Marking and drilling steel precisely

[FandZ]

Hi all. I hope I'm posting this in the right forum. Feel like an idiot for asking but it's the only way to find out sometimes. I'm in the mist of desighning a cnc machine and am close to starting the building process.

On this machine, I'm going to have to drill between 100 to 150 holes on my drill press. Some of it will be on 1x1/4 aluminum angle and others on 4x 1/4 cold rolled steel.

There has to be a method to mark and center punch steel and aluminum precisely to prep it for the drill press. Can someone enlighten me on how to accomplish this using hand tools and a drill press? I've some ideas but I figure there must be a better way. Is there an adjustable tool that grabs on to the edge and holds the center punch standing vertically? Is there some sort of spacer to use with a digital caliper?

There's probably more than one way to get the job done. I'm just looking for one that will be good with my lack of experience. I doub't I'll get the acuracy I'm looking for with a pencil and ruler.

Thanks in advance for any advice you can give me, Chris

[HackMax]

If I were to do such a task I would likely use layout fluid and a verier caliper to scratch the lines at the surface. This would only work if the edges were smooth and square and you had a big enough caliper to cover the whole area though.

Rick

[DareBee]

yup
scale, square, scriber, vernier.
You will be precisely within .02 (.01 if you hold your tongue right).

Not good enough? - pay someone to do it in a mill.

[HackMax]

[QUOTE=DareBee;540137]
You will be precisely within .02 (.01 if you hold your tongue right).
QUOTE]

LOL Too funny!

[Blu_Rock]

Here's what works for me. I use a cheap digital caliper to scribe off the edge of the material and a metal rule to measure between holes. These calipers are so cheap now, I re-sharpen them as necessary. I know it is considered a sin by some to scribe with calipers and I wouldn't do it with my quality set.

1. Scribe lines at least 10mm long so you can clearly see them.
2. Use a sharp centre punch to make an initial light punch mark.
3. Inspect the punched mark and check that it is precisely at the intersection of the scribed lines.
4. If it is slightly off centre, then engage the punch in the divot, angle the punch slightly towards the direction that the mark needs to go.
5. Lightly re-punch the mark so that it is "adjusted".
6. Repeat, if necessary, until punch mark is correctly centred.
7. Make a final heavier punch mark, ensuring that the punch is always sharp and held straight up and down.
8. This might be bleeding obvious, but... when drilling, make sure drill is sharpened correctly and running at the right speed for the drill bit size and material.
9. Use a bit of your preferred cutting fluid if drilling steel or kerosene if drilling aluminium.

[FandZ]

Thanks for the reply guys. I've been practicing my tongue holding technique all day at work.lol

And Blue Rock a big thank you for the mark finding and all your tips. I know I'll be using them.

Sounds like using a caliper to scribe is the way to go. I can figure out how to get the caliper square by raising the material I want to scribe and using a slightly higher square piece of metal on the edge of the metal to set one edge of the caliper on to get it square. Does that sound like the way to go?

I assume I'd have to use more than just a caliper since once it's open It wouldn't be able to scribe accurately from the edge on say a flat bar because the bottom jaw wouldn't be paralell on the edge I'd want to scribe. Make since?

Is there a technique I'm missing or not seeing in just using a caliper and an edge?

Thanks again for you help. I can stop pulling my hair out trying to figure out how to mark that center punch perfectly.

Originally Posted by DareBee yup scale, square, scriber, vernier.

[quote=HackMax;540140]

Originally Posted by DareBee You will be precisely within .02 (.01 if you hold your tongue right). QUOTE] LOL Too funny!

Originally Posted by Blu_Rock Here's what works for me. I use a cheap digital caliper to scribe off the edge of the material and a metal rule to measure between holes. These calipers are so cheap now, I re-sharpen them as necessary. I know it is considered a sin by some to scribe with calipers and I wouldn't do it with my quality set. 1. Scribe lines at least 10mm long so you can clearly see them. 2. Use a sharp centre punch to make an initial light punch mark. 3. Inspect the punched mark and check that it is precisely at the intersection of the scribed lines. 4. If it is slightly off centre, then engage the punch in the divot, angle the punch slightly towards the direction that the mark needs to go. 5. Lightly re-punch the mark so that it is "adjusted". 6. Repeat, if necessary, until punch mark is correctly centred. 7. Make a final heavier punch mark, ensuring that the punch is always sharp and held straight up and down. 8. This might be bleeding obvious, but... when drilling, make sure drill is sharpened correctly and running at the right speed for the drill bit size and material. 9. Use a bit of your preferred cutting fluid if drilling steel or kerosene if drilling aluminium.

[Geof]

If you are drilling hole patterns in different locations that will subsequently bolt together you need precision within the pattern, not accuracy.

Maybe you can make yourself a clamp-on guide for either the center punch or the drill. Get a piece of cold rolled steel and lay out the drill pattern using a fine scribe and steel ruler; also put a hole at the center of the hole pattern. Center punch the holes locations as carefully as possible and as Darebee says you will have then precise to with +/-.02".

Now drill these holes carefully on the drill press; first make a dimple using a spot drill on the center punch mark just holding the part by hand so the spot drill self centers, then with the drill turned off hold the part in place with the spot drill and clamp it down to drill the hole. If you are going to use this as a center punch guide you need a hole the exact size of the center punch shank, for a drill guide you need the drill size of course.

Now you clamp your guide into place where the hole patterns will be and mark or drill. The center hole allows you to easily measure between the centerpoints of two hole patterns along a frame member.


