Sanding Curves to match a template

[John Craig Brown]

I am having trouble sanding inside curves for Adirondack chair plans. Using an oscillating drum sander leaves transition marks as the drum is much smaller than the gradual curve. A pneumatic drum would help but still the curve of the drum is much less than the gradual curve in the template. Any suggestions?

[Bill Huber]

Are you making your templates and can not get them right or are you doing the finial sanding on the chair parts after you cut them out. If its the chair parts you should be able to sand them just by hand.

When I make templates I use 1/2 inch MDF, it sands really good and easy. I use a Ridgid combo sander (http://www.ridgid.com/Tools/Oscillating-Edge-Belt--Spindle-Sander/EN/index.htm) with the belt most of the time. With the 1/2 inch MDF it sands so easy you can really work it down to the line. I use the open ends for the corners and curves.

When I have curves, I make very light cuts and keep moving and move some what fast around the curve. If you try and sand very deep and slow you will never get a smooth curve, IMO

If I have the plans on paper I will spray glue them to the MDF and then just sand to the line, again the MDF sands so easy I can finish up by hand if there is a little place that needs it.

[John Craig Brown]

I am using 3/8 MDF - still coughing it up - and you are right in that I am sanding down to the line in segments as opposed to keeping the template moving quicker. I wanted to make the templates to use as a pattern for routing and I am not satisfied with the smoothness of the template curve, which is a gradual curve over 22-24 "

[Dan Lee]

Rasps suich as Nicholson #48 and #49 are excellent for faring curves after cutting close to the line. Sandpaper adhered to a thin strip of wood works well also.

[glenn bradley]

As stated, for curved patterns I cut close to the line with BS or OSS (or both) but then generally finish up with a hand rasp and a shop-made curved block and sandpaper. Often the machines, which are so very helpful, just don't offer enough finesse for this kind of work. I have been peeved more than once when the slightest dimple in a pattern gets transferred faithfully to my piece via the bearing guide.

[David DeCristoforo]

The "trick" to sanding curves on a drum is to keep the material moving and using a "light touch". But it's a "skill" that takes practice to master. You can get small drums with template guides like these:
http://www.rockler.com/product.cfm?page=16902
that will pretty much eliminate the problem you are having. You might also be able to rig up something similar on your ODS.

Another option is to use a router and flush trim bit to size your pieces and then hand sand the curves.

[John Craig Brown]

In terms of the template guide for the ODS is that I still need the template. Roland Johnson has a nice video on the techniques for using a spindle sander and a nice tip for a jig to smooth straight lines:

http://www.taunton.com/finewoodworking/ToolGuide/ToolGuideArticle.aspx?id=27731

[Martin King]

Your best bet for fairing curves is a flexible batten with the sandpaper
either glued to or wrapped around. With long gentle curves like in
your adirondack chair, you can avoid the scallops you are getting
using the oss, and get your templates perfectly fair.

[John Thompson]

I make a lot of templates. I use 1/2" MDF and cut to 1mm of the line drawn on it.. take it to the spindle sander.. keep it moving as mentioned to just outside the line and then finish with a rasp as mentioned. The good new using MDF is if you mess up.. it's cheap and you can have another try. The bad news is it takes much more time to make the template than the final routing on the table with a bearing pattern bit.

Good luck...