Bridgeport Table

[DAVE-O]

Hi RP,
I dont know if subscibe to the "out of sight,out of mind" philosophy.But if your problem is purely cosmetic,Why not just shear(or have sheared)a set of aluminum table covers and hold them in place with a aluminum cleat bolted to the bottom that engages the center slot? I have done this for several mills I have worked with over the years and not only does it cover the imperfections,it protects the table from further damage and gives you a better surface to rest your tools on!If you plan leave them on for long periods of time,just make sure you give the table a thin coat of oil for rust protection purposes.

HTH,
Dave

 

[rpmachining]

Thanks Dave. That's a good Idea. I've seen this done myself also. The one I saw pictured consisted of two halves (left & right) with the centers cut out to fit snugly around the base of the milling vise, and the long edges turned down to fit over the table to hold in place. I was thinking of doing this mainly to make cleanup easy by keeping the chips out of the T-slots. With aluminum, have you ever noticed any problem with galvanic corrosion? I was thinking of using galvanized CS or stainless.

RP

[This message has been edited by rpmachining (edited 02-24-2003).]

 

[Greg B]

RP,
I have an aluminum tabletop, 1.00"x17.00"x49.00" with eight rows of
1/2-13 holes, 2.00" between rows, 1.00" between holes. You could completely cover your Bridgeport table with this and have the benefit of much simpler setup of large and/or long workpieces. All of our CNC machines at work use this type of table. In fact, that is where I got this one. I just can't figure out a use for it in my shop(way to big for my Deckel or Benchmaster). Anyway, if you are interested, e-mail: [email protected]
Thanks, Greg B.

[This message has been edited by Greg B (edited 02-24-2003).]

 

[Paul Babin]

Try scothbrite brown pad , then to marroon.
Shouldn't keep vise in center of table all the time. Vary the position left and right monthly. This way the screws and ways will wear a little more evenly. Add a neoprene rubber way cove rto the rear of the saddle. Short money to save the ways from chip damage. The table top should have been ground when the bottom ways were scraped and or ground. I rebuild Bridgeports, hardinges, and Monarch EE's for a living and I've seen a lot thru the years. Any major holes can be plugged with cast iron. As far as bowing after grinding, it's true to a certain extent but a Bridgeport isn't a jig borer. We tend to reverse bow the tables that we grind. In other words, the table is parralel but bowed upwards about .0005" It will slightly improve with time and then bow down past straight. For vise work, no problems, for long stock, abby errors.

 

[rpmachining]

Greg-

Is this similiar to the plate you are describing?

http://cgi.ebay.com/ws/eBayISAPI.dll?ViewItem&category=12584&item=2512749292&rd=1

RP

 

[Greg B]

RP,
Yes, that is similar, but the one I have has more holes, and no coolant trough around the out side edge. Three edges are machined, one long edge is bandsawn because I cut the table in half to use part of it for another project. However, it would take no time at all for me to set it up on the Monarch at work and machine that edge.
Greg B.

 

[noahjlb]

To swith back to the discussion on stoning a milling table i would like to get some more detail from Forest Addy on this subject if possible. I have a milling table that has dings and the dings have created ridges. I'm not so concerned with the cosmetics but the ridges around the dings have got to go. These are a question of function not looks. So, what grit stone do i use to get those ridges off ? Any particular technique ? ie. move the stone over the entire table or just focus on the ridges ?

thanks

 

[Forrest Addy]

When God created woman from Adam's rib, He balanced the job by creating the fine India slip stone from the rib on the opposite side and gave the manufacturing rights for the stones to Norton who instantly screwed up and called them "abrasive files".

You're correct. For every scratch there are two ridges raised, one on each side of the scratch. You can't do anything about the scratch but you can remove the ridges with a gentle stoning.

You need a selection but among them be sure to have a 6" x 2" conbination bench stone with a fine India stone on one side and a round edge slip (#SS87175 ASAP tooling - they show a picture and give sizes).

Don't get the thin slips, they're very delicate and break easily.

Here's a website for ASAP Tool.

http://www.asaptooling.com/abrasives/round_edge_slip_stones.html

New abrasive files are quite agressive so stone with care until they develop a glaze. Always us a dispersant oil (WD40 is a miserable product but its qualities as a cleaning agent and a stoning oil are unsurpassed) when stoning areas. Stone only clean metal. If the stone gets pinned (metal particles tightly adhereing) pick them off with a sharp scribe.

Don't get the 10 stone assortment from Penn Tool. The price isn't bad but you'll never use half of them so it's a bad deal.

[This message has been edited by Forrest Addy (edited 05-29-2003).]

 

[noahjlb]

thanks, i will follow your advice.

 

[vortech]

I don't know who told you that grinding the table would break the skin of the casting, The skin was already broken when it was first machined from a raw casting. After 30 plus years the casting has normalized and moved all that it is going to unless you take some drastic cuts on it. Grind it and be done.
Jeff.

 

[rpmachining]

I'm no expert on castings, but I was told this by three separate sources that specialize in BP rebuilds: the grinders (Schaffer), a scraper, and a rebuild company. I can see a problem though if only the top of the table were ground without doing the ways at the same time. Since the table bows slighty, squaring off the top only will throw it out of parallel with the ways. Maybe this is what they are referring to.

 

[timekiller]

A rough way to do a quick check of table bow is to take a piece of aluninum 1/4" thick x 1" to 2" wide x 12" long. Support 1/2" of each end of of this aluminum bar on parallels resting on the table, and clamp in your vise with 1/4" x 12" edge up. Make a clean up cut on this 1/4" edge. Flip part in vise, and cut other 1/4" x 12" edge to clean up. After cutting measure the width of part at ends, (should be the same width), now measure middle. The difference between the middle and end measurements is two times the bow per foot.

i.e. if there is .010" difference between ends measurement and middle you have .005" per foot bow.

If you have a worn mill and need a long parallel part use the edge of the cutter or clamp the part to the table. Guess how I learned this?

I was fly cutting some aluminum parts 24" long and I was using two unmatched vises, supporting the part on two 1-2-3 blocks. Every one I cut in the vises had .036" difference in thickness, all thick in the middle. After resetting up and clamping directly to table using toe clamps solved the problem.

 

[timekiller]

A rough way to do a quick check of table bow is to take a piece of aluninum 1/4" thick x 1" to 2" wide x 12" long. Support 1/2" of each end of of this aluminum bar on parallels resting on the table, and clamp in your vise with 1/4" x 12" edge up. Make a clean up cut on this 1/4" edge. Flip part in vise, and cut other 1/4" x 12" edge to clean up. After cutting measure the width of part at ends, (should be the same width), now measure middle. The difference between the middle and end measurements is two times the bow per foot.

i.e. if there is .010" difference between ends measurement and middle you have .005" per foot bow.

If you have a worn mill and need a long parallel part use the edge of the cutter or clamp the part to the table. Guess how I learned this?

I was fly cutting some aluminum parts 24" long and I was using two unmatched vises, supporting the part on two 1-2-3 blocks. Every one I cut in the vises had .036" difference in thickness, all thick in the middle. After resetting up and clamping directly to table using toe clamps solved the problem.