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Frank Ford
10-31-2009, 08:13 PM
I make this little tool - it's a miniature version of a plumber's pipe extractor, and it's used to tighten electric guitar jacks. Here's the business end of the tool:

http://www.frets.com/HomeShopTech/Products/JackTheGripper/jackthegripper02.jpg

The active ingredient is the little 1/4" knurled bit on the end made from 0-1 steel, and hardend for durability and bite.

For more on the tool, go here:
http://www.frets.com/HomeShopTech/Products/JackTheGripper/jackthegripper.html

My next batch of these tools is going to be about 700, and I really want to streamline my steps, so I showed my process to Tibor, who makes lots of parts on Swiss screw machines fin his one-man shop locally. He said he generally approved, but suggested that instead of knurling each one individually and parting on the lathe, I could have some 0-1 rod knurled in lengths. Then I could saw them off on the bandsaw in far less time. He'd provide me with a reference to a shop who could do the knurling work.

Always wanting to learn more, I decided to try knurling the pieces myself, so I decided to spend my day off work doing just that. And, after some false starts and setups, I achieved success - almost a full 36" of knurling on 36" drill size "B" rods with a final diameter of .249 +/- .001:


http://www.frets.com/ForumPix/longknurl03.jpg

http://www.frets.com/ForumPix/longknurl02.jpg

Here's the setup.

http://www.frets.com/ForumPix/longknurl01.jpg

I made a tool holder for my Aloris post to hold a turret style knurling tool which has a machined insert to guide the rod in from the back end. I run the lathe at 300 RPM, and feed inward toward the headstock. When I get close to the headstock, I stop the lathe, open the collet, and drag more rod out by moving the carriage to the right. Then I close collet, restart and knurl back to the headstock. Then I pull the rod out from the collet, flip the tool holder and rod assembly over, and rechuck it to finish the knurling by going to the right.

Edit:

I've just posted the entire set of photos on HomeShopTech:

http://www.frets.com/HomeShopTech/Projects/LongKnurl/longknurl.html

A fun (but long) day off. . .

j king
10-31-2009, 08:26 PM
nice job on that Frank.Good looking knurls also.

Ken_Shea
10-31-2009, 09:07 PM
And another very nice job under your belt Frank.

"Jack the Gripper" :)
Good name, did you choose that ?

Frank Ford
10-31-2009, 09:16 PM
It was a bit of a toss-up. I had trouble deciding between "Jack the Gripper" and "Jack Grabbit." Turns out there are lots of various products with those names.

Tony Ennis
11-01-2009, 12:34 AM
typo: "final diameter of .0249"

What a nice way to spend the day. 30 inches of knurled rod makes, what, 100 of these pieces?

Black_Moons
11-01-2009, 03:24 AM
Could we get any more pictures of that knurling tool and its guide?

John Stevenson
11-01-2009, 07:49 AM
Frank, I do the same job from time to time for someone, 40 " of 2" stainless.
I use a steady ahead of a cut knurl and let rip then follow up with a centre loose in the end just to stop flapping.

No idea what they are for.
I do another job, gripper rolls for use in a laundry 3" long in 3/4" alloy and they INSIST the straight knurl is parallel, That is a horrible job, first couple of times it goes OK then wanders for no reason, then goes back straight, this is with a steerable cut knurl that works Ok on all other materials so I put it down to the alloy.

Now finish up hobbing these to keep straight, annoying as I know a slight twist will not affect the way the rollers / grippers work, just them being pedantic.
The job has been to about 4 local shops and all have turned down repeat orders so at least they pay decent prices for them.

Black_Moons
11-01-2009, 08:38 AM
maybe theres ways you could improve your chances of it staying straight, like maybe gash the rod once or twice with a pointed engraving endmill

2ManyHobbies
11-01-2009, 10:06 AM
I liked the corked spindle.

How long did it take you to make the final prototype vs how long it would take you to make one now? If I had to guess, I'd figure an hour for the first, but 10-20 hours for 700? Am I close, or absurdly off in my guess?

BobWarfield
11-01-2009, 11:08 AM
That's very cool!

Cheers,

BW

John Stevenson
11-01-2009, 12:05 PM
maybe theres ways you could improve your chances of it staying straight, like maybe gash the rod once or twice with a pointed engraving endmill

Good point, never though of that, I could put a screw cutting tool in the lathe on it's side and plane a groove in.

I'll remember that but I'm probably screwed on the existing job if it doesn't come out like the last lot they will reject them and the hobbing isn't hard now I have the fixtures.

Proves you never stop learning, thanks.

Paul Alciatore
11-01-2009, 12:21 PM
Neat idea and great job of making them. I never would have thought of knurling a rod and cutting it afterwards.

I hope you can sell a million of them.

quasi
11-01-2009, 06:03 PM
I have found knurling drill rod to be much more difficult than say 12L14. Do you use flood cooling while doing this.?

Frank Ford
11-01-2009, 10:07 PM
How long did it take you to make the final prototype vs how long it would take you to make one now? If I had to guess, I'd figure an hour for the first, but 10-20 hours for 700? Am I close, or absurdly off in my guess?

Well, that's a good question. Took quite a while to make the first prototype tool - never figured out that one. But, I've done two batches and was able to measure my precise time investment along the way.

There are three basic parts to make - the hardened knurled cam with its eccentric hole, the shank with its eccentric end, and the socket wrench handle. Of those the cam is the quickest, and your guess is very close if you're talking only about the knurled cam - I did 625 of them in 17.7 hours, using my previous method of knurling individually, parting on the lathe, holding in an eccentric collet, drilling, deburring, and heat treating.

First full batch of 120 took 33.68 hrs. or just short of 17 min. for each completed, assembled tool and accessory wrench.

Second batch was 540 ran 66.78 hrs., or about 7-1/2 minutes each. Now, that figure is better for a couple of reasons - the batch size and the fact that I switched to 112L14 for the tool shanks and wrench handles, and I simplified my process on the wrenches a bit, too.

I won't be timing any more of these because I know I'm doing very well, so I don't have to worry about it much, and because I'll be staying about half a year ahead of reorders, so I'll probably do the stuff over the next few months.

The tool comes with a wrench handle to access the nuts in recessed jacks - a simple but important part of the "system."

http://www.lmii.com/CartTwo/headerimage/EJTGjackthegripper8545.jpg

The little hollow wrench handle rides on the gripper shank and can hold the appropriate 3/8" drive socket to reach the recessed nut:

http://www.lmii.com/CartTwo/headerimage/EJTGjackthegripper8544.jpg


Edit:

I've just posted the entire set of photos on HomeShopTech:

http://www.frets.com/HomeShopTech/Projects/LongKnurl/longknurl.html