[DonKes]

I did a mockup in 3/4 MDF to get my gantry parts fitting and would like to use it to drill the .500 Aluminum gantry sides.
Since there is very little side load in drilling and my mill is too small, I want to mount a drillmotor and use my mockup gantry to drill my gantry. Most holes will be .25 inches.

Is it feasable?

Has anybody used a drillmotor for low speed work?

What is a good choice for low speed drilling?

Don

[wizard]

I did a mockup in 3/4 MDF to get my gantry parts fitting and would like to use it to drill the .500 Aluminum gantry sides.

Sounds good. Your pattern needs to be excellent in its accuracy though.

Since there is very little side load in drilling and my mill is too small, I want to mount a drillmotor and use my mockup gantry to drill my gantry. Most holes will be .25 inches.

What do you mean by mount? Maybe I'm not following what you are describing but when I hear drill motor I'm thinking of a handheld variable speed drill.

Is it feasable?

Can't really say because the use of the word mount has me confused. However using a pattern to locate holes in a piece of material isn't uncommon at all. Being MDF I'd supplement the pattern with a jig to keep the drill bit square with the part being drilled. In this case I'm thinking a handheld drill.

Has anybody used a drillmotor for low speed work?

You don't need low speed for aluminum. Most drills these days are variable speed along with a gear box, so your rpms are well within what is suitable for aluminum.

What is a good choice for low speed drilling?

Don

You have a lot of choices but I highly recommend battery powered drills these days for almost any handheld work. Make sure the batteries are lithium based. If the holes are mostly 1/4" I'd suggest a smaller 12 VDC model of 3/8" capacity or so. The lighter weight and ease of handling make these size drills very usable around the shop and home. Personally I like the Milwaukee brand as they have proven themselves time and again.

In any event I suspect the most important element isn't the specific drill motor used but rather a proper drill bushing jig to keep the drill square.

[DonKes]

By "mount" I mean attach to my aluminum Z axis so I can drill the holes in .500 plate for the sides of the gantry and the Y axis rail mount.

I think the accuracy using this and the CNC capability is much better than I can get otherwise.

My Theory is MDF mockup gantry should be stiff enough to drill .25 inch holes to accurately make the real gantry.

I have a 3/8 variable speed drill with a semi round attach point above the chuck, but that is not much support.

If something else is better I would like to consider using it.

I can see using the "drill motor'" later when I need low speed work.

Don

[wizard]

By "mount" I mean attach to my aluminum Z axis so I can drill the holes in .500 plate for the sides of the gantry and the Y axis rail mount.

Obviously I completelY missed what you are up to here. You already have a working gantry right?

I think the accuracy using this and the CNC capability is much better than I can get otherwise.

My Theory is MDF mockup gantry should be stiff enough to drill .25 inch holes to accurately make the real gantry.

If it isn't step drill. That is pared rill with an1/8" or similar sized drill and then step up to full bore size.

I have a 3/8 variable speed drill with a semi round attach point above the chuck, but that is not much support.

Many industrial quality hand drills have provision for a collar just behind the chuck, this would be ideal this would make mounting much easier. For the range of holes we are talking about here such a collar would likely be enough. Go much larger drill size and you will likely need additional support.

If something else is better I would like to consider using it.

How slow can you go with the router and maintain torque? Unfortunately unless you buy an entire spindle assembly (expensive) I don't know of a cheap way of doing this. You could build a spindle that gets driven from the router with a big step down ratio but that is a lot of work. You could alway look around for an old spindle assembly from a mill to help reduce the amount of build required but finding a decent used spindle at a decent price isn't easy.

I can see using the "drill motor'" later when I need low speed work.

Don

If you know that this might be used a lot then it might pay to build an optional low speed spindle.

There is one other possibility that might work with minimal effort and that would be to buy stubby carbide drills and just use the router spindle running at allow speed. It probably wouldn't be pretty but if you can drive the router fast enough in and out with plenty of lube/coolant you may be able to do your 1/4" holes with nothing more than a proper collet in the routers chuck. This would be a bit abusive of the router but it would save on custom hardware to support a slower spindle.

High speed machining is nothing unusual for aluminum, in this case the question is will the current gantry handle it!

[DonKes]

Thanks for the help.

I guess I will just go for it. Little to lose and a proper gantry to gain.

Don