Knurling brass, anyone experienced?

[Michael Kellough]

A friend/co-worker does decorative finishes on all kinds of stuff and has to replicate a missing part of an antique frame. On the flat lands of both sides of the raised part of a chair molding like profile there is running kind of checkerboard pattern that he thinks was made with a tool like this.

[attachimg=1]

At first I thought he could just buy a knurling tool but then realized that this tool has been knurled itself. The areas in between the diagonal lines are concave rather than convex.

I have a wood lathe. Is this so I could do to brass rod on my lathe or do I need to find someone with a metal working lathe?

The wheel is only 1/4” wide.

 

[jeffinsgf]

Knurling tools typically have two wheels...with the patterns running at an angle to each other. The pattern is a single set of parallel lines. You can use a regular metal working knurling tool on a wood lathe, as long as you can slow the lathe down enough...it needs to be pretty slow...like under 100 RPM if I remember correctly.

 

[Packard]

There is some math involved too.  This explanation was getting long-winded.  In short, your buddy may have to adjust the diameter in order to get clean knurls.  The explanation is below:

The company I used to work for, produced wire forms that were inserted into plastic.  The knurl was supposed to keep the wire form from rotating. 

They were just simple straight knurls.

The problem was that you could not press the knurls in with just one rotation of the wire.  It required several rotations.  So the knurling tool had to be calculated for the specific diameter of the wire or it would not seat into the previous’ rotation of the knurl.  We would then end up with metal “splinters”.

So we had tighter-than-industry-standards specifications for the diameter of the wire. 

You are talking about thousandths of an inch variation.  When you press the tool into the rotating piece you will quickly see if it is going to mesh with the next rotation.  For wood, I think it is going to be solved by trial an error with small skim cuts needed to bring the diameter in tune with the knurling tool.

I would note that were were never able entirely rid ourselves of the splinters.  We changed the straight knurl to an annular ring arrangement.  Math does not come into play with annular rings (like machine threads that are each independent of the other with no helix). 

 

[Michael Kellough]

The circumference of the part to be knurled needs to be evenly divisible by the tooth pitch of the knurl?

If the pitch is 1mm a diameter of 17.5mm should work. That has a circumference of 55mm.

Sound right?

 

[Cheese]

A properly executed knurl is a thing of beauty.  [big grin]  The last thing I knurled was the end nut for a slide hammer...that was about 50 years ago.  [blink]

The only things I remember about the experience was as Jeff mentioned go slow, use lots of lubricant to keep the knurl clean, like Packard mentioned there is a size ratio between the knurling tool wheels and the finished knurl diameter. You're pushing metal out of the way so there is a lot pressure against the object being knurled.

It's really really easy to get a 2nd or 3rd knurl rather than a single knurl. Here's a photo of a knurling tool for a small metal lathe.

[attachimg=1]

[attachimg=2]

 

[Packard]

The circumference of the part to be knurled needs to be evenly divisible by the tooth pitch of the knurl?

If the pitch is 1mm a diameter of 17.5mm should work. That has a circumference of 55mm.

Sound right?

I know I brought up the math issue, but our engineer did the calculations (he claimed).  I suspect he called our knurl die supplier and said, “We need to knurl 0.117” diameter wire, what pitch do we need on the knurl in dies”.

We used flat knurling dies in pairs that slapped together and “spanked” the wire and then slid past each other to spin the wire and impress the knurl.

Note:  The A.I. spell checker made 4 corrections on the previous sentence.  Not one of those “corrections” made any sense at all.  Ah, progress.

 

[squall_line]

Note:  The A.I. spell checker made 4 corrections on the previous sentence.  Not one of those “corrections” made any sense at all.  Ah, progress.

Apple's auto-complete/auto-correct doesn't use AI unless you're a developer who is using an unreleased beta version of iOS 18.

The screen keyboard autocomplete/autocorrect uses predictive typing and common fat-finger typos for its dictionary, but not currently in the form of AI or Large Language Models.  I'd venture to guess that the vast, vast majority of iPhone and iPad users are not using the word "knurl" on any sort of regular basis for it to ever be a normal suggestion for the general population.

