setting router depth- general question

[louis mason]

hi

i have mounted a Hitachi router with a router raizer to a bt3100 and i was wondering if there is a standard method for setting the depth of the router bit repeatedly? i am going to be tounge-n-grooving the sides of 3/4 plywood and i would like to always make my cuts centered to the 3/4 inch wood face. is setting the depth of the router just a trial and error each time the bit is changed? or can a height jig be made? how does anybody else do do this?


louis

[PALefty]

hi

i have mounted a Hitachi router with a router raizer to a bt3100 and i was wondering if there is a standard method for setting the depth of the router bit repeatedly? i am going to be tounge-n-grooving the sides of 3/4 plywood and i would like to always make my cuts centered to the 3/4 inch wood face. is setting the depth of the router just a trial and error each time the bit is changed? or can a height jig be made? how does anybody else do do this?

I am curious too. I have seen some various accessories on most woodworking tool sites to do this... usually in the $5 range. Is this what most people use? Is there one that shines above the rest?

[LarryG]

Not sure I understand the question, Louis. Are you talking about setting the amount the bit extends above the table?

If so, the easiest method to duplicate an earlier setup is to keep a control sample and use it to set the bit height each time you need to repeat that same cut. Simply lay the control sample on the table top with the bit fully retracted and crank the bit up into the existing groove on the control sample until the control sample *just* begins to lift off the table. Back off a hair and you're there.

Alternatively, you can use some sort of setup bar (Whiteside makes some, as does Lee Valley and others) if you need to match an easy dimension like 1/4" or 3/8". Crank the bit up until its tip is even with the top of the setup bar and that's that. If you don't have any setup bars, you can use a drill bit of the correct size (but be careful: the round shape of the bit makes it easier to make a mistake).

There are other ways, but most are variations of the same theme.

Or are you asking something else entirely?

[just4funsies]

If you've got a small piece of 3/4" UHMW (maybe about 4"x4") laying around, you can make a setup block. Once you've got the settings dialed in on the router, just run the block through just like you would a piece of wood, and the bit profile will be carved into the setup block. Then mark the block and put it aside. You can use it to reset the bit exactly the next time. I keep a few blank UHMW blocks around, so that I can cut a template on spur of the moment. Eventually, you will have a collection of them for use on projects down the road.

[louis mason]

thanks

OK- yes, you guys are answering my question. i will try the set-up blocks and refit the bit into the groove between bit changes.

thanks louis

[davidtu]

Do either of these items fit the bill and/or does anyone know if they are useful or just gimicks?

http://www.rockler.com/product.cfm?p...%20bit%20gauge




http://www.rockler.com/product.cfm?p...%20bit%20gauge

[drumpriest]

I personally make setup blocks for most everything. That makes it very easy to reset to a particular depth of cut. Just take a small scrap and rout it, then when you next need that same depth, put the piece over the bit, and raise until it lifts the setup block up, then back down until it touches, very easy.

[kwgeorge]

For quick height adjustments I use the brass setup bars. I always try to design my cuts around depths that are accommodated by these bars. For more complex things such as molding and such I fiddle with the height until I get what I want using scrap wood then I take a piece of scrap wood, make the cut on it, mark it with the bit used and save it. Now if my cuts include multiple bits I make several setup blocks and label them in the order of the bits used.

Works for me anyway.

[Bruce Cohen]

Louis,

This is what I've been using for a long time. Accurate as all get out and unlike wood go/no go gauges, they're not affected by humidity if you're looking for absolute accuracy.

Asso a trick I learned is to use the big 1-2-3- block to clame 2 pieces of stock to form a 90 deg. angle.



Bruce

[PALefty]

This is what I've been using for a long time. Accurate as all get out and unlike wood go/no go gauges, they're not affected by humidity if you're looking for absolute accuracy.

How are these blocks used? What are all the holes for...?

Also- without trial and error.. how do you know what block to use? ie- Can you always assume 1/2'' roundover requires a 1/2'' block etc?

[LarryG]

David,

I have a gauge like the first one you show. It doesn't work too well ... the legs between the notches don't always want to find a solid area of the router subbase to land on, and larger bits won't fit between the legs.

No experience with the second device but that's one of the classic designs for a height gauge and ought to work superbly.

I personally use the exact same methods Ken (kwgeorge) describes: brass setup bars most of the time, scrap wood samples when warranted.

[Bruce Cohen]

Lefty,

Each block (small ones) are as close as a woodworker wants to get to actual size. You can stack then up to add up to the sum of the blocks to get a measurement ( 1/2+1/4= 3/4) and so on. The large block with holes measures 1", 2" or 3" on the sides or faces. These can be combined with the small blocks to get measures that are more than one inch, 2 inches or 3 inches. (see photo).

The holes are both tapped and un-tapped to hold various fixtures usually associated with a machinist's work, I never had the reason to use them, but they're there.

I realize this is confusing in words, I tried to find a link showing you how to utilize them, but ran out of steam. Although I'm sure you can find links to books/articles demonstrating the correct use.



You can see by the phote that the 1" = 1/16" are combined to measure a distance of 1 1/16", this is a lot more accurate and repeatable than using a rule.

Hope this helps

Bruce

[scoly]

Made this a while back and have really enjoyed it. Can reset depth to .001. It does need a flat tip on the end of the slide but haven't thought of a way to attach yet.
Steve

[LCHIEN]

I have made two such gages. One that goes 0-1" using a .001" resolution dial gage. It's lightly spring loaded so that I can rest the flat-bottom probe on top of the bit and the gage will track the height as I crank the bit up and down giving me a continuous reading.





The second one is like Scoly's but I used a depth gage which uses the same readout mechanism but the mount is better suited than a caliper - $12-20 on eBay. This one I allowed a 4" range with .001" resolution.

[JimD]

My gauge is a lot simplier than Scoly or Loring's but uses the same principal. The only setup that I use it for is my HF half-blind dovetail jig. I used a scrap of plywood to make a U-shaped piece and then added a fine threaded drywall screw in the center of the U. When you get the setup like you like it, adjust the screw to match and write on the jig what it is for (if you have several). Not as nice and probably not quite as accurate but it works for me.

I would also be a bit careful in assuming that plywood is a consistent thickness so you can use exactly the same setup each time. I think you could get very close but I would expect to have to fine tune it a bit to get it exactly right. That is also my expectation with the jig I use for dovetails although in that case, I don't think the wood thickness should matter.

Jim