[roach]

some companies do use this
http://www.springerlink.com/content/m37316r60490r871/
SpringerLink - Journal Article
not as good but good enough for diyers lol

[roach]

ive done it so if u need help im here

[sergizmo]

This is a little bit OT, but along the same lines. I am building a benchtop CNC mill and will be screwing it down to an 18" by 12" by 3" granite surface plate.

It will have to be drilled in several places to accept steel inserts that will be expoxied in. These will then be drilled and tapped to serve as attachment points for the mill. The diameter of these inserts will probably be 3/8"-1/2".

I apologize if the answer to my questions are buried somewhere in this huge thread.

1) Do I need a hammer drill or will a standard drill work fine?

2) Will a regular masonary bit work or do I need a special bit for granite? I have seen hole saws for granite earlier in the thread but am not looking to make holes that big.

To anyone who can help me out, thank you in advance.

Serge

[ckelloug]

Serge,

You're probably better off to use a hammer drill though a regular drill will probably work albeit slowly. I've not done it but from what others have said on this thread, there should be no problem drilling granite or epoxy granite with an ordinary masonry bit. Just be sure not to drill holes less than an inch from the edge of the plate as it would be quite possible for the corner of the granite plate to break off (this isn't a hard and fast rule but certainly reasonable).

Regards all,

Cameron

[McNeillMachine]

Hi all,

This is my first post on the 'Zone, so please be gentle. I've been following this thread for a while. and I'm definitely leaning towards doing something out of EG myself next winter (only time of year I have a spare moment.) I'm thinking a slant bed lathe, but we'll see.

In regards to Sergizmo's question about how to drill holes in granite:
I'm a mechanical engineer that has used large granite slabs (4' x 8' x 12") on a couple of projects. My supplier tells me that what you need to effectively drill holes in granite is a diamond core bit. I imagine it would be much the same in EG. The procedure he outlined:

Rent or borrow a pneumatic drill. Granite countertop people are a good place to start. You will need to constantly flush the hole with water, and as we all know, that doesn't mix well with electricity.

The threaded inserts should be pre threaded, and mounted to a jig plate of some kind.

The inserts are epoxied in, and the jig plate removed. Be sure the inserts sit below the surface of the granite (or EG as the case may be).

Clean the surface of the plate with the appropriate solvent before the epoxy hardens.

When you are drilling the hole DO NOT let it go dry. The bit will die in seconds.

hope that helps,
Phil

[ckelloug]

Phil,

Thanks for joining us. The diamond core drill is a good idea and definitely the way to go for a bunch of precision holes. It may not be the most cost effective for a few non-precision holes however so I don't want to discourage Serge in that I think what he is doing will most likely work even if it is not the "best" way available. One of the things I had to get used to on this thread is that often our readers are trying to do something only a few times and with limited capital investment. Walter, the founder of this thread was successful with his $2.00 carbide masonry bit although it wore out pretty fast in E/G.

The lesson I'd take from your post is that the best solution is probably to take Serge's granite block to a countertop manufacturer and let them drill it since they will have better tools.

For E/G, the easiest solution is not to drill at all but to cast the inserts into the E/G.

An interesting discussion of filling mill drill columns and the damping effects of E/G happened the other day on homeshopmachinist see http://bbs.homeshopmachinist.net/showthread.php?t=28222

Finally, if there are any E/G thread readers in Dallas, TX I will be there Tonight March 24th until Friday morning on day job business. My most significant free time will be Thursday afternoon and I'm already scheduled to meet jhudler. PM me if you are interested.

Regards all,

Cameron

[sergizmo]

Phil and Cameron, thank you for your help.

I will try to pick up a 3/8"-1/2" (probably 1/2") diamond core drill bit locally and rent a pneumatic drill. Already have a decent sized compressor so this will not be a problem. If I can't get a diamond core bit locally I'll try it with a masonry bit first.

The hole locations will be laid out with silver/gold marker. Then a little plasticine moat can be built around the hole being drilled and this filled with water. The holes will then be drilled.

