Wednesday, October 7, 2015

Wadkin's Glen (2)

It's amazing how much time has been soaked up getting the Wadkin saw up and running. At the end of the last post I had started to take a look at some basic alignments, and found that the sliding table and main table were out of parallel by about 1/32", which was a large amount I thought.

So, digging into the Wadkin dimension saw commences..."welcome my son, to the machine....".

(a Pink Floyd reference in case you were wondering)

In the last post I had used a tap to clean out some holes for fixing screws which hold the wood table lips in place. The taps were 1/4"x20TPI and went in and out of the threads without issue. Seemed like a good fit. Seemed like the threads were in good shape.

Well, not so fast there young fella. Things were not quite what they seemed and I had mislead myself into a world of hurt and pain without realizing it. Issues with fasteners arose, you might say, as I came face to face with the dreaded monster known as 'Whitworth'.

British Standard Whitworth (BSW) was the thread standard -the first national thread standard ever in fact - invented in 1856 by Joseph Whitworth, a British engineer. This is a thread with a 55˚ angle and rounded thread crests and valleys, like this:



A perfectly reasonable thread pattern. During the 1840s through 1860s, this standard was often used in the United States and Canada as well, however in 1864 William Sellers presented a paper to the Franklin Institute in Philadelphia, proposing a new standard to replace the U.S.'s poorly standardized screw thread practice. Sellers simplified the Whitworth design by adopting a thread profile of 60° and a flattened tip (in contrast to Whitworth's 55° angle and rounded tip).

Here's a picture comparing thread patterns, with the most basic sort of shop cut thread on top, then the 55˚ Whitworth, then the 60˚ American:


(image from Wikipedia).

The Sellers thread was easier for ordinary machinists to produce, and became an important standard in the U.S. during the late 1860s and early 1870s, when it was chosen as a standard for work done under U.S. government contracts. It was also adopted at the same time as a standard by highly influential railroad industry corporations. Soon after it became the national standard in the US, and after WWII became the modern UNC (Unified National Coarse) and UNF (Unified National Fine) standards we here in the Americas have come to know and (perhaps) love.

Ah, Whitworth. When you come across another thread standard which is close to the one you know, but different, the exotic nature of the new does lead to a certain reflection about the one you've been using for years. One thing, for example, that I like about Whitworth is that for screw sizes below 1/4", the use of fractions is continued down the line: 1/4", 7/32", 3/16"...all the way to 1/16". That makes sense.

With the UNC/UNF system here though, once you hit 1/4", then the screws below that switch away from fractional sizes to a different system:

1/4", #12, #10, #8...down to #0 and even #000.

That system makes less sense to me even though I'm somewhat used to it. For some reason, below 1/4", gauge numbers are used instead of fractional sizes. Looking at the gauge numbers, I noticed that it's not simply that they are giving a different name for a size formerly described with a fraction, but the sizes used at each step actually have nothing to do with fractions at all. For example, a #10 machine screw measures 0.190" in diameter.

Now, how do they come up with this value, you might ask?

Turn out they use a formula, and it is a simple one:

"Major diameter = Screw # × 0.013 in + 0.060 in. For example, a number 10 calculates as: #10 × 0.013 in + 0.060 in = 0.190 in major diameter."

A #12 screw, the next size down from 1/4". It measures 0.2160 at it's major diameter (or, #12 x 0.013" + 0.060" = 0.2160").

As it turns out, the 'Unified System' isn't totally unified, it seems to me, and the 1/4" line is sort of a demarkation between the gauge system used below that line and the fractional system used above that mark. This makes some sense as the gauge equivalent to 1/4" is #14, and 14 x 0.013" + 0.060" = 0.242", which is only 8 thousandths off of 1/4".

I'm sure readers in Europe are rolling their eyes at this point. Stupid Americans! We like complex nonsense measurement systems it appears and some will defend our 'right' to them with guns if necessary.

Hey, I didn't create this system, I have to work with it though, and I'm sure from an engineering point of view, or historical usage/practice concerns there were good reasons for the use of gauge sizes below 1/4", now obscured in the murky depths of our industrial history. 

With these smaller size fasteners there is no compatibility between UNC and Whitworth, and because they are small fasteners and and it can be harder to figure out a tiny thread size, the potential is higher that a screw will get broken or threads trashed if you try to fit a Whitworth screw to a hole tapped for UNC, or vice versa.

