Friday, December 4, 2015

A Ming-Inspired Cabinet (13)

I was thinking at first it was time to get working on the main beams for the support stand, however there was some work remaining on the pillow blocks and I decided I wanted to complete all the cut out on those components before moving onto other parts.

Each pillow block pair required a pair of mortises and a pair of angled notches:


After mulling over whether I would be better off using the hollow chisel mortiser or a routing approach for those small mortises, I elected to use a 7/16" up-cut spiral carbide in the milling machine, which is a slight bit undersize of final dimension.

The mortising went smoothly (not pictured), and I am left with some end wall paring to tackle in the near future.

The angled notches would have been troublesome to deal with except for a handy piece of equipment which recently arrived. In thinking over a few of the various angled cuts I have to make on various parts of the cabinet, and some of the different ways that might be accomplished - and which of those ways might prove to be the most versatile in terms of future work of a similar nature - I settled upon a machinist's sine plate as the most accurate and widely-applicable option for me. Certainly it would be a notch up from cutting wooden angled wedges, making MDF hinged platforms, MDF contraptions upon which a router could be operated, and so forth, all approaches I have tried in the past to one degree of success or another.

I found a used 6"x12" sine plate, hinged on the long side, originally made by Suburban Tool. It is accurate to a few tenths (i.e., 0.0002" or so) and the price was at least digestible. I couldn't have afforded a new one in this size.

Setting up a sine plate is easy so long as you are comfortable using a little bit of trigonometry:



The formula is: G = C(SIN angle A)

Here's my set up for the angled notches on the pillow blocks, which are at a 20˚ angle from the horizontal (70˚ from the vertical):


I've clamped a 3"x12" gauge block on the end as a taller support fence.

The center to center distance from the sine plate hinge to the point where the round support bars meet the deck is exactly 5". It's called a Sine plate for good reason: if the desired angle is 20˚, then sine of 20˚ is 0.342020..., so multiply that by the 5" length and you have the required rise, equal to 1.71010...". If you're not comfortable with that bit of mathematics, a sine plate can still be of use as there are online calculators and books of table for different size plates.

Once you have the rise figured out you then make up a stack of gage blocks and shims until you have that same value, and stick that stack under the support bar, as you can see above. There's a swing arm on the other side of the plate which locks the setting in place. Suburban Tool's design is nice in that regard as the swing arm does not protrude above the work surface.

In this case, the notch itself would have a slight clearance allowance, so strictly speaking it wouldn't have mattered too much if I produced a 20.2˚ angle or a 19.8˚ angle. I suspect I was pretty close to the desired figure however, and would rather feel confident in knowing I was working to a closer tolerance instead wondering uncertainly if it would be close enough.

A 1-2-3 block was clamped into place to serve as a positioning stop, and the pillow block pair was clamped into place thusly:


I'm using a down-spiral 0.5" carbide bit here to give crisp sidewall cuts around the notch,

Another view - note that I have swung the rotary table around 90˚ so that I can use power x-travel while milling the notch instead of cranking the y-travel back and forth:


The back side of the set up, prior to taking another cut:


You can tell I'm not a regular machinist as I am using woodworking clamps to fix the work in position. I suspect a lot of machinists would have set up other clamping arrangements, and since I have a good assortment of T-bolts and nuts, along with adjustable risers and other hold downs, not to mention a cluster of Destaco products, it will hopefully just be a matter of time until I have gotten more used to using those things. The woodworking clamps certainly hold things okay, but what you want really is to have the clamping apparatus as out of the way of the cutter as possible. Learning as I go - what else is new?

Here, the cut has been made to the depth and width targets taken through a series of cuts and measures:


The machine's DRO proved invaluable and saved me a lot of time. I made all the notches about 0.005" under dimension, aiming for a light interference fit later on when these pillow blocks are assembled to the inverted 'T' beams.

The backside of a completed angled notch:


A later addition to eliminate tear out was a sacrificial block clamped onto the top face:


Another view:


The sine plate arrived yesterday in the mail and I was able to put it to use the very next day. I'm happy I have it now in my set, and I expect to use it with some frequency in my work. Probably one day I will obtain a larger compound sine plate as well (three plates stacked with two hinges to allow compound angles to be set).

At the end of the day the notches were cut and all the mortises:


A different look at the near-complete pillow block pair:


A while later, all 8 pairs were through this stage:


Tomorrow I will square up those mortises, which will complete all cut out on the pillow blocks. Then it will be on to those inverted 'T' section beams, which have been worked upon previously.

All for now. Thanks for visiting the Carpentry Way.