EDIT: I noticed this : I assume I'd have to use more than just a caliper since once it's open It wouldn't be able to scribe accurately from the edge on say a flat bar because the bottom jaw wouldn't be paralell on the edge I'd want to scribe..

What you need are called Odd Legs; this is a scriber that has one pointed leg for scribing while the other is slightly longer and has the tip bent so it can come against the edge you are measuring or scribing from. Try Googlin 'odd legs' and see what you find. The old fashioned name for these in England was 'Jennies' but don't ask me why.

[BobWarfield]

FWIW, I really like printing a 1:1 scale of my CAD drawing and gluing that to the workpiece as my guide.

Do be sure to centerpunch that drawing, and sometimes it will even help to center drill or spot drill to make sure the bits don't wander.

Cheers,

BW

[FandZ]

Thanks for your guidance Geof. I believe you help me in another thread talking about servo motors.

What I'm thinking is I'll take your idea and some of the guidance of the others to make steel a templet/guide for a punch holder and to center drill with. That'll be much more efficient when I start to drill my 150 or so holes. lol I may even design the metal plate and have it milled out accurately for me Even more time saving Hrmm... I wonder if I can get someone on the zone to make one and mail it out to me at a reasonable price.

BobWarfield: I have the worst luck gluing paper to a flat surface precisely..lol I always end up with air bubbles or getting it slightly eschew. Probably used the wrong glues and paper in the past. I may give a go though. Especially for making the stepper mounts and such.

Thanks again fellas

Chris

Originally Posted by Geof If you are drilling hole patterns in different locations that will subsequently bolt together you need precision within the pattern, not accuracy. Maybe you can make yourself a clamp-on guide for either the center punch or the drill. Get a piece of cold rolled steel and lay out the drill pattern using a fine scribe and steel ruler; also put a hole at the center of the hole pattern. Center punch the holes locations as carefully as possible and as Darebee says you will have then precise to with +/-.02". Now drill these holes carefully on the drill press; first make a dimple using a spot drill on the center punch mark just holding the part by hand so the spot drill self centers, then with the drill turned off hold the part in place with the spot drill and clamp it down to drill the hole. If you are going to use this as a center punch guide you need a hole the exact size of the center punch shank, for a drill guide you need the drill size of course. Now you clamp your guide into place where the hole patterns will be and mark or drill. The center hole allows you to easily measure between the centerpoints of two hole patterns along a frame member. EDIT: I noticed this : I assume I'd have to use more than just a caliper since once it's open It wouldn't be able to scribe accurately from the edge on say a flat bar because the bottom jaw wouldn't be paralell on the edge I'd want to scribe.. What you need are called Odd Legs; this is a scriber that has one pointed leg for scribing while the other is slightly longer and has the tip bent so it can come against the edge you are measuring or scribing from. Try Googlin 'odd legs' and see what you find. The old fashioned name for these in England was 'Jennies' but don't ask me why.

Originally Posted by BobWarfield FWIW, I really like printing a 1:1 scale of my CAD drawing and gluing that to the workpiece as my guide. Do be sure to centerpunch that drawing, and sometimes it will even help to center drill or spot drill to make sure the bits don't wander. Cheers, BW

[BobWarfield]

3M spray on contact adhesive available in art supplies helps with bubbles when gluing the template down.

Here's an alternative trick. Lay the template on. Spray WD-40 on it. This will make it stick somewhat, but you can easily squeegee out the bubbles. Now clamp the workpiece so the template is held tight. This is good enough to let you centerpunch, and also do center/spot drilling without ripping the template loose. Once you start doing your real holes, the template is gone, but by then, your all punched and spot drilled.

Cheers,

BW

[chrugel]

Originally Posted by Geof If you are drilling hole patterns in different locations that will subsequently bolt together you need precision within the pattern, not accuracy. Maybe you can make yourself a clamp-on guide for either the center punch or the drill. Get a piece of cold rolled steel and lay out the drill pattern using a fine scribe and steel ruler; also put a hole at the center of the hole pattern. Center punch the holes locations as carefully as possible and as Darebee says you will have then precise to with +/-.02". Now drill these holes carefully on the drill press; first make a dimple using a spot drill on the center punch mark just holding the part by hand so the spot drill self centers, then with the drill turned off hold the part in place with the spot drill and clamp it down to drill the hole. If you are going to use this as a center punch guide you need a hole the exact size of the center punch shank, for a drill guide you need the drill size of course. .............

When drilling patterns by hand I have also had great success with drawing in lets say in Solid Edge 2D and use centermarks in the drill holes and then printing it out and gluing the sheet to my metal pice. It is better to glue than use tape. Use a center punch and spot drill. I've found the printouts to be very accurate. Of cause bouble is always a problem. This have worked well on patterns for motormounts etc for me.

best regards
Chris

[DareBee]

Originally Posted by Geof What you need are called Odd Legs; this is a scriber that has one pointed leg for scribing while the other is slightly longer and has the tip bent so it can come against the edge you are measuring or scribing from. Try Googlin 'odd legs' and see what you find. The old fashioned name for these in England was 'Jennies' but don't ask me why.

AFAIK proper name for this device is Hermaphrodite caliper (I remember the stupidest things).

A $10 combination square goes a long way too.
You can set the ruler like a depth gauge, then hold your scribe against the end of the rule while dragging the square head along the edge of the part. In most cases I find this easier and more accurate than using Geof's old legs (oops..I meant odd).