I have an old Delta Homecraft 8-inch Bench Model Tilting Arbor Saw that my father bought used in the 1950s. This saw is a patchwork quilt of components, the core being made by Delta, the wings having been fabricated by somebody with a sheet metal shop and a welder, the motor being a GE model 1E161, which is an industrial 115 Vac (60 Hz, single phase) three-quarter horse capacitor-start 3450 rpm continuous-duty unit with built-in overload protection (the original motor is one half of a horse), all on a shop-built wooden base that doubles as a sawdust collection bin and spare parts cache.
The problem is that the arbor ball bearings are contaminated, and turn roughly to the hand. It feels as if some sand has gotten into the bearing grease. This is actually due to the bearing grease having completely dried out. Time to replace the bearings.
First chore is to obtain a pair of replacement bearings. The bearings are New Departure model ND-87503. While the New Departure company went out of business long ago, many firms still make these bearings, which were very widely used. On the web, there are many model 87503 bearings on offer with wildly varying prices and quality claims, and many of the offered bearings are reported in multiple user reviews to have very short service lifetimes. The solution turned out to be a local industrial bearing house (Action Bearing Company, 201 Brighton Avenue, Boston, Mass 02134), which had ND87503 bearings made by KSK in Japan, for US $10.27 each.
In the following description, Delta part and figure numbers are referenced, based on 'Homecraft 8" Bench Model Tilting Arbor Saw - Operating and Maintenance Instructions' (Delta document PM-1722 dated 9-19-49, 16 pages). PM-1722 is available at <vintagemachinery.org/pubs/1141/3643.pdf>. It is assumed that the reader will have a copy of PM-1722 in hand while reading the following.
Now that I have the bearings in hand, time to install them. First issue is how to get at the arbor. My initial approach was to unbolt the cast-iron table top (TAB-101) and remove it from the sheet-metal housing (TAB-110-S). This approach was abandoned because it was too much trouble to get the two hand-wheel shafts disentangled from the sheet metal housing because the 0.125" diameter by 0.75" long slotted spring tension (roll) pins (SP-2711) are difficult to remove undamaged without a special roll pin removal tool to prevent the roll pin from splaying and jamming as it is being driven out.
The second approach was to unbolt the entire cast-iron table plus sheet-metal housing assembly from the wooden base and place the table plus housing assembly as a unit upside down on my workbench, after the motor plus motor bracket assembly (and the saw blade) were removed and set aside.
Removing the motor and motor bracket (TAB-109 and TAB-117 and Figure 5) assembly as a unit is easily done, as shown in Figure 4. Disconnect the power cord at the motor (after recording which wire goes where), loosen the two square-headed set-screws (SP-301 in TAB-109), and slide the complete motor bracket assembly off the two half-inch posts (Figure 3, TAB-130 protruding from TAB-105).
With the saw table assembly upside down on the workbench, one can remove the arbor assembly (TAB-106-A) by loosening the 1/4" square headed set screw (SP-301) in the front trunnion (TAB-104 in Figure 3), and tapping the half-inch diameter steel hinge shaft (TAB-125) out with a short drift punch and a small hammer. One rotates the hand wheels (TAB-165-S, Figures 9 and 10) for blade height and blade tilt angle as needed to maneuver and extract the arbor. A pair of wide black steel wave spring washers (Figure 3, TAM-184) will also come out as the arbor is removed.
Now that I've removed the arbor once, I could probably do a subsequent remove and replace without removing the table plus housing assembly from the wooden base, but having the assembly on the workbench and easily seen was essential the first time, as I was not able to fully visualize how things were arranged in three dimensions from the figures in PM-1722 alone.
Once the arbor assembly (Figure 7) is liberated, one has the problem of taking it apart. There are two nuts to remove, both at the pulley side of the arbor. The first is a 7/8" hex nut (BM-23) on the arbor shaft (TAB-137-S) - this requires a deep 6- or 12-point socket to reach down into the arbor while clearing the arbor shaft stub. The arbor shaft was clamped by its hog ring (against which the saw blade is clamped using nut BG-23 and dished washer LCS-8) in a big vise with copper jaws, but the shaft tended to slip in the vise, and a little impact was required to break the nut free.
The second is a custom spanner (ring) nut (BG-12), with two 0.092" (3/32") wide radial slots spaced 180 degrees apart to accept a special spanner wrench. Attempts to undo this nut by driving it with a drift punch in the slots only served to mangle the slots, the nut being well recessed inside the arbor casting (Figure 3, TAB-106-A), and so use of the punch was abandoned.
