# Safe clearance of bit to inside guide bush?



## MarkD (Jul 25, 2006)

hello,
Recently I purchased a Lokbox Router Jig for installing fin boxes into fibreglass surfboards 
The templates that come with the jig require a 1/2" diameter cutter to be used within a 5/8" outside diameter metal guide bush that screws into the router base..Consequently the clearance between the cutter blades and the inside of the chromed metal guide bush is probably less than 0.5mm or 0.0197" . I don't have much experience of routers but this seems small enough to be asking for an accident. What do you think?
Thanks
Mark
PS couldn't get hyperlink to work sorry!


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## Mike (Nov 22, 2004)

It shouldn't be a problem Mark. Routers are designed to keep the bit running true. By the same token having that small amount of clearance could be a problem for chip removal. I would suggest you use a 3/8" bit first to remove the bulk of the material and then your 1/2" bit for a final clean up cut.


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## MarkD (Jul 25, 2006)

Thats reassuring. I did try the cutter and the guide in the router we had to hand - a cheapo - (Argos Worx WX15RT 1500W Router ) and there was enough play in all the mechanics so that I could lever the cutter blades against the inside of the bush if I was a bit rough with following the template.(Router not spinning to test) so I shall put this down to a rubbish router and go and check a good one. Mostly we are cutting polyurethane foam blanks, sometimes with 1/4" wood stringers in them and sometimes through a 1/8" max layer of GRP so hopefully chip removal not to much of a problem.

Mark


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## Mike (Nov 22, 2004)

Mark, you will find it is possible to overpower many plunge routers with brute strength. Your Worx router is rated as a best value by the August 2006 issue of Workbench magazine. I have my doubts about it because of the price but I am willing to keep an open mind. I suppose it makes sense to say all tools should be used properly and excessive force is not the answer, let the bits do the cutting.


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## MarkD (Jul 25, 2006)

Thats interesting about the Worx router being well rated. I agree about letting the cutter do the work and my description of "levering" sounds as if I was forcing it rather than what I think was reasonably accurately imitating probable workshop use/misuse. I have looked at our Worx router and find that there is play in the plunger 'arms' both where they meet the body and the base plate and after checking have found that it was knocked over onto the floor so it is probably far from new condition. The supplier of the Lokbox Jig and finboxes recommends first the DeWalt DW621 then the cheaper Ryobi ERT-1500V and have assured me that they have never had a cutter meet the inside of the metal collar guide. I am still a little surprised at the small clearance being acceptable but I shall be ordering the cheaper Ryobi and seeing for myself. Thank you to those who replied. 
mark


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## Hamlin (Dec 25, 2005)

If the base plate will allow, you can rotate the placement of the screw holes that mount it. This will "tighten" any play that you mentioned. As for the handles, you could possibly use washers to thighten them up.


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## MarkD (Jul 25, 2006)

I was not able to improve the amount of play because after carefully examining a new Worx I have found the problem is that the base tilts enough to cause the guide bush to be at an angle to the cutter (and therefore interfere with inside of bush) due to either plunger arm/rod being able to be pushed into its sleeve bearing more than the other. Probably the tolerance of rod to sleeve and lack of rigidity in the base and arm/rod attachment. Difficult to explain but easy to see. I tried the Ryobi and will send it back as its plunging action is very unsmooth even after lubricating the rods and also similar but not so bad play. Tried a new Worx, same problem as first. Going back to Argos.
Went and looked at a top range Trend (T11) and a friends top Freud and the difference in quality is worth paying over double for. None of this play at all. Smooth action. Of course you all probably know this already but there is nothing like experiencing it yourself. On one hand crazy to use a top range router for cutting rigid foam but the ony thing I would be happy to use considering design of jig and necessity of 5/8 guide bush.
SUMMARY Only the highest quality routers run true enough for this use. The Worx is way better than its price and might be worth modifying to improve base to arm rigidity.Thanks for your help. Now to spend the money on a T11 or 10 whichever is cheapest.
UPDATE I got quite exited about the Triton 1400W because of its less weight and rack and pinion depth adjustment mean there is less risk of marking or denting the quite sort foam blanks. I cant find info on the guide bushes from the Triton site but only from Amazon. 5/8" OD with 17/32 ID available as part of the 7 piece kit. So thats 1/64" clearance or 0.397mm between a 1/2" cutter at 20000rpm and a metal guide bush. Not too happy with that so will probably send the jig back as badly designed and make my own for a more sensible guide bush size.


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