I'm sure there is a rich history or accounts, shall i call them 'tales of woe'?,  where fasteners from these two systems were interchanged by an innocent mechanic, say where the mechanic didn't realize a fastener was Whitworth before he swapped in a UNC fastener he had on hand which spoiled the threading, caused a leak, lead to something falling apart, etc.. Have people died due to mix ups between UNC and Whitworth I wonder?

In the larger sizes, 1/4" and up, there are some apparent compatibilities between the two systems, as the diameter in UNC is the actual diameter (i.e., 1/4" screw is 0.2500"), as it is with Whitworth, and the number of threads per inch is the same comparing the same size fasteners, with the exception of the 1/2", which is 13TPI in the UNC system and 12TPI in Whitworth.

With screws/nuts having the same diameter and pitch, you may be able to put a Whitworth screw and a UNC nut together (or vice versa), however even if they will go together they are not properly mated threads so you would be asking for trouble. These would be unreliable connection under conditions of loading or tightening, so it is a definitely a bad idea to mix UNC and BSW fasteners with one another.

Now, when I started to work on the Wadkin, there was no sign or warning label anywhere telling me that there were Whitworth fasteners. I had to discover this myself as I blundered on in there. Fortunately nothing disastrous happened. The screws to fasten the table lips appeared to be UNC at first, so I wasn't even giving the matter any thought at all.

The first place I started having some head scratches though was when I tried to put wrenches onto hex head bolts, and found that my wrenches weren't fitting so well. Let's see, 1/2" wrench is too small for the nut, and the next size up is a 9/16" wrench, which is too big. WTF?

It turns out that Whitworth is not only a different thread standard than UNC, but a different bolt head sizing standard as well, and they have a completely different way of describing the different sizes on the wrenches (spanners).

Here's a picture showing a comparison between two 5/8" wrenches, the Whitworth on the left, UNC on the right:



"Two spanners, both nominal size 5/8", with a diagram superimposed to show the logic that allows them both to be nominal size 5/8" when their actual sizes are clearly different (across-flats distance vs screw diameter). The across-flats definition is the common standard today, and has been for many decades. "

Whitworth spanners are sized to the screw (bolt) diameter, while UNC wrenches are sized to the width across the flats of the nut. The head on the Whitworth bolt is around 1.5 times the diameter of the bolt, in case you were wondering. So a Whitworth wrench for a bolt that is 1/2" 12 TPI will say '1/2"' on it but appear to be a much larger wrench if you were used to a wrench in which the wrench size corresponds to the opening of the wrench. Each system makes sense, but can be confusing when you move from one to another.

And to top it off - believe me, we are not done yet with this insanity - the sizes of Whitworth nuts have some odd 'across the flats' measures. For example, a 1/4"W (meaning Whitworth) spanner would fit a nut measuring 0.525". A 1/2"W wrench spans 0.920" across the jaw opening. Thus none of your UNC-sized sockets are going to fit any of the Whitworth nuts on the machine since they are sized for the usual fractions, and not numbers like 0.525" or 0.920". I found metric sockets were useful the odd time on one of these Whitworth fasteners, and otherwise I used an adjustable wrench to loosen or tighten fasteners. An adjustable wrench is not the optimal choice (as they can slightly loosen and not fit a nut as securely, leading to rounding off of the nut in time) and my adjustable wrench isn't big enough to fit the largest bolt heads on the machine. Therefore, I now realize I should obtain a Whitworth wrench set to do any future work on the machine. That's on top of some selected Whitworth thread taps. And I'll have to obtain some of or most of the fasteners from the UK.

The best way around the headache this situation presents is to at least have the correct tools to do the work, to do that work without making a mess out of anything.

I thought early on that the fastener annoyance with this machine ended with Whitworth, but alas...no.

The Whitworth standard was replaced with the Metric standard in Britain in the 1960's I believe, And in the years after that various manufacturers converted their products to conform to the metric standard, including Wadkin.

I'm sure this process would have been slightly irregular between different manufacturers, some adopting before others, some more willingly than others - I can imagine some foot dragging here and there for various reasons. I remember when things changed over in Canada to metric and how a lot of people hung onto the imperial measures for a very long time afterwards. And there there might have been surpluses of previously-made parts on hand at the Wadkin factory (or its associated suppliers) which needed to get used up before certain fasteners used in a given manufactured product were converted to metric.

I'm speculating as to what happened with Wadkin and their points of changeover to metric and how it evolved over time, but the fact remains: there are metric fasteners on this machine. The support arm's pedestal bolts to the table top with M12x1.75 bolts. And, all of the bolts on the machine's trunnion seem to be metric. The bolts and threaded studs that form most of the fence setting control parts are all Whitworth.

