small but precise mill 2

[cambria]

I need to drill two 0.050 inch holes in stainless steel. The part is effectively a 1/16 npt bolt, which has been hollowed out. The hex head end has a circular recess 1/4 inch in diameter, and in that recess I need to drill the two holes. They need to be placed accurately, within 0.001 inches. The thickness being drilled is about 0.10 inches. This is a small part, so I dont need a giant turning center. We will be doing a few hundred a month plus prototypes. I would like to find a mill that would give that capability. Initial efforts comes up with mini-mills which seem like just low cost bench top drill presses. Any suggestions?

 

[SincoTC]

Depending on the space you have available, you might consider the very versatile Bridgeport Series l turret-mill, there should be plenty about with vari-speed heads and digital readout for not too much money.

If this is too big and you want quality (I agree with your comments about mini-mills), then look for a small toolroom miller like the Deckel FP1 or 2, the Aciera F1 or F2, or one of the many small universal mills (Adcock Shipley, Elliot, Fritz Werner Etc) get one fitted with a self powered, quill-feed vertical head. Be wary of the the vertical milling attachment fitted to a lot of small horizontal mills as they are often driven off the main spindle and so are quite slow, also, you have to raise the saddle as the head is fixed, making them not ideally suited for drilling relatively small holes.

 

[cambria]

Thanks SInco. I could imagine the wobble just looking at the photos of the mini-mills. I find it a bit alarming that, in a reasonable googling, names like Deckel Aciera etc did not pop. Perhaps its technique. I will chase these down now, thanks a lot.

doug

 

[BobM3]

Do you really need the .001" spacing? I think that would be tough to hold consistently on a mill. You might need a jig boring machine.

 

[cambria]

Yes, pretty much, could slide with .002. This is the base to an optical device. Infrared light is projected via these holes and into a lensing system. And yes, you may be right,a different machine may be more appropriate. We have a Grizzly mill as well as a lathe, but the backlash is so bad its pretty hard to repeat a process. It is worthit to me to have a specific machine to do this.

 

[SincoTC]

Doug,

Thanks for the star! I don't know where you are located, but here in the UK there are several other small mills (Tom Senior, Centec, Boxford and Myford) that predate all the modern light weight offerings and it is worth taking a look at model engineering suppliers and magazines.

However, If you don't have other potential uses for this small mill and really only need to drill these two accurately positioned holes in a few hundred modified bolt heads, then have you considered getting a jig made up by a toolmaker that holds one or more at a time and has hardened bushes to locate and guide the drill. The job can then be repeatably and easily done by a relatively unskilled operator on a simple pillar drill. Bearing in mind that you stated the holes were to be at the bottom of a quarter inch diameter recess, which in itself makes the job more difficult, especially pre-spotting for the drills which is necessary for accurately positioning a drill of this size on a surface which might not be truly flat.

 

[BobM3]

Just drilling the holes without reaming or boring or grinding them would give you maybe +/- .003 on the diameter and roundness of each of the holes. If you need to hold the .001/.002 dimension then I would think you'd also need to hold the hole diameter tight.

 

[cambria]

Thanks to both of you. I am in Seattle, thus perhaps reason for not picking up on the older classic machine tools - most equipment around here is heavy industry or cnc for aircraft. "Spot on" with regards to drilling and reaming. I can spot the hole and drill, giving me variance which is within my criteria, or make it a 2 or 3 step process. I will talk to a toolmaker on Monday regarding a jig. Ah, and perhaps I fogot to mention that the bottom of the recess needs to be flat, nearly optically flat (I use an optical epoxy which does give me some fudge tolerance).

doug

 

[BobM3]

With the flat bottom bore, my guess is you'd be looking at a CNC grinder. You might want to try some of the guys in this forum:

http://www.practicalmachinist.com/vb/forumdisplay.php?f=38

 

[unclesyd]

You might want to give Najet a call. Their equipment is very similar to the machines that we used to drill millions of 0.0090 to 0.030 holes in 316 SS. They have both the equipment and drills that will meet your requirements. You also might want to broach your drilled hole to give you a more precise hole.

http://www.najet.com/tooling/newDefault.htm

If you have use some other drilling head you should look at the reamer drill from Atom.

http://www.atomprecision.com/index.html

There are special drill bits that will get you pretty good flat bottom hole.

