[RAF.]

Is there a simpler way to draw Knurls????

This was a real PITA

:drowning:

[MikeC8]

Why do you need to model them? Bobcad is not the software I would use for detailed CAD modeling, its strong point is cam.

[RAF.]

Why do you need to model them? Bobcad is not the software I would use for detailed CAD modeling, its strong point is cam.

Yes much easier in other cad programs but Bob keeps getting better at Cad

I just consider it another workaround getting it to do something.

[jrmach]

Sooooooo,what you are really asking is "Mr. Burr,can you please show us how to do this ?

[InMesh]

Drawing them I have a bad time cutting them ...

[BurrMan]

Is there a simpler way to draw Knurls????

This was a real PITA

:drowning:

Hi Raf,
Well a couple things. First off, NICE Job! Only 23 features in the CAD tree... There is absolutely nothing wrong with that. A small amount of moves and commands to do it the way you did.....

Looking at your file, it appears your Nurl is "Inverted".... In other words, that would be a nurl if you cut those object from the inside surface of a tube or something....

Is there an easier way????

Well, not really but yes also. I think doing it that way, will be tuff on BobCad and the Booleans you need to perform to get a good nurl. and the amount of commands will be hard to get under the amount you have.

If I was going to do it, the hard would be in the setup, then just a couple commands to create the nurl, but you couldn't call it "easier" or it could be debatable if it would take more or less time.

The setup me would be more like "model the one single pyramid of the nurl, then radial array it into the nurl pattern.... The single pyramid would be the hard part, as it would need to be calculated out at the nurl parameters, then modeled that way.

So, a single nurl is NOT a square, straight pyramid. It is kindof bent, and twisted at the same time (with regard to its helical end result). If you are good at calculating these types of things, then it wouldn't take you TOO much time to get one laid out.... If not, that part may be hard also....

If you plan on using the nurl to do some other Boolean cut, then adding in some cheats will make it a little less painful. The cheats are to add "chamfers" to all the point and intersection areas (Small enough to not really be seen by a "real eye"... This will help because the calcs on exacting "sharp points" (you know, those things that don't really exist in the real world) will have less chance of having clashes at intersections which aren't exact (the part that's "REALLY" hard to make happen....if you are working in an exacting environment)

The easy one would be to do it with BobArt. Or even setup a cut pattern (pretty easy) then sim it and keep the sim STL to load back in. But I assume you really want a surface model and not a mesh.

Hope that helps... I probably don't have a solution better for you than "just start now and get it done" type of thing.....

[jrmach]

" If you are good at calculating these types of things, then it wouldn't take you TOO much time to get one laid out.... If not, that part may be hard also...."


In Machinist lingo the word is "Diametrical Pitch"

Google it or the Machinist Handbook goes into it in some detail.

"The cheats are to add "chamfers" to all the point and intersection areas (Small enough to not really be seen by a "real eye"... This will help because the calcs on exacting "sharp points" (you know, those things that don't really exist in the real world) will have less chance of having clashes at intersections which aren't exact (the part that's "REALLY" hard to make happen....if you are working in an exacting environment)
"

Some good info there,,thanx

[BurrMan]

Some good info there,,thanx

the other cheat I mention in the other thread is to make one of the patterns cutters be "slightly deeper" than the other. This can allow the Booleans to complete....

[RAF.]

Hi Raf,
Well a couple things. First off, NICE Job! Only 23 features in the CAD tree... There is absolutely nothing wrong with that. A small amount of moves and commands to do it the way you did.....

Looking at your file, it appears your Nurl is "Inverted".... In other words, that would be a nurl if you cut those object from the inside surface of a tube or something....



Well, not really but yes also. I think doing it that way, will be tuff on BobCad and the Booleans you need to perform to get a good nurl. and the amount of commands will be hard to get under the amount you have.

If I was going to do it, the hard would be in the setup, then just a couple commands to create the nurl, but you couldn't call it "easier" or it could be debatable if it would take more or less time.

The setup me would be more like "model the one single pyramid of the nurl, then radial array it into the nurl pattern.... The single pyramid would be the hard part, as it would need to be calculated out at the nurl parameters, then modeled that way.

So, a single nurl is NOT a square, straight pyramid. It is kindof bent, and twisted at the same time (with regard to its helical end result). If you are good at calculating these types of things, then it wouldn't take you TOO much time to get one laid out.... If not, that part may be hard also....

If you plan on using the nurl to do some other Boolean cut, then adding in some cheats will make it a little less painful. The cheats are to add "chamfers" to all the point and intersection areas (Small enough to not really be seen by a "real eye"... This will help because the calcs on exacting "sharp points" (you know, those things that don't really exist in the real world) will have less chance of having clashes at intersections which aren't exact (the part that's "REALLY" hard to make happen....if you are working in an exacting environment)

The easy one would be to do it with BobArt. Or even setup a cut pattern (pretty easy) then sim it and keep the sim STL to load back in. But I assume you really want a surface model and not a mesh.

