Retrieving an undersized dowel from a hole

Hi All:
Here's a technique I NEVER thought would be successful, but I tried it as a last resort and whadda ya know...it WORKED.
I have a bunch of 1mm dowel pins 4 mm long to place in some aluminum blocks and one of the dowels was undersize by a few tenths so instead of a hard push fit, it was a drop in fit, and it ended up dropping into the hole so far I couldn't get it back out (blind hole).
I tried every trick I know, but no joy.
Last kick at the can before I scrap the part...I take a bit of 0.015" diameter 316 stainless welding wire (nice and ductile) and laser weld it to the top of the dowel.
A gentle pull and here's what you see as the result.

Happy happy happy boy today...a fuckup discreetly fixed and nobody even needs to know!!

Cheers

Marcus
Implant Mechanix • Design & Innovation > HOME
Vancouver Wire EDM -- Wire EDM Machining

When all you have is a laser welder... something something nail....

A toaster oven set to 100C and an hour or so would have allowed you to flip the part over and drop the pin out.

Well, and maybe the other pins too...

I love things like this, completely impractical for me since I don’t have a laser welder, but wonderful none the less. Excellent creativity!

mnl said:

I love things like this, completely impractical for me since I don’t have a laser welder, but wonderful none the less. Excellent creativity!

Click to expand...

this method works with TIG also, starting on little larger things though

same problem in the photo, 2mm pin though, customer thought it is fine to send in a part to be anodized with steel pins pressed in, I call them to ask wth - they say, the pin was so low they couldn't grab it and pull it out so they left it in and thought it will be OK...

Thats pretty neat Marcus.One thing I do first in a situation like that is move an air gun with a small tip high velocity nozzle rapidly back and forth across the hole.Suprising that a lot of times the part will pop out.No big loss if it dosn't work, not much investment in time and materials but when it does it sure is quick!

How will you fix the oversize hole? Oh yeah color me jealous with the laser welder

Erich said:

How will you fix the oversize hole? Oh yeah color me jealous with the laser welder

Click to expand...

Dowel pin was undersize... Hole is good.

ratbldr427 said:

Thats pretty neat Marcus.One thing I do first in a situation like that is move an air gun with a small tip high velocity nozzle rapidly back and forth across the hole.Suprising that a lot of times the part will pop out.No big loss if it dosn't work, not much investment in time and materials but when it does it sure is quick!

Click to expand...

I have a really nice " Snap-On " ratchet screwdriver. The type with a magnetic end for holding interchangeable 1/4" hex bits. Whilst I'm busy concentrating on what I'm doing my fuck wit of an apprentice picks up the screwdriver and sucks up a loose ball bearing off my workbench into the business end of the screwdriver ! It's a really snug fit and it's rendered the screwdriver useless. All I could think of was doing what you describe and pass my compressed air blowgun nozzle over the end of the screwdriver. Almost right away the ball came flying out and the apprentice didn't get murdered !

Regards Tyrone.

For some reason I do not own a laser welder so I would try some super glue on a wire or welding rod. Maybe the ultimate Harry homeshop tool, JB Weld.
Bil lD

Actually Marcus, the fuck-up was reaming the holes as deep as the length of the dowels. How do you ensure the dowels actually cross the joint on assembly, that they didn't just push in? I build a lot of mold inserts that are located by dowels, typically slip fit in both pieces and always limit hole depth to 60% of dowel length for just this reason.

Dennis

Hi Dennis:
I didn't make those parts; I just get to assemble them together with all my parts.
I was given the parts and all the fasteners and components to put the whole works together because I'm the only shop in the vendor pool with a stereo microscope and I built most of the rest of the parts.

So I put in the dowels specified in the assembly model and promptly crapped my panties when one of the dowels disappeared in the blind hole.
I personally would have made them tight in the mating part (through holes) and a slip fit in these parts and ovalized one of them to boot, but I didn't get to control that part of it, so it is what it is.

I fully agree with you that the smart move for this particular design choice would have been to make the holes shallower or supply longer dowels.

Cheers

Marcus
Implant Mechanix • Design & Innovation > HOME
Vancouver Wire EDM -- Wire EDM Machining

So pardon the potentially stupid question, but if you dropped the dowel in the hole and gravity made it disappear, then why couldn't you just turn the part over and let gravity make it reappear?

Has that been answered already?

Hi FTF Engineering:
I had to force the dowels in with a little plastic pusher under the scope, all except the undersized dowel which I pushed vigorously too, and when I did, it was instantly GONE.
It was a sliding fit instead of a light force fit, and of course it was still too snug to just fall out.
This is a 1 mm diameter pin 4 mm long...it doesn't weigh very much, so it doesn't take much to hold it in place.

Cheers

Marcus
Implant Mechanix • Design & Innovation > HOME
Vancouver Wire EDM -- Wire EDM Machining

Thanks. Gotcha.

You threw me when you said it was a drop in fit. To me, that sounds like you dropped it in and it disappeared (because gravity took it from there). I figured it couldn't be that simple, but just had to ask.

I saw this thread title and your name and knew the laser welder was going to be in play!

I would love to get a laser welder, but I don't have enough work to justify the cost at this point. I only have the occasional oddball job along the lines of what you showed here and about once a month I need to weld some fine gage (28g or 30g) TC wire to some stainless steel. I have a capacitive discharge welder for the TC's, but doing fine gages onto a larger part is REALLY hard.

I buy a lot of used equipment, but a used laser welder seems like it can be a big gamble. I also need to figure out what I would really need.

All the shops I know with laser welding are either focused on production medical work or mold repair and aren't really setup ($$) for the quick walk in job. I am thinking I need to find a jewelry repair shop that has one and is willing to do my work. They are at least used to small jobs and walk in type work.

Good morning newtonsapple:
I understand exactly what you mean, and here's my experience.

I first saw one in use back when I was still a dentist...a lab tech buddy of mine showed off the one his lab had just bought and I was HOOKED!

Back then you could really only buy German and they were forty grand, so I lusted quietly for years.

One day I came across one on EBay and I bought it for eleven grand...when it arrived I had to put in another five to get it fixed, but now I had one of my very own and I thought I'd be drowning in work for it because I'm the only one in the Greater Vancouver (Canada) area offering laser welding services to commercial customers, and I was a moldmaker too, so I thought....

Turns out to have been the absolute WORST return on investment of any machine tool I have ever owned...by an order of magnitude at least.

Break even took years...I seem to remember 8 years to get back to the 16 grand I put into it.

BUT it is just SO DAMNED COOL!
I have never lost my appreciation for having it in my shop, and the odd thing is that it attracts business that comes to me for laser welding and stays for milling or wire EDM or other services, so I can pretend to justify it that way.
I also use it frequently as a support machine...either to rescue a screwup, or to quickly nail a workpiece to a stub so I can fixture it in the wire EDM, or to knock together a fixture that would take more work to make in one piece.

It now (after 20 years of ownership) brings in maybe ten grand a year, so I can still afford to have it around, but if I were a hard headed businessman, knowing what I know now, you'd never convince me to spring for one in the hope and fantasy that it would ever be a moneymaker for my particular business.

My business increasingly is prototyping complex devices and I like parts that are small enough to fit in my pocket (or smaller)...not that lucrative but fun to do.
I'm 64 and by now I just can't bring myself to get too worked up about acquiring wealth anymore...I want to do the cool stuff while I still can, and having the laser helps me in that goal.

So it was a lust purchase, not a business purchase...but hey, I like it better than I like a Porsche, so I bought it.

Cheers

Marcus
www.implant-mechanix.com
Vancouver Wire EDM -- Wire EDM Machining