Motor head and chuck
The head carries the direct-drive motor and chuck. The selected JBM-5 uses a 1/2 HP motor; consult the exact manual for electrical and duty details.
Power Tools / Joinery / Field guide
Mortising Machine
Understand how the auger, square hollow chisel and feed mechanism cut a repeatable mortise with controlled workholding.
Hollow chisel + augerCut
01 / Tool anatomy
See the assembled tool and its components
An original educational poster identifies 9 documented construction features. The numbered descriptions remain readable below the artwork on narrow screens.
- Motor head and chuck
Rotates the auger and travels vertically during a cut.
- Chisel bushing
Locates the square chisel below the chuck.
- Hollow square chisel
Shears four corners while the auger clears center waste.
- Internal auger
Rotates inside the stationary chisel to lift chips.
- Column and base
Guide and support the moving head on the bench.
- Feed lever
Provides controlled vertical movement of the head.
- Depth-stop rod
Limits the lower travel for repeatable mortise depth.
- Fence and hold-down
Register work and resist lifting during chisel withdrawal.
- Work table
Supports stock beneath the chisel and against the fence.
Technical references: JET JBM-5 official operator and parts manual · JET JBM-5 product information. The JBM-5-class head, chisel/auger, feed, depth stop and workholding assemblies are spaced to show construction relationships. The housing remains closed; the image is an educational arrangement, not an exact service sequence. Original educational artwork depicts documented component groups and their relationships; it is not a service sequence or a replacement for the exact model manual.
02 / Understand the tool
What it is and what each part does
A benchtop hollow-chisel mortiser makes square-ended mortises by boring and paring in one guided plunge. The JET JBM-5 manual documents the reference machine, including its head, column, feed lever, fence, hold-down, depth stop and chisel/auger setup. A plunge router or drill press mortising attachment has different registration and cutting behavior.
A motor rotates an auger inside a stationary square hollow chisel. The auger removes the center waste while the chisel's cutting edges shear the corners as the head descends. A lever feeds the head; a depth stop limits travel. The fence registers the work and a hold-down resists lifting on withdrawal. The auger must have the model-prescribed clearance inside the chisel.
Chisel bushing
A correctly sized bushing centers and secures the hollow chisel below the rotating auger.
Hollow chisel and auger
The auger lifts chips from inside the four-sided chisel. They form a matched cutting set, not one solid square drill.
Column and feed
The column guides the head; lever travel supplies a controlled plunge. The depth stop sets the lower limit.
Fence, hold-down and table
A straight fence registers the stock; a hold-down prevents it rising with the chisel; the table supports the work.
01 / Working relationship
How the main groups connect
02 / Cutter relationship
An auger clears; four edges square
02 / Working principle
Set, guide and control the action
These decisions make the mechanism useful at the bench.
Set auger clearance
With power disconnected, install the selected chisel and auger using the JBM-5 manual's order and clearance procedure. Confirm the auger rotates freely.
Register the work
Square the fence to the intended mortise line, secure the stock and set the hold-down close enough to resist lifting without binding.
Control depth and overlap
Set the depth stop; make successive plunges with chip clearance rather than forcing a long slot in one stroke.
Mortise-and-tenon joints
Cut rectangular mortises in frame or furniture parts, then fit a mating tenon to the actual result.
Repeated rail locations
A fence and stops make matching mortise locations repeatable across multiple parts.
Deep square pockets
The square chisel leaves corners without hand-squaring a round router mortise, within the machine's capacity.
03 / At the bench
Setup, technique and finish quality
Use the steps for a first pass, then inspect the work before changing the setup.
- Mark mortise boundaries and a consistent reference face; select a chisel/auger size suited to the stock.
- Disconnect power, install the chisel and auger with the maker's clearance method, then lock both securely.
- Set fence and depth stop; clamp or hold down the work as the manual directs.
- Make a test plunge on scrap; check location, depth, clearance and chip evacuation.
- Plunge steadily, retract completely, clear chips and overlap subsequent cuts according to the manual.
- Stop the machine before repositioning, adjusting or clearing a jam; fit the tenon to the actual mortise.
The chisel does not rotate
The spinning auger removes chips, while fixed square edges pare the corners. Incorrect auger clearance can cause friction or binding.
Withdrawal loads the stock
The chisel can lift the work on the upstroke; a correctly set hold-down is essential.
Chip evacuation matters
A deep slot packs chips. Small overlapping plunges and full retractions help maintain cut quality.
What changes by model or material
Floor machines may have longer stroke, larger stock capacity and different hold-downs; the illustrated setup is benchtop.
Chain mortisers use a different cutting system for larger work; these components do not describe one.
Router mortises have round ends unless squared afterward; loose-tenon joiners cut matching slots rather than using a square chisel.
Choosing the tool
- Check chisel capacity, stroke, fence travel and stock clearance against your joints.
- Look for firm head travel, accessible depth setting and dependable hold-downs.
- Allow for chisel sets, sharpening and bench support.
Useful accessories
- Compatible hollow-chisel/auger sets
- Work stops
- Chisel sharpening cone where specified
- Suitable bench mounting
Consumables
- Replacement chisel/auger sets
- Sharpening supplies for the fitted cutters
04 / Keep control
Care, troubleshooting and safety
Stop the tool and disconnect power before investigating a fault or changing a part.
Care checklist
- Disconnect power before installing or cleaning cutters.
- Clear chips from the chisel, table and head path; do not reach into a running cutter.
- Inspect chuck grip, chisel edge, fence and hold-down.
- Lubricate only as the exact JBM-5 manual directs.
Common mistakes
- Running the auger against the chisel with no clearance.
- Holding stock by hand without a secured fence and hold-down.
- Forcing a long mortise without clearing chips.
- Letting the chisel pull the work upward during retraction.
Safety at the operation
- Secure the machine and work; keep hands beyond the cutter's plunge area.
- Wear eye protection and remove loose clothing near the head and lever.
- Disconnect power for cutter changes or jams; wait for the auger to stop.
- Follow the exact manual for electrical setup and chisel installation.
When the result goes wrong
Stop and verify auger-to-chisel clearance, sharpness and chip flow.
Reset the hold-down and inspect fence registration before continuing.
Check fence lock, stock reference face, chisel alignment and head play.
05 / Sources to keep learning
Manuals and educational resources
Use the exact tool manual for setup, limits and replacement parts. These lessons, documents and model pages teach relevant techniques or help compare real variations.
Manufacturer manuals
Learn and compare
JET JBM-5 product overview
Official capacity and machine description.
JET woodworking video library
Maker demonstrations and woodworking machine resources; verify the demonstrated model before applying a setting.
Grizzly mortiser controls video
Manufacturer demonstration of hollow-chisel controls on other models; use JET instructions for JBM-5 settings.
06 / Manufacturer directory
Manufacturers & Brands
These maker-owned links document relevant tools and tool brands. A product brand may use another company's factory; compare the exact model before choosing parts or accessories.
JET benchtop hollow-chisel mortisersPowermatic hollow-chisel mortisersGrizzly Industrial benchtop and floor mortisersShop Fox mortising machines; a Grizzly-owned brandRikon woodworking mortisersRecord Power mortisers and woodworking machines
Choose parts for the exact model
Cutters, abrasives, guards, guides, dust fittings and service parts vary by tool. Check the model plate and manufacturer manual before ordering or changing a component.
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