The turned steel inserts (no thread) can then be epoxied into place. Standard 24 hour stuff should be fine. A piece of masking tape on the insert will ensure it is below the granite while being held in place with a rare-earth magnet. That is from earlier in this thread and I think it will work well. I'll be sure not to use to much expoxy and to drill the holes a good 1/8th of an inch or more deeper than the actual inserts. This should ensure no or minimal epoxy spillover.

The base of the machine can be secured/clamped somehow to the granite in the proper location and a transfer punch used to mark the inserts. A hand drill going through a drill bushing can drill the thread holes. There will be 10-12 10-32 threaded holes about 1/2" deep. That should be plenty to hold down my small machine.

Taking it somewhere else to have them do it would probably be the smartest course of action. But I like to do stuff myself when possible and don't like to rely on others. Plus this whole mill build is largely a learning experience, might as well learn a little more.

The ideal would be a cast iron plate. No inserts required. But they are so hard to find these days used (at least in my area.) Buying one new is atrociously expensive, I was quoted $2,346 for a 18" by 12" by 3" ground one. (nuts) No thank you. Picked up the cheapo granite one for $45 new. Not flat to .0001" corner to corner, but certainly flat enough for this application.

Again, thanks for the help guys. I really think this will work well. I don't know why more surface plates aren't used for small DIY mills. They are heavy, flat and soak up vibration extremely well.

Serge

[jhudler]

I can't bring myself to punch a hole in a granite surface plate. Perhaps that's why it's not done more often.

Use baby taps with that punch... it is after all, one way to split (or start to split) granite.

Also the pneumatic powered drill sounds a bit heavy and over kill. An electric one will do nicely.
A jammed drill bit is quick way to cracking granite as well.
Listen for the sound (I know it will be difficult with the air hammer); if it changes (usually down in pitch), then you've cracked the granite.

Check out a pool fencing installers, they have diamond core drills that are designed to make straight cuts.

The epoxy must be high quality or the inserts might creep on you. I've used JB Weld for installing inserts into granite for a stair rail.

[sergizmo]

I'll try it with a standard electric (not hammer) drill when the time comes. I'm just going to be careful not to get it wet. That will take a lot longer but there is no rush. Designing and building the mill is going to take hundreds of hours anyway. What's a few more?

I may try a test hole with a standard masonry bit on a corner as a test hole. If it doesn't work well a diamond core drill can be used.

These don't need to be super precision holes. They will be 3/8"-1/2" inserts and 10-32 screws will go into them so there is some room for error.

Thank you for the tip on JB weld. A local hardware store stocks the line, I will have to check the range of products out.

The transfer punch will be used on the steel inserts, not on the granite itself. There shouldn't be a cracking problem with this unless I wail away, which I certainly don't intend to do.

I couldn't drill into a new Starrett plate either. But some $45 plate? No reservations.

Serge

[jhudler]

I'll try it with a standard electric (not hammer) drill when the time comes. I'm just going to be careful not to get it wet.

GFCI

[garfieldsimons]

[quote=jhudler;430027]I can't bring myself to punch a hole in a granite surface plate. Perhaps that's why it's not done more often.

There are cheap diamond hole saws on ebay which will get your hole without any problems. Or risk. There are expensive diamond hole saws which are also easily had but how many holes do you want to drill?


garfieldsimons

[roach]

diamond holesaws are best but as long as your not near the edge a hammer drill kept wet will do it but it will blow off the back off the granite if you go thru
devcon liqiud steel/putty a is ideal for grouting in inserts as long as u clean both
kitchen counters are such an open grain and will crack easy
try epoxying it to your sub base first then drilling
their also not flat just polished
i know it sounds bad but find a supplier of gravestones just polished there about 40 £ over here and alot thicker
the devcon here is 20£ here its a metal filled epoxy

[sergizmo]

I already have the granite surface plate, no need to look into counter-tops or anything like that.

