Mark VII Gear Rack Replacement

[JPG]

Sorry to say I parted with the Mark VII. I used it for a while and had no problem with it. Hopefully the new owner monitors the forum and will chime in. It had some great features that I wish Shopsmith had included with my Power Pro.

Which end of the 45/60 bit did the gear tooth cutting?

[redleg]

Here's the 45°/60° bit used to make the teeth. I believe it would be the 45° end and I flattened the point. You end up with pointed teeth but just run the strip thru the bandsaw to get the gear to the right height. When rounding the back side I ran it thru twice on the 3/8" router bit to get the right profile to fit the bench tube.

[ATTACH]23567[/ATTACH]

[JPG]

Here's the 45°/60° bit used to make the teeth. I believe it would be the 45° end and I flattened the point. You end up with pointed teeth but just run the strip thru the bandsaw to get the gear to the right height. When rounding the back side I ran it thru twice on the 3/8" router bit to get the right profile to fit the bench tube.

[ATTACH]23567[/ATTACH]

Thank You!

I am not understanding how twice with a 3/8" cove bit(3/4" outer diameter?) created a 1 3/4" diameter curve on the back side.

I assume it 'got it close' with correct 'width'.

[redleg]

It is not horseshoes but is get it close. I grew up on a farm and with twenty years of military service learning many field expedient repairs from vehicles to weapons sometimes you just have to forget the pencil and paper and make it work. That narrow width of plastic on a 1 3/4" bench tube became very happy to have a new home.

[JPG]

Here's the 45°/60° bit used to make the teeth. I believe it would be the 45° end and I flattened the point. You end up with pointed teeth but just run the strip thru the bandsaw to get the gear to the right height. When rounding the back side I ran it thru twice on the 3/8" router bit to get the right profile to fit the bench tube.

[ATTACH]23567[/ATTACH]

Thank You!

I am not understanding how twice with a 3/8" cove bit(3/4" outer diameter?) created a 1 3/4" diameter curve on the back side.

I assume it 'got it close' with correct 'width'.

[redleg]

EDIT of Post #10: 12-30-2013 I spoke with the new owner of my old Mark VII today. He stated that it cranks fine on the rack but it pushes hard when the clutch is disengaged. I offered to give him another gear rack that I'm making but I got the impression that he doesn't use it a lot. A clutch adjustment may be in order.

I also have changed the bit I was using to cut the teeth. I ground a shortened 1/4" drill bit to 17.5° on four sides to make my own router bit. This gets it closer to the original angle between the teeth and creates a blunt nose v-groove at 35°.

[redleg]

I updated my gear rack jig. The first one was from an old fence extension and left to many hanging plastic feathers. I cut this one with the bit being used and with a backer board tight to the groove it helped a lot. The teeth were cut with the Power Pro under table. A speed increaser that is under table would work better and the jig would not have to be switched from front to back. The jig could also be adapted to a router table.

[ATTACH]23617[/ATTACH]

I used a scrap of wood the same dimensions as the gear rack to set the 3/8" core box bit. It takes three passes 1. close to the edge 2. flip end for end and run again 3. reset the bit to run up the center. It is easier to cut the back prior to milling the teeth.

[ATTACH]23618[/ATTACH]

Here are a couple of rejects that will probably still work (free) if someone wants to pay postage. One had chatter from going through the planer near one end. The other an extra half tooth over the length of the run. After these I found it was safer to plane a 3 inch wide piece down to 11/32" and then divide into 9/16" strips. If anyone wants to spring for a new bit I will make a set of gear racks for you.

http://www.aliexpress.com/item/Free-shipping-1PCx-35Degree-0-6MM-Marble-Granite-CNC-Hi-Quality-Diamond-Engraving-Bit-Router-Bit/1247318968.html

[ATTACH]23619[/ATTACH]

As I mentioned earlier the rivet needs to be long. The countersink hole in the rack needs to be 1/4", the rivet hole is 1/8". A spacer has to be used between the pop rivet head and the rivet gun. I used a piece from a wire terminal kit but it wasn't born lately so it was solid. Steel or copper pipe would probably be a better choice.

[ATTACH]23620[/ATTACH]

[JPG]

I updated my gear rack jig. The first one was from an old fence extension and left to many hanging plastic feathers. I cut this one with the bit being used and with a backer board tight to the groove it helped a lot. The teeth were cut with the Power Pro under table. A speed increaser that is under table would work better and the jig would not have to be switched from front to back. The jig could also be adapted to a router table.

[ATTACH]23617[/ATTACH]

I used a scrap of wood the same dimensions as the gear rack to set the 3/8" core box bit. It takes three passes 1. close to the edge 2. flip end for end and run again 3. reset the bit to run up the center. It is easier to cut the back prior to milling the teeth.

[ATTACH]23618[/ATTACH]

Here are a couple of rejects that will probably still work (free) if someone wants to pay postage. One had chatter from going through the planer near one end. The other an extra half tooth over the length of the run. After these I found it was safer to plane a 3 inch wide piece down to 11/32" and then divide into 9/16" strips. If anyone wants to spring for a new bit I will make a set of gear racks for you.

http://www.aliexpress.com/item/Free-shipping-1PCx-35Degree-0-6MM-Marble-Granite-CNC-Hi-Quality-Diamond-Engraving-Bit-Router-Bit/1247318968.html

[ATTACH]23619[/ATTACH]

As I mentioned earlier the rivet needs to be long. The countersink hole in the rack needs to be 1/4", the rivet hole is 1/8". A spacer has to be used between the pop rivet head and the rivet gun. I used a piece from a wire terminal kit but it wasn't born lately so it was solid. Steel or copper pipe would probably be a better choice.

[ATTACH]23620[/ATTACH]

My hand is raised!!!! Sending you a PM.

[redleg]

JPG,

Will send today.

Happy New Year to all.

[redleg]

IMG_0016 (768x1024).jpg (542.96 KiB) Viewed 14718 times

8/3/2017 Update


The rivet needs to have a grip range of 1/4" to 1/2". The countersink hole in the rack needs to be 1/4", the rivet hole in the rack is 1/8". A spacer has to be used between the pop rivet head and the rivet gun.

(Shape the end of the spacer to match the shape of the groove between the teeth, flatten and file or sand)



A couple of pictures to show the rivet, sleeve and resizing the flange on the pop rivet to fit the 1/4" hole in the rack to .23 inches, .22 inch flat head flanged rivets are available but I used the ones I had on hand. I put the rivet with the large end in a chuck (finger tight) on a Shopsmith and resized the flange with a file while running at 500 rpm. When inserting the pop rivet through the rack into the way tube you'll need to seat the pop rivet into the countersunk hole with a chisel or flat tip screwdriver.

IMG_0016 (768x1024).jpg (542.96 KiB) Viewed 14718 times

IMG_0018 (1024x768).jpg (576.18 KiB) Viewed 14718 times