Any Suggestions for Marking Blind Holes?

[Iplayfarmer]

pointed set screws are pretty cheap...and durable.
larry

That's great if you have a week to wait for them to come UPS. Or, if you can take the time to drive 30 miles to go get them (I don't even know where I'd get them around here). In my situation, I'm always fabricating after hours or on Saturdays, and I swear any time I've needed them it's been a different size bolt.

They do really sound like they'd work pretty well.

 

[sld]

Several times in past I have used 1/8 inch lexan to make a template. You can see thru it to mark the holes then drill and check them.

If it is something you do more than a few times these are good tools to keep. I just write what it was used for with a sharpie on the lexan.

The lexan is easy to get at Home Depot, Lowe's etc.

 

[horse7]

If you have a removed part that is small enough place it on a photocopier & use the copy for a template. Some of our repair procedures at work have photocopies of the gaskets to verify the replacement gaskets before disassembly. MikeD74T

Most photocopiers have a substantial difference between the original and the photocopy (5% or more). Do you compensate for this? Some photocopiers allow pretty fine adjustments, others don't, and maybe 5% isn't enough to matter.

[many years ago I had a D sized 1"=1' engineering drawing photocopied, and sent off for an estimate (photo copy clearly marked "NOT TO SCALE", as it was off by over 5%, had to use a photocopy as the white printer was out). Yeah, got a call later about how they were having trouble using a scale to measure stuff.... ]

 

[JRP]

I Measure - like this:

1. Screw a bolt in each of the two holes.
2. Use the OD jaws of a digital caliper ($20 from harbor freight) to get the measurement across the far edges of the bolts.
3. Use the ID portion to get the distance between the bolts.
4. Average the two measurements.
5. Set the caliper to the average value and tighten the lock screw. Use the two points on the ID portion of the ccaliper to scratch or scribe your hole centers.
6. Center punch, drill small, drill clearance size.

 

[Iplayfarmer]

I Measure - like this:

1. Screw a bolt in each of the two holes.
2. Use the OD jaws of a digital caliper ($20 from harbor freight) to get the measurement across the far edges of the bolts.
3. Use the ID portion to get the distance between the bolts.
4. Average the two measurements.
5. Set the caliper to the average value and tighten the lock screw. Use the two points on the ID portion of the ccaliper to scratch or scribe your hole centers.
6. Center punch, drill small, drill clearance size.

That gets you your distance between the two bolts. Then you have the distance from the edge(s), the distance from other bolt holes in the same piece, etc. That's where I go wrong alot of the time.

 

[JRP]

I understand.

Set screws are hardened and have the hex opening. Allen wrenches are hardened. You could screw in set screws, and then have small pieces of allen wrenches sharpened that you slip into the set screw with a little grease to hold them. Mark the part, then pull the hex points and and unscrew the set screws.

 

[jimmysisson]

For a few bucks you can get a set of dowel centers that woodworkers use to transfer a hole - like the screw center but just press in. Not so many sizes are available, but it will work for a non-threaded (locating) hole and is quick for just a couple-three holes.
Jim