Single-point knurling?

Have any of you guys single point cut knurling before?

If so, tips???

The reason I ask is because I want to produce a deep, aggressive diamond knurl in some 17-4 pH SS. I don't have a lot of experience knurling because I haven't had the need to do it very often. . .before I have only knurled aluminum and brass, both being very soft materials the knurling was easy to do and I was only knurling for extra texture on handles. . .now I'm making some knurled rollers for a grain mill and the forming knurlers aren't producing a deep enough knurl in the SS (303 is what I practiced on) for what I want/need so I thought I would try single point cutting the knurl.

I've produced knurls in SolidWorks using a 60* thread cutting profile and the helix and swept cut features so I figured I could do the same thing on a lathe with a threading tool and doing overlapping RH & LH threads, but it didn't work out to well. . .of course I didn't have the time to experiement with as many different TPI's as I would have liked today, but 10 TPI and 22 didn't produce the effect I was looking for. . .here's a pic of the type of knurling I would like to produce. . .

The Barley Crusher Home

This is a commercially available version of a grain mill that is quite a bit smaller than what I am working on now.

Thanks ahead of time for the help!

You'd probably be better off using a cut-knurling tool. I've tried to knurl 17-4 Cond. A, and been a little disappointed in the results. My rolls were a bit old, and maybe dull, but I didn't do what I wanted.

I have heard of, but not seen, an approach like you describe. It involved multi-start threads run in RH and LH, but at around a 60 deg helix angle.

Tony Wells said:

You'd probably be better off using a cut-knurling tool. I've tried to knurl 17-4 Cond. A, and been a little disappointed in the results. My rolls were a bit old, and maybe dull, but I didn't do what I wanted.

Click to expand...

I was kinda afraid of that. . .we have the quick-cut cut knurling tools, but I will probably need to order some coarser rollers.

Tony Wells said:

I have heard of, but not seen, an approach like you describe. It involved multi-start threads run in RH and LH, but at around a 60 deg helix angle.

Click to expand...

That is kinda what I was wanting to do. . .I didn't think of the multi-start part though.

How do you relate a helix angle to a thread pitch?

It's a function of the work diameter. Here's one of many online calculators for the helix angle of any given thread/diameter combination:

Calculators: Thread Cutting Values

atomicjoe23 said:

Have any of you guys single point cut knurling before?
<clip>
but 10 TPI and 22 didn't produce the effect I was looking for. . .here's a pic of the type of knurling I would like to produce. . .

The Barley Crusher Home

This is a commercially available version of a grain mill that is quite a bit smaller than what I am working on now.

Thanks ahead of time for the help!

Click to expand...

Looking at the item pictured in your link it looks like the pitch of the "thread" may be something like 1/2 thread per inch. That assumes the rollers are by guestimate each 3/4 inch in diameter and 3 inches in length. If you follow a single line of bumps swirling to the left or right, I think that row makes just about one and a half turns for the entire length of the roller. That pitch is going to be hard to acheive on a standard engine lathe. And even if you had such low gearing the path of the cutter is so shallow that you would surely have to grind your cutter profile oriented somewhere between a standard vertical orientation and a horizontal oreintation. Someone better than me with CAD programming could likely determine the proper profile. But it would be a challenge.

So, I think this is going to be difficult to replicate single-pointing. But maybe there is a practical way. There are a lot of very clever people on this forum.

Denis

After writing the above I tried Tony's Helix Anggle calculator and got 32.4 deg for a 1" dia part wtiha 0,5 pitch.

It may be a silly question but does it have to be a diamond knurl?
I had a similar broblem with 303 SS and decided to try a coarse straight knurl
and it worked out very good.
One thing I learned over the years is that the pitch of the knurl must match the cicumference otherwise you get a horrible mess

I've done it a few times, The first time was one of the first lathe jobs we had, and there was no money left at that point to buy a knurling tool. Little knobs, like 30 parts, some 1", some 1.5", besides its something I had always wanted to try.

I've done it as an "artistic" feature on the feet of these coffee tables.

The "artist" wanted a knurl, but he wanted it to be insanely aggressive, sharp and pronounced. 2.25" diameter, 30 something start left and right hand threads. The pitch of each thread was approximately the diameter.

You run into a bunch of problems. Helix angle obviously, to get a good diamond you don't have enough clearance on your tool, you could tilt it, but then you would need one for the left handers and one for the right handers.

If you don't get a steep enough helix (I didn't), you end up with like 30 degree diamonds, and that actually makes the knurl pretty slippery when you are trying to turn your knob, grabs your fingers great if you are trying to pull the knob though. I hope that made sense.

Feed rates get insane, my lathe is an old dog and would only feed so fast, so the surface speed was way down while the feed rate was through the roof.

Burrs, lots and lots of burrs, I had to rerun through all the threads again to knock them all off.

Not particularly functional, but they look snazzy, and now I can say I've done it, and I've since purchased a knurling tool.

I've got some pieces left at the shop I can take a closer pic of on Monday if you want



.

Snazzy looking tables!

Thanks for the helix angle to thread pitch calculator Tony.

My pleasure, Joe. That's certainly easier than calculating it the hard way.

