Knurling - how to?

Dave K2 · Mar 9, 2019

Hi all,

I have a possible repeat batch-job coming up but need to knurl around 75mm of an 8mm shaft.

I had a try this morning as not really done any before :rolleyes5:

, i have a clamp type tool and tried the fitted wheels first, these were the medium of the three provided but although it did cut, one of the wheels was bored off-centre (yeah i know, crap tool) and the little lathe was not happy, it started off bad but cut in the end, this is the right-hand of the two in the picture.

Then i changed to the coarse wheels and they ran better but now i get a double-cut on one angle?? (left image)

Is there a secret to knurling i need to learn? Does feed-rate matter, can i expect to knurl 3" / 75mm in one hit with no tail support?

Any tips ?

Thanks

MattiJ · Mar 9, 2019

Since you asked this on a more professional forum: Ditch those crappy cheap harry-homeshop tools and get yourself a proper tool.

Hommel-Keller (Zeus) or Quick comes to my mind since you are in europe and not with the US barbarians that prefer forming knurls

Red James · Mar 9, 2019

The stradle type knurl tool is ideal for the diameter/length the OP wants.
He needs to calculate the proper diameter of the work to adjust to the pitch of the knurl wheels (or reverse the math and calculate the pitch that is nearest for his shaft). For an 8 mm shaft, a 1.00 pitch knurl is close.

With the length of knurl so long a cut type knurl will require some sort of support, which is why the form knurl is better is this case.

Most manf. of knurling tools offer a calculator for sizing.

MattiJ · Mar 9, 2019

Point taken. Missed the desire to run without tailstock.

Conrad Hoffman · Mar 9, 2019

IMO, bad length to diameter ratio, so you need support, just as everybody said above. Getting great knurling is hard enough and I can't imagine doing it with junk tools. IMO again, it's also tough on a small lathe, and tough on the lathe itself, even with a scissors type tool. Never used one, but would a cut knurl tool do better for this?

Guest · Mar 9, 2019

With out a tail stock I just have to wish you the best of luck.

lazz · Mar 9, 2019

One thing to consider is the diameter of the object to knurl and the TPI of your knurling wheels.
I use this phone app knurling calculator.

A scissor style can work without the tail stock but it would mean using caution to not clamp too much and slip off. As in maybe 5 or 10 times more passes to get a good knurl.
You can find an Eagle Rock scissor style tool for around $200 US. There is also a 3 wheel style knurling tool that can be used by hand or on a lathe. The 3 wheel type would eliminate the tail stock.

Lubrication is very important. Flood would remove the small chips better. Re cutting the chips makes for an ugly finished product.

As for speeds and feeds... I start slow and ramp things up until something goes wrong... :willy_nilly:

MattiJ · Mar 9, 2019

Dualkit said:
With out a tail stock I just have to wish you the best of luck.

3-wheel cut or forming knurl would work for sure but they are not exactly cheap. Clamp/straddle style works also to some diameter ratio but with really long stickout the stock probably escapes from between the wheels.

traveling steady would also solve the problem, doesnt need even real traveling steady but a strategially bent piece of flat bar and piece of plastic bearing block would suffice.

Clive603 · Mar 9, 2019

I find the three wheel hand squeezed "nutcracker" style tool is much better behaved on small diameters. No need for tailstock. Mine, a commercially made one marked A.BRAUER PRODUCT made in England, works fine on small diameters. 1/4" is the smallest I've done. Probably need re-design with closer wheel spacing to go smaller. Guess its mid 1960's to mid 1970's vintage. I've only ever seen two so possibly not popular. Got mine thrown in when buying a used Pollard pillar drill from a machinery dealer. Intercepted from the scrap pile as "obviously useless". Having used the one we had at work I knew better!

Picture of mine below. If you fancy making one PM me as I've got two sets of published plans. One from Model Engineer for a near as dammitt dead copy and one from Popular Mechanics for a slightly larger one.

Clive

Gobo · Mar 9, 2019

Go CUT knurl or go home. Lower cutting pressure and more consistent knurls. You will pay more, but its worth every penny. Form knurling is inferior.

Dave K2 · Mar 9, 2019

Thanks all,

I don't usually post much here as I know its a pro site and i'm far from pro

But sometimes you need to ask the experts I think.

I can modify the part for tailstock support and cut off later, I also looked at Quick tooling but the cost is way above this part as repeats are going to be slow/low volume so splashing hundreds on tooling is out.

I'll look into cut knurling as well. A three-wheel tool seems ideal but very rare it seems.