 

[Crazyraceguy]

The thing about knurling is that it requires quite a lot of pressure. I doubt if it could be done on a wood lathe, since there is no mechanical way to generate that power/pressure.
As [member=297]Michael Kellough[/member] mentioned, the diameter is very important. The pitch of the knurler has to divide evenly into the circumference of the part, but not the turned (bare) diameter. It's actually half way between that and the ultimate diameter of the knurls. The diameter increases when the metal is pushed.
Otherwise the ridges runover each other.

 

[Packard]

Note:  The A.I. spell checker made 4 corrections on the previous sentence.  Not one of those “corrections” made any sense at all.  Ah, progress.

Apple's auto-complete/auto-correct doesn't use AI unless you're a developer who is using an unreleased beta version of iOS 18.

The screen keyboard autocomplete/autocorrect uses predictive typing and common fat-finger typos for its dictionary, but not currently in the form of AI or Large Language Models.  I'd venture to guess that the vast, vast majority of iPhone and iPad users are not using the word "knurl" on any sort of regular basis for it to ever be a normal suggestion for the general population.

I read that Grammarly does use AI.  I was happy with it when I got it a few years back.  Now it makes all these “predictive” changes.

I thought spell checkers were going to make me lazy and a poorer speller.  The opposite happened.  It drilled into my head the correct spelling.  Maybe it’s time I stand erect and go it alone.

 

[Packard]

Years ago, if you wanted to get a safety grab bar for your shower, it would be knurled brass plus nickel plating.

Lately, I’ve been seeing them made from stainless steel and then hit with metal flame spray which welds on a random spatter of stainless steel.  On the plus side, the pieces are now stainless steel and cheaper to produce.  On the minus side, compared to the older knurled versions, they are ugly as sin.

 

[Michael Kellough]

In reading about knurling I found a rule of thumb about speed.

The rpm’s should produce a maximum surface speed of 150 feet per minute.

At 17mm that would allow up to 900 rpm (much faster than anticipated) so at least that spec is within the capability of a wood lathe.

Since this tool is for embossing gesso on wood I’m thinking maybe I could use nylon rod. As in maybe it will be hard enough… Nylon is thermoplastic so I could just use heat and light pressure from the knurling tool to emboss the nylon.

 

[Cheese]

In reading about knurling I found a rule of thumb about speed.

The rpm’s should produce a maximum surface speed of 150 feet per minute.

At 17mm that would allow up to 900 rpm (much faster than anticipated) so at least that spec is within the capability of a wood lathe.

Since this tool is for embossing gesso on wood I’m thinking maybe I could use nylon rod. As in maybe it will be hard enough… Nylon is thermoplastic so I could just use heat and light pressure from the knurling tool to emboss the nylon.

How about some PVC rod instead of the nylon, nylon is harder and may have too much memory. I'd still start at a lower speed if possible, that could be a less frenetic experience.  [smile]

 

[Michael Kellough]

Jeff was afraid a wood lathe wouldn’t go slow enough. At least that is out of the way.

The biggest obstacle is getting enough pressure. A hand knurling tool would work but it seems to need a rigid support platform at exactly the right height. Not impossible but a bit of a pain.

With a standard knurling tools height doesn’t seem to be critical but the tool needs to be fed into the side of the rod with no extraneous movement.

Since I don’t have any of the tool holding rigs available for metal lathes I’m leaning towards thermoplastic’s like Delrin, nylon, and pvc and adding a little heat to minimize the pressure needed.

When I was kid building slot cars to fit a new nylon crown gear to the brass pinion gear on the motor shaft I’d set the crown gear tight against the pinion then run the motor while holding a match underneath the gears. In a few seconds the horrible noise quieted and the gears were nicely meshed. I wasn’t a great driver and using the track cost money so I spent more time building faster cars. A very good driver used one of my cars to break the track record.

 

[Packard]

Back support with two rollerblade wheels?  They are made from urethane and would not damage the knurled, and they can support the weight of an adult (2 wheels).  Plus they come with bearings and are very cheap.

You would have to fabricate a method to hold them in place at the opposite of the knurling tool.  I still don’t know if the centers for wood turning can handle the pressure, but the wheels would help. 

I see them selling from $3.00 to $4.00 each.
https://www.google.com/search?q=rep...wheels&ie=utf-8&oe=utf-8&client=firefox-b-1-m