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[C-3PO]

Every time I go near plywood it's seems to splinter on the reverse cutting side!

I need to cut slots approx 13mm x 26mm in a piece of 7mm ply. I need to do lots of these so not practical to cut by hand. My current thought is to use my router (even though it's gone AWOL in my workshop)

Is there a way to get good clean cuts? Does this involve having it on a hard wood sacrificial work surface on the underside? Is there a particular router bit that would be better than others?

Any help and guidance will be much appreciated

Regards
C-3PO

[Charlie]

How about Routing down to half the depth of the ply, then turning the piece over and Routing from the reverse side?

[imsinking]

How about Routing down to half the depth of the ply, then turning the piece over and Routing from the reverse side?

 




You would need a template to do that , there would be horrible steps all over the place.   
Bill

[Charlie]

  ]
  You would need a template to do that , there would be horrible steps all over the place.   

True, but a step is better than a splinter

[TailUK]

Make sure the piece you're cutting is held down tight to a, as you call it a "sacrificial" piece, it acts as a "chipbreaker" but remember that the cutter need to be into the chipbreaker, not level with surface as it just wont work.  Don't be afraid to pin the 2 together but remember to put the pins where the cutter wont hit them.  Use the best cutter you can afford and with thick pieces a "spiral cut" cutter will work best.  HTH.

[grendel]

fretsaw or powered fretsaw with a fine blade, I have been cutting 5mm ply and not a mark on the other side, another trick is to mark the side that splinters out using a strip of masking tape over the cut line, this allows for less splintering

[grendel]

another option would be a 1/2" morticing bit in a morticer

[Ron Rees]

If you need to cut 'lots of these' as you say, then it is worth making a guide plate from something like 1/4 ply or MDF. Clamp down tight the guide, the work and a piece of sacrificial ply or similar. Don't use one large cutter in one go but rather go full depth with a smaller cutter which will give you tighter corners and allow space for shavings and hairy bits to be removed. Remember that routers go in one direction, you'll get a better, cleaner cut if the bit is rotating one way that the other, (Against the main grain direction or with the grain direction). Go slowly but not so slow that the wood burns.


Some router bits have a ball race which runs around or inside the guide which you must allow for when making the guide. If it is a straight(Un-ball raced cutter) then you can get a simple guide plate that looks like a top hat that fits into the routers' base plate. Both of these work well to do what you are doing. Every time to move the guide to cut another slot, move the sacrificial plate to an uncut piece.


Hope this helps.


Ron.

[Stavros]

Simply mark the slots on the otherside of the ply,score with a stanly knife and cut away.....thars what i do ans also use a jig saw blade intended for metal...thats waht i do and it works....try it on a scrap peice before

Dave

[C-3PO]

Thank you for all the advice - I will digest and have a go on some waste ply to perfect the solution using the advice kindly given when the router decides it wants to be found.

I have got to cut 198 slots so I'll be busy!

Thanks again
C-3PO

[RAAArtyGunner]

fretsaw or powered fretsaw with a fine blade, I have been cutting 5mm ply and not a mark on the other side, another trick is to mark the side that splinters out using a strip of masking tape over the cut line, this allows for less splintering

Way to go 

[Onetenor]

A worktop cutting router blade and template to suit or a scroll saw although you do have to unship the blade each time The fine blade cuts very cleanly