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8-10” Center punch or extension

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bradleydavidgood

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I need to center punch a broken bolt that is recessed about 7 inches.

Is there a center punch that length?

Or is there an extension that I can add to the center punch to reach 8 inches in?

If not, I guess I'm going to cobble together a flat punch to the back of a center punch somehow with monster tape or a hose clamp or something.

Thanks!
 
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bradleydavidgood

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NUTTSGT said:
I looked at a few places online and didn't see one that long.

Maybe along piece of SS rod and grind a point ?
Click to expand...
I don't know, sounds like work that I would not be able to get right, and not sure that steel is going to be hard enough.

Maybe I'll put something like this on the back end and hose clamp it together, unless there is a better way to combine them:

1732477863266.png
 
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NUTTSGT

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Have a welder ?

It's not going to be a high use tool. Maybe find a cheap center punch and weld a section of Key stock to it.
 
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sparky 1971

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This is a longshot, but Klein makes a scratch awl where the shaft runs through the handle. The plastic handle could be cut off leaving a 10" long ice pick. I use mine (with the handle still attached) as a center punch all the time.

Copy and paste won't work. Google Klein 650DD.
 
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nadogail

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When I worked at a Gas Turbine Overhaul Shop, I "Liberated" some of those long bolts that hold the rotor segments together.
After modifying them so they could not be reused as aircraft parts, I converted them into Long Punches and Chisels.
 
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Kkmk

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If its just for a one off, you can use pretty much anything metal. Old broken screwdriver, threaded rod, a piece of old rebar. I often reach for a lengthy bolt.

Hold it against a linisher and twist it around.

Cut the head of the bolt off, hold it in a drill and spin it against a flap disc on a grinder. Might need to touch it up after one or two punches.

A deep socket that the back of the centre punch fits in.

Get creative, dont get fancy.

Unless you’re doing it a lot. Then get fancy creative.
 
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cannuck

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cvairwerks said:
Use a regular transfer punch and if it's not long enough, hit it with a second punch end to end. Might need a magnet retriever to pull the transfer punch out of the hole.
Click to expand...
bradleydavidgood said:
I need to center punch a broken bolt that is recessed about 7 inches.

Is there a center punch that length?

Or is there an extension that I can add to the center punch to reach 8 inches in?

If not, I guess I'm going to cobble together a flat punch to the back of a center punch somehow with monster tape or a hose clamp or something.

Thanks!
Click to expand...
Can we assume you need the punch to put its indent dead center in the broken bolt? A transfer punch will allow you to do that within 1/128 of an inch but what are you going to do with the bolt once you have marked the center?? The problem with using some random size piece of steel is hitting center but getting that transfer punch out will be quite a challenge. I would use drill rod to be able to get the diameter and length you need ground of course to a concentric point.
 
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bradleydavidgood

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Kkmk said:
If its just for a one off, you can use pretty much anything metal. Old broken screwdriver, threaded rod, a piece of old rebar. I often reach for a lengthy bolt.

Hold it against a linisher and twist it around.

Cut the head of the bolt off, hold it in a drill and spin it against a flap disc on a grinder. Might need to touch it up after one or two punches.

A deep socket that the back of the centre punch fits in.

Get creative, dont get fancy.

Unless you’re doing it a lot. Then get fancy creative.
Click to expand...
Oh, I like the deep socket idea...impact socket and extension. That could work. Stuff some rubber around the punch before inserting it into the socket to center it. Sounds really good!

Everything else I've heard is good ideas, thank you, but this is probably one and done and I don't have these fabrication tools and skills other guys are talking about. Just the basic stuff here like files and angle grinder, I do have a bench grinder in a box somewhere but have not installed it at this house yet...need to do that.
 
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ecotec

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I have drifts and taper punches up to 18”, but I don’t remember seeing a center punch as long as you need.

What good is marking the center 7” down a blind hole?

You want to do what is in that video 7” down a hole?

If you pull it off… you need to video it.
 
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bradleydavidgood

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It's actually up where I'm going. It's a small bolt mounting the evap canister to the chassis of a CRV. It's not a hole, and it's not blind, but so tight that no tools can get within 7" of it. I'm good at videos but I'll be tight under the car and don't have a head cam. I can probably video stuff as I go along after an action but probably not while I'm working.
 
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Firebrick43

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They make sized transfer punches that will automatically center in the hole. Even if they are not quite long enough you can tap the end of the transfer punch with another punch and retrieve it with a magnet.