It's a mix of fastener thread standards on the same machine- oh joy. I laugh a bit about it, when I'm not clenching my teeth and spitting venom, and one consolation is that I do at least have the metric tools on hand.

Anyway, enough about issues with fasteners. There were other matters with which I dealt in getting the table saw ready for use. I separated the extension table from the main table, then unbolted the main table from the base to see what was what. I discovered that the main table has two locating pins to fix its position relative to the base.

Onward and upward...

The blade squareness was checked:


Adjusting the stop for the 90˚ position was involved, and I also found that the angle protractor for blade tilt was bent out of position so a few tweaks were in order to get the plate and needle in closer proximity:


The sliding table was then set to good alignment with the blade, with aid of an indicator measuring in 0.0001" increments:



The close alignment achieved comes with a caveat however, since the table itself has at least 0.0015" of lateral slop, and the saw blade is an inferior reference surface for that sort of work. So we'll hold off on the champaign and balloons for a while yet.

However, I can say that I 'more or less' got the table sliding into a satisfactory parallel with the saw blade, which should lead to a reasonably clean cross cut.

At that point I also checked that the miter fence was square to the sliding table:


The main table was then put back on, with the two locating dowels and I then checked again to see how parallel the main table's lip rebate shoulder was with the edge of the sliding table's lip rebate shoulder. I used those references since that were ground into each table, and presumably milled in a straight line. The spacing, upon re-check, was still well off of parallel. Since the sliding table was parallel to the saw blade, that meant the error in parallel lay most likely with the main table. That table now looked to be factory pinned in a location which did not seem to be parallel to the blade.

Well...hmm. What kinda nightmare scenario is unfolding here folks?

I knew the saw blade ran true, and the saw spindle was part of the casting of the trunnion and couldn't be shifted out of alignment by changing bearings or anything like that. Thinking about it further, it seemed to me that there were a couple of possibilities to account for this state of affairs:


  1. The main table, though located with the two pins, was out of alignment somehow despite being pinned to a location at the factory.
  2. The saw trunnion, also pinned, was somehow out of alignment and should be brought into alignment with the main table, after which I could realign the sliding table to the blade again.
  3. Both trunnion and main table were out of alignment some amount (possibly from their original setting, possibly misaligned from new).


The trunnion carrying the motor and saw blade is connected to the machine base at the top by way of a pair of cast plates- called 'lip plates', one on each end, each end of which is held together and to the machine base by five large bolts and four locating pins (two pins on the upper part of the plate connecting to the trunnion and two pins connecting the plate to the base):


(image from: http://www.ukworkshop.co.uk/forums/wadkin-pp-rebuild-picture-heavy-t66377.html)

Here's a closer picture of the plate (not my machine):


(http://www.ukworkshop.co.uk/forums/wadkin-pp-rebuild-picture-heavy-t66377.html)

The trunnion does not connect directly to the machine's table in any way. The lip/support plates had been factory set and don't appear to have been disturbed from that. I decided that there was no good reason to mess with the trunnion mounting on the base, though if need be it could be separated. I'll try other solutions first though.

Now, one could look at it from another point of view and see that the alignment of the main table edge to the blade is not the important thing. The important thing is that the rip fence, which slides back and forth on a cross-wise dovetail slot on the table top, is appropriately positioned with respect to the blade. I say "appropriately positioned" because you don't actually want the rip fence perfectly parallel to the blade, but set up so that it opens away from the blade ever so slightly as the wood moves along the fence.

According to the machine manual,

"the ripping fence is initially pitched 0.004". This is measured at the front and rear of the saw, with the saw fully raised, the dimension at the rear of the saw being 0.004" greater than at the front of the saw".

So, before doing anything with the main table mounting, I decided to scope out the rip fence alignment to the saw blade. Since the sliding table was nearly exactly parallel to the saw blade, I could run the indicator magnetic base off of the sliding table, dragging the indicator tip along the face of the fence plate.

I set the rip fence up in position, clamped it down, checked the fence plate for squareness to the table and adjusted until it was square. When I then checked the fence plate for parallelism to the sliding table, and I found it was out of whack by at least as much as the main table, an amount far more than the 0.004" opening to the rear to which the manual suggests it be aligned.

While the rip fence has a set of 4 grub (or 'set') screws to adjust it in relation to the support casting, the amount of adjustment required was greater than could be effected by the grub screws - they would come close to coming out of their bores if screwed so far back. The grub screws are curiously short in length, at 3/8" diameter and just 3/8" length, presumably British standard Fine Thread (BSF). That makes for three three standards on the machine now. Thanks. I am under the impression that longer grub screws would be a good idea.

