Sawblade stabilizers as dado spacers
red2erni
| Posted in Jigs, Fixtures, Tips & Tricks on
Does anyone have experience or advice with regard to using a saw blade stabilizer disk or disks to space apart the outside blades of a dado set to cut both sides of a tenon in a single pass? It seems like a sensible thing to do, but I only find very thin shim sets. I’d like to make, say half inch wide tenons using reclaimed wood having different thicknesses due to planning. When I use s single blade set up with the tenoning jig and turn the part around to get the second tenon cheek, the tenon width varies with the thickness of each board. The same effect would result from pressing the part up against a fence once on each side.
red
Replies
I've done the same but used a bushing. It's typically done with shapers, too. The only issue is having enough arbor to fit all the cutters and spacer. Large, 14" cabinet saws often have an interchangeable arbor but you are stuck with what you get on 10" models. You can make a bushing from plywood or MDF, etc.
Beat it to fit / Paint it to match
Red,
Years ago, what you're suggesting is what I tried to do several times. You can buy machined washers that are very precise to use for this purpose, but I'm still a bit leery of the practice. You're putting a big blade way out on the arbor with a spacer between it and the other blade on the shaft. I never got too far with trying to make tenons this way, as the practice scared me a bit. It's a good idea, and with the right tooling and equipment would probably work great. But I don't know about trying to adapt a standard tablesaw to these demands. Maybe others have had better luck with it though...
What you're experiencing with varying-sized tenons when you flip the stock around during the cutting is common too. At least it is in my shop when I try to cut tenons this way! A better way is to make all the cuts on one side of the pieces first, then adjust the fence or jig so you can run the same reference face of the stock through the saw again.
In other words, don't flip the stock around. Use the same face you ran for the first cut to make the second cut after you move the fence or jig over. That way you get perfect tenons with reference to that side of the stock. And they'll be of consistent width...
Zolton
Zolton, Thanks. It's good to know I'm at the edge of the practice here. All the points you mentioned need to be addressed. Another thing I'd like is a tennon jig with a self tending center, but I expect that's at least one step to far for now. I'll keep you posted and thanks.red
The shaper is made to do this, and I regularly make tenons this way, but using spacer bushings between the blades. Use blades that have rip tooth patterns. The big advantage of the shaper is the long axle, as well as the sliding carriage which allows you to clamp the workpiece and slide past the blades.
David Ring
http://www.touchwood.co.il/?id=1&lang=e
David, Thank you for your reply and advice. I would like to add a shaper to my tool set for at least the reasons you mention. You and me and Archemedes all seem to like large moment advantages. But for now what I have is a rather common 2.2 HP - 5/8th" arbor table saw. Some of the folks on this blog and a review on this site of dado sets helped me select an 8" dado set with which I'm very happy. I've also found sets of various diameter stabilizer disks, for instance from Forest. I'm trying to find out what the gage is for these disks. I also found and bought two plano ground 5" dia. stabilizer disks that are .1125" each so they build up a .225 hollow kirf. I'm having fun making zero clearance insets from .5" phenolic plate which really helps the cut quality. I'll keep ya'll informed on my pilgrims progress.red
Those stabilizing discs are very accurately hollow ground on it's sides (Cup shaped)to pinch the area of the blade above the arbor area. Methinks, they can be distorted using them as you suggested
Mr. SteinmetzThanks for your input. Little by little the folks on this blog are hacking away at my ignorance, but I have so much of it ... I'm thankful for every reply at all. So, .. I found flat ground tool steel shims, well not really shims but 'dampers'as they are called. I found one set of 3" discs at the Sawdust Shop in Sunnyvale CA. where my friend Bruce had them behind the counter where some one had abandoned them after special order. I found another line on the web at Forest, where they have several diameters with 5/8" arbors that are flat ground. Then Lee Valley had some hollow ground that seemed to be 1/4" each and stack right away to 1/2" (of course Mike points out that is too much given the cut of the outer Dido blades. The Lee Valley ones look pretty sturdy. So for sure now, I'm gonna weed this row. An 'al 'ya'll (as a friend of mine puts it) gonn'a SEE! what come' up.red
Yes if you can a find friendly machine shop to machine some precision spacers for you if your arbor is long enough it works a treat.I would do it myself for you but I am a bit far away
You can make it fool proof but not idiot proof
Edited 6/26/2007 4:30 am ET by Bolts
Edited 6/26/2007 6:30 am ET by Bolts
Mr. Boltz sir, Thanks. This is a small crusade but one I might win. The arbor is long enough for a 3/4" dado the stock compression washer and the nut with half a thread hanging off, so that should be OK for a .5" center spacer and the two cutters. I also found both flat and hollow ground spacers and have them coming on the wings of ".truck" . When I flip over re-planed lumber on the tenon jig (you know, 'turn the other cheek') the jig is not only sloppy on the ways and lock down, but the indicator has huge parallax ( it is a quarter of an inch proud ans has three different finials although it is bright red) and there are only 1/16" markings on the tape. (Beep beep beep, rebuild, rebuild, rebuild) With the flip over, the miss on the tenon width is multiplied by 2 X so everytime I have to reposition for another reworked board it's 'Holy Cow' all over again, those jig guys probably never actually used that thing; and they are all almost exactly the same but the jig was cheep if the cost of the results is not taken into account. So this is going to work, like you say, and with the zero clearance insert, it will make slick tenons in one pass. (Notice the results of the glue-study where the strength was almost always highest for the tight joint?) But the problem of on-center remains so I'm thinking how can I use both the Jig/ mortise and, say the fence or the blade datum to locate the true center of the part prior to the lovely little puff of dust coming back to me from the very smooth, slightly off center tenon cut. Any ideas there?red
