">Originally posted by CCWKen:

No, I wasn't taking aim JT.
</font>

Ok, no problem then. My mistake, sorry.

BillH
02-18-2005, 08:48 PM
<font face="Verdana, Arial" size="2">Originally posted by John Stevenson:

OK first off this is a knurl test bar to prove the formulae is just an old wives tale.

http://homepage.ntlworld.com/stevenson.engineers/lsteve/files/knurltest1.jpg

This is just a steel bar about 1" in diameter with a skim taken off it to clean up.
Then just using the dials I have stepped this in 5 thou steps [ diameter ] so the start end is 25 thou thou smaller than the chuck end.

I have no idea what the diameters are and the steps are only roughly 5 thou steps. The idea is I don't need to know because it's not relevant.

Now starting at the small end we do a straight knurl and run up to the chuck, under power, same setting.

http://homepage.ntlworld.com/stevenson.engineers/lsteve/files/knurltest2.jpg

This is the finished job. You can see the steps.
You can also see that even though there are 6 different diameters of God knows what size all the knurls have come out good.

Now if thar formulae old wives tale was correct at least some would have come out cack handed but they haven't because going back to the theory buster the difference between ONE tooth is only 1/3 of the depth so at some point infeeding tou have to hit that and once you do the flow of the knurl will guarantee that it carries on.

Now can I get back and get some bloody work done ??

John S.

</font>


Hey John, just wondering, Was the knurl ran across the stepped workpiece at the same depth?


[This message has been edited by BillH (edited 02-18-2005).]

Lynn Standish
02-18-2005, 11:31 PM
I'm an amature with very little experience, so I won't claim to be an expert. I will say this:

I read a few posts here and there about knurling, and came to the conclusion that the scissor type was best for my toy 7 x 10 lathe that I got to try and learn basics on. I got one, and adapted it to work on the toy.

Then I got a 13 x 40, and it worked on that one also.

Bottom line is that I've never had double tracking or any of that crap, regardless of the workpiece diameter.

I think you're killing us with science on this. If the diameter of the un-knurled workpiece is X, the diameter of the finish knurl at the bottom of the knurl is X - d, so at some point, the pitch of the knurl won't be a multiple of the diameter of the work.

Take a scissor type knurl, eyeball it to vertical and horizontal center of the work. Lock everything up and tighten the adjustment nut on the tool SIGNIFICANTLY, turn on the lathe to a fairly slow (125 RPM?) speed, and hand feed it SLOWLY left and right until you have the area you wish to knurl covered. Stop the lathe and look without taking the tool off the knurled area or loosening it. Check to see if the knurl is full depth. If not, tighten the adjustment nut on the tool some, fire up the lathe again and traverse by hand left and right, shut the lathe down, and check again. Don't let the knurl wheels off the work until the knurl is full depth. If you tighten the adjustment nut right, you can do the whole full depth knurl in one pass.

As I said, I don't know squat, but I don't believe this is a problem, particularly if I don't have a problem. If there's a problem out there, I'll find it.

kap pullen
02-19-2005, 12:01 AM
John,

I agree with you on this one old buddy!
You push it in far enough, it's bound to hit the correct diameter somewhere.

Lots of coolant flushes off the slivers that make a crappy looking knurl job.

Are we allowed to use the cr---- word here?
Sorry!

I got chewed out for using the pr--- word somewhere else.

By the way, I don't think South Bends are crappy. You South Benders made a big investment of household gold and should treat it with care and respect.

Just as Andy said, not built for heavy, or light knurling. Get a pinch knurl and save your lathe.

I'm just spoilt! I have two Monarchs in my custody at work, and a Pratt and Whitney at home. I'd never knurl anything on my jap lathe except with the pinch knurl.

John,

Is Birminghan close to Nottingham?
I may have to go over to the motherland for a week or so to do some job for NASA at some university. Don't know the details yet.

Boss just asked if I would be willing to go today. I said sure I love England. Lots of steam stuff over there.

The tech over there got ill and had to come home. He's just a cnc machinist anyway.

Maybe we can share a kidney pie?

Sorry about the shield picture. NASA liked those so much we outfitted six Bridgeports and clones with them. I got a bonus for that Idea and design.

Kap

happy02
02-19-2005, 12:28 AM
Hell I wish you'd told me 15 years ago that I couldn't knurl because I don't have a 6500 pound machine.

zl1byz
02-19-2005, 01:12 AM
This post is like a phoenix out of the ashes. Wow, I thought it was dead and buried. http://bbs.homeshopmachinist.net//smile.gif
I'm with John S and others on this one. I had not heard of the nead to do calculations for knurling b4 this and it's never been a problem. I'd screw up the calculations anyway, so maybe ignorance is bliss on this one. http://bbs.homeshopmachinist.net//biggrin.gif

John.