I think the first cut i tried failed at the beginning due to chip recutting, after it started i flooded it with oil and the knurl got better, as these wheels are poor quality, maybe a better set in a clamp tool with tail support is all i need, along with some flood/oil.

MattiJ · Mar 9, 2019

If quick was too expensive You might consider upgrading your knurler with brand name wheels. Or build your own around better wheels.

Dave K2 · Mar 9, 2019

MattiJ said:
If quick was too expensive You might consider upgrading your knurler with brand name wheels. Or build your own around better wheels.

Yes,if i had many parts to do then i would not worry about dropping £2-300 on a tool but this is a low volume part so makes sense to get it done with low outlay.

I will look for a better low-end clamp type tool with wheels of a pitch suited to this job, no idea what pitch my wheels are - so cheap its not even marked :rolleyes5:

Marty Feldman · Mar 9, 2019

Dave K2 said:
...but this is a low volume part so makes sense to get it done with low outlay.

You are certainly in the best position to know your own business, but speaking personally the approach you are taking is not one that I see as smart. First of all, it is hard to predict that you will never have to do this job or one like it again, or that if you do it will only be a matter of a few parts. The second, and more important thing, is to consider what sort of customer business you will get in the future if you let any job, no matter how small or trivial, out the door with less than your best effort in it. Customers have a habit of talking to potential customers, and potential customers often turn elsewhere if they come across a shop whose work is low-end. Since you say you are in a position to drop a few hundred pounds on a tool if the job warranted, this can't be a matter of simply not having the money.

-Marty-

Terry Keeley · Mar 9, 2019

I messed around with cheap knurls for years and was only frustrated, finally got a nice Dorian:

Dorian Knurling Tool, Fixed, 3 5/8 In OAL FKT-50-D | Zoro.com

If you shop around you can find them for US$90.

Ditched my QCTP and made a super rigid set up with a 4 way TP just for knurling.

Also you need to tweak the diameter to match the TPI of the knurl, here's some good info:

Conrads Easy Knurling Method

CGTK - Knurling Calculator

EmGo · Mar 9, 2019

The heck with all this stuff, throw it in the Fellows and cut serrations on it

Clive603 · Mar 9, 2019

Dave

For obvious geometrical reasons clamp tools are tricky on small diameters.

I have a proper Marlco one with the lever "sensitive feed" so you have a better feel for whats going on than with the screw down types but its still dead easy to get into trouble much below an inch in diameter. Two wheel clamp down ones don't care what the pundits say. They will try and spit the work out or pull over during the process however careful you are to start them dead on centre line. Need either good slide locks or backlash taken out the right way. Preferably both. Even with tailstock support a slender job can whip on you as you run the knurl down it.

As its a low budget job spend £40 or so with Zoro for some half decent wheels. Make yourself a three wheel nutcracker one, probably won't take much longer than the time you will waste faffing and cursing about short cut and "cheaper" methods. Then get the job out of the door.

Clive

Froneck · Mar 9, 2019

I understand using the proper diameter but the knurl on the left the one knurl is tracking properly so the diameter is OK if the other knurl is the same. Check out YouTube Joe Pieczynski does a good job explaining knurling. I use a Dorian Cut Knurl but the cost of that knurling tool holder is quite high.

Dave K2 · Mar 10, 2019

Marty Feldman said:
You are certainly in the best position to know your own business, but speaking personally the approach you are taking is not one that I see as smart. First of all, it is hard to predict that you will never have to do this job or one like it again, or that if you do it will only be a matter of a few parts. The second, and more important thing, is to consider what sort of customer business you will get in the future if you let any job, no matter how small or trivial, out the door with less than your best effort in it. Customers have a habit of talking to potential customers, and potential customers often turn elsewhere if they come across a shop whose work is low-end. Since you say you are in a position to drop a few hundred pounds on a tool if the job warranted, this can't be a matter of simply not having the money.

-Marty-

HI,
yes your reply makes sense, what i tend to do is make the first trial/demo part as low-cost as possible if tooling is needed, as long as quality is ok. Then if job is agreed i can usually get a good idea of qty and repeat frequency then invest where needed.

I did have a chat with them yesterday for some more details and they have mentioned that the grips could even be coated with what i now know as Plasti-dip, the rubber coating stuff you see on hand tools. Its merely to stop the part from being dropped when in use.

lionelt · Mar 10, 2019

A three wheel knurling tool is good for long thin part.

But not the cheapest to buy.

Knurling - how to?

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