What material are you drilling? If possible a change in material could be very beneficial in your process.

 

[cambria]

Material is stainless, at this time 316 but can possibly change alloy. Atom Precision has the drills for sure, thanks. Will call Najet, their website did not have images of their equipment (I understand) so will see what they have. Aside from that it may very well be a jig. Quick search for the good-old tools from the good-old days show nothing on the west coast.

SO:
1) jig
2) pre-drill with small drill
3) next size up
4) finish with reamer.

or find a neat-o drill or mill that will do the job.

 

[Jordonlaw]

BCA jig borer; see here :-

http://www.lathes.co.uk/bca/index.html

Got one in my workshop and it's brilliant. One came up for sale recently.

 

[SincoTC]

Regarding "good old tools" from your side of the pond, I knew someone in London a few years ago, who had an American made Clausing 8230 tool mill that was pretty neat. Also the Hardinge TM was often fitted with the Bridgeport Type M self powered quill-head, and I believe Rockwell made small vertcal mills at one time, but like the Millrite from (I think) Burke they may be too large.

I'm still inclined to think that the jig is the best option, if for no other reason that you've got to effectively work blind in the bottom of a small recess, with tool changes for each hole and get each one right. With a well designed jig you only have to worry about the odd drill breakage.

 

[cambria]

Thank you everyone. First, it saddens me a bit to see that an entire ecosystem of wonderfully precise, manual instruments are gone. Its like peering into a Greek text and seeing that they did perform brain surgery 3000 years ago. Its a significant loss to have these great tools and their makers pass into history. We are less for it.

It seems like the route with a jig is the most practical, and I shall proceed in that direction. A good source of mill bits which machine dead-flat at the bottom is on the shopping list. But, having said that, I think I shall be gunkholing in search of that perfect antique that will do the job, just for the enjoyment of "doing it right". Thanks again everyone.

doug

 

[unclesyd]

Here is one type bit that we used for flat bottom holes. We also used a two flute center cutting end mill. Also in use are bits where we grind a drill point for a flat bottom.

http://www.kennametal.com/e-catalog...romloc=srch&parentId=2450291&sid=11FECA0B4496

There are several companies that make flat bottoms on SHCS for UT testing. We have had several hundred in use at times.

http://www.phtool.com/pages/fbh.asp

If you are going the jig route you might want to look at the AutoDrill products. Build your own.

http://www.autodrill.com/index.html

If you are still interested in small mill/drill machines look at these two sites.

http://www.smithy.com/products.php?cid=1

http://www.use-enco.com/CGI/INSRIT?PARTPG=INSRAR2&PMAKA=109-1015&PMPXNO=953984

 

[ornerynorsk]

Just have a swiss shop run the parts for you. Have you gotten any quotes? A couple hundred a month does not justify owning the equipment. Swiss precision shops are begging for work right now.

 

[cambria]

Thank you gentlemen. Regional shops here bogged down in airplane production, but will give it another try. Some desire to have in-house capability for prototyping. I think I am set to move forward. Thanks.

doug

 

[unclesyd]

Here are two cross drilling jigs you might want to look at. We had several of the Heinrich models and used them for various processes.

http://www.heinrichco.com/drilljig.htm

http://www.pegasusautoracing.com/productdetails.asp?RecID=1192

You also might want to look at the Blue Ridge Machinery Catalogue as they carry most of the small mill drill machines. They were good people to deal with. I bought 2 pieces of equipment from them and have gotten very good service

http://www.blueridgemachinery.com/metalworking_equipment_catalog.html

 

[cambria]

Thanks again.

 

[51Chevy]

Hi Cambria,

I am new here and am looking for ways to use my new/used Deckel FP1 and FP2 Universal Milling/Boring Machines. The company where I received them from never used them other than a drill press and that was only with small drills. They are practally new, and are in excellent condition. Any comments of course will be greatly appreciated. Thanks!

Bob