PM719 Mortise Machine
by Jim Sherwin
|First impressions of the PM719 are that it is an extremely-solid,well-made, and carefully-machined tool. Even the hardwood shipping crate is sturdy to the point that disassembling it for firewood was areal chore. The machine is heavy at 188#, but you can take the crated machine home in the back of a mini-wagon or pickup. Do seek help getting it up onto the bench, however. A stand, P/N 6292482, is available, but I prefer a bench so I don't bark my shins against the stand's front rail. Bolt holes are provided in the casting so it can be firmly fixed to a bench or stand. Actually, its mass is so great that I have never bothered to bolt it to the bench. It is shipped completely assembled except for small bits & pieces. All motion controls and the vertical stops can be seen in Figure 1. The mechanism at right edge of the table is the adjustable workpiece stop.|
|The base is 12"
x 151/2", but the machine will occupy a space of about 22"
x 22" on your bench plus whatever horizontal space is needed for
the workpiece to the left and the workpiece stop on the right .
33" plus additional for the operating lever. A 1/2" chuck is included, and chisel capacity is 1/4"-3/4". Chisel travel is 6", fence to center of chisel is 3" max. and there is 61/2" under the chisel so you can work to the center of 6" stock. Table movement is 4" front-to-back and 141/2" side to side on ground V-ways. The cast table itself is 61/4" x 18" with a 3" fence height.
|An adjustable workpiece stop is fixed to the right end of the table. Three generous-sized handwheels control front-to-back position, side-to-side motion, and the workpiece clamp. The clamp itself is angled down toward the fence to provide both horizontal and vertical clamping force with its ball-jointed cast pressure plate. The table-motion and clamp handwheels appear in Figure 2. V-ways for X and Y horizontal motion are also visible. The two knobs at rear of the fence are horizontal-travel stop adjustments.|
|Chisel travel and table side-to-side motion is by rack and pinion; the horizontal rack is visible in Figure 3. All motions are fixed at right angles by double V-ways with gibs adjustable for wear and clearance. Gib-adjustment screws and lock nuts are also visible in Figure 3. A long lever, adjustable for length, controls chisel motion; and the lever may be fixed in its hub at any of 6 radial angles by means of 3 cross-drilled holes and a clamping screw. The vertical-control pinion shaft and its cross-drilled hub appears in Figure 5. There are adjustable stops for both ends of side-to-side motion and upper and lower chisel travel. Horizontal stops and adjustments appear in Figure 4. Front-to-back motion can be locked in position with a clamp screw visible in Figure 3. When changing chisels, I recommend placing a thin piece of wood or other soft material on the table under the chisel in case the chisel slips when being changed.|
|Overall machine quality seems excellent, with no burrs or sharp edges and no sloppy paint work. The table measures dead flat side-to-side with a Starrett straightedge over the 3" of the surface nearest the fence. Beyond that, the table gradually becomes slightly crowned near the front edge, eventually reading 0.006" crown. The fence is flat to within 0.003" at the bottom, and is crowned to 0.006" at the top. The fence is at 89.6( to the table, tilting forward at the top. Bridge City square measurements at either end of the fence show no deviation from flat (or straight) in the vertical direction.|
Dial-indicator measurements show the chisel travel to be straight within 0.003" over the full 6" travel, left-to-right table travel to be perpendicular to the chisel mount within 0.002" in 6", and fore-and-aft travel 0.000" in 4". Pushing sideways on the chisel mount can cause (0.003" chisel motion, and pushing sideways on the operating handle can cause (0/006" chisel motion. The chisel-ram support column is mounted to the base casting with only two 12m-head hex cap screws which can be seen in Figures 4 & 6. The column is not pinned to the base, and may be misaligned when delivered. It is not necessary to correct the alignment as the chisel may be set parallel to the fence to correct any misalignment. I found that the cap screws were slightly loose, allowing the chisel ram to rotate slightly when pressure was applied to the side of the ram casting. Tightening the screws helped, but did not eliminate this rotation. The undercarriage photo shows the side-to-side rack, both sets of V-ways, gib adjustment screws with locking nuts, and the front-to-back position lock. No evidence of sloppy assembly or poor quality is evident here.
