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Shelly142 06-14-2017 02:00 PM

Small Rotary Table
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I would like to begin by acknowledging that this may not be the appropriate forum category for this post.

My dilemma is in the fabrication of a Direct Turning Rotary Table designed by Harold Hall of the UK. The majority of the project is typical machine work but my problem originates from locating one of the details of the design.

In locating what is called the Stop Post which allows a knurled removeable pin that needs to C/D with 24, 15/64 diameter holes drilled in the periphery of the table. I fabricated essentially a small duplicating punch of the proper size and made from a drill blank.

The problem is that the 24 holes in the table are blind holes and the fabricated punch for marking of the hole to be located in the Stop Post is now stuck in the blind hole of the rotary table.

I’m asking for any suggestions on how I might remove the stuck pin without destroying the project. The blind holes are the same size diameter as the drill blank used for the punch and is probably as hard as any drill I might have available to me.

Any possible suggestions to remedy this situation would be appreciated.

milomilo 06-14-2017 02:12 PM

Drill it, tap it, and insert bolt and pull it out.

randydupree 06-14-2017 02:53 PM

This may not help,but it may give you an idea or 2.
On lots of GM cars theres a pin which goes into a blind hole in the rearend,this pin shears off in the blind hole and then you cannot get the rearend apart.
I drill a small hole on the side of the blind hole and use a high pressure air hose to blow the pin out.

arizonian 06-14-2017 03:10 PM


The blind holes are the same size diameter as the drill blank used for the punch and is probably as hard as any drill I might have available to me.
Anneal it with an acetylene torch, then try drilling through it. If that doesn't work, EDM.

alchemist 06-14-2017 04:39 PM

What kind of drill blank is it. Is it o1 drill rod? Maybe drill a hole in something and weld through the hole onto the rod.

greywynd 06-14-2017 05:38 PM

If it's an actual drill blank, it's already hardened, usually they are M2 or similar material. About 62-64 Rc.

Use a good penetrating oil, it will help, we do it with seized ejector pins and it works it's way in over time.

What diameter is your knurl? Can you get a good grip on it using a small three jaw chuck to pull and twist at the same time?

Time for a new signature line!!

Grizz 06-14-2017 09:12 PM

I would trim a steel washer a tiny bit smaller than the hole/ blank and use the washer to protect the table. then weld a nut or piece of tubing or pipe, to the blank, getting as much heat into the blank as possible. let it cool slowly, the blank should shrink enough that you can pull it out (it will try to expand radially when you heat it but the hole will prevent it, so it should expand slightly longer. when it cools it should be a slightly smaller diameter.

GWIZ 06-14-2017 09:34 PM

I would think you can drill a slanted hole from the underside 90 degree., 45 or whatever and hammer the pin out if need be.

At 90 deg. you can fill the hole with oil and hit a close fitting pin the hydraulic pressure will force the pin out.

some use oil and play-doh and hit that with a hammer.

Ironman 06-14-2017 10:17 PM

You can get a carbide bit, a correctly sized carbide center drill comes to mind, and it will happily drill through any file, high speed steel, planer blade or whatever. Just drill it out.
I also like the EDM idea if it is available.
By the picture it looks like it is broken off at an angle so you may be better to touch it up with a carbide end mill first, befor drilling it out. Run about 1000rpm and a light touch. Carbide likes speed but is brittle.

greywynd 06-15-2017 08:44 AM

Ahhh, missed the last picture of the actual broken pin. Die grinder and a small carbide or diamond burr, keep working a hole into the centre and slowly open it up.

Time for a new signature line!!

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