3 comments:

  1. This seems to get the results with much less stress, and I get the impression of significant time savings, compared to your earlier project. This while still learning the ins and outs of the new equipment. I appreciate the quality of the fit and the beauty of the results, but I wonder if you feel a little less in touch with the process. I am sure the the final result will be spectacular; however this far it is tool-making more than woodworking. This is just from my perspective, with my biases and I understand that getting the results from handtools would much harder, with more waste of a precious and limited resource. I'm sure that you can tell that I am conflicted. Part of me is jealous of the equipment and part is sorry to see you seeming to move away from handtool use. Richard

    ReplyDelete
    Replies
    1. Richard,

      I appreciate the comment. I am sorry to hear you are feeling conflicted. Not me. I'm feeling high degrees of satisfaction.

      For me, 'the process' is al about conceptualizing a design and exploring the design until I have created something I, and the client, are pleased with. Then the fabrication process is al about realizing that design as faithfully as possible, subject to a certain minor process of discovery and refinement along the way. If I cut a surface, I want to cut it cleanly. I would much rather cut it than grind it. If I am using a precious wood, I want to use it wisely - hence a lot of consideration must go into the design and the approach to fabrication.

      For me the greatest satisfaction with joinery work is achieving a close tolerance fit. Of course that can be accomplished by hand tools, and I often have had no other choice in the past, due to lack of other equipment or due to a joint have surfaces which cannot be readily cut other than by hand. However, now that I have more tooling and equipment, I often have a choice in how i might achieve a certain result in cut out. Do I hand rip the stick into strips or use the bandsaw? Do I cross cut that piece with a hand saw, the chop saw, or the sliding table saw? Do I hand plane 3/16"of material off of a board or do I take it to a place to get it thickness sanded? Do I hand chop that mortise or do I drill it out first, or rout it out, or use the hollow chisel mortiser and finish later by chopping and paring?

      If you compare the steps shown in the post above to a similar post from the 'Square Deal' series (post #22), the steps are pretty much the same. The pillow blocks for the 'Square Deal' were straight grained, not curly, so I was able to more readily power plane them to thickness. I gave them a skim with the hand plane afterwards. This time, I have a new piece of equipment available, one which proved to be excellent for dimensioning the curly stock for the pillow blocks without tear out. As the surfaces produced were at dimension and had no planer marks, and were not exposed to view, I felt no need to touch them with a hand plane.

      Processing the coves on the pillow blocks this time, and previously, was done on the router table. As I do not have a suitable coving plane, the router was the means of accomplishing the task. Rough cutting the lap notches this time was done on the sliding table, while last time it was done on the chop saw. Last time I dimensioned the notches with an MDF jig and router, this time I did it with the milling machine. Last time i made up an elaborate paring jig out of hardwood and MDF so I could pare the mitered abutments. This time I used the milling machine and the results were a little better and accomplished with far far less trial and error.

      Last time I subbed out the coffee table slab dimensioning to a CNC place, as it was the best option available. I would rather have been able to do it myself, but I don't have equipment to handle that. If I had an enormous thickness sander, like most commercial shops, then that would have been an option. Hand planing 1/2" of stock off of each face of a curly bubinga slab was never going to be an option.

      For me, having other tools to realize a task does not mean moving away from hand tool use, hanging up the planes and grabbing the belt sander, or anything like that. Similarly, using my sliding table saw this time to cut notches doesn't mean I will no longer use my chop saw for such a task. I will pick the tool I think will obtain the best results. Sometimes that is a powered tool and sometimes that is a hand tool. I agree there is a little bit more direct visceral feedback from the hand tool, however I still get a sense how hard this wood is, and still know what the shavings and chips smell like, when bringing a powered cutter to bear.

      continued...

      Delete
    2. ...

      Another issue relates to the material I am working with in this case, which is very hard and difficult to work. If I was purposely orienting my work around hand tools for some reason, then I would probably not have picked this wood. I'd pick woods like Cherry, Walnut, butternut, mahogany, straight grained cedar, poplar, etcetera. This material choice tends to push me to use carbide as much as possible. I could use a $1500 Miyano hand saw to cross cut the pillow blocks, and it would do fine at that task, and cut perfectly accurately, but I choose to use carbide and preserve the precious hand saw. I'd hate to break a tooth on any of those saws.

      To my way of thinking, I am bringing a cutter to the work and taking chips off when using the milling machine. It gives a vast improvement in rigidity and work holding over other means of doing the same task. It allows me to take the wood to dimension without tear out. If I didn't have the mill, I'd be taking parts to a sub contractor to have them thickness sanded, and the results would be inferior. I'm so happy to have the mill as an option.

      ~C

      Delete

All comments are moderated, so if you're planning to spam this, know now that your clicking and pasting is in vain. I do read the comments before posting, so your mission is doomed from the outset. All this time and effort trying to put your inane spam onto blogs -- is this how you want to spend your time on earth?

Please do me the courtesy of appending your name to your comment, even if posting under the 'anonymous' option. No name = deleted.

Comments NOT accepted include:

-those containing links unrelated to blog content
-spam of any kind, or ham for that matter
-did I mention that attempted spam postings will be non-starters?