Not so sure about the up/down cut router bits, I've never used them, but I'm not too keen on them
"pulling" or "pushing" the work. Simple is better. You're making pretty shallow cuts, standard router
bits have worked well for me and should do well for what you want to do.
Jim - they don't push or pull the work itself, but the dust one way or another, so it can be efficiently removed from the cut area. The cut itself is cleaner because
these kinds of bits are of spiral rather than linear edge design. But they're not made in a low price point range. Some simple straight bit cut well on the end, some
don't, and that is an important distinction regardless of carbide vs high-speed steel. But one problem doing precision work in the flatness of the template itself. I
prefer using phenolic over something like plywood, which isn't all that flat to begin with. But correctly making the template itself requires some precision router work.
I can easily work within .001" tolerances, but not using plywood or masonite etc. How accurate is accurate enough depends on the intended focal lengths of the
lenses and typical working apertures I guess. But ya gotta be fairly close to avoid light leaks anyway.
Drew - The spirals do offer better chip and dust ejection, but the spiral flutes will cause a tiny bit of pull/push in my estimation,
I saw that when I didn't lock the quill tight enough on my milling machine, which is somewhat related since all my end mill bits are spiral.
I probably wouldn't use them for hand routing, but if they're used in a table setting it might be negligible.
Milling cutters behave somewhat differently than router bits intended for wood, which ideally have very different edge geometry. Properly made they can be extremely smooth, without any tugging effect. Keeping your work rigid is always a necessity, regardless. The most frequent mistake amateurs do with router tables is have one which isn't completely solid and is capable of vibration. Either that, or the work itself vibrates. Unfortunately, one cannot simply walk into the typical hardware store or home center and pick up ideal router bits. You might get lucky, but generally it takes a specialty shop. I sell to an extremely diverse variety of
pro trade, and have done more than my own share of experiments (including making most of my own darkrm equip), so have a lot of hand-on experience as to what works and what doesn't with specific materials. Perhaps I am indeed spoiled having the advantage of borrowing a high-end piece of gear for personal projects, but really, it's encouraged both by the company and the specific manufacturers to keep me informed.
I made a picture for you. This is a very simple yet effective method that will allow you to achieve the result that you want.
First, by a decent quality trim router as even the better ones are only around $110. The bit you need is a 1/2" mortiseing bit with a bearing at the top of the bit. All trim routers have 1/4" collet, so make sure to get a 1/4" shank bit.
Next, remove the plastic base from the router and trace the bear metal "sub base" and screw holes on one side of the material. Insert the bit in router, but don't burry all the way until the bit bottoms out...
You want the bearing to be sticking above the opposite surface once the router is mounted. You'll probably have to remove a bit of material on the mounting side in order to accomplish this. The mortise doesn't have to be nice just large enough tot easily fit the router sub base. Drill a 3/4" hole right were the bit centers.
Once this is accomplished and the router is mounted to the 3/4 material you can make the spacer frame for the camera back.
Here's the cool part; the bearing on the bit will ride on a surface and will allow the bit to cut the material above the spacer exactly flush. Determine the height of spacer needed in order for you to make a cut deeper than you'd like. Determine the outside dimensions of you rabbit (the name of the type of cut your making). Cut spacer material so it's sufficiently wide enough to not be tippy, and is located at the boundary the cut you want to make.
Secure the space to the back. Double sided tape, 23ga micro nails (my favorite), brad nails, etc. Adjust router so you make a small cut into you material, don't try to take it all at once, you want to "sneak" up on this critical cut. Make successive cuts until you've achieve the desired dim. Remove spacer material.
You'll be left with radiused corners. Take a sharp chisel and par away the wood until you have a nice square corner. Sand to desired final dim. (Which should be minimal) and your all set.
A few more things. Make sure that the spacer material is all the exact same thickness and the table is relatively flat and you exert even downward pressure at the cutting area, as all of these things will effect the depth of cut at any given point.
Feed the material into the bit the "right" way, wether fed from left or right into the spinning bit will make a difference, you want to have the bit feeding into the stock from where material has already been removed. You don't want the bit wanting to "climb" or feed itself as adverse cutting can occur and the cleanest surface is hard to achieve.
I hope all this makes sense. Let me know if you've got questions
-Josh
Yes, that does make sense, and good ideas as I didn't know how to setup with a spacer and a bearing bit. Heck, I never used a router, but that never stopped me. I built a wood boat with tiny hand saws, just to do it, and it's hanging over my head right now.
This is a long term project that I will attack as I gain time, understanding and desire.
Thank you!
Originally Posted by speedfreak
A few more things. Make sure that the spacer material is all the exact same thickness and the table is relatively flat and you exert even downward pressure at the cutting area, as all of these things will effect the depth of cut at any given point.
Feed the material into the bit the "right" way, wether fed from left or right into the spinning bit will make a difference, you want to have the bit feeding into the stock from where material has already been removed. You don't want the bit wanting to "climb" or feed itself as adverse cutting can occur and the cleanest surface is hard to achieve.
I hope all this makes sense. Let me know if you've got questions
-Josh
If you've never used a router, just realize that these can rout a lot more than your intended material, including your fingers! There are numerous on-line safety
videos you might want to watch first.
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