Just a thought here. Why not turn a series of 60 degree groves, looks like a thread with no helix and then machine 60 degree grooves in line with the centerline to make a 90 degree knurl. That is if you haven't found a cut knurl as featured in the March-April issue of the Home Shop Machinist. Peter

Thanks Peter. . .I'll look into that, I think that would be just as functional as a regular knurl.

I built something similar about 3 years ago. You just need to run the knurling tool back and forth many times, adding a little more pressure each pass. Once you engage the part, don't take the tool off the face until you get the point you want. Don't worry about cross hatching. The grain does not care.
I geared the two rolls together. I also put mitre gears on the other side to use my drill press to drive the thing. Works great.
have fun
i_r_

I plan on gearing the rollers together as well. . .

doing this on a mill might might be better. advancing the table 3X the part diameter for each turn gets close to 45 deg helix, 5:1 gets a 60 deg helix.

gearing a headstock to the table feed isn't much of a problem but you also need a way to time the multiple starts. there are of course dedicated attachments for this as well....live tooling on a lathe would also work as long as you could get the right feed:speed ratio.

Knerling

If you have available a universal horizontal mill and a fully universal dividing head the setup would be fairly simple. You did not mention the diameter or length you plan for the new rolls. 12 tpi would require a reasonable number of 'teeth' on the circumference.
Machinery Handbook has tables of the gearing to achieve various helix angles. The code plates have enough different numbers of holes to get very close to the pitch you want.
I have a manual mill and div head that would be suitable.
Send me a PM with email or phone info if you want to discuss the project.
Hugh

These knurls are geared together and actually cut rather than displace metal. Should do exactly what you are looking for. Look at the quality of the knurls on the tool itself, clean and sharp. Peter

single-point knurling

No one has yet mentioned using a lubricant,I've knurled 303 SS and the results with a diamond knurl are improved with lubricants,even with carbide tooling. BREWSKI

ZAGNUT said:

doing this on a mill might might be better. advancing the table 3X the part diameter for each turn gets close to 45 deg helix, 5:1 gets a 60 deg helix.

gearing a headstock to the table feed isn't much of a problem but you also need a way to time the multiple starts. there are of course dedicated attachments for this as well....live tooling on a lathe would also work as long as you could get the right feed:speed ratio.

Click to expand...

Whenever I get a mill at home this is the type of thing I plan on getting set up. . .my mentor at work has his mill set-up to do this type of work, but there is NO WAY IN HELL I could get away with this type of thing at work. . .apprentice project or not. Unfortunately a lot of the people that are currently in the shop are very against doing anything that isn't "normal" and because they never took the time to experiment and make things for themselves when they are learning they think that we shouldn't be allowed to now regardless of how valuable the knowledge and skill we are learning is. . .these guys are only there for a paycheck rather than a passion for the trade, but that's changing the last 3 years of apprentice classes (of which I am one of) have all become very passionate about the trade and are trying to bring the old non-CNC skills back to the shop.

bytewise said:

If you have available a universal horizontal mill and a fully universal dividing head the setup would be fairly simple. You did not mention the diameter or length you plan for the new rolls. 12 tpi would require a reasonable number of 'teeth' on the circumference.
Machinery Handbook has tables of the gearing to achieve various helix angles. The code plates have enough different numbers of holes to get very close to the pitch you want.
I have a manual mill and div head that would be suitable.
Send me a PM with email or phone info if you want to discuss the project.
Hugh

Click to expand...

We have two manual horizontal mills that we also have rotary tables for. . .they gear together and I could swing this as an apprentice project. My mentor has talked about it a couple of times and pointed it out as well, but we just haven't gotten around to doing; this project is the perfect excuse. . .guess I need to figure out the exact diameter and length of rollers I want so that I can turn some practice mild steel blanks down to practice on.

oldbrock said:

These knurls are geared together and actually cut rather than displace metal. Should do exactly what you are looking for. Look at the quality of the knurls on the tool itself, clean and sharp. Peter

Click to expand...

I just ordered all of the back-issues for this project!

BREWSKI said:

No one has yet mentioned using a lubricant,I've knurled 303 SS and the results with a diamond knurl are improved with lubricants,even with carbide tooling. BREWSKI

Click to expand...

We have Acculube, Circle Cut 729, and Habcool at work. . .I primarily use Circle 729, but Habcool is really good stuff. . .unfortunately the sulfur that makes it so good also makes it not that good for you. We're holding our breath in the shop because we are pretty sure they are gonna take it away from us pretty soon. That's how we ended up with the Circle Cut. . .we were hoping it would be a good replacement for the Habcool, but more health and environmentally friendly. It works very well, but every once in a while I still feel the need for the Habcool. . .usually when tapping 304 SS.

The knurls are not geared together! The outer housings are geared together.

"Real" roller mills use rolls of at least 8" diameter, on the smallest models that I have seen (for rolling feed, but the principle is the same: to not produce flour but only crack and flatten the kernels). The larger diameter produces a much better pinch throat than small diameter rolls.

And the rolls only have about 4 or 5 grooves per inch, with a smooth area about 3/16" wide between grooves that performs the actual crush. This is most efficiently produced with a shaper. Helical grooves are not necessary, and circumferential grooves are bad because they 'leak' whole kernels.

Now I realize that this is a small capacity mill being discussed here, but I think a low profile mill, with 8" diameter rolls, maybe 2 or 3 inches wide might have some sort of sales appeal in the specialty market. And no super deep knurl required to make it feed. Just a thought.