Horizontal boring for doweling

[JPG]

Do not overlook the 'detail' that the SS horizontal boring ability preceded those other alternatives(they simply were not invented yet).

[DLB]

IIUC the OP is saying that he is using the 'standard' table stabilization of tying the main and extension tables together then adding the less intuitive step of adding adjustable legs at the left side of the main table. He is doing that because he is using inconsistent but firm downward pressure on the material being drilled. One thing I would check is table flatness, front to rear, in this area on the main table. I mention this because I've bought a used one that wasn't flat in this area and learned that table rigidity left of the opening wasn't nearly as solid as to the right of the slot.

I think this is a great idea. I'm usually satisfied with the significant improvement we get by tying the tables together. But I'm open to further improvement. One question I have about this is when you are placing the adjustable legs are you pre-loading the table by providing upward pressure when you are locking them? As opposed to locking them into position without pre-load.

- David

[RFGuy]

Do not overlook the 'detail' that the SS horizontal boring ability preceded those other alternatives(they simply were not invented yet).

JPG,

Yes and that is a good point. The OP reported having boards that were up to a 1/16" off on being flush when using horizontal boring which is NOT ideal. With that in mind, I just wanted to remind the forum community that just because a feature is there doesn't mean you always have to use it. When a better mousetrap is available, I tend to want to use it. IF one has no other joining methods available, then of course use horizontal boring if you have a Shopsmith machine.

[Matanuska]

IIUC the OP is saying that he is using the 'standard' table stabilization of tying the main and extension tables together then adding the less intuitive step of adding adjustable legs at the left side of the main table. He is doing that because he is using inconsistent but firm downward pressure on the material being drilled.
. . .
One question I have about this is when you are placing the adjustable legs are you pre-loading the table by providing upward pressure when you are locking them? As opposed to locking them into position without pre-load.

DLB,

OP here again. Yes, what you describe is what I did to resolve the problem. And yes, I'm pre-loading the legs with a bit of compressive force when I set them up under the left end of the main table. I haven't checked the table flatness lately but since the brad point is now lining up with the dimples I think it's good unless the slight pre-load is bringing a misaligned table into line rather than just offsetting a deflection I've imposed with downward pressure. The next time I get it set up for horizontal boring I think I'll try raising the legs off the floor and see if I can observe 1/16" of downward deflection at the point of the bit when I apply downward pressure on the workpiece.

Matanuska

[jsburger]

I guess I don't understand why you are applying so much down force to the stock to flex the table. If the stock is not flat to begin with then you will have problems. I have never had to push down on the stock to drill.

[Matanuska]

Okay, OP with an update after running some tests. So much for my original theory, table flex does not appear to be the reason for misaligned dowel joints. I set up the machine in horizontal boring mode and tried the worst case scenario: I checked for deflection while pushing down on the left side of the main table with no telescoping legs and the main table not tied to the end table. The table is much more rigid than I expected - even with a much firmer push than I would actually use the deflection was almost imperceptible, less than 1/64". I drilled a test dowel joint on two short pieces of wood with more moderate pressure and the joint was dead flush.

I think the issue is back to the wood I'm using - 100 year old reclaimed 2 x 4's that I've run both sides through my surface planer, jointed 1 edge, ripped to width, and crosscut to 2 foot lengths. Since the problem occurs only intermittently I think it's more likely due to a twist in some of the pieces that the planer doesn't remove. This causes the wood to not lie flat on the table causing misalignment, typically just on one end of longer pieces. The solution would be to surface joint one side of the stock before surface planing to remove any twist.

Lesson learned. I was too quick to blame the equipment rather than my procedure. The Shopsmith main table actually seems to provide very good support for horizontal boring, even without additional bracing.

Matanuska

[BuckeyeDennis]

Thanks for reporting back, Mantuska. That’s a valuable lesson, from which many can benefit.

[GreyOwl]

You said that you are surfacing both sides and jointing one edge before cutting to size. Are you not jointing the first side before surfacing the second side? If not they won’t be flat.

[RFGuy]

Okay, OP with an update after running some tests. So much for my original theory, table flex does not appear to be the reason for misaligned dowel joints. I set up the machine in horizontal boring mode and tried the worst case scenario: I checked for deflection while pushing down on the left side of the main table with no telescoping legs and the main table not tied to the end table. The table is much more rigid than I expected - even with a much firmer push than I would actually use the deflection was almost imperceptible, less than 1/64". I drilled a test dowel joint on two short pieces of wood with more moderate pressure and the joint was dead flush.

I think the issue is back to the wood I'm using - 100 year old reclaimed 2 x 4's that I've run both sides through my surface planer, jointed 1 edge, ripped to width, and crosscut to 2 foot lengths. Since the problem occurs only intermittently I think it's more likely due to a twist in some of the pieces that the planer doesn't remove. This causes the wood to not lie flat on the table causing misalignment, typically just on one end of longer pieces. The solution would be to surface joint one side of the stock before surface planing to remove any twist.

Lesson learned. I was too quick to blame the equipment rather than my procedure. The Shopsmith main table actually seems to provide very good support for horizontal boring, even without additional bracing.

Matanuska

Matanuska,

Well, I am glad you figured it out. Also glad you have such a wonderfully stable Mark V with a rigid main table. Sadly mine is NOT one I would characterize as such, no matter how much I stabilize it by connecting it to the aux table and using telescoping legs. Congrats!

[Matanuska]

What vintage is your Mark table system? Are you the original owner? I bought mine new in 1985 as a 500 and upgraded along the way to a 510 and now a 520 PowerPro. I’ve found the 520 table system to be a big improvement over both the 500 and 510 models.

Matanuska