I have a 1961 vintage Bridgeport mill that I am fixing up so I can finally learn to use it properly. The machine is mostly in good shape but the table has been crashed into several times with tooling. Does anyone see a problem in resurfacing the table? I figure it will take about .100" to .150" to clean it up and planed to use the surfacer at a friends engine machine shop. The surfacer designed for decking engine blocks and heads will get the table nice and flat but the surface finish will be a little rough. From there I planned to just hand polish. I just want to make sure I'm not missing something like the dimension change effecting some operation or the hardness of the table service, etc. Thanks for any help.
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resurface Bridgeport table
- Thread starter NITRO702
- Start date
- Replies 14
- Views 8,557
Spyderedge
Titanium
- Joined
- Aug 28, 2013
- Location
- NY
Taking off .100"+ will reduce rigidity and probably warp the entire table. It's most likely fine the way it is. Remove all the high spots and burrs with an oilstone. The low spots don't matter, but if it bugs you you can fill them in with JB weld.
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JohnEvans
Titanium
- Joined
- Sep 23, 2009
- Location
- Phoenix,AZ
Leave it alone !As said most likely cause more issues by doing that. Draw file with a old fine file to remove the high spots,quicker than a oil stone.And using a dullish file you will only knock down the high spots.
J_R_Thiele
Stainless
- Joined
- Jan 22, 2003
- Location
- Columbia Missouri
Your estimated .1 to .15 to clean it up lead me to think the problem is holes from drills or endmills, or endmill tracks. Though ugly they usually do not affect function of a vice, rotary table or fixture with a large bearing area. They can also collect chips, which seem to come out and tilt things when least expected. These holes can be filled with steel filled epoxy, and then leveled with a file.
If you have holes where it affects using table clamps or other loads, they can be filled using cast iron discs in bored holes, held in with adhesive, threaded in, or both. The cast iron then needs to be leveled by machining, files, and then scraped. Its going to be a lot more work, but is a better repair as it replaces cast iron with cast iron.
If you have holes where it affects using table clamps or other loads, they can be filled using cast iron discs in bored holes, held in with adhesive, threaded in, or both. The cast iron then needs to be leveled by machining, files, and then scraped. Its going to be a lot more work, but is a better repair as it replaces cast iron with cast iron.
rons
Diamond
- Joined
- Mar 5, 2009
- Location
- California, USA
Fill the deep holes with plugs. The long mill cuts can be filled by a competent welder. Then surface the table down just a tad. I have seen a table with nice welds at a rebuilder's shop. The weld areas will be noticeable but will look better than the ugly table hit that was there.
I recall a BP owner suggested that you can pound in a frozen round cylinder into a table hole and surface it down with a milling cutter with the machine. You can get pretty close. But if you screw up or the head isn't trammed in then the spot will look worse.
A standard practice is to pound a surface onto the table top that looks the same as a scraped surface. It hides imperfections. It's sort of a bull shit way to finish the table, but don't mention that to the rebuild person. It will hurt their feelings.
I recall a BP owner suggested that you can pound in a frozen round cylinder into a table hole and surface it down with a milling cutter with the machine. You can get pretty close. But if you screw up or the head isn't trammed in then the spot will look worse.
A standard practice is to pound a surface onto the table top that looks the same as a scraped surface. It hides imperfections. It's sort of a bull shit way to finish the table, but don't mention that to the rebuild person. It will hurt their feelings.
michiganbuck
Diamond
- Joined
- Jun 28, 2012
- Location
- Mt Clemens, Michigan 48035
A good quality flat file works like a honing stone and will make quick work of making a mill table as flat as it needs to be..You want to take the surface down to just leaving the old color in most places with all the high bugs feathered in to near but not full clean up...then if you wish an oil stone can work on high spots...A mill table need not be Grinder Chuck flat to do like new work.
Harbor fright files are not flat so they do a very poor job of making things flat.. perhaps OK for de bugging parts only..Nothing wrong with good old original paint..
