machinist@lists.ibiblio.org
Subject: Machinist
List archive
- From: Lawrence London <lfljvenaura@gmail.com>
- To: machinist@lists.ibiblio.org
- Subject: [machinist] Knurling 101 Question
- Date: Fri, 14 Feb 2014 18:05:36 -0500
http://www.practicalmachinist.com/vb/general/knurling-101-question-279777/
Thread: Knurling 101 Question
-
Knurling 101 Question
I'm a hobbist "want-to-be" machinist, and have been doing some knurling (12 TPI) semi-successfully. The procedure I use is just kiss the knurling tool up to the part and then look at the pattern (diamond shape) if they match up I continue on, if not I back off and trim another 0.010" off the diameter then try again, been working pretty well. Now I'm trying some 24 TPI knurling and I'm running into funny problem, when I kiss the knurling tool up to the part I'm getting two different patterns (other then the two angles), one looks to be correct but the other is like double the pitch of what the other is! Now how does two same diameter and pitch knurling heads come up with two different patterns on the same part at the same time!!?? I've trimmed the diameter of my part down so much it's become a "practise piece", and I get to try again. Hopefully I'm making a foolish mistake and some wise individual can point it out to me and I myself can become wiser!!! ;-)
-
02-07-2014, 09:36 PM #2
- Join Date
- Feb 2005
- Location
- Hatch, NM Chile capital of the WORLD
- Posts
- 4,781
Not to be a dick, but. You are diddle fucking around.
You are getting a double knurl, happens all the time when you are diddle fucking around.
You want to know how deep you need to go, and you want to get there in one revolution. That is from off the part completely to full depth within one rev.
There are calculators that will tell you depths of cut, proper diameters and all that, and that never hurts to know. I've never had much luck with it, and
its never seemed to make all that much difference.
Just slam it in there, slowest RPM you have. Slam it in as hard as you are comfortable with, then you can pick up the revs (depending on the lathe) and feed it off,
in either the X or Z, depending on what you are doing.
Double knurls are common, and aggravating, and they look like crap, common problem. Knurling as a general rule, sucks.
A few things I've learned over the years, anytime you "kiss" something while working with metal, you get screwed, and its not the good kind of screwing.
I'm guessing since you are "kissing" metal, you also like to "sneak up" on a dimension. Don't do that either. -
02-07-2014, 10:07 PM #3
- Join Date
- Jan 2007
- Location
- Southern New Hampshire
- Posts
- 743
-
Originally Posted by Spencer in NH
And check your tool height.
You using the wrong type knurlerRay Behner likes this. -
I've had more luck with scissor knurling tools. The one sided pressure knurlers, not so much.
Knurling is a crap shoot, goes well when you nail down the process, but like most who do it on occasion, it's a pain.
TomRay Behner and jrmach like this. -
-
02-08-2014, 01:22 AM #7
- Join Date
- Oct 2006
- Location
- San Leandro, California
- Posts
- 502
Bobw has it right. Just to rephrase in case it makes a difference, I like a scissor type knurling tool. I give the clamping nut a good crank before starting the spindle and by the time the part has made 1 revolution, the wheels fall right into the grooves where they started. All the stuff you hear about having to turn the diameter to a calculated size is just unnecessary time spent to compensate for lack of technique. If you're using the old type of knurling tool that pushes in from the side, start with the wheels half off the end of the part so it doesn't take as much force to get the pattern started but, get the wheels deep before they can double track.
stephen thomas likes this. -
I'm "diddle fucking around" ...Last time I was acussed of that was by my Drill Sgt! HEY, ...Bob you weren't in th Army by any chance!??
SO I can't ease into this operation I have to start out "full force" from the get go ...I can do that! ...THX Fellers, I'll let you know how it turns out. -
1) If you're using cheap knurls, throw them in the scrap bin right now, before you scrap something important. A cheap two-roll knurling tool with a height compensation hinge to equalize knurl pressure is OK. Set the tool height close to center.
2) Buy a set of convex knurls. They work much better, 90 degree alignment to the work isn't as important and they require less force.
3) To test the workpiece diameter, lightly touch off on the workpiece and run a full revolution allowing only one knurl to contact the work. If the lines meet you're good to go. If they don't, calculate the material to remove by the change in circumference necessary to "close" the last set of lines at the depth of the knurl.
4) If you have a threading depth stop, set it with the knurls just touching the work and use the compound slide to set the knurling depth. (Use a test piece to decide how deep to knurl for the pattern you want.)
5) Start your machine at a slow speed and jam the knurls into the work as Bob suggested. Don't be shy here. JAM them in until you hit the depth stop in one quick, smooth motion. This is necessary to get the two knurls to "synch up". Otherwise, you'll get the dreaded "double pattern."
6) Feed about 1/4 the width of the knurls per revolution. Don't diddle here, you'll just end up with a mutilated pattern. Use a steady stream of thread cutting oil or good coolant.
