pre align hole to drill you cannot see

[haryv]

Okay. I do not have a block of clay to stick onto my metal plate. I want to do this so I can know where to pre-drill a hole on a plate, where I cannot see the hole in the side of the engine block when the plate is against the side of the block.

If clay was pressed against the backside of the steel plate, I could easily press the plate against the side of the engine block, and get a impression of the bolt holes to be drilled square on.

But is there other ideas to use to make a center hole? I was also thinking of finding some kind of flexible arm to attach to the frame, then point a laser at the center of the bolt that is in the hole, then remove the bolt and place the plate square on the surface. Use a felt marker, mark the red laser dot which designates the exact place to drill a hole.

BTW, I do not think bubble gum will work. I imagine it could not stick to the plate and instead, stick inside the tapped bolt hole.

 

[Jetboy]

How accurate do you need to be? Why can't you measure it?

 

[rusty_tlc]

Put a center punch(cut to fit) in the hole and tap on the plate?

They make a center finder pin for application like this.

 

[haryv]

rusty, good idea

I can see it I can use a center punch or, a bolt in threaded bushing that would make it adjustable.

There can be other cases where swinging a hammer against the plate or using a punch would be difficult doe to room constraints.

 

[WarDamnEagle]

You need a blind hole transfer punch. They come threaded or smooth. You put one in the bolt hole in the side of the engine block, align the plate where you want it and then tap the plate with a hammer. The punch will mark the center of the hole on the backside of the plate.

McMaster-Carr

 

[Pin_Head]

The quick and dirty way is to copy the pattern to a piece of paper by taping a piece over the holes on the engine boss and rubbing it with your dirty fingers. Then transfer the paper to the part you want to drill and locate the holes with a center punch.

 

[Photoman]

Another quick and dirty way I have used is the spread on a thin layer of grease. Then press the plate or a piece of cardboard like a paper folder against the grease.

 

[TRAIL TAILOR]

If you have the area, I go to the hardware store and buy 1/16" clear plexiglass. Put it up against the object and then mark items/holes and the transfer to plate steel or whatever.

 

[rusty_tlc]

You need a blind hole transfer punch. They come threaded or smooth. You put one in the bolt hole in the side of the engine block, align the plate where you want it and then tap the plate with a hammer. The punch will mark the center of the hole on the backside of the plate.

McMaster-Carr

I knew there was a name for those. I've used them before just never knew what they were called. Thanks!

 

[pb4ugo]

Another quick and dirty way I have used is the spread on a thin layer of grease. Then press the plate or a piece of cardboard like a paper folder against the grease.

I've done the opposite, cutting a bolt to make it a stud or get a stud, or just a bolt & screw it in the hole. & put grease on the end of it. Then hold the part or cardboard at its location to tranfer the grease to the part/cardboard. It's probably not as accurate as the previous mentioned transfer punch, but same idea.

 

[scottm]

It's easy to make a transfer punch from a setscrew or similar, just sharpen one end and put some flats on the sides of the point so you can turn it. It won't last like a carbide version, but you can just resharpen. We have real ones at the shop I work at, but I've had to make them.

 

[haryv]

I tried this idea, and it worked really well

What I did was buy two new bolts then cut the heads off. I did not have a lathe to spin the bolts but used a drill and spun the bolt to a grinder. I could have also grind down the last 1/4 length of the bolt shank in the shape of a hexagon to remove the bolt should it get stuck in the threaded bolt bore. In this case, I used a tap to clean out the threads which made the installation of the bolt really easy to remove. After installing the center point bolts, placed the plate over it, and with two taps of a hammer, had perfect centered holes.

If and when I have alot of free time, I may just make a bunch of center punch bolts and never have to worry about this again.

Now, a Laser on a adjustable arm, would also work. Would be much faster to setup.