about to shape an alder body [ around 1 3/4 " thick ] with an inverted cutter [ home made router table ] . the bit itself is 1/2 shank with a 2 1/2" cutting edge. my question is this, would you advise me to run slow given the information above ?. i have bandsawed the shape quite closely so the bit does not have too much to remove. i am hoping to do it in one very careful full body thickness pass. your thoughts are appreciated.
Slow bit speed is bad for this operation you will get more tearout,
Use the highest speed you have avaliable and feed the body into it at a moderate even pace..
Plus if you get too much burns, slow down.
If you are new to this I strongly suggest you do it in multiple passes, homemade router tables and adapted hand held routers have play in them and play equals trouble. If you get a kickback or a 'grab' and do not have proper guards you may also hurt yourself. You might also like to look up back cutting to counter having to machine against the grain. Router speed and feed rates for various tools/tool diameters are facts of life for machine shops - if you are on the web look them up and they may help you get a better feel for what you are about to do.
It's a free world Nick, but I look back on my early procedures (or lack of) and equipment and just plain shiver about how I got through with all my fingers and thumbs. Rusty.
thanks for your informed replies all of you. i'm with you all the way on the safety aspect rusty, the thought of a snapped 2 1/2" cutter heading for my face does not appeal !
I use a sort of a home-made router table with 1KW router. Normally I do such a job on template with a ball-bearing bit, with the bearing at the shank, and template attached to the body face down.
I do this jobs in several passes, taking the bit 0,6 to 1 cm upper on each pass till I reach the middle. The body is turned face up and I do the rest.
This leaves the line marks which are easily removed with 80-grit sanding paper on the cylindrical sanding block. This contour sanding with 80 - 100 - 120 - 180 - 240 - 320 takes only 30 minutes to one hour depending on the wood hardness and produces quite a smooth surface. Plus it removes any burns router can leave.
If you do the routing in one step you risk to get chip-outs, and the chip-outs go across the whole thickness.
to clarify folks, doing the job as igor said, on a template with a ball-bearing bit, with the bearing at the shank, and template attached to the body face down. i'm guessing that the 2 1/2" router cutter would not suit the "multiple passes" method and i should use a shorter cutter.. pic attached shows router table and jazz bass template.
I see. I would test on scrap first in various directions to the grain. I do templates of 1/2 plywood so they are thick enough for the bearing, and shorter bits. I have a couple of long ones, but never use them, somehow they look a bit scary to me.
i'm with you on that one igor, the long cutter looks like a great solution in theory but i think it would be brutal and unforgiving. i will do a dummy run on scrap pieces first.
These long bits are difficult to align vertically, plus any disbalance on the bit causes vibration and inaccurate cutting. I just afraid of them, but this can be only my personal phobia.