Thread: What am I doing wrong??

Originally Posted by Colin Howkins

It's been a while since I visited the forum, but what else would you turn to when you are in trouble??

I have been recently making some objects of a particular shape, for which I have a template made.

Said objects are cut close to size using the bandsaw freehand. Oversize objects are then fixed to the template and final shaping is done on the router with a pattern following bit.

Made a few up using Tassie Oak, Myrtle and Silky Oak - no problems.

Have started to make some up out of timber of unknown origin except that it is old and recycled - could be like ironbark, or some other eucalypt specie.

When getting to the final shaping with the pattern following bit, as you approach the area when the bit comes into contact with end grain[the objects are oval] it grabs, smashes the timber and flings it to the other sie of the workshop - pretty frightening experience.

Tried cutting closer with the bandsaw so that I am only trimming of 2-3mm at most - still no good.

Feed rate is very gradual

Tried using a spiral cutting bit - still the same problem.

This problem did not occur with the Tassie Oak, Myrtle or Silky Oak.

Would any of you esteemed and experienced person have a solution

Hi Colin, You could use an oversize bearing or two to limit the cut of the bit and when you have the correct size bearing in place for the final trimming, several (many) layers of masking tape on the template will help to limit the cut.

Cheers
Michael

Are your routing in the correct direction?
You could try "back cutting" in the opposite direction at the start of the end grain - but do this a little at a time.
If you have a variable speed router you might try a slower speed - I know that you said you are feeding at a gradual rate.
It may be that the timber is very dry and brittle and cannot be worked well/easily on the end grain.
Have you a good supply of the timber - because it may be trial and error until you get it right?
Let us know how you get on.
Regards,

Hi Colin,

I had a similar problem when trying to use a router to shape around an oval like shape. It did seem to be worse on harder timbers.

In the end the only thing I could come up with was that the the router bit was tearing the grain out as it went around the oval / circle / ellipse and shifted from cutting with the grain to cutting against the grain (much like trying to plane against the grain). The solution was to modify the template so that I could turn the workpiece up side down and rout with the grain.

If this is not an option, setting up a collar to follow a template on a sander may allow you to get the shape you want. This will depend on the sort of sander you have and how complex the shape is.

Regards

Thanks for your input.

Michael, I had been trying to figure out a way to minimize the cut, and the masking tape idea I think has legs.

Smithy, you are right about one thing the timber is very old, very dry, and hence very brittle, and that may be compounding the problem. I have done this sort of thing many times before, but never previoulsy on old recycled hardwood.

Once again thanks for your assistance

Reminds me of trying to rout dovetails across the grain - splinters and chunks flying off everywhere, haven't tried that again

Colin,
I just saw a video on FineWoodworking.com where the guy with a template guide went half way - with the grain and them flipped the piece and locked it back onto the template and repeated the rout with the grain to eliminate tear out. This might solve the problem!!! let's know if it works - if you still need to do it that is.
Regards,

Originally Posted by jaksam

In the end the only thing I could come up with was that the the router bit was tearing the grain out as it went around the oval / circle / ellipse and shifted from cutting with the grain to cutting against the grain (much like trying to plane against the grain). The solution was to modify the template so that I could turn the workpiece up side down and rout with the grain.

This is exactly the problem. One solution which I have found to work well is to cut away half of the template with a pattern bit, then change to a flush trim bit, flip over the template, and do the other half.

The more significant the rise angle of the shape, the more likely you are to experience this problem. HTH