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HH Roberts Machinery Ltd logo
Questions ?
Call us at 905-624-5536
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H.H. Roberts Machinery Limited
1324 Matheson Blvd E., Mississauga, Ontario, Canada. L4W-2Z7, Fax 905-624-9065
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Replacement Milling Machine Heads.
Available for 220/1/60, 220/3/60 or 460/3/60 power supply
and can be interfaced to most CNC controls for programmable spindle speeds

Replacement heads for Bridgeport, Topwell, First, Kent, Supermax and most Taiwan made Bridgeport clones.  If the T-sot in the ram on your machine has a 6" diameter, these should fit.

A complete system.  The replacement head will bolt directly onto Bridgeport and all Taiwanese Bridgeport clone rams we have seen.  Mount the electronics cabinet on the side or back of the column and connect your power supply.  The head is fully wired and ready to go.

The back geared heads are most popular because they deliver much more torque at low rpm.
Top speed is 6,000 RPM.

Use CAT-V-40, BT-40 or NMTBA-40 tools on a Bridgeport format head with increased spindle rigidity. The optional #40 spindle has 3 high prescison P4 spindle bearings at the bottom for extra rigidity. See pictures and explanation below.

These heads are ideal for upgrading quill type CNC machines because they can be controlled by most CNCs. We use the same vector drives on our CNC mills and machining centres   They can be configured for CNC control of spindle speeds.

E stop buttons are now standard as shown on the picture.

Click here to download the heads catalog.

Click here to download the drawing of the head mount for the heavy 5 / 7-1/2 Hp heads
Replacement head on an old Brigdeport
Showing the HH Roberts replacement milling head on a old Bridgeport milling machine

electronics cabinet for replacement milling head, closed
Cabinet mounted on the side of the column
electronics cabinet for replacement milling head, open
Showing a typical electronics cabinet with cooling fan and air filter,
relay, and inverter drive.

All connections to the head are done.  You just need to mount the head on the side or back of the column and have you electrician bring power into the cabinet.

A left side view of the HH Roberts 7 1/2 Hp milling machine head with a face mill.
R-8 spindle. # 30, # 40 and Erickson spindles are available.
Shown at left is a head with #40 Cat CNC tooling and with the optional power draw bar.

The upgraded #40 spindle has 3 sets of 7008 P4 precision spindle bearings whereas most Bridgeport R-8 type spindles have only 2 sets of 7207 P4 bearings.


Back geared head  give 15 to 750 rpm and 100 to 6,000 rpm

Available for 220/1/60, as well as 208, 230 and 460 three phasepower supplies.

This is the 5 to 7-1/2 Hp head suitable for fitting to our Topwel, some Hurco, Webb and Kent machines.  It is pictured with an Amercian made Hi-Torque power draw bar.

Direct drive head 100 to 6,000 rpm or flip the belt to low range
of 65 to 4000

Back geared head  15 to 750 rpm and 100 to 6,000 rpm
Showing the heavy 7 1/2 Hp milling head

Parts diagram for the HH Roberts Milling head This diagram shows the moving parts in the top half of the GL head.  It is in fact a lot like today's modern machining centers with the drive train consisting of

1) the motor shaft and pulley
2) the drive belt
3) the spindle pulley and splined coupling
4) The spindle itself ( not shown ) There are about 85 fewer moving parts.

Maintenance is near zero and is normally only a replacement of the timing belt after years of service.

The RG verson of the head has a back gear pair.


Getting a #40 spindle into a Bridgeport size quill
This presents an interesting dilema for a machine tool builde. An R-8 spindle has a hole through it to take the 7/16" diameter drawbar.   A #40 drawbar is 5/8". If you bore out the spindle to get the 5/8" drawbar through it you get very thin walls left and rigidity is seriously compromised .... when half the reason for wanting #40 is to gain rigidity.

Our solution is to stay with the 7/16" drawbar, but make a special adaptor like a machining
centre pull stud that accepts the 7/16" drawbar at the top and a Cat-V-40 tool thread on the bottom.
This leaves the full wall thickness of the spindle.  The adaptor can be seen on the right in the photo below.  On the left is a drawbar, adaptor and a Cat-V-40 CNC collet chuck on the left.  The special draw bar is available with a hex top for manual tightening or splined for a power draw bar.

Then Topwell fits 3 sets of 7008 high precision P4 bearing at the bottom of the spindle to improve cutting performance.   All R8 spindes that we know of have only 2 sets of high precision bearings.


#40 taper spindle arrangement

#40 spindle in an R-8 quill

The two pictures below show the standard bearings on an R-8 Bridgeport
type machine on the right. And on the left the 4 bearing set up of Topwell's
# 40 spindle upgrade. You can see that there are 2 precision bearings at the
bottom or the R-8 spindle and a set of 3 precision bearings on the #40 spindle.
Both spindles have a standard bearing up at the top.

spindle bearings set up
spindle bearing set up


replacement milling machine heads for Bridgeport type machines
A shipment of milling heads received into our shop for preparation to sell.

adaptor Drawings and Photos
Bridgeport sized head
H-D #40 taper head
dimensioned drawing
dimensioned drawing
photo #1
photo #1
photo #2
photo #2