This can only mean that for some reason the main table, pinned in two spots, was either not in perfect alignment with the saw blade originally, or has somehow come out of alignment over the years, through some combination of cast iron movement in the table, the base, and/or the trunnion.

I found myself being a little skeptical about this all the same, thinking there might be some other cause for the situation I wasn't seeing, or that my inspection tools were faulty or misleading me in some way. They put these machines together every day and presumably had all sorts of setting jigs and working procedures to get things dialed in. That's how I imagine it anyway.

Whatever the case may be, I figured it would not hurt anything to remove one of the main table location pins so as to be able to tweak the table over into better alignment with the saw blade and trunnion. Again, what counts at the end of the day is that the rip fence be appropriately aligned to the saw blade.

With this plan seeming reasonable, I then had to separate the extension table from the main table again, and unbolt the main table from the base and move it laterally until I could get at one of the locating pins. After about an hour, things were back together again, minus one of the locating pins. This time I was able to get the main table bolted down parallel with the sliding table, and then fine tuned the fence into the correct alignment to the blade. To obtain that good alignment I had to put a shim - a 0.014" feeler gauge leaf - in the front of the fence. This is a stop-gap solution until I can obtain longer grub screws to set the adjustment by that means.

The alignment problem appeared fixed, but it still left questions in my mind. I'll stew on those for a while yet.

Here's the rip fence, removed from its support casting:


You can see an allen wrench engaged with one of the allen-head grub screws for adjusting the fence plate, if you look closely at the fence support casting. The holes in the fence plate itself are for mounting a wooden fence front piece with screws.

A curious thing I noticed was that the fence plate casting showed a mark:


'PK 16'. PK was the previous line of dimension saws, and for some reason, although other castings on this saw are labelled 'PP XXX', the rip fence is a PK casting. I wondered if it had been fitted from new, or had been replaced somewhere along the line after the machine had been sold and the castings were interchangeable?

I'm guessing it was fitted from new-  that was one part which was not changed from the PK series to the PP series, so they didn't bother making a new casting pattern, and a check of the parts list confirms that the 'front fence plate' is indeed listed as part 'PK-16'.

The support piece also has a casting mark, but this one is PP222:


The mark indicates the part number, and my parts manual jibes with that - the above piece, PP222, being termed the 'fence slide'.

At this point, after two days of mucking around, I have the rip fence and sliding table with miter fence aligned as they should be to the blade. I have also freed up the raise/lower of the blade, mostly by way of a thorough cleaning of the ways and some tweaking of a few set screws on the lateral gib bar. It is not, after all that tuning, perfectly smooth and effortless to raise, merely somewhat improved. I suspect that in order to get that sliding action perfect again that the trunnion would have to come out and the parts separated, inspected, and then scraped back to where they need to be. I won't be tackling that in the near future.

I've also found a few more areas of concern. While the sliding table travels smoothly, if I grab the miter fence extension bar and use it as a lever, I can get the sliding table to rock from side to side more than I would think ideal - enough to spoil a clean cut face anyhow. To deal with that issue the sliding table would have to come off, all the parts of the sliding mechanism pulled out and then things thoroughly inspected. Maybe some ball bearings are worn, or maybe the sliding table or it;'s support casting has moved over the years. That depth of rebuild also won't be happening anytime soon. for now, I'm going to get the machine all back together and see how it cuts wood, while realizing clearly now what is going to be involved to get it back to potential 'perfection'. Still don't know if it was 'perfect' in the first place. I'm curious about the matter of the main table alignment pins not putting either the table or the rip fence into a good aligned position relative to the saw blade. What could account for that?

Once I make some new table lip pieces and can take some test cuts with the saw, I can make some further tweaks. Ultimately, I'm looking for clean straight cuts without blade marks being left behind on the cut face. Not looking to polish a lens to a few microns or anything like that. Seems like it should be achievable with this machine, and hopefully without recourse to more extensive rebuilding and scraping actions. We'll see.

The other machine in shipment, the Zimmermann milling machine, has cleared customs inspection in New Jersey now and will be in Boston by the end of the week I expect. If all goes well I could have it in my shop sometime next week. I'll update as things move forward.

Thanks for visiting the Carpentry Way.

12 comments:

  1. If the slider is now aligned at 90 degrees but is out of alignment at 45 degrees of tilt, I believe you need to shim a corner of the table top and start again. Pretty straight forward on a small shop cabinet saw as you are aligning to the miter slot rather than a sliding table.