However better yet, since you have a long hole, would be to turn or have a friend turn a tight fitting sleeve and drill the sleeve for the size of extended drill bit you will be using. Then you don't have to worry about drilling off center or having the drill bit wonder.
 
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bradleydavidgood

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Firebrick43 said:
They make sized transfer punches that will automatically center in the hole. Even if they are not quite long enough you can tap the end of the transfer punch with another punch and retrieve it with a magnet.

However better yet, since you have a long hole, would be to turn or have a friend turn a tight fitting sleeve and drill the sleeve for the size of extended drill bit you will be using. Then you don't have to worry about drilling off center or having the drill bit wonder.
Click to expand...

It's not a hole, it's a mounting bracket under a car with such a tight spot I can't get tools within 7". I will take a video of the situation and post it tomorrow.

I think I'm going to be fine with a deep impact socket on the end of an impact extension, with a center punch surrounded by a small bit of rubber sheet into the deep socket.

Then use a drill with an extension on it and a drill bit in the end.

Thank you all for all the amazing ideas. This forum is awesome, so active, and so much knowledge. Very grateful to have been told about it.
 
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bradleydavidgood

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ecotec said:
I really like Firebrick’s idea of making a sleeve to drill in.
Click to expand...
It's not down a hole, I am not capable of turning a sleeve, I don't know what that means, I don't have a friend who does, and I think I'm going to be fine with a deep socket on an extension to a center punch. But thank you. Will try to post video today of the location/situation of the broken bolt so that you can see.
 
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JradM

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Anything metal, long-enough and ground to a point, is probably sufficient for a one-time use center punch. Maybe not if that's a 12.9 grade bolt you're hoping to extract, but that should work fine on most things.

If you're after a longer term tool, I'd just grind a point on a taper/drift punch in a suitable length.
 
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ching0n

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can you dump it out after or fish it out w/a telescopic magnet? And can you fit a center punch in said recess? If so, use center punch w/long rod behind it.
 
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ching0n

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bradleydavidgood said:
Click to expand...
That's a rough one. Can you even fit a drill after?

You could sacrifice a magnet between center punch and extension. Magnet will shatter but you'll get a punch.....no word on accuracy though. Alternatively, you can sacrifice a small extension and grind it to a point, making a socket center punch....might need hardening after though. Or get a punch w/a hex shape you can fit a socket behind it + extension.

www.homedepot.com

Mayhew Punch Set (3-Piece) 89082 - The Home Depot

Mayhew Tools - 3-Piece Punch Set - True industrial grade tool. Heavy-duty, alloy steel construction. Rust-resistant. USA. - THD SKU# 560182
www.homedepot.com
 
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bradleydavidgood

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Thanks for the ideas. What I am going to try first is:

For punching before drilling:

1. A flat end punch on the back of a center punch held together with a hose clamp.
2. A deep impact socket on the end of an impact extension. A center punch wrapped in rubber sheeting and jammed into the deep socket.

For drilling:

A hex extension and a good metal drill bit.
 
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ching0n

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bradleydavidgood said:
Thanks for the ideas. What I am going to try first is:

For punching before drilling:

1. A flat end punch on the back of a center punch held together with a hose clamp.
2. A deep impact socket on the end of an impact extension. A center punch wrapped in rubber sheeting and jammed into the deep socket.

For drilling:

A hex extension and a good metal drill bit.
Click to expand...
I've used something like this before to run through walls, come to think of it you can probably use either of the ones below to hold a punch:


Looks like HF carries something w/a chuck:
 
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Steve_P

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I'm not going to read the 50 posts, but McMaster sells hardened drill rod, >RC60, if you actually want to make a long punch.
 
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RTM

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Looking at your video, the stacking a punch with something else looks reasonable. Can't see how deep below the surface the bolt body is, but maybe a transfer punch to hit the center is a good idea.

The drill with an extension will be much more of a wild card in my opinion. The length will add wobble, as will the extra joint in the middle. As others have said, if you can hold it in a sleeve, that may help.
 
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bradleydavidgood

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Just ordered these....never heard of them before but just watched the video below. Look good. Could just put one of these on an extension and it will probably go right into the bracket hole and do well.


Video:

Extensions I already received:
 
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tarbellb

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Those Self Centering bits are made of cheese and only good for wood working

You can however replace the bits w a higher quality HSS and likely get some decent results. They are prone to clogging and jamming if drilling alloys
 
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