Knurling tool

[Graham MeekParticipant @grahammeek88282]

Hi Clive,

Regretfully my memory is not what it was, so I cannot produce word for word, but here goes.

During my career in industry I have only ever known straight knurls to be used as a single wheel. George H Thomas showed his single wheel knurling tool in his article on Micrometer Dials. I also recall it was GHT who advocated the correct pre-knurling diameter, but where escapes me.

There is no way other than by pure luck, that the knurls will be in synchronization with each other when used in a calliper knurling tool. Yes the knurls will produce a knurl, but it will probably be finer than the pitch on the original knurling wheel. If it is the same then that is down to luck.

The only way it might work out perfectly is if the circumference is evenly divisible by the by the pitch of the Knurls. Think of two gear cutters diametrically opposite cutting an even number of teeth, these will synchronize. Now consider the same set-up but with an odd number of teeth, anything but a gear will be produced.

My take on using a single straight knurl is to cant the wheel towards the tailstock. Such that the leading edge is in contact with the work first. This canting over does not have to be excessive, only about 2-3 degrees. This allows more pressure to be applied over a shorter distance than if the tool was presented to the work square on.

The first pass over the work is started off the work after first touching on and applying a cut. This depth of cut is something to be recorded, once a good knurl has been established. This should give a knurl with a nice sharp crest each and every time. The feed does not want to bee too slow. I use about 0.1 to 0.15 mm per rev. (0.004 to 0.006" approx).

If the knurl starts to chew itself up then the diameter is too large for the pitch of the knurls to divide into evenly, slightly skim the diameter to correct. This skim does not need to be too deep, remember the pitch of the knurl is not that big.

Lastly the knurling tool is turned square on and the tool is brought up to engage the knurls while the mandrel is revolving. A slight pressure is applied and the knurling tool is oscillated over the knurl to impart a sheen or burnish. Cleanliness of the knurls is paramount and I never apply oil to the knurl using a swarf brush. Not only will the brush get trapped but it will also introduce small bits of swarf from previous work. Apply a drop of oil at the start from the oil can, that way it is known to be clean.

I also chamfer before and after knurling. A chamfer gives a softer engagement to the knurling wheel as it advances across the work. Clearly define the start and finish of the knurl with a chamfer, and never rely on placing a rule near the knurl to gauge the length. I have seen rules become files from this practice. An example below of my take on straight knurling.

I hope this rather lengthy set of notes helps?

Regards

Gray,

[CirclipParticipant @circlip]

Bet the late Sir John is doing a few rotations, think it was on one of the American sites where he posted a photo of about a foot (Err 305mm – 30.5cm) long straight knurl that looked to the uninitiated like a straight cut fine pitch gear using a home cooked knurl milling tool.

Regards Ian.

[MeunierParticipant @meunier]

Posted by Circlip on 17/08/2021 11:31:10:

Bet the late Sir John is doing a few rotations, think it was on one of the American sites where he posted a photo of about a foot (Err 305mm – 30.5cm) long straight knurl that looked to the uninitiated like a straight cut fine pitch gear using a home cooked knurl milling tool.

Regards Ian.

https://www.model-engineer.co.uk/forums/postings.asp?th=112364

Think this is the one you have in mind, Ian, from 2015

DaveD

[clivelParticipant @clivel]

Thanks, Gray,

That is very helpful and makes perfect sense.

Regards,
Clive

[Graham MeekParticipant @grahammeek88282]

Hi Clive,

You are welcome, I am glad my scribbling was of use.

Regards

Gray,

Generally,

There seems to be some confusion between "Cut or Milled" straight knurling and the "Deformation, or Forming" process carried out by a conventional straight knurling tool.

The outside diameter of a "Cut" knurl will always be the start diameter, or, slightly less. This discrepancy depends on how far the cutting tool is fed-in, too much and the initial diameter will be smaller. Think of a gear being cut, the outside diameter remains constant. Like the gear, the PCD of the "Cut" knurl is below the initial outside diameter.

The outside diameter of the "Formed" knurl will always be larger than the start diameter. Unless the start diameter needs to be skimmed to suit during the knurling process as I mentioned above. In the "Forming" of the knurl the initial outside diameter of the knurl is the PCD of the finished knurl, or very near. Thus if the Pitch at the PCD of the conventional Knurling Wheel is not evenly divisible into the start diameter, then there will be problems.

Regards

Gray,

[SillyOldDufferModerator @sillyoldduffer]

Posted by Graham Meek on 18/08/2021 10:50:09:

…

Generally,

There seems to be some confusion between "Cut or Milled" straight knurling and the "Deformation, or Forming" process carried out by a conventional straight knurling tool.

…

My feeling too! Deformation knurling isn't the same as Cut Knurling. The DIN Standard recommends ratios for cut knurling and I don't think the same mathematical approach applies to deformation knurls, of the sort by the clamp tools under discussion!

Deformation knurling is like the page following Good King Wenceslas rather than an HSS knife cutting a thread:

“Mark my footsteps, good my page;
Tread thou in them boldly;
Thou shalt find the winter’s rage
Freeze thy blood less coldly.”