I do a lot of my tennons using the outside blades on a dado set. I could never find a machine shop that wanted to, or could, make spacers at a reasonable price, so I made up a selection of spacers from scrap pieces of MDF, tempered masonite and thin steel & copper I had on hand. I used a hole saw on a DP to cut the discs then bored the center hole to size before unclamping the piece from the DP's table. So, these spacers were essentially free.
Through trial and error, I figured out the combinations of these spacers needed to make commonly-sized tennons and put a chart with that info on one of the spacers with a Sharpie.
Spacers need to be custom-made for your dado set, since the teeth of the blade are wider than the saw plate, and this varies by blade.
Mike Hennessy
Pittsburgh, PA
Mike, hi again. I just posted some ideas in reply to Mr. Bolts, below. So thanks for the go ahead and, yes that was another nagging little thing that was in the back of my mind. I think you suggested some different dado makers for me to consider, maybe that was you. (Funny how I meet so many nice new people that seem to already know me these senior days.) Anyway, with my micrometer and a keen interest to do here, I am on my way to measure the the lateral runout the Amana dado set I ended up getting. By the way I like the 46 teeth on the cutters, but want more teeth on the chippers than the two that come with that set; in addition to scarry like a chain saw movie, that set up is noisy, even in soft wood.A really helpful guy, John Laws at Whiteside (1-800-225-3982) is setting me up with a three blade router set up to do the same thing, so I want to see which I prefer. A brief calculation at constant feed ends up with the saw having a smaller chip size and I already know that has alot of noise and vibration. So how about another table saw cutter set that is straight cut? Aren't there other such cutter pairs for drawers or other repetitive cuts that are line to line?red
Regarding measuring the "runout" of your blade -- don't bother. ("Runout", as I understand it, is how much the blade deviates from planer when rotating -- i.e., wobble.) If you mean measuring how far the teeth extend beyond the saw plate, I tried that and it's not reliable. Instead, set up your blades with a spacer, width not important, and cut a tennon. Then measure the difference between the thickness of the tennon and the distance between the saw plates. Also, you might not want to make spacers for exact measurements like 1/2", 3/4", etc. I find that exact measurements do not fit mortises made with my mortiser very well -- too tight. Instead, I made mortises with my chisel set and then made spacers that produced tennons exactly dimensioned to fit my mortises.
Mike HennessyPittsburgh, PA
Mike, Thanks again for the tips. In this case the 'runout' also refers to me since I'm also a little sloppy. Back in my days doing metal work, the term 'runout' was used to refer either to the dimensional "variance" for instance, of the tool spindle or the cutter or the overall assembly which has clearly defined statistical meaning for factors such as the ones you mentioned, but more often in casual conversation it was used to refer to the dimensional difference that was transferred to and measurable from the per-print 'runout' of the part. So I tend to use it in the latter case, meaning whatever difference can be measured from the cut part. That was what I did with the Amana Dado set when it came in. The directions for assembly for a specific dado width were really confusing and even then the closest I could come to half an inch was .507" which, as you indicate, made assembly with the mortise side sloppy so I want to fine tune that to increase the 'satisfaction' factor. I recently saw a phrase quoted where the writer pulled out an old shipbuilding phrase, 'if it looks fair, it is fair'. So I could add the paraphrase, 'if it assembles fair, it will glue up fair.'So now I'm doing what you suggest and collecting a set of different shims. I just can't bring myself to use those little flimsy plastic micro shims that came with the Amana to fine tune the various M/T pair sizes. They get bent over and collect dust. One vendor slots them and shows them going on drop-in with tweezers, I couldn't believe grown men could be that silly. Anyway I'm trying this out on nominal 1/2" parts in redwood for a garden gate, but I want to build some cabinets and chests with hard wood face frames. What tenon/mortice dimensions would you suggest for those? Also, do you have any rule of thumb for 'clearance' either positive or negative, which is of course what I'm really interested in, or for 'tolerance' which would be the +/- that follows the clearance, either in absolute units or as a percentage. I did a quick web search and didn't fine any tables for this on a first pass. I'm sure there must be a reference somewhere?red
Regarding sizing tennons, I usually use the 1/3 rule -- the tennon is about 1/3 (or maybe a bit more) the thickness of the stock. That's good until the stock gets wide enough for double tennons. If that's the case, I try to keep the tennon about the same thickness as the wood on either side of it.
