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View Full Version : Knurling revisited



John Stevenson
12-22-2009, 02:47 PM
Well seeing as it getting near Christmas and the scary news thread has died, I though I'd rehash the knurling thread with a few pictures.
Today I needed two 15" long lengths of knurled bar for a simple job, specs were very loose 27mm diameter, course knurl but it had to be parallel along it's length, material not critical so just cooking steel.

There are two schools of thought on knurling, [1] calculate the OD based on the pitch and [2] sod it and wind in, as the OD was specified I used method 2.

Centre, run in a revolting centre and turn to 27mm down from 30mm.
Attack the end with the knurling wheel and feed in until you get a nice knurl, lock the top slide and apply power feed with a drop of coolant.

http://www.stevenson-engineers.co.uk/files/longknurl1.jpg


Job done in one pass, close up of the job.

http://www.stevenson-engineers.co.uk/files/longknurl2.jpg


Nice level knurl and repeat on second pre-turned bar.

Crappy vid taken with a stills camera here. [ warning about 4 meg ]

http://www.stevenson-engineers.co.uk/files/P1000900.MOV

I say crappy vid as it doesn't show speed clearly but for the record speed was 350 rpm and the feed was 12 thou per revolution.

.

motorworks
12-22-2009, 02:56 PM
What pitch was the knurl wheel?
I built a cut knurl tool as well, but I have a hard job keeping the "lines of knurl" straight :(

tyrone shewlaces
12-22-2009, 03:04 PM
Damn you JS.
OK here we go.
Well I pick #2 too.
When it comes to knurling, you can do math if you want and fool yourself into thinking you got all "rocket surgeon" about yourself, but I feel there is always at least one complex variable you won't count on which determines if you are successful or not, whether you put thought into it or not.
When it comes to knurling (or many other human endeavors) "Ours is not to reason why. Ours is but to do or not".
Warning - end result may tend toward success, but is random in the end.

John Stevenson
12-22-2009, 03:06 PM
What pitch was the knurl wheel?
I built a cut knurl tool as well, but I have a hard job keeping the "lines of knurl" straight :(

No idea on the pitch Eddie, just course, I can count it tomorrow if needed but this is what makes a mockery of the "work the OD out determined by pitch" brigade.
I don't know the pitch but still get a good knurl, the pictures don't lie.

Again I'll post pics of the knurl head tomorrow [ dark and cold now and that bloody workshop is haunted ] as this one can be 'steered'. usually stays OK but I may have to tweak it when doing soft materials like alloy as they tend to lead because they are easier to cut.

.

camdigger
12-22-2009, 03:19 PM
Nice work John.

I don't use straight knurls, but I do as much knurling in the drill press as I do on the lathe. Home made doodad with commercial knurl wheels. Maybe some day I'll take pictures... never thought it worth comment..

dp
12-22-2009, 03:28 PM
Somewhere in your pictures you have a photo of a knurled bar where the diameter is stepped smaller along it's length. Regardless, the knurls are continuous despite of the diameter changes. I thought that to be the slam dunk evidence to end the pitch/diameter controversy. Still have that?

Allan Waterfall
12-22-2009, 03:57 PM
You just wanted to stir it all up again for Christmas.:D

I've only got one set of knurls,no idea of the pitch or diameter,but they've never failed to produce a knurl in whatever size bar happens to be in the chuck at the time.

Am I doing something wrong ?:rolleyes:


Allan

Ryobiguy
12-22-2009, 05:12 PM
Speaking of the knurling vs. diameter, I was curious about what would happen if a taper was knurled - seems like that might test the theory.
I didn't do that, but I knurled a face, with just one of the diamond knurls. Turned out to be very interesting looking. Someday I'll make some cuff-links this way:

http://img.photobucket.com/albums/v129/Ryobiguy/Knurling/FaceKnurl.jpg
-Matt

dp
12-22-2009, 05:33 PM
That looks like it was done on a Rose lathe.

j king
12-22-2009, 05:33 PM
Looks nice John. Looks as if it were broached!never did a straight knurl.. Jim

Rich Carlstedt
12-22-2009, 06:25 PM
Just one of many of Sir John's skills !
I hear he can walk straight after a few pints too !

Good job

Rich

shoprat
12-22-2009, 06:35 PM
as always nice work,could you tell me what you would use a straight
knurl for ? is that for a press fit in plastic or something ? thanks
shoprat

John Stevenson
12-22-2009, 06:53 PM
as always nice work,could you tell me what you would use a straight
knurl for ? is that for a press fit in plastic or something ? thanks
shoprat

Even simpler than that, pieces parted off at 50mm long, eached one drilled eccentric so they bolt to a frame, twist and lock onto some fabric in an automatic laundry machine, a bit like those cheap tie downs.

There is no reason for it to be a straight knurl, in fact the first ones I did were crossed knurl as the drawing just said knurl but they returned them as the original [ which they didn't send ] was straight.

When they realised the 'mistake' they insisted on straight and they specified they had to be straight.
Some customers are anally retentive like this, annoying but I look at it this way, if they are that anal I don't mind taking coin off them.

.

Your Old Dog
12-23-2009, 07:15 AM
Just one of many of Sir John's skills !
I hear he can walk straight after a few pints too !

Good job

Rich

Where'd you hear that?

John, I liked it better when the guys thought there was deep math necessary. Made me look like I knew what I was doing! I'm of the school of thought that if that steel bar was putty, you would find several diameters along the way that would yield perfect knurls, sort of like harmonics.

lazlo
12-23-2009, 08:44 AM
I'm of the school of thought that if that steel bar was putty, you would find several diameters along the way that would yield perfect knurls, sort of like harmonics.

That's quite true YOD. Either way works fine (measure and knurl, or mash and knurl).

Or if you want a checkbook solution, get diametral pitch knurling wheels. The circumference is a multiple of Pi, so they're on the right diameter at common fractions of normal stock sizes (1/4", 1/2", 3/4", 1"...)

I find it amusing that the same quality diametral pitch knurling wheels from the same manufacturer are quite a bit more expensive. As in, "we know this is going to save you a lot of time dorking with the knurl, and only Pro shop buy diametral pitch wheels, so bend over and smile." :)

mototed
12-23-2009, 09:52 AM
Very nice work. I hope you get the time to post a picture of the tool. I could make use of some straight knurls like that.
Ted