Shopsmith Forums

So getting a dedicated 1/4" or 3/8" dado seemed like a good idea; none of that messin' with shims.

Great I thought, until I used it. Perfect 1/4" passes. Perfect 3/8" passes. What if the stock used 'grows' in a high humidity shop? Screwed!

I only need 1/4" fingers in nominal 1.5" stock. So how about slipping in a shim or two between the 2 blades of the SBOX8? Freud have a set for the regular dado blades from 4 thou up (Forrester even have a magnetic version but they start at 10 thou). 10 thou per finger is around what I need.

The jig I made with a beautiful 1/4" pin needs some adjustability so I thought a thin slot that I can slide a feeler gauge alongside the pin of the required thickness would address that part. I already made the jig adjustable for different sized dado's.

I'll probably call Freud to see what they say but I suspect they shall demure due to liability issues rather than a sound technical critique.

So, any input? My concerns center on the blades requiring intimate contact for strength and/or catastrophic vibration issues. Exciting huh?

Alternatively, anyone looking for a barely used SBOX8 box joint maker?

A couple of things you can do -- assembly the parts immediately after cutting the box joints or store the parts in a plastic bag immediately after cutting until you can assemble them.

There's no reason you can't put a shim between those two blades, but I don't see what that accomplishes if it's high humidity that's preventing you from assembling the parts. The same thing is going to happen with or without a shim.

If the parts don't fit together immediately after cutting the joints, your spacing is off and you need to adjust your jig so that the pin width matchs the slots.

Art, thanks for the reply.

The lumber is stored for at least a week before being worked. Fitting the joints is not the issue.

The finger joints are perfect (actually a little too tight but reducing pin to blade distance makes the problem worse) but as the stock has grown during storage, the last cut leaves around 10-20 thou of wood. Adding a shim (and increasing the pin width and position) would eliminate the need to aggressively sand the finished product flat.

The finished dimension is not critical but cutting the fingers to match the width is.

The SBOX8 has fixed width which is great with stock that is exactly divisible by 1/4 or 3/8 inches at the time of sawing. I don't have the luxury (nor need or desire) of jointing/planing to achieve that level of precision. Adding a shim would solve the issue but I am a little concerned with pieces of shattered blade flying at me.

I am a lot more aware of how wood is "constantly in motion". I picked up a cheap thermometer/Hygrometer. Humidity is usually 75-85%, Not seen it below 70% and often at 90+%. Then again this is Oregon in a pretty wet period (weather.com shows humidity at 100% 07:15 PST 01.27.12). Summertime can be as low as 20%.

Found an interesting average humidity site here (61 years of data for Portland). Not as much variation across the entire country as I thought there would have been.

I'm pretty new to woodworking (and the Shopsmith) and do a little research prior to acquisitions but I didn't really understand how the box joint jigs worked (I do now) and I didn't think through the implications of finger size (I will now).