Dial bugs the same way..good file to take bugs to just down to feather-in not full clean up.. then a business card with a piece of fine crocus cloth to hand hold as you spin..this leaves the most stock and makes number edges keen and sharp..never wire brush number dials..
For re-paint... some mills have a lot of casting filler...so taking down to bare casting can make a bigger job of it..for many machines it can be better to sand old paint so you don't have to re fill the casting errors..
Newman109
Diamond
- Joined
- Sep 4, 2006
I agee. JB weld is your friend. When I got my Webb 10 X 50 Mill, it had a few small divots in it. I used the slow-curing JB Weld and waited a couple of days. Then I stoned it down flat. After 7 years, you almost can't see where the JB Weld is.
I also agree that taking that much metal off of a table for what is essentially cosmetic reasons would do more harm than good. It's almost certain to warp a bit after that,.
swatkins
Titanium
- Joined
- Jul 24, 2011
- Location
- Navasota / Whitehall Texas
Have you measured the table to see just how much " bend" is in the table?
Tables generally "droop" at least .010" over the years from tighting the T nuts too tight. The top of the T slot is peened over time causing not only the top but the bottom of the table to bow. Surfacing just the top will Not take care of the bottom of the table and you will end up with a thin middle and thick table ends..
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Tables generally "droop" at least .010" over the years from tighting the T nuts too tight. The top of the T slot is peened over time causing not only the top but the bottom of the table to bow. Surfacing just the top will Not take care of the bottom of the table and you will end up with a thin middle and thick table ends..
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DMF_TomB
Diamond
- Joined
- Dec 13, 2008
- Location
- Rochester, NY, USA
.
usually waste of time to resurface table. normally the table is never assumed to be perfectly flat anyway. standard practice to to bolt on trim pads which are marked up with red marker and .001 removed. then the trim pads are indicated to confirm flat within .0005" or what ever your tolerance is. trim pad is basically a bolted on piece designed to be machined .001 just after bolting on. trim pads can be trimmed hundreds of times before needing new ones. usually use 3 to 6 trim pads depends on part shape
I'v been looking at getting a Bridgeport and noticed that a lot of them on ebay have scrapped tables, from the previous posts it seems like you are saying that they are basically doing this for show. I am new to mills and would be interested in hearing your opinions on this.
michiganbuck
Diamond
- Joined
- Jun 28, 2012
- Location
- Mt Clemens, Michigan 48035
Just skim the top might be good but not to clean up all the drilled, milled and nicks in the table..A good file flattening is best then run an indicator to see what might make it better..some mills one can fly cut the highest places shaving .010 or so...Vise work and the vice can be trued. Big work the work can be trued..
DMF_tom mentioned trim pads.. that is a very good idea..I do that on grinders when needing zero and no time to grind a chuck.
DMF_tom mentioned trim pads.. that is a very good idea..I do that on grinders when needing zero and no time to grind a chuck.
DMF_TomB
Diamond
- Joined
- Dec 13, 2008
- Location
- Rochester, NY, USA
.
its similar to soft jaws on a lathe. you trim jaws .001 after bolting on and runout is usually near zero
I suggest you leave it as it is - that's the best option. If you remove the table and surface it you run the risk it'll LOOK nice and flat and be anything but - how are you going to register the table on the "surfacer" ? You could replace a number of small random errors with a single significant one. Clean the table well with some thinners and rub it with a large(ish) brake disk and 80 grit. This will show immediately where the problems are. Attend to those using a file/scraper whatever. Now, you could carry on lapping it and checking with a dial indicator etc. but it won't make it a jig borer.
triumph406
Diamond
- Joined
- Sep 14, 2008
- Location
- ca
Standard practice on a BP? Never seen that, and I've seen 100+ BP's over the years. Is that how they do it at your company on a BP?
michiganbuck
Diamond
- Joined
- Jun 28, 2012
- Location
- Mt Clemens, Michigan 48035
Pads are simply a bolt on pad with a CB hole to the T slot or two so bolt head is not sticking up..then you skim with an end mill to make all the same height.. pretty much like skimming a surface grinder chuck..yes it makes the top very good for part set, but does little for the error when traveling. tool to the pad s good.