The bit is driven by a 1hp, 1(, 3400 rpm TEFC motor without external cooling fins (a disappointment). I burned no wood or bits at the 3400 rpm with either 1/4" or 3/8" chisels in red oak, Douglas fir or white pine. It is important to set the bit slightly out of the chisel opening so that the bit does not rub against the chisel, else the bit will overheat with the usual blue-color result. Clico chisels will fit, however the blue-box Delta chisel bits have much too short a shaft to be safely clamped in the chuck. Most Taiwanese bits should fit as well ¾ if you really want to use them. The Plexiglas covers over the chuck cavity, shown in Figures 5 and 6, effectively prevent workpiece contamination by any oil-splatter from the spindle. Note in Figure 5, the horizontal brown mark on the Plexiglas from thrown oil.
The vertical- and horizontal-travel stops are effective and easy to set. They are rugged, and do not lose their position accuracy, although I would rather see cast-iron stops to match the quality feeling evident in the rest of the machine. As with other machines of the type, you must carefully set the chisel square to the fence by your own method. I run the chisel lightly up against the fence to make sure it is aligned square with the fence and workpiece before clamping it in position. I would like to see a chisel collet with a machined D-shaped hole to facilitate precise chisel alignment, but I don't suppose that is likely to happen. As it is, the clamping screw seats against the flat on the chisel shank, but no precise alignment aid is built into the machine.
All in all, I am quite happy with the machine with only the caveats mentioned relative to the manner of fixing the column to the base casting, chisel alignment and cast motion stops. Accuracy measurements obviously apply only to my sample.
After submitting the PM719 review, I realized that the fence was probably too far out of plumb to do really-good work, as it leaned forward at the top by 0.033" in its 3" height. That is really 89.4 degrees rather than the 89.6 degrees I wrote in the review. Such a tilt on the mortise could cause a 20"-long tenoned rail to be tilted by nearly 1/4"(0.22") at the end.
I contacted PM via e-mail, giving them this information, and they e-mailed back in a day or two saying that I should return the machine to the dealer for a replacement. I did this, and was given my choice of 3 units as replacementt. I measured fence tilt on all three, and chose the best which was out of square 0.015" in 3", or 0.005"/inch (a fence angle of 89.71 deg). I use a Bridge-City square and a feeler gauge to make this measurement. This angle is possibly satisfactory, although I think the measurement should be within 0.001"/inch, or 89.94 degrees, for precise work.
I repeated all the measurements of the review after uncrating the unit today. This is a better-made unit than the unit I returned. First off, the vertical chisel-ram support column has been redesigned for greater cross-section at the base which translates to greater strength and possibly less flexure. The column is now bolted to the base with four 12mm-head hex cap screws in place of the two used previously (photo at right). Second, the motor is now 1725 rpm instead of 3740 as previously. Steel covers have replaced the plexiglass covers over the chuck cavity.
Measurements are as follows:
The table measures dead flat with a Starrett straight edge. The fence is flat except for a gradual 0.002" crown near the center. The fence is tilted forward at the top edge at 89.7 degrees or 0.005"/inch. Dial-indicator measurements show the chisel travel to be perpendicular to the table within +/-0.002" side-to-side and +/-0.0005" front-to-back over 5" of chisel travel. Table travel is perpendicular to the chisel mount within 0.001" in 6" left-to-right and fore-to-aft. Moderate side pressure on the chisel ram caused +/-0.002" sideways deflection of the chisel.
Table fore/aft V-way gibs were loose upon receipt, allowing noticeable play in the table; but adjusting the gibs to remove the play was a simple task. Column-mounting bolts were reasonably tight. Table travel fore/aft is smooth, however side/side travel is rough; and it has been impossible to adjust the gibs for both smooth travel and minimum play at both ends of horizontal table travel. Adjusting the right-hand gib-adjust screw to remove table play makes it impossible to move the table past center to the right. Therefore, I live with some play when the table is fully left, and a somewhat sticky and rough horizontal movement. This certainly is not ideal as the previous machine had better table-movement/control. Addition of one or two gib-adjust screws in the center would help as the brass gib shims are too flexible to maintain the table position unless at least two gib screws are spanned by the table. I may add those by drilling and tapping the casting.