The inserts will probably be only .75" long, so .875"-1" deep holes will be drilled. The plate is 3" thick, so no problem there.

JB weld sounds similar to that Devcon product. Metal filled epoxy. Either should be sufficient.

I'm going to do it with an air drill. They are about $50-60 for a decent one (plus say another $15 for oil and fittings) and I don't have to worry about electrocution.

Also will buy a diamond core bit. May as well do this right.

There is an absolute ton of work to be done on the machine (just finished designing) before I get to the point of drilling the plate. It will be used in the build itself, so will only be drilled when everything is machined.

Thanks again guys for the advice.

Serge

[jhudler]

Seriously, you 're worrying a bit too much about electrocution, the amount of water you need is low and you're NOT going to spray water down the insides of a plastic encased drill. Used in conjunction with a GFCI (suitably tested) it's just as safe as the air drill.
You might use anywhere from a quart to a gallon for a 1/2 inch hole.

[brunog]

Serge,
If drilling holes in a the granite plate is too preoccupying, there are other ways of fastening the machine base to it.

You can groove the edges and use brackets to hold it down, you can use adhesives join the plate to the base, you can make make a frame with angle iron or Al and insert the plate in it and secure it again with adhesives like construction adhesives or epoxy, it all depends on the forces applied to the plate while machining but you really don't need to drill holes in the granite if you are not confortable with the idea.

You can post photos of the base and plate, we can help you find solutions, we are all here to help.

Best regards

Bruno

[BrendaEM]

For drilling holes, if you are going all the way through, you might be able to "trephanate" the EG in the same way that holes are drilled through telescope mirrors. It only works if you are going all the way through.

Mount a piece of metal tubing in a drill press. The tubing itself is thinwall, often with a few fine slots running down its centerline. If the tubing is very thin, you might not be able to use a a slot.

Make a dam around the hole to be drilled with clay or some other material. In the dam, put silicon carbide compound, such as automotive valve grinding compound, mixed with a little water; hence water soluble compound works better.

Spin the tubing in the drill-press, or if need be, a drill steadying gadget, letting the grit do it's thing. Gentle pressure is all that is needed. It helps to let the tubing come up enough for more grit slurry to work itself under the end.

The going might be slow, but there is little chance of heat issues. Except for the punch-through, there is little chance that the part would be damaged. Using thinwall tubing, you don't have to abrade the material in the center, so the going might not be bad for a large hole.

[Years ago, I was able to drill a hole though the side of a bottle to construct an, ehem, "tobacco" smoking device. I did it with a hand-held power drill too.]

[sergizmo]

Serge,
If drilling holes in a the granite plate is too preoccupying, there are other ways of fastening the machine base to it.

You can groove the edges and use brackets to hold it down, you can use adhesives join the plate to the base, you can make make a frame with angle iron or Al and insert the plate in it and secure it again with adhesives like construction adhesives or epoxy, it all depends on the forces applied to the plate while machining but you really don't need to drill holes in the granite if you are not confortable with the idea.

You can post photos of the base and plate, we can help you find solutions, we are all here to help.

Best regards

Bruno

Bruno,

I think drilling for inserts is the way to go. The base of the mill is made up of several pieces, and by having 12 holes I can secure all the pieces flat to the surface plate with even pressure. Also, this way I can unscrew the base from the plate when it needs to be moved, and it eventually will be.

Now I'm not worried at all about the process. Before I was a little unsure as to the methodology and how I should proceed, but thanks to the advice given here that is not a problem. If worst comes to worst I scrap a $45 plate and use what I've learned from this to do it properly to the next plate.

There is so much work to do before that time anyways. Making a spindle. Making the whole base structure, saddle, table, column, head. Looking like 40 machined parts with around 470 holes total. And this will be done on Sherlines.

Again thanks to everyone for all the help and advice. The information available on this forum is just unreal.

Serge

[speed33317]

I am going to cheat

[speed33317]

3000!

I am sorry I had to do it.

[dsquire]

I am going to cheat

Your right, But I'm 1 up on you.

Don