As for what's a good fit, you said it yourself -- "If it looks fair, it is fair." I've never measured, but I would guess for a machine-made M&T, 4 - 6 thousandths would be a snug fit.
Mike HennessyPittsburgh, PA
Hay Ray and Mike,Thanks you guys for taking the time. That one third rule sounds like a good plan. I can have some fun AND do some of that. But what are you guys going to do with this stuff that won't stay put. Who's in charge here? The nerve of some wood! And Mike, you didn't say when it is wide enough for two tenons?Over the weekend I'll post some pictures of the fixtures I've put together so far. I'm rebuilding the Woodcraft tenon jig, plate by plate. Every time I touch it, something else looks coarse or feels sloppy. From the review of tenon jigs on this web site and from talking to folks, I think that jig is very representative of the mid cut of jigs on the market. And I still feel there must be a simple way to make it single pass and also self centering. But for now, I'd be happy just to have the sled feed on the 'one-bar' way without shuddering and jumping and with less back lash and much less parallax between the indicator and the gauge tape. So the 'old oil-can machinist' can make some contributions there while I'm learning to enjoy the smell of sawdust. I'm also doing some cool stuff with a used optical table that I'll post on the bench-top thread. I'm eager to get a set of tools fixtured so they feel 'right enough' (bearing in mind that perfection is the enemy of the good) and start on some cabinets and chests to get my workshop/garage in order. I found a couple good sets of Dido spacers (dampers) for single pass tenons and I got a second Dido set to have some 6 point chippers and some outer cutters with no outside over cut, so I can reach 1.250" for mortise track location, and solve the NV&H (noise, vibration and harshness) problem I had with the 2 point chippers. etc. I'm also working on Sketch-Up so I can get some of my ideas for more ambitious projects on digital paper. red
"And I still feel there must be a simple way to make it single pass and also self centering."
I'm sure there is -- along the lines of a self-centering dowling jig. The problem is that nobody makes a self-centering tennon jig. Probably because there is really no reason to.
When I first started making tennons with power tools, I too worried about getting things exactly centered. What a collossal wast of time! Now, I just eyeball it, sorta-kinda centered, and make sure to use one face of all the parts consistently as my reference. I.e., make sure the mortise is equally off center and it won't matter.
When is wide enough for two tennons" I know of no rule, but I don't think I ever needed to use double (side by side) tennons for furniture work. As for multiple end-to-end tennons, I do that whenever I am concerned that a single long tennon will weaken the sides of the mortise. That depends on the nature of the wood you are using and the configuration of the piece and nearby joints. Again, just use common sense.
Mike HennessyPittsburgh, PA
red,
Two side by side tenons would be used in an application where extra stability against twisting might be wanted, and/or to avoid having to cut a single huge tenon 1/3 of a big stick of timber. Mortising a 4" bedpost, one might use a pair of 3/4" mortises, each 3/4" from an edge, with an inch or so in between, instead of a 1 1/4 " single mortise, for instance. Or a drawer rail (divider, blade) for a chest or table, might be 2 to 3 inches wide, with a pair of 3/8 " tenons, 3/8- 1/2" from each edge, and 3/4- 1" between them.
Ray
Joinerswork,Thanks, I have some 4 by and some 4 X 6 rough cut maple for a work bench base for a novel bench top. So that might profit by doubling up the tenons.red
red,
Mike is right- the rule of thumb for sizing a mortise is 1/3 the thickness of the stock. The size of the tenon vs the size of the mortise is a little harder to define quantitatively. Soft woods will compress a bit more than harder woods, so that redwood or white pine accept a tighter fit than cherry or walnut; sugar maple or ipe will want less interference yet. How many thousandths? I dunno, cut and try til it's right. Tomorrow, if the weather changes, it'll need to be a different set of measurements yet again, cause the wood will have gotten thicker (or thinner). Woodworking calls for a paradigm shift for a machinist. The stuff won't stay still!
Ray
This forum post is now archived. Commenting has been disabled