Strange Hole Punch For An Instrument Cabinet

Phys,

Here is a link to a well-known catalog house with the page for "D" punches, perhaps this is what you are looking for.

http://www.mcmaster.com/#knockout-punches/=9qxfwi

I order from McMaster Carr nearly every day. Tried that.

I think I'm picturing what you want right. Can you take a 20mm punch and grind the punch itself down to get the right sized semi circle and then just take a flat punch/chisel of the right size and punch out the flat part?

I could be off, I'm picturing a circular hole, but one side is flat.

Yeah - that may work. Now i will search for a 20mm punch.

http://www.wihatools.com/200seri/234serie.htm

http://www.stainelec.com.au/2.html

I am a bit concerned that the punch manufacturers make what is called a "D" punch, which is what I am looking for, but not in the size I want. Why do they not just grind a side flat as you suggest, instead of making a custom punch and receiver in the D shape? Will your suggestion hold up for 28 holes, or start to pull in the flat section as the punch begins to dull from wear?

Sometimes, you just gotta improvise.

I don't know. That second site I put up looks pretty good for different shapes.

You may have to do some tapping with a hammer and filing to make it pretty on #1.

These folks might have the D punch you need.

http://www.nittokohki.com/tools/products/machinetools/punch-dies-for-ha-hs-series/index.html

Not sure if this is feasible, but it would be quick.

Punch your 20 mm holes, and then weld one single strip of sheet metal across all holes on the side you want to be flat. The flat part would be slightly off set, don't know if that would matter.

It sounds as if a slab sided hole is what you speak of.

Here is a punch set for a double slabbed hole, common for cam locks. Major diameter of hole is .770" (19.6mm). There is a punch for a single slab ('D' shaped, or flat tire), but I'll be danged if I can find one. I know they are around. Is this the right idea?

This is the closest I could find: http://nsch5.q9j34.servertrust.com/Punch-D-Shaped-0-769in-p/4ja61.htm

0.769 ≈ 19.53 mm

I wonder if the receptacle part is just enough undersized to fit.

GA. And it is from greenlee. Perhaps they do make one.

Got the email right here from Greenlee where they tell me to try elsewhere - they do not have it.

The solid section extends way to far into the hole. There is only 1mm of offset in the desired hole, not more than 3mm as with this punch. The after punching machining on this would take more time than the idea of a 20mm hole with a weld blob and grind to fit. Nice try - but I already had seen that punch.

We used to do such jobs years ago. Making a punch like that is also not difficult: machine your pieces with M30 steel with some tolerance, depending on the thickness of your plate. Harden it and with a reasonable drill press you punch it. Otherwise a caliper and plasma cutter. Fast and cheap.

In the 1960's I had many octal connectors (Amphenol) mounted by upsetting.

A 5mm dia. flat ended punch half on the metal will push out enough to stop connector rotation. A stroke with a file will adjust the fit if required. Two 4 mm upsets close together and a little more filing will give an even better job. This is a 30 minute job for the 28 so not worth more effort.

You could get a die cut by wirecut EDM in gauge plate and punch turned and free-hand flatted with 0.2 mm clearance and 28 holes would not require heat treatment of punch or die; if your customer insists.

Have you asked Turck if anyone makes a punch?

Did you read my post the whole way through???????????

No I didn't

I use hollow gasket punches often. I don't know how hard the material is that you desire to punch through. Would it be possible to modify the hollow gasket punch by grinding away the short flat area, and welding in a straight piece of steel and using that on your material? The custom welding would only have to be done once, not 28 times.

Hoffman 304 ss cabinet - pretty darn hard.

If all else fails, find a good machine shop that can make and harden what you need. I know that this seams like allot, and it is for your present situation. At least you will have one for the next time.

Don't know if it's still an option, but if you spec the holes and where you want them, Hoffman will put them in for you. They just laser cut it in the flat. If it's on the door and you already have the cabinets, pull the hinge pin and have a local shop laser cut them in.

