looking for help pricing a Mark VII to sell

[rpd]

When we were sliding it, the plastic teeth on one tube partially broke off. Any idea where I can get those? I didn't see anything in the manual or parts book. Any other info anyone has, just let me know. Thanks!

At one point someone was 3d printing them and selling on eBay, but I don't see them now.

There is a file to 3d print the rack on the Facebook Shopsmith Users Group.

https://www.facebook.com/groups/6844615 ... 9626253819

one of the members here cut his own.

viewtopic.php?p=145503#p145503

[lahola1]

I wouldn't bother with the time, labor and expense getting a replacement rack from ebay unless your planning on keeping the MKVII for yourself because your not going to get more than $300 for it unless it's cleaned up very well and running great with all of the important parts. I would sell it for the best price you can get and give the new owner the broken piece of rack and any info you learned on replacement rack pieces available on ebay.

[edma194]

I wouldn't bother with the time, labor and expense getting a replacement rack from ebay unless your planning on keeping the MKVII for yourself because your not going to get more than $300 for it unless it's cleaned up very well and running great with all of the important parts. I would sell it for the best price you can get and give the new owner the broken piece of rack and any info you learned on replacement rack pieces available on ebay.

Agreed if you are selling it. You rarely get back money you put into it for a resale, unless it's a crucial part that it needs to sell at all. There is plastic rack for sale on Amazon frequently, although not always for the right gearing. And anyone doing this should look into metal rack replacements. You'd probably be better off removing the remaining rack. Whoever buys it either won't know that something is missing, or understands the cost of replacing it already.

I'm not sure how useful that rack is for horizontal movement since adjustment can also be made with the quill. The question is its usefulness in drill press mode. Can it lift the weight of the headstock? Is trying to do so the cause of broken racks?

I think I'd be interested in a Mark VII with no headstock or one in great disrepair. I like the look of the stand and apparently conventional headstocks will mount on the way tubes so the cost of shipping the base and tube framework might not be absurd. I don't see much advantage to the MK VII headstock except possibly a working bi-directional motor.

Which reminds me, what happened to old fashioned truck freight shipping. I've seen 300 pound car engines shipped across country for $75. Seems like that's what it would cost to ship a pillow these days. Of course I'm probably in geezer mode and remembering the old days back in the 1900s again when everything cost a lot less.

[lahola1]

edma194 said: I'm not sure how useful that rack is for horizontal movement since adjustment can also be made with the quill. The question is its usefulness in drill press mode. Can it lift the weight of the headstock? Is trying to do so the cause of broken racks?

I wouldn't trade my rack for the world. I use it a lot. Yes, it works great in drill press mode too. I think it's one of the best advantages on a MKVII.

[RFGuy]

I wouldn't trade my rack for the world. I use it a lot. Yes, it works great in drill press mode too. I think it's one of the best advantages on a MKVII.

Yeah, I didn't quite "get it" with the Mark VII until I saw a recent video that showed the operation of that rack with both the headstock and table moving together. Definitely wish they had continued pursuing this feature on future generations. Also, it seemed like they overly relied on cam mechanisms on the Mark VII. Not sure if this was an industry trend at the time, or if some young mechanical engineer fresh out of college went crazy designing the Mark VII with cams everywhere. I think it was Scott's video where I saw this detailed...even the miter gauge has a cam mechanism in it right? I was surprised how many places they tried to put a cam where it wasn't immediately obvious to me that it was a benefit. Still, I continue to be intrigued by the Mark VII and its design.

P.S. the one plastic cam and the plastic racks are available from Shapeways 3D printing and can still be purchased as far as I know. Check out the link below. I thought they used to sell these in metal versions as well, but I only see different plastic options now. I think you can still get the cam in either steel or aluminum if you can afford it.

https://www.shapeways.com/product/NNG83 ... arketplace

https://www.shapeways.com/product/ENZED ... arketplace

[lahola1]

Yeah, I didn't quite "get it" with the Mark VII until I saw a recent video that showed the operation of that rack with both the headstock and table moving together. Definitely wish they had continued pursuing this feature on future generations. Also, it seemed like they overly relied on cam mechanisms on the Mark VII. Not sure if this was an industry trend at the time, or if some young mechanical engineer fresh out of college went crazy designing the Mark VII with cams everywhere. I think it was Scott's video where I saw this detailed...even the miter gauge has a cam mechanism in it right? I was surprised how many places they tried to put a cam where it wasn't immediately obvious to me that it was a benefit. Still, I continue to be intrigued by the Mark VII and its design.

P.S. the one plastic cam and the plastic racks are available from Shapeways 3D printing and can still be purchased as far as I know. Check out the link below. I thought they used to sell these in metal versions as well, but I only see different plastic options now. I think you can still get the cam in either steel or aluminum if you can afford it.

Engineering plastics were coming in big in the 60's. Even in car engines, (i.e. timing chain gears and other parts). The trouble is back then they didn't follow best molding practices. Meaning, the thicker the part, the colder the mold to shorten cycle molding times. Trouble is this molds stress and weakness in the plastic part. (plasic timing chain gears don't hold up well when occasionally drag racing your car or forgetting to lube the bearing on the speed adjusting sheave so the plastic cam melts).
As far as the 3D printed parts I would want to know the specs on the plastic they use. I have no idea what they mean by "versatile plastic" or "fine detail plastic". It shouldn't matter much on the rack but you need a high temp plastic for the cam. The temp on my cam follower has gotten to 150 deg F. I've seen PETG and ABS plastic mentioned in 3D printing. PETG should be good for a cam. I wouldn't use ABS.

Plastic works very well when the proper plastic is used and molded properly. For many years now they have plastic intake manifolds and top and bottom tanks on radiators in cars.

[RFGuy]

Plastic works very well when the proper plastic is used and molded properly. For many years now they have plastic intake manifolds and top and bottom tanks on radiators in cars.

Interesting. Yeah, I agree to a point on plastics. There are definitely some well engineered versions in use for specific parts across a range of industries. However, having lived in the AZ desert for far, far too long, I now loathe anything plastic. Just about any version of plastic or resin molded part has issues with longevity in the AZ heat. Even plastic parts inside my garage (no UV degradation) at a lower temp (ductless mini split HVAC) still have issues with the climate here. Perhaps it is more about low humidity than high heat...I don't know? I just know that plastics tend to die an early death here and some even get "hairy" or have other surface texture issues here that I never witnessed when I lived in other places.