Waterjetting comparision to laser

[plkracer]

I add 2 thousandths to each side of keyed parts when they go off to laser. Did the same for Gene's parts and they turned out just like we planned.

[Voodoochikin04]

our local speciallty machine and fab place, has plasma, WJ, and they just got a laser machine a few months ago. i have no idea where to start if i wanted to build anything, and no idea how to present it to them.  or what to expect for pricing.

[BDKW1]

I add 2 thousandths to each side of keyed parts when they go off to laser. Did the same for Gene's parts and they turned out just like we planned.

Add or subtract? I usually leave .010-.020 around the keys so that they actually fit together without any touch up.

[fabr]

whICH BRINGS UP A GOOD POINT.hOW MUCH CLEARANCE IS NEEDED( OR NOT NEEDED) FOR AN EASY ASSEMBLY AND ALSO A NICE SNUG FIT UP ?

[Engineer]

I always add .010 to hole diameters for my Industrial machines.  Never had a bolt that wouldn't fall right in.  Of course bolts are usually a hair under as well.  The .010 over on a bolt hole is a nice fit.  That being said  I think you could get away with .005 or even on size, with the idea that you could touch it with a drill if there was a burr.

On the key's I always leave a total clearance of .01, .005 per side for a long key, but then leave .01 at each end.  And here is the reason.  They do not like to run the laser into a dead corner (no radius) because it make the machine halt then take off the next direction.  I am sure differenct laser people will say differently, but mine say no dead corners.  So instead of having them choose the radius, I put a .01 radius on the inside corners of the Key, as well as the inside corners of the slot.  If I put the radius in then they use it.  With these clearances, the parts will fit together tight.

Of course this is the way I have worked with my laser guys over the years.  They will still leave the holes out if they are under material thickness, unless I explicitly direct them to be cut...... Sigh.....  I do quite a bit of 1/2" and 1" material, and they can cut a beautiful .385 hole in 1/2", but the rule of thumb is no holes with a diameter smaller than material thickness.

Of course other cutters may be different.

Picture for key and slot illustration.

[Engineer]

Ok now I will let a cat out of the bag that I really didn't want to until you saw it on my car and said WTF?

This is how I like to treat the corners of parts that are going to be welded together.  The full size tabs suck.... nowhere to weld.  With this method, I make the keys of both parts only half as tall as material thickness.  Then when you lay them together, you have a corner to weld in, and it alternates from one part to the other.  I have never tried it on sheetmetal, but on 1/4 and thicker, it is kinda cool. IMO.

[plkracer]

I go .005 over on holes. Exact is too tight. Sorry i was not more clear, it's .002 over (offset) on the holes. I make the key exact dims, then offset the holes where they fall in. This makes the square holes .004 over. I have never needed anything more than a tap with a mallet.

[Doug Heim]

Carl I do the same. I make the keys only about 1/2 the hight of the material it locks into. I leave .005 in all my bolt holes. I did make them to size but just running a drill or reamer in them sometimes will get ruined with laser as the hardened edge.

I leave .005 overall, .002 - .0025 per side. I have never had issues with it not going together this way with the company I use for cutting. Like said above. Some companies use different methods.

[Rick S.]

On tabs I also keep them half the material thickness in height. (for welding) On 3/16 and thinner I engage them a little more than half way. If I know I'll be welding both sides, I keep tab use to a minimum. I only use enough to jig the parts.

[fabr]

  I got corrected but was waiting till I got the parts to post them.I assume they'll be here soon. . I'll be the first to admit this keyed stuff is new to me and have been ALL EARS . That welding of the tabs has been a concern to me for quite some time. I was just going to 45 the corners before welding but  this short tab thing is just so simple and better I'm ashamed I didn't think of it!   :-[ :-[ I guess it was just too obvious.

[Engineer]

On tabs I also keep them half the material thickness in height. (for welding) 

Carl I do the same. I make the keys only about 1/2 the hight of the material it locks into.

Just when I thought I had and original idea............  :P :P

 

[Doug Heim]

Great minds think alike.

All this talk about tabbing parts is driving me nutz for some unknown reason... I refer to it as puzzle fitting myself. Just the term I'm use to using. Just in case you all wanted to share the terminology.

Any who....