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Tips For Knurling Stainless Steel

Kroll

Active User
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#1
Guys,I am down to just the knurling part of my knobs which has me very nervous at this point.Looking for some tips that will put things in my favor since there's alot working against me.Any pointers,advice that you can give other than "don't try it"?I have watch several utubes on how to figure the OD to get it as close as can be so that's a plus.Thanks for the help
 

Kroll

Active User
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#3
That would be good information to know,dang my memory.Anyway thanks for asking,I have one of those scissor knurling tool Eagle Rock which I just purchase a set of wheels from Accu-Trak that are the 30TPI RH/LH type which I hope is the diamond pattern(think its called)When I order the wheels I told them that I am trying to knurl SS so this is what they suggested.I know nothing about knurling,this will be my first time
 

Wreck™Wreck

Active User
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#4
I have used one of the Eagle Rock tools.
Like any form knurling tool with 2 knurls run them onto the part as fast as you can, on a CNC lathe I feed the tool into the work at .025" Per Revolution, I believe that Eagle Rock reccomends more then that, on a manual lathe a cross feed stop would be a good idea but not necessary. Run the feed in as fast as you can until it hits fairly hard then move it a bit more. If you go to far the backlash in the lead screw will cause the knurls to pass center and pull the cross slide with them, knurling takes a great deal of force.

This is a test piece with the eagle Rock tool, 1/2" 304 SS, I ran the part the same way and it double tracked so I had to make another part, it worked just like the test the second time, go figure.

I work in a fair sized machine shop so we have thousands of pounds of drops lying around.
Good luck

knurl_zpssl7qtqce.jpg
 

Round in circles

Active User
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#5
I've not done knurling for almost 50 years , my memory dims with time and health in general .

Is there a formula for knurling a known recommended diameter ? ( Any lists / charts on line ??? )
On the knurling wheels do the engraved numbers indicate such a related formula ?

Is knurling best done between centres or the chuck and a live centre point or would the live centre point get in the way ?
 

Kroll

Active User
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#6
I found a chart on Utube which I downloaded,even after using it to come up with a correct OD I still think that I am doing it wrong.My knurling just don't look right.Wreck/Wreak I read your post couple of times and I don't understand which means I don't know if I'm doing it correct or not,I have never in my hobbist life done any knurling until this weekend.Anyway let me explain and please correct me,my eagle rock is the scissor type which I move it over the part (top/bottom) on center.I turn on the lathe and turn the nut down till it tight and make a pass using hand feed.After one pass I turn the nut a 1/4 turn then make another pass in the opposite direction which after the second pass I call it good cause I don't know either way.If I find my camera I am going to post some pics.----Carroll
 

Wreck™Wreck

Active User
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#7
Did you get the instructions that came with the tool? If so follow them.
If not.
In brief, square the tool (in practice on a small hobby type lathe you may have to set it out of square to offset any flex in the machine) put the knurls as close to the X axis centerline as possible and note the dial position.
Tighten the scissor screw by hand until the knurls touch the work then back off the cross slide, turn the adjusting nut 1/4 or more turns, turn the spindle on and run the cross slide in to center as fast as you dare, feed to length. You may want to let it dwell at the beginning and end. Trying to pick up the pattern for a second pass rarely works well.

Knurling is more of an art then a science, I have never met a single person in the business that likes it, they usually give it to me in this shop because I'm the one whom dislikes it the least (-:
Disclaimer: I do this for a living and have an estimated job time to meet which rarely gives time for screwing around doing tests, I am expected to get it right the first time, every time.
 

Kroll

Active User
H-M Supporter-Premium
#8
Thanks Wreck,I now understand how to go about the setup.Will give it a shot,quick question on diameter.Using the information that I found on the net for 30tpi wheels I come up with .742 dia for the perfect knurl but mine is far from it.Then I also read other post not to worry about the diameter that does not matter and will look just fine well it don't.Any advice on the OD on how to figure the size?
My wheels I purchase from AccuTrak,they are the ones that are convex in shape,but when I am knurling I am getting shavings which I read that the tops of the diamonds is being cut off.What is the TPI on the one that you did in previous post
 

Wreck™Wreck

Active User
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#9
Can't help you with the diameter as I have always had to knurl the parts at the specified diameters on drawings. That being said the diameter is probably less important then the process being employed and the machine itself, doing it on a spindly flexy lathe with any repeatable results will be difficult at best.