Hope that helps... I probably don't have a solution better for you than "just start now and get it done" type of thing.....

Thanks Much Burrman

The challenges are what keep some of us interested in Bobcad trying to get every little drop out of it.
Some may ask why bother --- well out here on the chicken ranch Bob may be to only program available and usually if it can be can be drawn in Bob it can be cut with a Standard 3D package and a indexer.


So lets put that Knurl on a 8' pipe with minimal equipment.


Another sample I did which is a little faster and also seems to allow for good Booleans

[jrmach]

So lets put that Knurl on a 8' pipe with minimal equipment.

A Lathe,ha

Every Chicken Ranch should have one.

[RAF.]

Is this correct for External Knurl?

[jrmach]

It's better than I could on my lathe.

looks Great,,in practice you have like a .005 to .010 flat on top so it's don't cut you.


Here is an example of a knurl I cut on a flat surface.I just used line geometry and a angled cutter

[RAF.]

It's better than I could on my lathe.

looks Great,,in practice you have like a .005 to .010 flat on top so it's don't cut you.


Here is an example of a knurl I cut on a flat surface.I just used line geometry and a angled cutter

sharp and pointed never kept my hands off but in this case it may be better!!!!!

Thanks JR.

RAF.

[jrmach]

When you make knurls on a manual lathe you are not cutting,you are "forming"
Under great pressure it indents and raises the overall OD.
To make quality knurls on a manual lathe is right up there in the difficulty range.Lots of attention to small details to get a good knurl.
General practice is to follow up with a brass wire brush for deburring and a light hand filing.

Now on CNC Lathes and Mills you can actually cut them.
Lathe cutters are pretty expensive (actually real expensive),,but the result is perfect cut knurls
On a mill you just use a form cutter and line geometry and go.
And then you can use a 4th axis for round bar also,,,,That would be great results,but not a fast method,,but on a Chicken Ranch,,it would be great

[magicniner]

I use a Quick LA/KF cut knurling tool for small work and an Integi CNC 21 55 25R for large stuff on my manual lathe to get nice sharp knurling.
They're both aimed at the automatic/CNC market (probably due to their huge cost) but if they're properly adjusted for diameter and presented correctly to the work they function extremely well on manual machines too.
It's worth keeping an eye on the various auction sites for these, I picked mine up second hand but nearly new at a fraction of retail ;-)

- Nick

[jrmach]

I got El' Chinese Cheapo for the holder,,,I think I live on a Chicken Ranch sometimes
BUT
I buy the Best quality Knurls that are out there.You don't skimp here,,or forget even bothering.
And
To make everything work,,there are all the little details I mentioned earlier.That's a whole other topic.

Nick you got a link ? Am I understanding right ? You got a Knurler made for CNC,,,but you use it on your manual lathe ?
Is it "Forming" or is it "Cutting "

[magicniner]

Nick you got a link ? Am I understanding right ? You got a Knurler made for CNC,,,but you use it on your manual lathe ?
Is it "Forming" or is it "Cutting "

The Quick LA/KF is one of these - Cut-Type Knurlers | MSCDirect.com , it's described by the manufacturer thus - "This tool is intended for use on long-turning automatic machines, small lathes and, because it can be used as left-hand and right-hand tool, it is also suitable for use with CNC lathes." so they don't view it as the exclusive preserve of CNC.
The Quick is definitely cut knurling and not formed, I bought it when I was making some small parts in a free machining brass that doesn't form well, breaking up on the peaks when using formed knurling.
I bought the Integi ( MF 21.55 ) for a job which needed a knurled section in the middle of a length of thin walled stainless tube, it wouldn't hold up to the pressure of formed knurling and making a supporting mandrel was not an attractive proposition, Integi describes suitable machine types as "Swiss type, multi-spindle, conventional and CNC lathes"
I think the received wisdom of Cut Knurling being only for CNC has grown up based on the fact that cut knurling tools are generally too expensive for those without the money for CNC but they work equally well on a manual lathe, the reduced pressure requirement actually makes them ideal for smaller manual lathes, the model engineering crowd have been aware of this for years, several DIY tool builds have been published.
Because there is no size increase with cut knurling if you want a raised area of knurl you need to leave that section with a slightly larger OD.
You really need to set the job up with a test piece, setting the height for perfectly even contact, noting contact OD and plunge depth but the results are worth it,
Regards,
- Nick

[Malish]

So how would you program cutting that knurl?

[RAF.]

So how would you program cutting that knurl?

Cut as per then Index (rotate) 30degs or at 10deg multiples beings that is what the knurl was based on --cut / index cut-cut index--etc. till done and wala big Knurl.

I used Planar for cut for fast sim but use what ever Cut Features to your liking.