Fine-Tuning a Dowel Boring Machine

Setup tips for accurate boring and assembly. September 7, 2006

I have recently gone to frameless and bought a Viptap T21 to do some dowel construction for finished end cabinets. I can't seem to get it lined up to do the job consistently. Is it the machine, or are all dowel machines a pain in the butt? I have spent hours and piles of scrap leveling and squaring up and test fitting with poor results. Must be a better way!

Forum Responses
(Cabinetmaking Forum)
From contributor A:
I bought a Maggi 23 spindle construction drill about 5 years ago, and had similar problems for awhile. The side fences were fairly straightforward to set up, but aligning the front fence had me baffled. What I finally realized after much trial and many errors is that all I needed to do was first put the head in the vertical position first; push a piece of the material you're about to use (it should be as wide as the opening between the side fences) against the pivoting fence; adjust the sliding top fence so it is snug on top of your material all the way across. By doing this, you've just aligned your fence for the horizontal position. You need to do this every time you change to a different material (melamine, veneered panels, solid wood, etc.) because a slight change in thickness changes the alignment of the sliding fence. Once I figured this out, I threw away all the jigs and measuring blocks I'd made.

From the original questioner:
Does your dowel machine have a one piece sliding fence? Mine has two, one on either side. I was thinking of bolting them together with a piece of angle iron. I seem to get the best fit when they are a bit past snug. The problem is that I can't really slide the material under them then. How are you putting your pieces in? I put the sides (obviously) face down with the tape next to the fence and the top and bottom face up, tape against the fence. I have tried the top/bottom face down but since they maybe a different thickness, I thought face up made more sense. I hope I can get it to work - I am ready to sell it and get a two head machine.

From contributor A:
The front fence on my machine is basically two parts: the pivoting steel fence, with no adjustment, and sliding fence which is one piece and spans the same distance as the pivoting fence. With boring head in the horizontal position, I push the material against the pivoting steel fence, then push the sliding head down until it's very snug against the material and then tighten the clamps holding the fence. This should align your fence properly. Is your boring head set to drill dead center on the edge of your panels? If so, you might have better luck with the head set a few millimeters above or below center. This makes it much more obvious that your panels are correctly oriented during assembly. My employees were always getting the horizontally bored panels reversed during the dowel insertion process and then trying to clamp the box together. With the holes offset from center, it's difficult to make that mistake.

From the original questioner:
I'll give the offset a try. It makes good sense.

From contributor B:
We just got an SCMI Startech 23 and we're also trying to get an optimal process for it. Does the T21 do its vertical drilling from the top or bottom? I'm wondering why you run your tops and bottoms face up, since you'd want to reference the joinery from the outside of the carcass. Maybe this is a source of some of your problems?

We've got our alignment OK by doing what Contributor A says. What we're trying to figure out is, do we set the side fences so that the panel is centered on the boring head; or do we set the side fences so that they are as far out as they'll go (bore the panels with edgebanding against the fence as the original questioner describes). Or, do we set the side fences so they are centered, but a little bit larger than the panel - thus allowing us to insert and remove the panel easily, while making it so we don't have to move bits around like we might if the fences are set as wide as they can be. How are other people doing it?

From the original questioner:
The T21 drills from the bottom. That is why I am drilling the top and bottom inside face up. The way I see it, that would reference the outside. I guess it could be the problem. I spent about another half hour today thinking I would dowel some drawers. I gave up for lack of time but made some extra drawer material to play with. I can get it pretty close but the next time I try it it's off again! A frustrating machine for sure!