As I mentioned above the picture was a test on a piece of the material used to make the part, same piece of stock, same lathe, same tool, same setup, same program, same hour.
The test was a success, the actual part was a failure the first time.

Eagle Rock also recommends using 2 coolant nozzles, one for each knurl which I did.
 
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bfd

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#10
feed slow speed slow lots of cutting fluid. many passes until you get what you want or like. practice on scrap. blow the fine chips off the part as you procede bill
 

Tony Wells

Former Vice President
Staff member
Administrator
#12
Since you are forming instead of cutting the material, you should not be seeing any material come off. If you are, something you're doing isn't right. I find that most people feed too slow, and that allows the rolls to chew on the stock. Once they have formed the diamond pattern, there is no use continuing to let them roll against the material.
I also have one of those Eagle Rock scissor tools. I never run it right on the center. It will have a tendency to pull into and over center. You can find the center to set the rolls though, and when you tighten the adjustment nut down, don't run it all the way back to center. Stop just short. I dial in while rocking the chuck forward and back until I have a good "bite" on the work, then make a couple of revolutions by hand to see how it's going to track. Usually turns out ok. Once I am happy with the depth I set, I engage the feed and start the spindle at about the same time. You can't let it dwell. It's always best to get the knurl done on the first pass. Naturally, the further out from center, the more pressure you end up putting on the work, same as a bump type, but if you stay pretty close but not on or over center, you will be fine.

On SS, remember, most of it work hardens rather quickly, so don't mess around. Get your settings right on a scrap piece and then go for the part straight away. Knurling is not to be taken with light, timid passes. That's the big advantage of the scissor tool. You aren't relying on a stiff part or a heavy, massive machine to apply a lot of pressure. Jump on it and get it done.
 

Wreck™Wreck

Active User
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#15
feed slow speed slow lots of cutting fluid. many passes until you get what you want or like. practice on scrap. blow the fine chips off the part as you procede bill
If you are generating chips with a FORM KNURLING tool this is not ideal, no chips should be produced, you are forming the part surface not cutting it

A cut knurl is a different matter however.
 

bfd

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#16
I have produced many fine knurls and have always found slight flaking occurring on all materials not just stainless. these are the chips I refer to sort of like fine metal bits in a used oil filter. bill
 

chips&more

Active User
Active Member
#18
I have never needed to do any math when knurling. I just knurl it and it comes out great. I use an Aloris scissor type. I DO NOT come straight down on the work. That could make problems with how the diamond pattern comes out. Instead I come in from the end with the knurling tool pre-set for depth and do one pass with a lubricant…Dave
 

cathead

Active User
Active Member
#19
View media item 95653
Here is an easy method if you are having trouble with knurls. I machine grooves spaced 60 thou apart with a
60 degree thread cutting tool. Then I use the single knurl on the right side of the photo and run over the
rings relative agresively. The result is the "knurl" on the left. Technically one could call it a "pseudoknurl"
but it looks nice and relatively easy to do. They are really grippy too.

Another thought on regular knurling... If I have a knurl that sort of "herringbones", I machine off a couple thousandths
and retry and the second run usually knurls quite nicely. Usually I am not machining to a specific diameter but
rather making a hand hold with a decent looking knurl. This works because the knurls have to match up to the
circumfrance.
 
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Wreck™Wreck

Active User
H-M Supporter-Premium
#20
I have produced many fine knurls and have always found slight flaking occurring on all materials not just stainless. these are the chips I refer to sort of like fine metal bits in a used oil filter. bill
In the past I have produced chips as you describe with a form knurl when hitting the part far to hard, have since made a habit of "just enough" knurl. A few weeks ago I put an agressive 12 pitch knurl on an aluminum tool, it chipped and buggered a bit. This was not a problem as the customer merely wanted a stem that the employees could easily hold in use, it did not come back as Non Compliant.