Thread: Collett extentions

Jamie, I bought one several years ago. I found when I used large diameter bits in it I got vibration. I don't know if that is common or it's just my setup.

Mike

Originally Posted by Garell

I cant quite get the height out of the raised panel bits and other bits we use. These routers are not vairable speed neither. Whats your thoughts on using extentions.

I'm in two minds, as kids from year 10 upwords would be using them from time to time, with supervision and being shown how to use them first of course.

When a router is designed to spin a cutter at the cutter's optimum length away from the lower motor bearing, any lengthening of this distance is, IMO, detrimental to the router and will inevitably cause run-out and out-of-balance problems too.

Everyone I know who has used an extension has always admitted that they've had to get it balanced by trial and error before using it. That tells me something right there Jamie- I wouldn't use a bit that I'd got to mess around with until I'd got it balanced, that's why I will never use an extension.

Given all that, you will realise why I shudder at the sentence "These routers are not vairable speed neither." With larger bits, especially panel-raisers, I'd say that variable speed is a must, but where there are balance issues included it's absolutely essential.

The final topper for me was that "kids from year 10 upwords would be using them" - I'd hope that your liability insurance is topped right up!

I appreciate that there are contrasting opinions on extensions, but I will not compromise on safety when spinning razor-sharp cutting tools at high speed. In my view, extensions are an avoidable compromise and to use them in the circumstances you describe is asking for trouble.

Ray.

Thanks every one for your replies.

I tend to agree about using the extensions. I'm not keen on the idea, and the more I think of it, the more dangerous it looks. However, I have no problem's with the large raised panel bit. I can get enough height out of that to clear the bed and make the cut. I make sure that they take two cuts not one.

Its the cutters that do the rail and style's that I have the problem with, especially the rail cutter. I have found that it is easier to make the cut so that the rebate is flush with the back of the rail and styles, this enables the raised panel to sit flush on the back of the door rather than inset into the door, if you know what i mean. This can be a problem as the rails and styles have to then be 17mm. The upside its easier to set up. The down side is getting the heightout of the rail cutter.

The problem I think lies partly in the slide. The base is 5mm thick with hold down clamps on top of a piece of 19mm stock to rest the rail against, its an easy and safe way of doing it with the kids. I don't really want to change that unless there is a better way.

We havent really had any problems with the speed of the router's, however doing lock miters is a bit of fun at times.

Any suggestions would be appreciated. Its always harder to explain in words. I should try to take pics where possible but its getting the chance with classes every day.

Anyway please let me know of your thoughts.

Regards Jamie

P.S. Picture is the panel set we have.

Haven't had to resort to shaft extenders so I won't pitch in on that one. However the notion of using large bits like panel raisers on a fixed speed router is very suspect. Most bit suppliers have some form readily accessable diameter/speed chart or table, there certainly are some in the Carbatec catalogues and on most web sites that market quality bits.

Most routers are set up to have a top speed in the range of 20,000 to 25,000 RPM, which is suitable for bits up to about 20 - 22mm diameter. For larger bits, the tip speeds become extreme and the bit overheats or the work gets scorched unless the RPM reduces to contain the tip speed.

I acknowledge that you mentioned panel raisers without indicating whether you are considering horizontal ones or vertical ones. The tip speed arguments above apply to the horizontals, but with the verticals you are still extending the load point a long way out from the collet because of the design of the bit. Operating these in a less than very rigid setup can lead to major problems.

Every bit in the set you show is larger than 25mm, in fact they are about 38mm for the smallest bit, running these in fixed speed routers which generally are around 22,000 rpm is an accident waiting to happen.

I have the set pictured and generally run them at lowest speed for initial cuts, about 13,000 rpm , then increase to around 15,000 for final cut.

Many people run larger bits in fixed routers and claim they have no problem, you can walk across the road with your eyes closed for a long time with no problems as well, if you are teaching students, for gawd's sake learn about maximum router bit speeds before you do another thing.

The tips of a 75mm panel raising bit are travelling 3 times faster than the tips of a 25mm bit at the same rpm, doing staged cuts does not reduce the danger.

Thanks to every one that has replied to my question

Since posting this on the forum, the teaching staff and myself have discussed the matter and we have come to the conclusion no mater what we do the collet extension, even in a variable speed router are just too risky around students.
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I have since purchased 2 new variable speed routers to replace the fixed ones in the tables. The price for the same router (Makita) in variable speed as compared to the fixed speed was quite dearer than expected, however when it comes to safety, I don’t care what it cost as long as it works.
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I had always been courses when using the fixed speed routers. There not bad when you are doing roundovers and trenching but other than that I agree they are just too risky spinning a large router bit, and I have never liked doing it.
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So there you have it, routers replaced and extension collets not purchased.
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Thanks for your advice every one.
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Kind regards Jamie</o></o></o></o></o>

Jamie,

I have made a handy little winder to fit the adjuster knob on my Makita.
It makes both fast and fine adjustment so much easier.
Much faster bit changing as well.

Mike

Thanks for that.

I will have to make a couple (if its ok to use your idear). There is nothing worse than trying to adjust the router in a tight space.

Kind regards Jamie