Preventing or removing drill debris from staying in blind hole? Ideas?

I have some parts on a horizontal where I mount the raw stock lightly with something like a set screw or Mitee clamp pushing on it to hold while I drill holes in non-functional areas for mounting screws. There are already tapped holes below where I am drilling, and we put in socket head cap screws and then the part gets roughed.

I am using a coolant thru carbide drill and drilling hard and fast with 1,000psi TSC. The problem is that sometimes there is a little "pip" or disc of material that gets stuck in the tapped hole under the part when the drill breaks through the back of the part material. This happens on maybe 10-20% of the holes but it's a pain in the ass to poke out that pip before installing the screws. I would like to implement something to prevent it, as there are LOTS of parts and screws on this fixture and it would save operators a lot of time.

I tried adjusting feed/speed but can't reliably get rid of all the pips. The tapped holes the screw go into are blind and helicoiled. I do not have clearance to make the tapped holes through. I thought about making a tool that is just a nozzle (maybe just a single hole through or perhaps some cross-holes on the end?) hoping the coolant would eject the little pip? Or maybe coming back in with a smaller drill to poke the pip loose and flush it out? I dunno.. anyone ever solved this problem?

Back-chamfer the hole after drilling?

Regards.

Mike

Maybe use a drill with more of a point on it?

It has been a mystery forever to me why this happens sometimes and not others, and always seems resistant to rational analysis and solution. I often use a backing plate in doing small volume/prototype stuff, but that's not a real solution for any production shop typically. Mike's solution seems to be best if you can get another tool set up to do backside chamfer.

An alternative to deburring the back side might be to drill almost through and then break through by interpolating with an endmill

Finegrain said:

Back-chamfer the hole after drilling?

Regards.

Mike

Click to expand...

Not sure what this would do?

The disc of material isn't stuck to the stock... it comes off but winds up in the tapped hole in the fixture below the hole I am drilling. Most of them flush upward and out of the hole, but some get stuck inside.

SRT Mike said:

Not sure what this would do?

The disc of material isn't stuck to the stock... it comes off but winds up in the tapped hole in the fixture below the hole I am drilling. Most of them flush upward and out of the hole, but some get stuck inside.

Click to expand...

Oh. Then I would just slam a smaller drill through. Start it at the bottom of the stock and run it to the bottom of the fixture's tapped hole.

Regards.

Mike

DanielG said:

An alternative to deburring the back side might be to drill almost through and then break through by interpolating with an endmill

Click to expand...

Sooo add a toolchange and another operation? Why not just rotate it 180° and add a whole set-up?

OP, you can slow the Spindle Speed down at the very last second, for the break through.

R

SRT Mike said:

I have some parts on a horizontal where I mount the raw stock lightly with something like a set screw or Mitee clamp pushing on it to hold while I drill holes in non-functional areas for mounting screws.

I am using a coolant thru carbide drill and drilling hard and fast with 1,000psi TSC. The problem is that sometimes there is a little "pip" or disc of material that gets stuck in the tapped hole under the part when the drill breaks through the back of the part material.

Click to expand...

So you’re temp clamping on the real fixture & then going back with real capscrews to do the heavy work… And sometimes you’re getting a nice disk in the back that doesn’t wash out on drill exit.

Since you have to get in the machine to remove temp clamps & install capscrews you could either modify a blow gun with a small tube or use the HP coolant with a hose with a small tube that will insert deep.

I have an assortment of air blow gun junk that will go deep (all with restrictors removed ). Also a small dental pick will help twist/fetch shit in small holes. I have wished many times I had put on my fibre metal impact resistant face shield before doing the dirty deed using a blow gun.

Or mill escape/eject channels on the backside of the fixture before you mount it next time. Like real old time factory & much punch press tooling is made.

Good luck,
Matt

Matt_Maguire said:

So you’re temp clamping on the real fixture & then going back with real capscrews to do the heavy work… And sometimes you’re getting a nice disk in the back that doesn’t wash out on drill exit.

Click to expand...

Yep, exactly

Since you have to get in the machine to remove temp clamps & install capscrews you could either modify a blow gun with a small tube or use the HP coolant with a hose with a small tube that will insert deep.

