Knurling advice

[mikey]

If I only had the money. And that's not even the saddest part. I make guitars on the side and I just started getting into making the hardware for my guitars, hence the machining. Just a few years ago I could have had ten times or more that amount of high end machinery since my father-in-law, a very generous guy and somebody I was close with, bought and sold machinery. He sold into the hundreds of thousands every year and bought up little shops like this ad shows with his pocket change. He used to tell me, "anything you want". Sadly he's incapacitated in a nursing home now.
My guitars are unique in that the wood is joined on curves. Pictured is not inlays but maple and walnut joined on curves.

Beautiful work! I admire guys who can create objects of beauty like that.

Sorry about your father in law. Hell of a place to be for a machine guy, I think. Personally, when its my time to go I hope I drop dead in front of my lathe.

 

[Maplehead]

Thanks, yeah his life is a living hell right now.
His old company use to turn the axles for the Trident submarines. Talk about a lathe.

 

[mikey]

Thanks, yeah his life is a living hell right now.
His old company use to turn the axles for the Trident submarines. Talk about a lathe.

Next time you see him, tell him someone on the forums wishes him well.

 

[David S]

Maplehead I have a small Atlas 618 lathe and I have the scissors style knurler. It has a knob on it similar to yours but I wasn't able to get enough pressure on it. So I drilled some radial holes in the knob so that I could use a tommy bar and really crank on it. I make sure the knurls are dead top and bottom, then crank them down till they touch firmly and then give it another good crank quarter to half turn with the tommy bars, and keep cranking down as I rotate the chuck. I often do as you do with just hand turning the chuck. In brass I needed much more force than I could muster up with just the knob alone.

David

 

[Maplehead]

Good to know David. Thanks.
Part of this as a beginner is learning how much something really needs. One of my issues is the tool not staying straight when I crank it down. Last night I made a t slot nut and block to sit aside my tool post on my cross slide to keep it from turning. It's reaction was to just turn the other way, away from the support block.

 

[David S]

Yes Maple head my scissors type is of poor quality. I had to modify it. But the big improvement was being able to really crank it down.

David

 

[mikey]

You can also use a hand knurler and this might be the best option for you. Eagle Rock makes some of the best knurling tools around and they also produce a hand knurler. Here is one on ebay for a not bad price: http://www.ebay.com/itm/EAGLE-ROCK-...261101?hash=item1c3eb6f1ad:g:vlEAAOSwcUBYUBy2

 

[brino]

It is the finished knurl size that matters, not whether the knurls will track and this is a point of confusion for a lot of folks.

What?!?!
Mikey can you explain this a bit. I was following this thread right up to that statement.

I have NEVER cared about the finished size of a knurled section. For me they are only handles and if it's 10thou bigger or smaller, my hand will never notice. I ONLY care about the tracking. I hate the double track and consider that a scrapped piece.

I tend to agree with Will here:

It's for calculating the starting workpiece diameter to match the pitch (teeth per inch) of the knurling wheels so you get an even amount of "lines" cut in the circumference of the round stock. In other words to prevent double tracking.

Aren't you saying the opposite?

-brino

 

[mikey]

Let me come at your question this way. Way back when I started to knurl stuff, I used calculators because I thought it would tell me the OD I needed to get my wheels to track. The documentation of the calculator I used then said so, and since it was all based on math and tpi and helix angles I thought it had to be right. I calculated and turned, calculated and turned and still couldn't get my wheels to track. I even did as the documentation said; turn down a few thou and try again, and again and again and still had poor tracking.

So, I called (back then, email wasn't common) Form-Rol, the guys who make the knurls I used at the time, and asked them how the heck do I figure out the OD needed to get the wheels to track. The response I got was surprise! The tech guy told me that the calculations are intended to give me the OD needed to bring the knurl to the expected size when a full pattern was formed so that my part would fit properly. I said I just wanted the wheels to track and I didn't care about the size of the knurl. He told me, "... just increase pressure."

My experience since that time has led me to agree with tech guy. If I want the wheels to track, I crank down on the arms and the wheels track. So now the only time I calculate is if I need a specific fit. I turn the work to the calculated OD and then I crank in the pressure needed to produce a full pattern knurl and check for fit.

Don't take my word for it; try prepping a blank and increase pressure on the knurls. They will track. For materials that work harden you need to get it to full depth or whatever depth you need and cut it in a single pass. I do this for stainless all the time ... but I don't calculate.

 

[brino]

Don't take my word for it; try prepping a blank and increase pressure on the knurls.

Oh I fully believe that! No question.

It's just that all the talk and all the calculators I have seen point to turning the OD to get a whole number of the knurl pattern around the work.

Thanks for the background.

-brino