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Homemade Power Drawbar
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06-25-2015, 06:15 PM
Mike,
Do you happen to have the brand and part number for the cylinder you used? I'd like to get one so I have it when my mill arrives. Thanks, Ed 
06-25-2015, 07:14 PM
Ken,
I've broken 2 drawbars, since then the replacements were made from a section of 7/16"-20, B7 grade, hardened all thread. Since then I haven't broken the draw bar.
jack
06-25-2015, 09:13 PM
I've been at this about 38 years now and haven't yet broken nor stripped threads on any drawbar or collet. Either I'm just lucky or the drawbars are of a better quality material and manufacture. Probably a bit of both. All the "turret mills" I've run were either a genuine Bridgeport or two different Alliant (Taiwan) machines with OE drawbars.
I bought a Dorian for the Alliant I have now because it didn't come with one, and later got a spare from a local Craigslist seller. I would build a power drawbar if I had no other priorities in shop equipment repair/upgrades. Right now I have to take apart my cheapo Chinese hardness tester to see why it won't calibrate, get my Black Diamond drill grinder "calibrated", make a new 50T gear for my lathe, and two more index plates for my dividing head. Other things are getting in the way of all of that, so I'm going to do the right thing and take off on my bike in the morning and forget about everything. 
06-26-2015, 01:13 AM
Keep riding then Ken, as those will be waiting for you when you head back! Perhaps we should focus on one of your projects next time I visit...
Hunting American dentists since 2015.
06-26-2015, 08:12 AM
(06-25-2015, 06:15 PM)EdK Wrote: Mike, Ed, sorry, no part number. I found them on ebay and bought a lot of 2 that had a 1" stroke, double acting (no internal return spring), 1/8" NPT ports and 3/8-24 thread at the rod end. I believe McMaster Carr may have them in their catalog but I cannot confirm. (06-25-2015, 09:13 PM)PixMan Wrote: I've been at this about 38 years now and haven't yet broken nor stripped threads on any drawbar or collet. Either I'm just lucky or the drawbars are of a better quality material and manufacture. Probably a bit of both. All the "turret mills" I've run were either a genuine Bridgeport or two different Alliant (Taiwan) machines with OE drawbars. I agree Ken, I have been using an import (Chinese) BP clone at work for many years and have not had an issue with the drawbar. We did replace it with a quality one upon first getting the mill though but I cannot remember what brand it is. After the week I have had I am ready to get on my bike this weekend and take off as well. We have had our annual safety audit this week at work and being the maintenance manager I have been neck deep in it. My nerves are about shot and the wife and I are hopping on the bike tomorrow and taking off somewhere, don't know nor care where. Just get away for the weekend.  Mike. Thanks given by: EdK
06-26-2015, 11:23 AM
Mike,
Sorry for all of the questions but I'm not very knowledgeable when it comes to pneumatics. Can you describe those two valves that you called "needle valves" in your video? What are they used for? Thanks, Ed 
06-26-2015, 11:28 AM
06-26-2015, 01:38 PM
(06-26-2015, 11:23 AM)EdK Wrote: Mike, Ed, they are check valve/needle valves. They are designed to block air flow in one direction and adjust air flow volume in the other. These are required so that air does not try to flow to both sides of the butterfly gun when air is flowing to the air cylinder for lowering onto the drawbar. The ones needed are the ones that meter on the exhaust of the valve. Here is a link to McMaster Carr's product page with the part number 4076K22. http://www.mcmaster.com/#catalog/121/1029/=xslyu0 Mike. Thanks given by: EdK
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