Holes in bandsaw inserts

[Wend]

Hi folks,

My bandsaw insert is starting to look a little chewed up, so I though I ought to do something about it before it's too late. And as I sometimes have small pieces fall down the gap, I thought I would try to make something closer to a zero clearance insert.

I planed some 6mm ply down to 4.8mm, and cut/sanded it into a rough circle - pleasantly surprised by how well both operations turned out! I also made some smaller circleish pieces of ply to be glued underneath, to strengthen the insert. I don't know how important that is, but there didn't seem to be any harm in doing it. All in all it's been a simpler project than I feared it might be, although I haven't actually tried to cut a slot in the right place yet, let alone see if they actually work!

What I'm not sure about is the holes in the original insert, though. It seems to me that these can't be essential: For some cuts they are all covered by the piece of wood for most of the cut. And they'll weaken my plywood inserts, so all things being equal I'd rather not have them. But I guess their purpose is to help with dust extraction, so maybe I should put some in the insert I normally use? And perhaps I could leave them off an insert that I use when I'll be making small bits of off-cuts?


Thanks for any thoughts,
Wend

 

[Phil Pascoe]

I made mine from an old plastic chopping board.

 

[Doug B]

I’ve recently changed my bandsaw & it has a plastic insert with holes, I’ve seen no noticeable improvement in dust removal with this insert over my old machine which had an insert similar to the ones you’ve made without holes @Wend.
My shop made inserts worked fine for many years & the new machine will get a similar insert when the factory made one needs replacing.

 

[Nick.]

Hi Wend, You are right that a lot of inserts have holes in - Ha, I've never even thought about this before and don't profess to know the answer why they have them, but for what it's worth ours are solid pieces and I've never heard of any issues.
Surely even with holes in they are covered by the timber being cut so end up being redundant? I really don't know and it's tested my brain late on a Sunday thinking about strange things like this, thanks.
I'd just go with solid.
Cheers, Nick

 

[toolsntat]

Unless the dust extraction port is sealed from underneath I cannot see much advantage of holes in this instance.

A plausible scenario is that the more content you leave out of a plastic item the cheaper it is to make.

Cheers Andy

 

[Wend]

Thanks all! I think I'll give the drill press a rest, and just leave them all solid, then

 

[Richard_C]

Maybe its a bit of "kidology marketing", so the customer thinks its special and doesn't make their own. Why turn away an opportunity for profit on after-sales. Or maybe when you injection mould the round ones the holes mean they are less likley to distort as they cool so you can get higher throughput.

Theres lots of things that you mass produce in one way in a factory but can be done differently for one offs.

Plus ofcourse you can always add holes later if you do get a dust build up. Adding holes is easier than taking them away.

 

[CaptainBudget]

Or maybe when you injection mould the round ones the holes mean they are less likley to distort as they cool so you can get higher throughput. I reckon it will be to do with the injection moulding process, probably more to do with raw material. Your biggest cost is the mould itself, after that it is the plastic you are injecting. By filling it full of holes you need to inject considerably less plastic (reduced cost); having had a look at mine it's probably reduced the mass by ~20%, so the raw material goes 20% further. Obviously if you go too far you weaken it too much but it makes sense to remove as much "excess plastic" as possible to reduce your costs (if you make 10,000 of them, and adding holes makes your material go 20% further, that's an extra 2,000 pieces from the same volume of plastic at near-as-makes-no-difference zero cost). If you're machining from solid (plywood in the OP's case) that's just an additional cost for minimal gain and can probably be ignored (all I can think of is it's extra holes for dust to fall through, but as others have already mentioned they're covered 99.9% of the time anyway...) It may also have aesthetic advantages as a bonus? ("looks" more professional, so customers feel it is a higher quality product?)

 

[TheTiddles]

Holes in an injected part are best avoided, they make for awkward fills, weak points and ejection issues. Unless you’re using something fancy commodity plastic is phenomenally cheap, hence why it gets thrown away so much.

I can see someone thinking it helps with dust extraction, I too don’t think it does.

 

[CaptainBudget]

Fair enough, I genuinely couldn't think of any other reason why they'd be there...