 

In his master’s steps he trod,

Where the snow lay dinted;

Heat was in the very sod

Which the Saint had printed.

Must be right – there's a sod in the carol too!

Anyway, I suggest deformation knurling isn't a precision process and I don't think it requires a 'quality' tool!

Dave

Edited By SillyOldDuffer on 18/08/2021 11:33:15

[Graham MeekParticipant @grahammeek88282]

I regret the connection with the Page in The Carol and knurling is lost on me.

Just to clear up any further confusion with the mention of a further DIN reference.

The DIN spec I mentioned earlier is for "Formed" knurling, on the page reference stated. I know this because of the formulae provided.

The "Nominal" or Finished Outside diameter is "d1", the "Initial diameter", "d2", and "Tooth spacing" on the knurling wheel, "t".

For Straight knurling, DIN ref RAA the formula is d2=d1-0.5.t

For 30 degree Diamond knurling, ref RGE, the formula reads d2=d1-0.67.t

Standard t values are given as 0.5;0.6;0.8;1.0;1.2;& 1.6 mm.

As I mentioned I have never used these, but will give them a try.

With regards to the single wheel knurling tool for straight knurling. It is not so simple a tool as it would first appear as someone who used to make large quantities for Neil Hemingway when he was trading knows.

For one thing the axle of the wheel needs to be square in the guide slot otherwise the wheel is not presented to the work parallel with the lathe centreline. This misalignment could be out in the vertical and horizontal directions. Ideally the slot and the Reamed axle dowel hole would be machined at one setting. If the error is out in the vertical it will skew the knurl on the work, up or down, making it helical.

This type of misalignment is shown up when the axle is inserted and the wheel locks up solid. To the Novice this is usually rectified by making the slot wider than is necessary, but this then introduces another problem.

The fit of the knurl on the axle needs to be fairly good or the wheel will wobble. More so if the axle is not square in the slot and sitting in a wider slot than is necessary. This wobble usually produces a knurl where the edges are fuzzy.

I have always used Hardened Dowel pins for the axles. These being cheap at the time, were a good running fit in the knurl being used and a press fit in the reamed hole of the holder.

The slot for the knurl is always offset towards the chuck. The thin leg of the slot is merely keeping the knurl on the axle when in the drawer and allowing knurling closer to the chuck.

Regards

Gray,

[SteviegtrParticipant @steviegtr]

Well after quite a few months , I finally made the Hemingways sensitive knurling machine. I thoroughly enjoyed the whole project. It came with brilliant drawings , but no instructions. But after much head scratching & a bit of info from some members I got there. Below are a couple of pictures of the finished article. Also a link to the youtube vide part 1. If anyone is thinking of making one then please watch away. If not then don't bother as it is 8 parts long & will send the pro's to sleep.

It was made using the Myford Super 7B lathe & the Tom Senior milling machine. With plenty of work on the rotary table which was a great bonus to have. Hemingways sensitive Knurling tool

Pictures below.

[JasonBModerator @jasonb]

Looks good Steve, Must catch up on the last few vids, I'm looking forward to some nice knurls.

[Nicholas FarrParticipant @nicholasfarr14254]

Hi Steviegtr, yes, a tidy looking job.

Regards Nick.

[Howard LewisParticipant @howardlewis46836]

An end to your problems!

And nicely done.

Came in too late to suggest the Hemingway clamp tool, so have to say a good choice.

Wherever possible, I use the clamp type of knurling tool.

Only use a single wheel knurl when absolutely necessary, (Want a straight knurl and only have a single straight wheel ) because of the loads that it imposes on the bearings in the Headstock (And my machine has taper roller bearings! )

Howard

[John HaineParticipant @johnhaine32865]

This might be of interest (in French, but I'm sure Google would oblige):

**LINK**

There is also a video of making a simpler tool.

**LINK**

[SteviegtrParticipant @steviegtr]

Thanks for the comments. I did have another go yesterday with slightly better results. My main problem is the QCTP is rotating on its stud . So i either need to pin it or try to get the knurling device closer to the post.

The problem is the hand lever is to the right & fouling against the toolpost. So i may strip the knurler & move the handle to the left side.

Steve.

[bernard towersParticipant @bernardtowers37738]

Don’t quite get why your QCTP is moving as if the knurling wheels are centralised on the workpiece this doesn’t put a strain on the QCTP or are you trying to traverse the tool with too deep a cut on the wheels, try traversing several times with slightly deeper settings each time. As far as movement of the toolpost is concerned make sure it is squeaky clean and has a relief in the underside putting the pressure towards the outside edges of the toolpost. The tool I made I put the lever to the left , makes it more comfortable to use.

[SteviegtrParticipant @steviegtr]

Bernard that is what I have done today. Moved the lever to the left. Works much better now. Yes it was traversing which caused it. Some members shun doing this but did not seem to effect the knurl. I have done a little I'd which I will be posting soon. Showing what I did.

Steve⁸

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