best router bit for grp?

Discussion in 'Fiberglass and Composite Boat Building' started by nevilleh, Sep 17, 2011.

  1. nevilleh
    Joined: Sep 2008
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    nevilleh Junior Member

    Any suggestions for the best type of router bit available for GRP?

    We are cutting scuppers through 15mm thick laminate. Have been using tungsten tipped but finding we are only getting 3 holes per bit.

    We are roughing the scupper out with a plain bit then finishing with a top bearing straight fluted cutter.

    Holes are approx 12" x 4"

    Suggestions would be appreciated.

    Neville
     
  2. michael pierzga
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    michael pierzga Senior Member

  3. alan white
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    alan white Senior Member

    Carbide tipped cutters come in many configurations. The design of the flutes varies to cut different materials from wood to plastic. Laminate cutters would be suited to very thin hard plastics, though thicker (1/4", e.g.) plastics such as a boat hull would probably need to be cut with a bit designed for somewhat thicker materials.
    Mostly, you want a bit that stays cool and doesn't load up. A typical straight fluted bit can be adjusted up and down to present many new cutting surfaces before it wears out. 1/2" collet routers can take 2" tall straight fluted bits which translates to 8 available cutting surfaces in 1/4" material.
    RPM of the router is also important. Though many routers are fixed speed, some have variable speed. By varying the speed you can home in on the best cutting speed for a particular task. The lowest speed that will still do the job smoothly is probably the bast way to go.
    Heat will melt plastic so never let the bit get hot enough to load up the bit. A loaded-up bit won't cut or eject material well and the result will be having to clean the bit in a strong solvent or possibly even replacing it.
     
  4. PAR
    Joined: Nov 2003
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    PAR Yacht Designer/Builder

    Double spiral cut, fluted bits will do the best job, but as mentioned speed is important. A router isn't the best way to cut laminate, though you can be precise, it make a lots of dust and eats up bits, like my ex-wife did boyfriends. A slower moving tool such as a reciprocating saw blade will leave much less dust and you can still get a level of precision. An air saw, running a big tooth blade, at fairly slow speeds will last the longest and it's what I use to cut out heavy laminates. It produces small chips instead of dust and the blades last longer then a high speed router bit.
     
  5. nevilleh
    Joined: Sep 2008
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    nevilleh Junior Member

    Hi Guys, thanks for your input. Looks like I will be on the phone to the shop in the morning for a more suitable cutter. Only problem is whether we will get the correct type with the top bearing.

    I have used recipricating saws for this in the past but I have just found that the router works best. Its noisy & its messy but when we use a template and a cutter with a guide bearing the end result is fantastic.

    The holes have round ends - I used to do it with a holesaw on each end and then use a recipricating saw to cut the straight bits out but there was still quite a bit of time & hand work to finish.

    This way gets them done in about 20 minutes each compared to over an hour each the old way for an inferior job.

    Neville
     
  6. SamSam
    Joined: Feb 2005
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    SamSam Senior Member

    Heat is bad for the bits. A rough cut with a saw, leaving as little material as possible, and finishing with the router leaves a finished edge with way less wear and tear on the carbide bit. You also might try a small stream of water on the action to cool the bit and eliminate dust.
     
  7. nevilleh
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    nevilleh Junior Member

    Thanks guys, I guess tomorrow we should try speed adjustment
     
  8. tunnels

    tunnels Previous Member

    Its real simple !!

    If it is not diamand you are wasting you time because it is never going to last !!:D

    Have diamond cutters ,Router bits and saw blades that are more than 10 years old that are cutting as good as when they were new
     
  9. waikikin
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    waikikin Senior Member

    I agree, a diamond edged holesaw & disc for the straits will be quick espescially if you make a positioning jig to speed set up & marking out.
     
  10. nevilleh
    Joined: Sep 2008
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    nevilleh Junior Member

    Hi, I have found a diamond tipped router bit , am going to check out the cost next. The holesaw idea is how we have doneit for years but the finish just isnt quite good enough . Ill let you know how we get on. Thanks
     
  11. tunnels

    tunnels Previous Member

    Have always been of the belief that if you spend that little extra for good quaility tools and equipment it will last just about life time of continual use and never let you down when you need it the most but take care of it !!.
    Diamonds are forever !!just dont try cutting steel or anything other than just glass !!:):D:p:p:D
     
  12. nevilleh
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    nevilleh Junior Member

    Tunnels,

    I remember for years I cut grp with a 4" grinding blade, with the advent of the diamond disc the speed was doubled and machinery life trebbled! Hopefully i will get the same result on the router bit
     
  13. PAR
    Joined: Nov 2003
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    PAR Yacht Designer/Builder

    I wonder if a custom scupper shaped blade (or maybe half of one) could be made for the multi tools that have been showing up. Just align and push, flip align and push.
     
  14. tunnels

    tunnels Previous Member

    With diamond you get a router bit custom made then they are able to coat with diamond dust and its yours for ever ,Any shape or size .
    I went to the composits expo in shanghai last week and discovered a company that does bandsaw blades any size !, or length and deepth !!from the small to the really big because the diamond is not actuly a tooth you can have fine cut or course cut on one blade simply by taking the blade off and flipping it and then refitting , I shock my head in disbelief ! I never seen anything like it before . Fantastic !!:idea::D:p:p
     

  15. PAR
    Joined: Nov 2003
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    Location: Eustis, FL

    PAR Yacht Designer/Builder

    I wonder what those diamonds do to the wheels and guides on the band saw.
     
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