If niether of these are an option, have a custom panel punch made. It'll likely cost you several hundreds of dollars and eat away an margins you've got in the job. If the work will repeat for a while, you may decide this is the way to go.

The last option is to just punch the 20mm hole and make the mounting nut real tight.

Hey Phys,

I just came up with another thought that I think would work.

Drill a hole that fits inside the D shape that you need.

Use a drill bit that touches the top of the arch and the flat edge of the D, a punch would work also.

Then just take a metal cutting jig saw to cut out the corners where the arch meets the flat edge, followed by a quick de-burr with a file.

Thought it might be helpful to have a picture to look at. I think the one on the right is what you are needing, correct?

Tom D

Yes, that is it.

Note to all:

Finally heard from Turck - there is no punch designed to do this. They seem to think ALL electrical panels will be made from scratch, not bought pre-fabricated, and the holes can be machined in, water jet cut, or laser cut whilst fabricating the individual parts. (much easier to do this while still a flat sheet, not a wall in a box) They have known this is a problem for 3 years. By now, you would think they would have seen a cash cow at hand and had Greenlee make a custom punch for them to sell with the receptacles.

My comment #15; do you need an explination of upsetting, nothing about crying; just displacing metal by impact. The only problems with my well tested method (#15) are the customer's feelings.

Please comment, any comment?

I also did think for a minute about "coining".

But since, it has turned out to be a light gauge and stainless, then, apparently it is a box, (of unstated dimension, and unstated hole position), so I guess putting it in a press is not in the running anyway.

This is assuming I'm remembering the various 'leaking of information' correctly.

No - there is - as ever - no enough information to venture real advice.

So; I'm a bit surprised you would nag on "upsetting" (coining), which is a fairly high tonnage process to start with in 30,000 t/in² material - and about a bazillion gazillion to 'migrate' 90,000 t/in², work hardening, SS, that far.

But then what, if you could - die grind it straight?

No - if he cant bring himself to mark out and file - perhaps send them out to laser, or water cutting - presuming 28 will fit on one truck - and the client will pay extra for what was in the specs, but overlooked in the quote?

It's a hard world.

Phew, I have not made the answer clear.

First, the sole function of the flat is to prevent the connector's rotation, either during fixing-nut tightening, or while coupling or uncoupling the connector.

Second you want a simple unambigious answer, my appology for earlier, antipodean terminology.

Third, I have taken a piece of stainless steel sheet to test practibility of my suggestion and used a hole from a previous job. You will have to cut or punch the 20mm circular hole, then:-

Fourthly, place the cabinet on the flat horizontal face of an anvil (or some subistitute on hand) with the 20mm hole some inch or so from any hole or edge.

Fifthly, take the 4 or 5mm flat-ended punch in the left hand and place it's tip half over the 20mm hole and half on the adjacent metal. Grasp a 32 or 24 oz hammer in the right hand.

Sixthly. Hit the punch. Look at the protrouding "upset'. Gauge for fit with a connector. Too small? Hit it again. Too large? A stroke or two with a file will fix that.

Well under a minute a hole, no oxidation, no welds and completely hidden by the connector. My prefererence would be two 4mm upsets,close to each end of the flat. Anyone who can centre-punch should find it easy but practice on the scrap blanks from the holes to gain confidence.

If access is inconvenient support the inside and impact from outside. Good luck!

Clearly there is no punch available. Your options are to have one made or to adapt. I would use a smaller 18 mm round, and do two cuts side by side, and file the left side side into a curve and the right side flat. Not that long a job, but long enough. If it was a rush job, I would simply hire the water boy to work for a couple of hours and get them done. Or get as close as you can, and file the rest.

Punches are only one option though. water jet, laser cutting, will work, and hand held plasma is dirty but also will work. (I don't like plasma with galvanized steel, but with stainless, it should be okay) Stainless is the devil's own job to cut with a jeweller's saw. None of these suggestions are really much good I know, they would work if you cut a large disk, had the "D" lasered into it, and welded the disk over a hole in your box. This would have the advantage of being quick and cheap.