John Stevenson
02-19-2005, 05:00 AM
Bill H,
Same depth all along. If a formula was needed it would alter the pitch as it moved from step to step.

Kap,
Birmingham is about an hour away from Nottingham.
Just south of Brum is the M42 motorway, this links up to the M1 at junction 24.
We are about 4 miles from that junction.

John S.

Norman Atkinson
02-19-2005, 06:13 AM
I cannot see what all the fuss is all about.
A set of knurls has a fixed circumference and in that there are a number of teeth of a fixed width. They go over the job which has a fixed circumference- and if they don't meet exactly= there is an overlap- and a botched job.

For those who claim that they have no problems employing the S*** or Bust Method, they turn off the b**** up job and re-knurl it on perhaps a suitable circumference.

Tooth Fairy

John Stevenson
02-19-2005, 06:29 AM
<font face="Verdana, Arial" size="2">Originally posted by NORMAN ATKINSON:
I cannot see what all the fuss is all about.
A set of knurls has a fixed circumference and in that there are a number of teeth of a fixed width. They go over the job which has a fixed circumference- and if they don't meet exactly= there is an overlap- and a botched job.

</font>

Norman see the pic above with the stepped shaft. Same knurl so same pitch or tooth width but the OD differs and no overlap.

Your anology doesn't work as there is NO fixed circumference.
You actually have three different diameters on a knurl.
The OD, the root diameter and the pitch circle diameter.
When you start off the knurl teeth are on the OD but finish up on the root diameter so what diameter do you calculate on ?

John S.



[This message has been edited by John Stevenson (edited 02-19-2005).]

Norman Atkinson
02-19-2005, 08:03 AM
Thanks, John
Obviously, all you can do is to do the calculation on the OD. I looked very carefully( after a night on the booze) the various examples knurled.

There is one factor which emerges and that
the depths of cut don't seem to be the same.

It may mean that I need a new monitor or more Ibuprofen but if the depths of cut vary, the circumference changes to a exact number of teeth.

Probably the ideal test is to do the test again- but with something like a gear cutter with fewer teeth.

Must sign the pledge- must sign the pledge!!!!

Hic!

spope14
02-19-2005, 12:37 PM
Oh man, this comes up again just like bad mexican food.......

I printed this out and tried all the calcs and such, an my head was going to explode as noted by another.

Question, can you regulate depths on a scissor knurler, and how? Tried indicators on top, put at 1/3 tangent and used th dial, heck even went DRO balistic. FCut diameters to 1/14 increments for my 14 TPI knurlers, such on and so forth.

Knurling is a learned art. had my best success with my method, but was able to hold diameters using both experience and calculations.

What i like about this board so much is that you can find so many ways to "skin a cat", and it is so fun to try using the experience of others. Actually, with this subject coming up again, it is kind of good as it gives a chance to note the great experience on the board, and our collective dedication to craftsmanship and our differing views and methods (though sometimes a bit onrey at that).

keep these type of posts coming, they make me a better teacher!!!!!!

J Tiers
02-19-2005, 10:37 PM
OK, I'll bite.....

If the various different diameters have exactly the same knurl pitch and depth and all have fully formed "teeth", with no flaking, there is maybe something funny going on. There is some metal unaccounted for.

If John S kept the same POSITION OF THE CROSSLIDE over the whole length, I believe it 100% that all were made at one setting etc, etc, etc.

In fact I'll agree that THE DIAMETER OF THE PART MAKES NO DIFFERENCE.

But....how about this..........?

THE RADIUS AT WHICH THE KNURL IS POSITIONED MAKES A DIFFERENCE.

The "imaginary" surface at the "pitch diameter" of the knurl, if not on one of the "good spots" might not come out right.

But, there is no law that says there has to be metal there...so a part NOT at right diameter can be knurled evenly if the knurl is set to the right diameter from part centerline.

The knurl might be incomplete, or the knurl might be "overcomplete, so that it flakes off some. But it can be made evenly around the part....and may look OK.

Its a reasonable theory, and it seems to explain everything that everyone has said.

It accounts for "flaking sometimes".

It allows different sized parts to be knurled Ok and shows why diameter isn't a big deal.