Using a lathe and a vertical mill, fabricated the needed special spanner wrench from a piece of 12L14 steel left over from another project. The business end of the wrench is a cylinder 1.568" OD and 1.270" ID, with one end milled across the diameter such that there are two protruding ears, each ear being 0.090" wide and 0.100" high. These ears fit neatly into the radial slots on the ring nut. The cylinder portion must be at least 0.250" deep (not including the two ears) to reach down into the arbor casting and fully mate with the ring nut within. There must be a central hole through which the arbor shaft (TAB-137-S) protrudes (a 1.000" ID hole is generous), and a way to apply torque without interfering with the arbor shaft. I drilled a pair of 0.257" ID holes parallel to the arbor shaft to accept the pins of an Armstrong model 34-154 3-Inch Adjustable Face Spanner Wrench that I already had. With this newly-fabricated special spanner wrench, the ring nut was easily removed. While there are many ways to fabricate a ring spanner wrench, the point is that such a wrench is essential.
We now have both nuts removed. Now to remove the arbor shaft from the arbor casting. This was accomplished by tapping on the pulley end of the shaft with a lead hammer. The components that emerged are as follows, starting at the saw-blade end: hog ring (an integral part of the arbor shaft TAB-137-S), ball bearing (ND-87503), two narrow bearing-loading wave springs (LTA-516), and a machined steel spacer (TAB-124). The spacer is 2.018" long. Note that while PM-1722 (written in 1949) specifies that one wave spring should be used, in fact a stack of two spring washers was installed. One assumes that this is a later change, to increase the bearing preload. At the pulley end, one ND-87503 bearing remained, stuck in the arbor casting. This bearing was removed using an impromptu puller consisting of some half-inch all-thread, two nuts and a big washer. The bearing was not pressed in place, but had been glued in place by old dried oil. Everything was cleaned with acetone and brake cleaner to remove all the dried oil.
One bearing is still on the arbor shaft, very close to the hog ring, and couldn't be pried loose with screwdrivers and the like. A large gear puller will make short work of this, except that the puller jaws are too large to fit between bearing and hog ring. A large steel washer (2-1/2" OD, 1-1/16" ID, 3/16" thick) was purchased from the local hardware store, and a roughly square piece was removed to yield a C-shaped washer. This was slipped between hog ring and bearing, allowing the three jaws of the gear puller to apply well-aligned force to the old bearing, which promptly slid free under the urgings of the puller.
The arbor shaft was then cleaned up with crocus cloth and solvent, ready for installation of the first new bearing using the puller and a big steel washer. Be stingy with the crocus cloth, to avoid changing the desired very light press fit to a slip fit. The lubricant used is traditional for press fits, Castor Oil (which can be bought in small quantities from drug stores, where it is sold as a mild laxative). Mobil-1 synthetic grease (available at auto parts stores) would also work.
The arbor was then reassembled with the new bearings in place and liberal application of grease. ND87503 bearings are asymmetrical, where the inner race protrudes beyond the outer race on only one side. Note that while it's hard to be sure from PM-1722, the bearings are installed back-to-back with noses protruding outward, and the machined spacer is between the backs.
It all took 12-14 unhurried hours, including the fabrication of the ring-nut spanner wrench and the C-washer, the unsuccessful attempt to take the cast-iron table off the sheet-metal housing, and some machining of the left wing for a better fit to the table.
The above text and the following photos may be found at the Metalworking Dropbox. We don't provide direct links, to reduce spam. Google for "Delta_Homecraft_Bearing_Replacement", without the quotes, to get the files.
Photo 1: Front view of the saw, for context.
Photo 2: Perspective view of the saw tabletop and blade.
Photo 3: Various components mentioned in the text. At the top is the Armstrong Adjustable Face Spanner Wrench. The middle row is a thick washer used for pushing a bearing up against the hog ring, a thick washer with a piece removed for pulling a bearing away from the hog ring, the shop-made spanner wrench for the ring nut, and the bottom row is a six-inch rule for scale.
Photo 4: Closeup of the shop-made spanner wrench for the ring nut.
Photo 5: The back of the saw, showing the motor and motor bracket attached to the rear trunnion. There is a trouble light in the saw housing. The orange belt is a link-belt; this was a great improvement over a standard V-belt.
Photo 6: Closeup of the saw blade (this is a 7-inch blade, although the saw will accept an 8 inch blade). Replacing the Arbor Bearings in a Delta Homecraft 8" Saw
27 January 2015 J.M. Gwinn