This is a classic case of economy of scale. If only you had two thousand of them to do, to justify the four hundred bucks it would cost to get a custom punch made!

Yusef has an idea there, does anyone make a D shaped tab washer of the right size? This could be welded in as Yusef suggests or have the tab fit in a small hole.

they would work if you cut a large disk, had the "D" lasered into it, and welded the disk over a hole in your box.

I sent this suggestion to the customer yesterday. We have had water jet cutters and laser cutters both complain about handling a full cabinet box, but a small piece of plate is no problem. Waiting to hear if they'll accept this option.

The heat from the weld may discolor the stainless.

Thanks for the concern. Don't worry about that. We build stainless steel tanks up to 10,000 gallons, heat exchangers up to 48 inch diameter, filter housings up to 16 rounds, manifolds up to 8 inch tubing, full process skids that weigh in at around 30,000 pounds - all from 304 and 316 ss for the pharmaceutical industry in sanitary finishes. I don't think a bit of weld heat on a cabinet is going to be a problem.

Count your blessings regarding response to weld heat blemish.

Our pharma customers examine the finish on their SS panels like they're the proud owner of their first brand new automobile off the show room floor. The lengths we go to to prevent the slightest scratch or blemish on an exposed panel surface . . .

Their concern is the plant tour by their customers' brass who apparently know that appearance is the end all and be all, just like those 12 year old girls at the mall.

What I meant by my weld heat remark was that we have the ability to correct it - we have a huge polishing department ( 2 polishers for every welder we have) with several employess with about 35 years of experience in polishing and matching finishes. Once the weld is done, they will make the panel look like it was built with this plate in place. Yes - pharma is overly picky about finishes.

Phys,

I am sure you read my threads, and have discarded them for good reason. Could you please tell me why?

Perhaps you have demarcation disputes in your workforce.

Do you feel a blacksmith to upset, followed by a fitter to file is your shop's way?

Do you feel that a hammer is a forbidden tool in your place?

Is grinding the point off a small centre punch to make a flat ended punch verboten under H&S law?

Do you use McMaster-Carr, you will find many suitable punches in their catalogue?

I truly had the upset method used for some hundred jobs in the late 1950's through 1960's in the production af electronics for research projects in the world's most isolated (1800 miles from the next uni.) university.

Those tube sockets are now listed as relay 8 pin sockets on Newark's website,

I feel that I could have done the 28 boxes in the time I have spent helping you, please answer my enquiry.

To make the job less visable a 3mm punch at each end of the connector's flat might be even better.

First - I stated that the customer insisted there must be a punch to do this and wanted us to purchase it. Well, there isn't, at least not commercially available. (see point three) This implies to me that they want a very neat hole in the shape of a D very close to Turck dimensions.

Second - I have used our very skilled welders and grinders to make the inverse of the classic 30mm oil tight switch hole to perfection. (tab sticking in, not out from hole) So, I know that we can very easily fab a flat in a round hole. For a time, this was how I was proceeding in lieu of a true hole punch. The end result would have looked very much like it was punched. It would have been a bit time consuming, but very neat. The customer was not sure they wanted me to proceed this way, despite assurances that the end result would look like a punch made the hole. There was no way I would get your suggestion by them.

Third - Turck has finally come through and admitted that a competitor, who also has an M23 receptacle with a flat side, makes the fit up plate or washer with the required D shaped hole, and has them in stock at a distributorship in Florida. For $3.00 I can have a square plate a bit bigger than the 20mm hole with a D shape of the appropriate dimensions. And, most importantly, they are sitting on their shelves.

Thank you very much for the reply.

I thought the customer would have compromised for speed and function but always right has won out.

Cheerio, Zaf.

Speed is important in the pharmaceutical industry, but appearance is of far too much concern. A very hard and fast rule.

Plasma cutter?