Click to expand...

Right now the guys use an old aircraft drill and poke it in the holes, but it's a real PITA because there's something like 100+ screws on the fixture (like I said, horizontal that's absolutely max'ed out on # of parts that can be squeezed on the pallet). I'll try the suggestions above and see how that does.... thanks!

litlerob1 said:

OP, you can slow the Spindle Speed down at the very last second, for the break through.

R

Click to expand...

That's the sort of thing I was hoping for... so, maybe the last .020 drop the RPM's in half or something? Or will I just need to experiment to figure out the feed/speed towards the end?

SRT Mike said:

That's the sort of thing I was hoping for... so, maybe the last .020 drop the RPM's in half or something? Or will I just need to experiment to figure out the feed/speed towards the end?

Click to expand...

I'd start with a much lower feed for the last .02" so if there is a pip, it's much thinner than it would be and hopefully disappears from the normal cutting and coolant forces.

Regards.

Mike

litlerob1 said:

Sooo add a toolchange and another operation? Why not just rotate it 180° and add a whole set-up?

OP, you can slow the Spindle Speed down at the very last second, for the break through.

R

Click to expand...

If you can tweak the cutting parameters on the drill to get rid of the cap, then that would obviously be ideal. If you can't, then the process to beat is manually removing them. If you really think that adding a toolchange and an endmill toolpath is as much work as flipping a pallet load of parts 180, then I don't know what to tell you.

Once you solve the cap problem, you just need the mill to put in the bolts for you and then you can run the pallet load complete with no intervention.

Yes!..a 118 degree point is less likely to pop out a disk than a 140 degree but also more likely to leave a burr. Is there a separate deburring/countersink op for the back side of those holes?

SRT Mike said:

Right now the guys use an old aircraft drill and poke it in the holes, but it's a real PITA because there's something like 100+ screws on the fixture (like I said, horizontal that's absolutely max'ed out on # of parts that can be squeezed on the pallet). I'll try the suggestions above and see how that does.... thanks!

Click to expand...

100 screws on a setup! OH MY... That's a whole other craft, involving a torque limited driver prolly.

Good luck indeed,
Matt

After drilling 100 holes. Stick in a holder with no tool- like your smallest end mill holder, and blast the holes with the 1000 psi TSC?

I have wondered a few times about using the spindle to install/remove screws/bolts... If you built a system where the bolts had holding locations on the fixtures, adjacent to their final positions in the part, couldn't you install them using a torque limiting 'screwdriver' style driver mounted in the spindle? It would have to be spring loaded in Z as well I guess, but if you could put something like that together it might save a whole lot of time! You could take them out at the end of the cycle too, return them to their starting locations.

Use a screw-retaining hex bit to make sure the screw doesn't drop off: McMaster-Carr
With a slip-style torque driver like one of these: https://www.amazon.ca/FIT-TOOLS-6-35mm-Adjustable-Screwdriver/dp/B073B1FG9K

You'd have to make some sort of spring loaded spline in tube assembly to transmit the torque while allowing travel in the Z direction... Honestly I think there are lots of applications for something like this if you got it worked out.

aarongough said:

I have wondered a few times about using the spindle to install/remove screws/bolts... If you built a system where the bolts had holding locations on the fixtures, adjacent to their final positions in the part, couldn't you install them using a torque limiting 'screwdriver' style driver mounted in the spindle? It would have to be spring loaded in Z as well I guess, but if you could put something like that together it might save a whole lot of time! You could take them out at the end of the cycle too, return them to their starting locations.

Use a screw-retaining hex bit to make sure the screw doesn't drop off: McMaster-Carr
With a slip-style torque driver like one of these: https://www.amazon.ca/FIT-TOOLS-6-35mm-Adjustable-Screwdriver/dp/B073B1FG9K

You'd have to make some sort of spring loaded spline in tube assembly to transmit the torque while allowing travel in the Z direction... Honestly I think there are lots of applications for something like this if you got it worked out.

Click to expand...

It's tricky to install bolts reliably with a machine tool. This is how we did it for bolts in through hole, putting a bolt in a blind tapped hole will be trickier.