7) Wonder why everybody else thinks knurling is so hard. -
-
02-09-2014, 09:52 AM #11
- Join Date
- Mar 2013
- Location
- Oshkosh, Wis. rauchle@ntd.net
- Posts
- 633
Set your tool at a slight angle, come in on it fairly hard, engage power feed, add oil. Repeat. Originally Posted by 11echo
I'm "diddle fucking around" ...Last time I was acussed of that was by my Drill Sgt! HEY, ...Bob you weren't in th Army by any chance!??
SO I can't ease into this operation I have to start out "full force" from the get go ...I can do that! ...THX Fellers, I'll let you know how it turns out. -
Years ago I was in the camp that started out trying all the measuring and figuring to get the stock to the right size so the knurls would line up. Like so many others have said, I didn't see any difference what so ever. My dear ol dad told me "just press the damn things in hard enough to get the pattern started before you feed in and they will line up". As usual, he was right. Originally Posted by 11echo
CR*P...It worked! ...Worked like a charm first crack out of the box! ...Thanks everyone!
Talking to him, he figured the outside size of the stock doesn't make any difference because once the pattern is started, the knurl is pressing into the stock and effectively changes the size of the stock anyway. Unless you are cut knurling you are just pushing the surface material around and it will fill the open area of the knurls. If you magnified the finished knurl pattern and laid one of the knurl wheels in it, the fit of the pattern on the part to one knurl wheel might be loose as shit. That doesn't effect anything about the finished part because it is just a diamond pattern and that is what you were after. It doesn't have to hold any tolerance or mate up to anything else.Stu Miller likes this. -
02-10-2014, 07:48 AM #13
- Join Date
- Aug 2008
- Location
- near Cleveland
- Posts
- 683
For straight knurling, you need to have a whole number of "teeth"- calculate circumference, divide by the decimal equivalent of the pitch, for example, 0.025 if a 25TPI knurl.
If you're doing a diamond knurl with two knurls, you need to use the transverse pitch forthe calculation. Note that there is some slippage involved here, but it's usually not significant. Also, the knurl will onlyraise up so much before collapsing.
See:
http://www.reed-machinery.com/pdf/kn...ata-master.pdf -
02-13-2014, 03:19 PM #14
- Join Date
- Oct 2006
- Location
- San Leandro, California
- Posts
- 502
I don't agree. Straight or diamond, I never met a diameter I couldn't knurl cleanly using the method I described previously. One thing that the calculations help with is if you only have coarse knurls, you can calculate the diameter you need to have the knurl precisely double track when you gently apply it to the workpiece so you can produce a fine knurl with the coarse wheels. Originally Posted by machinistrrt
For straight knurling, you need to have a whole number of "teeth"- calculate circumference, divide by the decimal equivalent of the pitch, for example, 0.025 if a 25TPI knurl.
If you're doing a diamond knurl with two knurls, you need to use the transverse pitch forthe calculation. Note that there is some slippage involved here, but it's usually not significant. Also, the knurl will onlyraise up so much before collapsing.
See:
http://www.reed-machinery.com/pdf/kn...ata-master.pdf
Calculations are good if you're running production on a screw machine or you like theory but on a manual lathe, bury the knurl and get it done.Greg White likes this. -
02-14-2014, 01:47 AM #15
- Join Date
- May 2005
- Location
- Interior British Columbia
- Posts
- 1,145
Bobw got it in a nutshell except for one thing.
Don't feed it in as hard as you are comfortable feeding it. You need to push harder than that. Put the screws to it like it owes you money.
Guys that dink around trying to calculate out a perfect knurl with a mic and some formula or other generally seem to spend much of their life redoing the parts.
Power feed and an adequate flow of coolant are really nice, but get in, and go hard, are really words to live by. Practice!
Cheers
TrevGreg White likes this. -
02-14-2014, 04:41 AM #16
- Join Date
- Jan 2007
- Location
- Pinckney Mi.
- Posts
- 2,227
-
02-14-2014, 02:19 PM #17
- Join Date
- May 2005
- Location
- Interior British Columbia
- Posts
- 1,145
Originally Posted by Greg White
trevj
your getting a double like for the above advice.
Gw
Taught a lot of apprentice Tradesmen to do basic lathe and mill work in the Canadian Forces. Knurling rated right up there with grinding tools, and threading, as 'feared'. They got over it pretty quickly, once they spent a bit of time actually doing it.
The lighter duty the lathe, the scarier it is to really wind in on the feed screws. You pretty much have to learn how every part flexes, and how to adjust for it all.
Two other bits of advice I think worth trying.
If your part has any bevels or shoulders at the ends of the knurl, do them after the knurl to be able to remove the rolled over edge.
Knock the tops off the knurls with either a light pass with the lathe, or a few seconds with a lathe file, it takes the rough 'teeth' off the top and still leaves a nice grippy surface. Feels nice!
Cheers
Trev
Reply
- [machinist] Knurling 101 Question, Lawrence London, 02/14/2014
Archive powered by MHonArc 2.6.24.