Pro-Tools HMP 200 Tubing Bender Build
There are several builds documented online using these plans. The value my post holds is that my bender was built entirely in my garage with equipment I own. I did not build it in a machine shop or a even a well equipped home shop. The materials used were all purchased online, not through a commercial shop. Neither were the materials free commercial shop scrap. If you want to build a tubing bender and are not sure what tools you need or where to get the materials, this post will help you out.
I used 1″x5″ hot roll steel for the Base Plate. The material was supposed to be 1018 cold roll 1.5″ thick, but that was not available at Online Metals so I substituted. I cut the plate roughly 1/8″ long to allow for the inadequacies of the band saw.
I clamped the plate edge up in a vice to mill the ends flat and cut the length down to 7.000″
I clamped the plate again directly to the milling table to get all the height possible beneath the spindle. I drilled the bolt holes in the edge of the plate using collets to hold the drill bits (again for added height beneath the spindle). I tapped the holes in place using a dead center in an R8-MT2 adapter to hold the tap true.
The Die Wrist Pin Sleeve like the base plate requires its length to be precisely 7.000″. After a rough cut in a band saw I finished the ends with a milling machine.
The 1″ bolt did not slide easily into the Die Wrist Pin Sleeve. The Die Wrist Pin Sleeve is a piece of DOM tubing with an inner diameter of 1″. I used an adjustable reamer clamped in a bench vice to ream out the DOM. I used a pipe wrench to rotate the tubing about the reamer.
The Side Brackets are toward the upper limit (in length) of what can be easily machined on a 6×26 milling machine. The Side Brackets were shortened by 0.5″, compared to the Pro-Tools drawing to account for the Base Plate being 0.5″ thinner than called for. Since the bracket is shortened, all holes need to be measured with respect to the top except the holes for the base. I did not slot the holes for the base as the drawing showed. I drilled them exact at 0.5″ from the Side Bracket Bottom. I machined the plates clamped together to save set up and machining time. I also did this to improve the accuracy of holes lining up. The holes for the Base Plate attachment and the tapped holes that hold the springs were drilled in one setup. I machined the Die Wrist Pin holes and Roller Pin slot in another setup.
Below is an example of tapping with a dead center in a milling machine. Using this setup for tapping holes ensures the tap is perfectly aligned with the hole. I used a quill lever to feed the tap in order to avoid avoid using too much pressure.
The Side Brackets were clamped to the table using 1/8″ parallels as spacers. I used spacers so I would not drill into the mill table. Two narrow parallels were clamped on top of two wider parallels (wider ones used as spacers). I used a small machinist’s square to line up the parallels before I clamped them to the table. This method worked fairly well for squaring the Side Plates to the table, although I think it was off a few thousandths over 16″. Since the holes for the Base Plate were not slotted, it is important for the Side Plate to be square with the mill table. If the Base Plate Holes are not perpendicular with the Roller Pin slot and Die Wrist Pin Holes, the Hydraulic Jack would not line up correctly. If the jack is not lined up correctly, either due to machining set up error or the Hydraulic Jack cylinder not being normal to the Jack’s base plate, then the Jack’s base plate may be shimmed to account for the error.
I used a center finder to locate the center-punched hole. Centering the Side Plate is not that critical, an error of 0.010″ or maybe more would have been acceptable. Having the holes and slot co-linear is important to reduce side loading on the Die Wrist Pin and Roller Pin.
Center drill -> 1/8″ bit -> 1/4″ bit -> 1/2″ bit -> 0.975″ 2 flute end mill was used to drill the holes and ends of the slot.
The slot was completed in several passes with a 2 flute 0.975″ end mill.
The Die Wrist Pin holes were finished with a boring head. The Die Wrist Pin (1″ bolt) has a different diameter for the shank and the threaded portion, so each Side Plate received a different hole diameter. The smaller diameter was bored in all the Die Wrist Pin holes, then the larger diameter was bored through only one of the two Side Plates. The slot ends were bored to the exact diameter of the Roller Pin (which is a 1″ CR steel rod). Two intermediate areas of the slot were also bored to the final size to give a visual indication of when the slot width was reached. I used a 1/2″ end mill to widen the slot to the final width.
The Side Plate bottoms were squared with an end mill. A small machinists square was used to line up the Side Plates perpendicular to the mill table. This setup was used only because the milling machine lacked the necessary Y-axis travel.
I replaced the Stabilizer Tubes list in the HMP-200 plan with threaded rod and nuts. I had seen this done on another build and it seemed to reduce the complexity slightly. The only extra step is the threaded rod stabilizers must be adjusted carefully with an inside caliper to achieve 7.000″ exactly. The Roller Pin was cut to size on a band saw and faced on a lathe. The Roller Pin length dimension is not critical. The Roller Pin holes were drilled using a lathe and the holes taped while chucked in the lathe. The radiused ends of the Side Plates was done by hand with and end mill which is why it is sloppy looking. Using a rotary table would have been a better method of radiusing the ends.
The Roller was cut from a 2.5″ CR steel rod. Using 2.5″ tubing with 0.75″ wall would have been ideal, but it was difficult to obtain. The rod was cut to a length such that it could be chucked full depth in the 4 jaw chuck with 3.5″ protruding. A 4 jaw chuck was used to more accurately center the piece. The Roller was drilled with a center drill -> 1/8″ bit -> 1/4″ bit -> 1/2″ bit -> 3/4″ MT2 shank bit. The remaining diameter was bored with a carbide insert boring bar to 1.125″. After the hole was bored the roller was faced and outer diameter turned down a few thousandths to be concentric with the bore and also to improve the surface finish. The Roller was cut to length on a band saw then the cut side was faced in a lathe. A bronze sleeve bearing was inserted into the Roller.
The Roller Block was the most difficult part to make due to its geometry. The rough cut Block was squared on both sides.
Multiple holes were drilled in the block to cut out the center of the block.
I used a band saw to cut the sides of the Block; however, the cuts were not complete due to the blade angle.
The finishing cuts were done with a hacksaw. After the scrap piece was removed a fly cutter was used to finish the bottom of the of the channel.
The Pro-Tools plans were abandoned for boring the bottom of the Roller Block. The hole has two diameters; the larger diameter for the Hydraulic Jack cylinder and the smaller diameter for the screw-out jack extension. The tolerance was made as tight as possible to reduce the play of the Block attached to the Jack.
The Roller Pin hole was drilled in two different setups, but the boring was done in one setup.
I did not have any means to bend 0.25″ x 4″ CR steel 90 degrees to create the Support Bracket. One piece of the Bracket was slotted with a milling machine before the two pieces were welded together.
I TIG welded the Support Bracket.
The completed assembly turned out well.
(4) 1/2″-20 x 1″ grade 8 hex bolts purchased locally from Ace Hardware.
(4) 3/8″-16 x 1.25″ no grade hex bolts purchased locally from Ace Hardware.
(2) 3/8″-16 x 3/4″ no grade hex bolts purchased locally from Ace Hardware.
(4) 3/8″-16 hex nuts purchased locally from Ace Hardware.
(10) McMaster-Carr Materials (see image). ($54.43)
(7) Online Metals Materials (see image). ($214.52)
Total: $308.94 (note this is before shipping or tax and omitting the bolts and nuts that may be purchased locally)