My new Thudbuster installation instruction states " The rear bolt must be tightened
to 60 in*lb (6.8 N*m) with a 4 mm hex wrench"
I don't have the proper tool. I'm wondering if I can complete a satisfactory installation
without torquing the bolt. I'm usually careful not to over tighten bolts using a "snug and secure"
rule of thumb, and avoiding that last bit of force. But I have no idea if that would approximate 60 in lb's.
Any help would be greatly appreciated.

30 years on you get a feel .. the torque spec numbers are a way of saying 'how tight'

it may be time to buy that torque wrench set .. 1/4 + 3/8 at least.

Some torque ratings are for not overtightening fears. Others are for making sure the clamp doesn't come loose. Both situations have some wiggle room. Tight enough to not damage but also to not self loosen is the best tightness. Andy.

6.8 nm is pretty tight by hand with a standard L shaped hex wrench. I would think that you could safely get to the point where it won't slip without going over. A torque wrench would be better, of course, but I'm just saying.

60 inch/pounds refers to 60 lbs. of pressure exerted on a wrench with an inch-long handle, or one pound of force exerted on a tool with a 60" (5') handle.

Playing with these numbers, you can see how a tool with a one-foot handle would exert 60 inch/pounds if you put 5 lbs. of force on the handle. Heft a 5 lb. household item (e.g, a bag of flour or sugar) in your hand and see what it feels like. Try to replicate that amount of force on your ratchet handle (a little more force for a typical 8" handle) and you'll be close enough. The handle should stop rotating when you have applied this amount of pressure or you'll be exceeding the desired torque.

Unless a torque wrench is brand-new, undamaged, and perfectly calibrated, it won't be spot-on either. I own a couple of torque wrenches, but there is sometimes insufficient clearance to use them, so you learn to make reasonable guesstimations.

thanks, I was able to make the seatpost 'dern tight' without damage. It's holding very securely and performing exactly as I had hoped.

"Dern tight" is exactly right. The seatpost on my domane asks for 7nm, and I was astounded how tight that is compared to how tight "derned tight" feels. Gettin to 7nm with a torque wrench took a lot of effort, and I'm no wimp when it comes to these things. For me, durned tight for the seatpost ends up being about 5.5nm. 6 is another 1/2 to 3/4 of a turn, and 7 is another 3/4-1 whole turn beyond that! Holds fine at 5.5.