Routing semicircles?

[wizer]

yes having now thought about this I'd make a template, bandsaw to 1mm from line and then router with bearing bit. If it's Utile then it's the same family as the Balau that bit me, HARD. Take less than 1mm passes with the router. Really creep up on it or your student might not be as lucky as I was....

Tho as his teacher, you should really be telling him how to do it and if the router is causing problems then find another way. Such as bandsaw or jigsaw near to line and then good old sand paper with a flexible sanding pad.

 

[Niki]

I think that he is "Biting" too much for each pass.

I made some circles and increased the depth by 2mm (or less) for each pass...there was some breakage but not like you describe.

Please have a look at this post
https://www.ukworkshop.co.uk/forums/view ... highlight=

niki

 

[JonnyD]

Route a template out of plywood and attach with double sided tape. Use a bearing guided cutter with a bearing at both ends then you can invert the work so you can rout downhill from the centre outwards but still not climb cut.

John

This is how I would do it.

Jon

 

[jasonB]

Me too, I've got one of teh wealden replaceable multi trim bits which is ideal in this situation.

Jason

 

[Setch]

This issue comes up all the time when routing guitar bodies - you need to start the cut at the widest point, and work towards the narrowest point. This will require some climb cutting, so it should only be done with the work securely clamped, and the router taking a very shallow bite.

Personally, I'd route several shallow passes with the router on a tramel, then switch to a template bit to cut one side, and a flush cut bit for the other. By working from either side of the workpiece you could cut both without having to work against the grain.

 

[Night Train]

Tho as his teacher, you should really be telling him how to do it and if the router is causing problems then find another way. Such as bandsaw or jigsaw near to line and then good old sand paper with a flexible sanding pad.

I teach 90% hand tools and hand working and had suggested band saw and compass plane. However, he insisted that he wanted to do it with a router so I set him up to do that.

Thing is I told him and showed him a simple and safe workable method the first time round and everything worked fine.

When he felt he needed to do it again I checked he was ok to go and then let him get on with it, as is usual with mature students, figuring that he had the jigs and process in his log book fromthe first time.
He went off and decided to do it 'his own way' the second time and that's when it all went wrong.

I didn't notice how he was setting up as I had two classes on at once all trying to get their work finished for both marking and exhibition. The first I heard was when it went wrong which sometimes happens when students are learning and decide that their way is better then the teacher's way!

So I end up with figuring how to help him resolve it. He just doesn't want to do it with hand tools.

Sometimes old men can be so stubborn.

 

[Night Train]

I think that he is "Biting" too much for each pass.

I made some circles and increased the depth by 2mm (or less) for each pass...there was some breakage but not like you describe.

Please have a look at this post
https://www.ukworkshop.co.uk/forums/view ... highlight=

niki

That is sort of how I set him up but with the work fixed and a hand held router on a trammel. The first cut was a 1mm depth full pass. The following cuts were 2mm on short runs leaving bits un cut so it was like a dashed line. The cuts were progressed through the board 2mm at a time until cut through. Then the remaining bits were cut 2mm at a time until a sliver of each bit was left supporting the waste. That was then hand cut off and sanded clean.
The work was clamped to the bench on a sacrificial board and the cramps were moved about to clear the trammel as required.

It works every time I have had to do something similar.

 

[toolsntat]

Not withstanding buying the right double bearing cutter and making a template another way to go at it could be thus...

Belt sander on side using roller radius or bobbin sander in pillar drill.

Using same trammel point but fixed to an overall base with sander attached make sweeps to reduce initial roughed arc.

Light cuts, no back feeding and be in control of top at all times...

:idea: A slot and pin trammel point would be better as it allows you to pull away from the sander when necessary :idea:

Not sure about edge profile but same method with shaped sanding bobbin in pillar drill could do the trick.....

Andy

 

[wizer]

Sometimes old men can be so stubborn.

I can only assume this is a case of Normitus ? I guess you can only keep advising him of what is essentially an easier route. As I said above, I'd make a temp and then do it with a bearing bit, making sure I was only removing 1-2mm per pass.

He'll eventually learn that the wood's in charge, not the router wielding maniac

 

[Digit]

I dunno if its worth starting a thread on it but this thread has started me thinking.
How many members try to avoid hand work. I chose machines/jigs when I believe that is the better route, but I prefer to work by hand.
What about the rest of you? Any comments?

Roy.

 

[wizer]

Since my 'incident', I avoid the router like the plague. I've got to cut some grooves for a little project I've been on for the past year. But I'm pretending it's not important Generally I now enjoy smoothing and shaping by hand. But I'll never prepare stock by hand. That would probably just halt production for me.

 

[Night Train]

I dunno if its worth starting a thread on it but this thread has started me thinking.
How many members try to avoid hand work. I chose machines/jigs when I believe that is the better route, but I prefer to work by hand.
What about the rest of you? Any comments?

Roy.

.
Go on, start a thread.

I am a hand worker and I avoid machines where I can. I can appreciate a well designed jig for repetitive or batch work though.

Generally I machine as far as thicknessed boards and then it is hand work and bandsawing as required. I even have a nice pair of hand rip saws that get used every now and then though not as much as my Japanese rip saw.

 

[Digit]

That would probably just halt production for me. Wink

Ditto!

Go on, start a thread. Very Happy

Your wish is my command!

Roy.

 

[OPJ]

If you have a look in the new issue of British Woodworking magazine, Steve Cole has made what appears to be a very safe jig for shaping on the router table. It's similar to what the HSE advise people to use against a ring fence on the spindle moulder... Couple of toggle clamps to hold the work down with your hands clear from the cutter.

Also, in the same issue, Steve Maskery mentions wrapping the bearing of his cutter with a strip of masking tape for the first cut. Once the tape is removed, he's left with a very fine, final trimming cut of less than 1mm - a great tip there! 8) :wink:

 

[FatFreddysCat]

Steve Maskery mentions wrapping the bearing of his cutter with a strip of masking tape for the first cut.

If you make-up a template jig for use it with a guide bush you can get the same effect but with much greater durability. A 12mm cutter with a 20mm guide bush has a 4mm offset - change to an 18mm guide bush and the offset is 3mm, i.e. you reduce the diameter of the workpiece by 1mm.

I agree with the guitar maker who says that you should start at the widest point every time, but my own preference would be to try climb cutting the short grain (on the left of the diagram) in very shallow passes providing the router is heavy enough. I'd also suggest going to a larger diameter cutter if possible. In the last couple of years I've moved from using 1/2in to using 3/4in cutters for template work and at the same time going over to replaceable tip cutters. The net result has been cleaner cuts, especially on stuff like Marmoleum/plywood composites (reception counter tops) and less tear out on solid wood bistro table tops. I've just started using a 28mm diameter cutter (with reduced speed) and the initial results are even better. I'd avoid spirals for edge work, though, unless the edges are subsequently to be radiused or chamfered. The up-feed or down-feed only types can break out the "waste" edge on timbers such as ash and oak whilst the compression cut (up and down cut) type mentioned by one poster always leave a witness line which needs to be sanded out