The first difficulty is holding the bolt securely enough that you can reliably insert it into the hole. Unfortunately the magic-ring hex drivers don't control the angle of the bolt, there is nothing forcing it to be concentric to the driver axis. There are two general ways that we used to hold the bolts on the bolt inserter. You can either have gripper fingers. The ones I worked on were for flat-head bolts, so the rivet fingers located on the underside of the head and the start of the shank. The bolt is held by the fingers until it is started in the hole, then the fingers snap out of the way. The second way, if you didn't want to do fingers, was a very springy plastic collet. The opening to the collet was a close fit and guided the bolt into the hole, then a pneumatic ram shoved the head through the collet and seated it into the part.

Next, since this application requires that we drive the bolt, as opposed to the nut, we have to insert the driver into the bolt head. You can do this by coming up to the bolt, applying some pressure while you turn slowly. When the hex lines up, it will slip into the socket. Because there is a chance that you will line up on the first go, before rotating, you have to monitor the position and know where the driver should be when it's fully inserted. As an alternative to knowing that, you could come up with some sensor to detect when you're seated in the hex.

Now run the bolt in. Luckily, this is a solved problem and you can buy an off-the-shelf nutrunner. They will monitor both torque and angle to ensure that you aren't cross threaded, bolt is all the way in, fully torqued, etc. A spindle theoretically can do all this, but integration with the machine control will be a task. Alternatively, you can run the bolt in blind, but someday, something will go wrong.

One of the hardest parts of doing this on a standard machining center using something mounted in the spindle is that getting feedback is tricky. There's a reason that the probes are all wireless. It would get easier if you could design custom bolts, rather than using an off-the-shelf SHCS.

On the big bolting machines, we had anywhere from 4-8 tools mounted on a shuttle to drill/fill/fasten a hole. At the low end, 3 would be ideal (spindle, bolt inserter, nutrunner). The 4th slot was in-process diameter/ovality/c-sink depth measurement. One option, if you were doing this a lot, would be to attach some specialized tools to the side of the spindle housing. This would decrease your available travel, but it would make designing/building a robust fastening system a lot easier.



I've been playing around with an idea for a way to do this using a toolholder for a while. Someday, in my copious free time, I'll have to build one.

SRT Mike said:

I have some parts on a horizontal where I mount the raw stock lightly with something like a set screw or Mitee clamp pushing on it to hold while I drill holes in non-functional areas for mounting screws. There are already tapped holes below where I am drilling, and we put in socket head cap screws and then the part gets roughed.

I am using a coolant thru carbide drill and drilling hard and fast with 1,000psi TSC. The problem is that sometimes there is a little "pip" or disc of material that gets stuck in the tapped hole under the part when the drill breaks through the back of the part material. This happens on maybe 10-20% of the holes but it's a pain in the ass to poke out that pip before installing the screws. I would like to implement something to prevent it, as there are LOTS of parts and screws on this fixture and it would save operators a lot of time.

I tried adjusting feed/speed but can't reliably get rid of all the pips. The tapped holes the screw go into are blind and helicoiled. I do not have clearance to make the tapped holes through. I thought about making a tool that is just a nozzle (maybe just a single hole through or perhaps some cross-holes on the end?) hoping the coolant would eject the little pip? Or maybe coming back in with a smaller drill to poke the pip loose and flush it out? I dunno.. anyone ever solved this problem?

Click to expand...

Yep been there. You know Insert drills (which are lots of fun to use) oft times will leave a sharp thin circle of surgical sharpness just either hanging down there in a hole or wedged in there. Keeping the feeds and speeds ideal along with enough coolant flow helps a lot yet you require it to be right all the time.

Regardless of how you tweet it you still must verify how your changes effect the outcome and so after changes you still must M00 it to remove debris otherwise it likely will mess things up.

There may only be one way to be sure you are not mashing chips when you instal your bolts. You could use the drill for that tapped hole and drill to depth each hole drilling mostly air to relieve any chips that should break the up yet I would still M00 is and bow out each hole. At least what is in there will most likely be loose. Can you machine some slots around the hoes allowing a escape for the sharp blanks? Use a air nozzle with a long enough reach to get into that hole. That might work for you.