To drill cores out of foam material.

Thorvald

Active member
Hi.
Ok - we use Danage foam targets for our targets. We have a system to maintain the targets, by drilling out the weared out center, to drill out replacement centers in a reserve foam matt and put them into the targets. This system is a relative cheap way to prolong the lifespan of a 44x44 foam module. Because each core drilled out of the reserve foam matt, costs appr. 25 DKK (2,71 GBP) (if 10 cm in diameter). The thing is that we drill the cores out by hand, and that is a hard job. How to do it in a easier way. Maybe we can pick each other's brains and come up with a good solution that is inexpensive. I have been looking at drills that can be mounted on a regular drill machine - but they are quite expensive. Plus they have a center drill, that makes a hole in the center.... (Maybe that's why it is called a center drill....).
Since this is a leverbow community, another thought of course also crossed my mind: To use lever action to press a circular blade through the foam. But how much force is needed to press through 245 mm foam?? The disadvantage with this is also that this would not work on a vertical surface like the foam wall - only on the reserve foam matt.
So come on clever guys and girls! Somebody have a great idea?




 

Berny

Active member
Fix a disk in the cutting cylinder with a spindle insert as for say grinding wheels which then goes into the chuck of a suitably powered
drill.
The disk could be plywood epoxied in or even metal welded, just make sure the spindle hole is central.
With careful use, low speed start on variable speed drill, to ensure perpendicular operation normal hand/body pressure
will ensure penetration of cutter.
 

Thorvald

Active member
Fix a disk in the cutting cylinder with a spindle insert as for say grinding wheels which then goes into the chuck of a suitably powered
drill.
The disk could be plywood epoxied in or even metal welded, just make sure the spindle hole is central.
With careful use, low speed start on variable speed drill, to ensure perpendicular operation normal hand/body pressure
will ensure penetration of cutter.
I think I understand this. But I think it is too heavy for a hand held drilling machine.
 

geoffretired

Supporter
Supporter
What would happen if you sawed the foam onto square ended blocks? Then cut the corners off to produce an octagon? Would that be a close enough fit to be pressed into the holes in the targets. That would reduce the drilling by half.
 

Thorvald

Active member
#Geoffretired: What you suggest would in princip give some waste in the reserve matt - but the same waste is with drilling the holes. And perhaps there would be even less waste with the square section blocks.

But maybe it would actually be possible to saw/cut square sections from the foam wall also. The trick would be to do it with good enough accuracy and straight - a tight fit is better, so no glue is needed. When such a square section center once have been made, then it will be easier to take the weared out center out and replace it with a new one. Maybe I should try this variant once. But I think I should have a saw with a not so wide blade. I don't know if there is such one in the clubs workshop. I think maybe. There is a normal saw, but I think it is too big, if one wants to keep the holes 100x100 mm or so.
 

geoffretired

Supporter
Supporter
Hi Thorvald, cutting the foam depends on the foam and its stiffness. It looks as if it is the kind that might cut with a sawing action. Sometimes that can be done sawing with a knife that has a serrated edge. Sometimes a hacksaw blade will work. Fast strokes and gentle pressure.
 

Thorvald

Active member
Maybe a saw like this, just longer, to saw out of the foam wall. A normal wood saw to cut the replacement centers. Maybe it could work? Without taking too long time. To make the square section centers from the reserve foam matt, would not be bad, I think. I am more concerned about how well it will work in the foam wall.
 

geoffretired

Supporter
Supporter
The blade length needs to be a good bit longer than the foam thickness, when you are cutting from the wall. Is there space behind the foam for the saw end to go into rather than hitting a hard panel?
Cutting from a foam wall, might be easier with the saw and cutting out squares; then plug with square plugs.
 

Howi

Member
would something like a cookie cutter work, how about one made from a soup or bean tin can, cut one end off (there are some tin openers that will cut just under the rim, leaving a very sharp and even end, just twist the cutter through the foam.
 

Thorvald

Active member
The blade length needs to be a good bit longer than the foam thickness, when you are cutting from the wall. Is there space behind the foam for the saw end to go into rather than hitting a hard panel?
Cutting from a foam wall, might be easier with the saw and cutting out squares; then plug with square plugs.
Behind the foam wall is a little space, maybe a few cm or 5 and then is hanging a rubber matt.
 

Bald Eagle

New member
What about an elecrtric carving knife to cut off the corners of the squares? There was one in a local charity shop for ?4 the other day!!
 

Thorvald

Active member
would something like a cookie cutter work, how about one made from a soup or bean tin can, cut one end off (there are some tin openers that will cut just under the rim, leaving a very sharp and even end, just twist the cutter through the foam.
I am not sure what you mean. Right now I am thinking about a bread knife, but they are not long enough. Wait! What about a insulation knife like these??
 

ver.ba

New member
Take it to someone that has a water jet cutter, like a knife on butter. Were are you getting your foam?
 

Phil Reay

New member
cut them square but tapered at the back. arrows hitting them will try to push them in deeper but won't be able to but hitting them from the back will punch them out so that you can put new ones in. don't need glue that way.
 

Thorvald

Active member
Take it to someone that has a water jet cutter, like a knife on butter. Were are you getting your foam?
Well, that is not possible - well for the replacement cores maybe yes, but then there is the target wall. The maintenance of the targets should take place in our shooting basement, in general.

We get our foam from Danage.
 

Thorvald

Active member
cut them square but tapered at the back. arrows hitting them will try to push them in deeper but won't be able to but hitting them from the back will punch them out so that you can put new ones in. don't need glue that way.
Both yes and no. First of all it complicates the operation to make a tapered cut. Secondly it seems like the younger archers in our club have not learnt as basic archery knowledge, to hold on the target with one hand, with arrow between two fingers and pull with the other hand. Or they have got so used to the firm target wall, that they just pull with one hand. So the foam centers will eventually come out - that's why we use to glue them. Another thing is that there is not access to the back of the targets, at this target wall, so you cannot push the centers out from the back. I think a firm fit is perhaps better - trying to make the replacement center a few millimeter bigger than the hole in the target. We have a very big hammer, to push them in, if necessary.
 
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