Knurling tool build

[bretthl]

Another idea:

I have an aluminum dovetail that I made for my AXA toolpost. I am thinking of mounting this tool on that part instead of a regular tool holder. With one less interface the geometry should be better. I don't see a lot of force on the center pivot so I am thinking aluminum will be OK in this application. Otherwise I have a piece of 5/8" keystock (shown above.) What say ye?
Robert

I would avoid aluminum and stick with steel. The side forces exerted while traversing with a knurling tool are substantial. I have seen my BXA post rotate even with good clamping force. If I knurled regularly I would pin the post to the compound T-nut. With an AXA post you will have the same side force but perhaps less resistance to rotation at the post.

 

[rwm]

MMCMDL-don't rush those screws into the mail! I think there may be a problem. If I use screws for the axle in my design, the screw force will clamp the arms closed on the wheels and lock them. I do not think I can use a threaded axle. I probably should go with a straight axle and have another screw hold it in.

Here is my design ready for the CNC bandsaw:

Robert

 

[aliva]

I tried making one from a large Kantwist clamp. Didn't work, the material was too thin and flexed a lot under load.
I like RWM's idea much thicker material should work out fine.
I looked at Eagle Rock' products, too expensive for me.

 

[rwm]

Now that I have some parts in my hand this feels like it will be a very solid tool.
I think I am going to make spacers that have .250 bosses to fit the .250 holes and then tap these 10-32.
Still contemplating the upper arm. I may drill two holes and tap one side and screw the hole thing together rather than braze. I could also tack weld some edges.



To be sure the holes are properly registered, I left tabs on the corners and then TIG welded these together. When I grind off the tabs the parts will separate! Clever plan I hope?



That .750 hole is scaring me...
Robert

 

[rwm]

I used this setup to drill and bore the larger holes:



I decided to reduce the threaded pivot hole to 5/8". That should be plenty large. I had about 1/8" clearance on the swing.

Here's where we are.



You may notice I used DTMS welding on the wings. This causes a lot less distortion than TIG.

I have a plan to propose; back to the axles: One issue is the arm spacing needs to be fairly accurate for the knurl wheels to run properly. The wheels are 0.375 wide. I would like the arm spacing to be about 0.378. The only way I can see to effectively accomplish this it to use an axle with a shoulder that abuts the arms. My plan is to use a hollow axle. It would be 0.250 diameter and 0.378 wide. It would be drilled to accept a #8 screw and clamped in place by that screw between the arms. I would like to use a #10 but that would leave the wall thickness of the axle at about 0.030" which I don't feel good about. I don't see a #8 screw shearing under this load? I could use O1 tool steel if people think a hardened axle is important? I could also make spare axles easily. I am open to other suggestions.

I am excited to grind the tabs off the arms and separate the two pieces!

Robert

 

[rwm]

...another option would be to make an axle that was solid with the central portion being 1/4" and smaller bosses on each end. The bosses could be like 3/16". That would be hard to shear. I could make these from drill rod? Hmmmm. What version of axle to you like? Please vote now.
Robert

 

[rgray]

You could make a large 5/8" or so dia axle with ends turned down to 1/4" and weld the ends.
Making that lower set of arms somewhat one piece.

 

[jwmelvin]

I like your second idea much better.

 

[rwm]

You could make a large 5/8" or so dia axle with ends turned down to 1/4" and weld the ends.
Making that lower set of arms somewhat one piece.

Thanks Russ- I was referring to the axles for the knurling wheels. They must be 1/4" to fit the wheels. Maybe I misunderstand your comment?

I like my second idea better for strength, however this would make changing the wheels more cumbersome since I would need to take the entire tool apart. After consideration, I don't see that being practical. Would it be satisfactory to have a hollow axle (#10 screw inside it) with an .035 wall? Could I harden that axle sleeve? Maybe O1 would be hard enough in its natural state? Maybe I could drill a section of Grade 8 bolt?
Robert

 

[rgray]

I was referring to the axles for the knurling wheels

When I first read that I thought you were talking about the knurl wheel axle. Then I though "no can't be"

I'll try to do this in one picture.
Pinch knurler at the top. Great idea built by someone in the usa originally as I understand it. Then farmed out to china and built there. Then I buy it. Multiple problems we won't get into but the point is the axle. It's hard but you can see the wear.

Next ....we'll go clockwise... 1" boring bar. I built lots of boring bars in the past and sold some on ebay. Anyway this one is 1" and is set up to do internal knurling on one end. The axle for the wheel is hardened o-1 steel. These axles didn't fair much better than the one in the china pinch tool. And became hard to remove once worn. (pictured one is new). Hard to apply much pressure on a tool like that it has lots of leverage on your tool post so I don't think I was just heavy handed and causing my own problems.

Next is a homemade pinch knurler I made. I used hss axles and "tried" to retain them with the little set screw running parallel to the axle. Arms are D2 steel that was already hard so I had trouble drilling and taping 4-40 so there are some broken bits and broken taps in some of those holes. Top arm has a screw on each side retaining the axle, but the bottom arm has nothing retaining the axle and it has never mover when knurling. It will fall out on the floor if turned sideways so gotta watch that. It's axle and wheel are laying there no wear on the axle. It's been used plenty the small tap holder is an example.

Last knurler is 1/2 of my cnc lathe knurling set up. Other one is mirror image. My lathe is twin turret so I use those as pinch knurlers bringing the turrets together to knurl. I built those they also have hss axles retained by the 4-40 allen screw. There is a groove ground in the hss that the screw enters to keep it in. The screw does not lock it down the axle free floats a small amount.
That pair has run hundreds of those bolt knobs pictured below it. and probably 50 of those handles above it. Black handle is 4130 and has been hardened, shiny handle is W-1 and is not yet hardened.
I actually did a thread bragging that I had the biggest pinch knurler. Lol and posted a u-tube link to a video of the cnc lathe knurling one of those knobs. But that was just before a system crash of this site and that thread was lost.

Whew that's awfully long winded just to say that I think the axles need to be solid hss.