BillH
02-19-2005, 11:39 PM
Ok, so the depth of the knurl changes so you dont get overlap, where people are getting hung up on is if they want the same depth knurl cut on different diameters.

pete913
02-20-2005, 05:26 AM
You guys are givin me a headache. I've never used a scissors type knurling tool, at home or at work, and I've knurled quite a bit of stuff with several kinds of bump knurlers on whatever diameter, and never had the slightest problem getting a perfect knurl with any of them, including my el cheapo phase 2 bump knurler at home. I'm not flushing chips off, I get perfect points, blah blah blah. Go out and do it, and save reading the damn handbook for after supper. As to getting a knurl to a perfect size, I'm sure the stock diameter would make a difference in that case, but I've never yet had a bump knurler double track on me, on any diameter. On a decent lathe, I don't see any burning need for a scissors knurler, and I've yet to see one in a commercial machine shop. Maybe theres good reason for it. People that seem to think knurling is abusing their lathe have obviously never worked in a commercial setting where knurling would be a mild excercise compared to an 8 hr shift of heavy hogging with negative geometry inserts.

[This message has been edited by pete913 (edited 02-20-2005).]

JCD
02-20-2005, 07:38 AM
It looks like opinions are like parts of our anatomy, so hear is another one.
Make sure the knurls are square with the work piece.
Center is the best place to knurl.
If the tool doesn’t float, a good pattern could be a problem.
The centerline of the knurls need to be parallel, with each other. It sounds like that may not be the case. Sometimes the knurling tool holder is not square. If not, tracking will always be a problem.
This type tool needs to float, it compensate for small errors in setup pitch, etc.

JCD

Your Old Dog
02-20-2005, 08:56 AM
Finally, vindication!

Math has never been my strong suit but I enjoy playing with it. I've investigated every formula I could think of in search of a rhyme or reason as to how the magic knurling tool worked but never found one. Even my none scientific mind could cough up more then 4 or 5 variables (there's likely more I didn't think of not counting the phase of the Moon) to throw into the mix and that was way over my head. My questions are:

Question 1. If there are 4 or 5 variables in a given knurling job, how can a formula that does not address them all be accurate unless there is enough forgiveness in the mechanical process of knurling to hide (smudge over) an in-correct computation on paper?

Question 2. If there is enough slop in the knurling process to "smudge over" an incorrect computation then wouldn't those who say "Damn the torpedoes, full steam ahead" be correct in their assertion?

I suspect that those who have success with formulas have it because un-knowlingly they have eliminated some variables by consistant work habits that fit well with the formulas they are using. Does it not make sense that if there is a formula, that there is only one formula? And it ain't surfaced yet? It must be a bear! I don't count any formula that only takes in 2 of 4 or 5 variables as definitive, just luck.

I've done quite a bit of gun engraving under a microscope. Under a scope the metals I've worked with look just like relatively damp putty. The chisel simply "displaces" the material. Depending on the direction of force and shape of the chisel it can displace up and out of the cut or over to the sides of the cut and raise an edges. Knurling is a displacement to the side and raising an edge (read point) process. That leaves a lot of fudge factor as you can leave a knurl flat topped, bring it to a diamond point or take it beyond the "diamond point" stage by some degree of compaction (however slight). After reading this thread I'm starting to think there is far more fudge factor in the process then I originally thought.

It's nice (actually comforting) to know the knurling tool is not the easiest tool in the shop to master. I still feel stupid, but not so "damn" stupid!

I think it's been a great thread. All along I thought it was just me! Now, "damn all the math, full steam ahead!

J Tiers
02-20-2005, 10:23 AM
<font face="Verdana, Arial" size="2">Originally posted by pete913:
Go out and do it, and save reading the damn handbook for after supper. </font>

Yah....Yah....Yah.... Hey...el dude-o....

Where I found out about good and bad diameters WAS in actually doing it.

I didn't read no stinkin handbook. I just tried to knurl stuff, with a straight knurl.

I got dogsh$t results, re-cut points, chips coming off, all that stuff.

I was doing small diameters, with a one-wheel "force-it-in" knurl on a machine that shouldn't be abused like that.

I was cussing up a storm, getting nowhere.

Then I said to myself "this looks like a gear, lets try figuring it as if it were a gear...."

Shazam....cut the diameter a little, to what figured as a sweet spot, and got every one of the $*^%%$ things knurled perfectly. No failures.

I don't care what names you call me...I found out what worked, and it wasn't from a handbook or your d##n MR 3 & 2 manual either.

But, John S suggested something that I am going to do, that allows doing good knurls on work with a lightweight machine without a stinkin scissors knurler.

We'll see if I have to re-learn the procedure for that.