    Mike

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    Replies
    1. Interesting. I haven't checked the position of the saw blade relative to anything when it is at a 45˚ tilt. I'm not even sure how I would get an accurate indicator reading off the tilted blade. Something to think about. Shimming the main table would be no issue, however it would have to be done relative to the top of the slider as well.

      I could remove the infill bars from the main table and reference off of that, but it still presents the issue of getting a clean reading off of a tilted blade.

      ~C

      Delete
    2. Also, if you mean that I can shim a corner of the slider table, that isn't really possible as it runs on rails. I would have to adjust the castings bolted to the base which hold the slider support castings. There are adjustments provided under those castings with a pair of set screws, but the castings are also pinned.

      ~C

      Delete
    3. Shimming table top to the machine base was what I was meaning. You'd almost have to measure from the ways that the slider fits in/to I suppose. Most accurate reading when the indicator stem is positioned at 90 degrees to the blade.
      This is most nasty on contractor type saws where the trunnion is affixed to underside of the table top - which is what led to my original research and the revelation that a "cabinet" saw is easier to adjust.
      Videos and descriptions abound on the web. I have a horrible time visualizing how this misalignment looks in 3d - no way I can describe it in words.

      Regards and good luck,
      Mike

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    4. I think that I will certainly be checking whether the sliding table runs in the same plane as the main table, and check with a straightedge to see if both are reasonably co-planar. I'll also see what the situation is with the blade tilted to see if there is any change as far as the indicator reading goes.

      I think this machine can be aligned, but it may take some more serious digging into things before a truly satisfactory outcome is obtained.

      ~C

      Delete
  2. I thought it was odd that you had used a 1/4-20 tap....Back in the 60-70's when I was a mechanic..all the english cars were British standard....the wrenches also were of a closer tolerance...1/2 wrench would fit very tight...so tight that you had to wiggle back and forth to get it on/off the bolt. at the time british standard tools were scarce so I modified a set of SAE wrenches by grinding them "open" ever so slightly and saved them just for those english car repairs!
    Also be careful when replacing bearings..can not use the bearing number alone...you need to use a micrometer to make sure your getting the right size, also some bearings have rounded edges, not square...that usually came up with axle bearings..the SAE square edged bearings would not seat properly on the rounded edge bearing journal on the axle....moral of this story.....not only check numbers but sizes!!!!!!!Good luck with that beast...will be worth it in the end...

    ReplyDelete
    Replies
    1. Joe,

      appreciate your perspective, and next time speak up sooner before I wander too far out into the reeds. Please!

      I figured that since this machine was made in the 1970's it was likely to be all metric. Wrong. I wasn't anticipating a mix of threads however.

      Fortunately, the machine was fitted with new bearings, obtained in England, so I guess I can at least hope the correct ones were fitted. Not sure which grade the bearings might be however.

      ~C

      Delete
  3. I thought it was odd that you had used a 1/4-20 tap....Back in the 60-70's when I was a mechanic..all the english cars were British standard....the wrenches also were of a closer tolerance...1/2 wrench would fit very tight...so tight that you had to wiggle back and forth to get it on/off the bolt. at the time british standard tools were scarce so I modified a set of SAE wrenches by grinding them "open" ever so slightly and saved them just for those english car repairs!
    Also be careful when replacing bearings..can not use the bearing number alone...you need to use a micrometer to make sure your getting the right size, also some bearings have rounded edges, not square...that usually came up with axle bearings..the SAE square edged bearings would not seat properly on the rounded edge bearing journal on the axle....moral of this story.....not only check numbers but sizes!!!!!!!Good luck with that beast...will be worth it in the end...

    ReplyDelete
  4. At the end of the years 70, the Airbus A310 was in final stage of design. Wings were made in UK and the dimension were imperial. Slats were made in Belgium. The rails guiding the slat movement had external dimensions in imperial to fit to the wing but all other dimensions like material thickness and holes were in metric.

    Sylvain

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    Replies
    1. Sylvain,

      thanks for sharing that anecdote. I'm glad were mostly past the days of mixed fasteners on devices.

      ~C

      Delete
  5. This is a very detailed and informative post. I always believe that when it comes to tools, there is always a sort of “relationship” with its owner. So the way you use it and adjust to work for you could be different from others. Thanks for sharing on your thoughts about this; I believe it was a personal post.

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    Replies
    1. Mary,

      thanks for the comment. I am developing my relationship with this saw, and time will tell if it is a relationship that will last.

      ~C

      Delete

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