Holes in 58-62RC A-2

[M. Anderson]

I am in need of advice!

 

Looks like we are getting a job that has around a total of 6000 holes in 18 parts.

 

The holes are different sizes - .043, .078, and .110, and are down in a .350 deep slot and will go on thru another .465 of material.

 

There is a requirement of a #8 finish inside the holes.

 

The material is A-2, it will be hardened to 58-62RC. Positional accuracy is not a real concern +/- .005, neither is hole size +.003/-.002

 

I have come up with:

 

1. Drill start holes, HT and then Wire EDM the holes?

 

2. Drill holes, Ream holes and after HT polish? (someway??)

 

3. Drill holes - HT - Ream? (If it would even work?)

 

4. ???????

 

What would be a way to do this just using a mill is really what I am after? I am looking for a alternative to #1 - as I will have to farm out the wire edm part - ours is currently having major problems!

 

Any suggestions???

 

Any?

 

Thanks,

 

Mark

[Lars Christensen]

#8 finish, is that 8 micron?

[connormac]

They make a roller burnishing tool that I think would get you the finish you need. I'm just not sure what sizes the tools come in.

[M. Anderson]

Lars,

 

8ra?, just has a 8 in the check mark - pretty d@*n smooth!

 

Connormac,

 

I have used one of them on a lathe - have to see if they make one that small? Thanks!

 

Later,

 

Mark

 

[ 05-19-2005, 10:41 PM: Message edited by: M. Anderson ]

[Aaron AKA. Zippy]

You could use a Miget lap to polish after heat treat, but 6000 holes, damn!! That would take for ever one at a time. Never tryed but you might be able to run them in your CNC. Wire is probibly the easist route.

 

Good luck,

Aaron

[Lars Christensen]

Wire would be easy, however getting that finish in a WEDM might take some, depending on how accurate it is going to be checked. You can have 500 holes that are 6 and 5500 there are 10, using the same settings on your WEDM, AND just because your WEDM settings are telling you that you can get a 6 finish, well from experince that is not allways the case, sadly most newer WEDM machines do not have controled spark gab, because of demands of speed.

 

Just my 2 cents

 

Lars

[Hardmill]

Mark, I'll see what I can come up with.

I'll get a hold of you tommorrow.

E-mail your info to me.

 

 

PEACE

[jeff]

What type of heat treat are you going to use?

I ask because we have used dynablue in the past (i think thats the name) and it doesnt seem to affect the finish at all.

you would want to try and finish B4 H.T. if you can for sure.

6000 holes is alot of wire edm time!

Is plunge edm an option after ht?

what kind of finish does that leave?

[Guest CNC Apps Guy 1]

With that size and that material hardness, EDM seems like the logical choice, except, have you looked at Ceramic Drills from Guhring??? I've cut Rc 48 with them and they gave a reamed finish, but for getting that finish for sure... "Extrude Hone" seems like the easiest way to treat those holes. That will get you where you want to be I believe. Roller burnishing works great but I've never seen holes that small get burnished.

 

HTH

[betts]

OK here is my .02

 

Since its A-2, and you have some play in the hole size and location, I would finish before HT as A-2 is very stable and as long as you do a little calculating, dependig on total length of part, you should be able to easily get hole within the tolerance.

[betts]

Another tip would be never give the heat treater 4 point spread. To keep parts as close as possible to the same, tell them 58-60 Rc.

[Kevangel]

6,000 holes....I would make up test block and compare various processes..and not get trapped. I have seen some amazingly good finishes with LATE model wire EDM,and if that finish is not quite good emough, maybe try lapping with DIAMOND compound from like J & L or MSC,etc. Sometimes with reamers you can have some "rings" to polish out...(I have hand polished out tapered sprue gates by hand) Do NOT trap yourself with 6,000 holes and a bad process. my 2 cents worth..test,test,test

[M. Anderson]

WOW!

 

Guy's - thanks for all the thoughts and suggestions.

 

After doing some talking with the customer today, they have agreed to some testing for this part, (kevangle), for me, it will be - LOTS OF IT!!!

 

Based on what I have got for some of the cycle times, WEDM is going to be out ($ cost) even if it would get the finish needed which is doubtful at best anyway, they seem to want a shine on the bores!?!

 

We all came up with the fact that the parts need to be finished, and the holes as smooth as possible before HT (reamed?)-DUH!!- so we all came to the conclusion for the testing of lapping the holes after HT, with some custom made laps. This is supposedly the process used on the last design of this part when it was in prototype (if you believe the Un-ga-nur). They made the last parts in house at one of their overseas divisions (England I think?), which is now sold off from this group.

 

Going to check into the HT of this, for the finish aspect – thanks, Jeff!

 

We also came up with the Extrude Hone process as a possibility, (James), for backup if this doesn’t work out.

 

I am not real concerned about the larger of the holes – but all those .043 holes – man them are EF'N little!!!!

 

Steve, if you come up with anything – E-mail me.

 

TO ALL:

 

Thanks for your suggestions and if you come up with anything else – E-mail me or post it here!

 

Thanks,

 

Mark

[Aaron AKA. Zippy]

Mark I found the Midget laps I mentioned earlier.

they make them from .032-.250". you can check them out at www.moldshoptools.com

 

Good luck

 

Aaron

[M. Anderson]

Zip, you da man!!

 

I looked on the net (Google) I didn't find any laps that went that small!

 

Thanks!

 

Later,

 

Mark

[simon peter]

hi

why don't go for gun drilling. it gives you reamed finish.

[Lars Christensen]

M.Anderson,

 

Please lets us now how you are going to make out.

This a nice challenge you have got you self into here

 

On the WEDM you would probely have 150 to 200 hours just cutting and threading the wire.

 

Lars

[Thad]

quote:

---

On the WEDM you would probely have 150 to 200 hours just cutting and threading the wire.

---

Lars, I was thinking along those lines also. I don't even want to do anything that feels good for 200 hours!

 

Thad