Bridgy column riser rigidity

There's an on-line auction for a Bridgeport seven inch column riser. I plan on putting this on my Excello CNC knee mill. Right now, I'm the winning bidder at $300. More than likely, the price will go on up.

Two related questions. Will rigidity suffer due to a riser block? This machine is WAY better than a bridgy in this regard right now, but I don't want to compromise it.

Second, I really only need a four inch riser. I could have this burned out of steel and make my own for less than $300. Do I lose more rigidity with steel vs. cast?(I think so) I think I gain rigidity by going with 4" vs. 7" riser, will this make up the difference?

Karl

Reply to
Karl Townsend
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What makes you think a Bridgeport riser will fit an Excello?

Stan-

Reply to
Stanley Dornfeld

I'm sure I'll have to modify it to work. But the ODs match. This is the other half of my interest in just making one out of steel.

Karl

Reply to
Karl Townsend

Steel is 2~3X stiffer than most cast irons, but I doubt you'd notice the difference between the two materials in this case.

Ned Simmons

Reply to
Ned Simmons

So what's the difference between cast iron and aluminum of the same dimension with lead bolted on? Why isn't steel used for precision lathes?

Tim

-- "I've got more trophies than Wayne Gretsky and the Pope combined!" - Homer Simpson Website @

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Reply to
Tim Williams
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I can't tell you whether a B'port riser will fit an Excello but I can tell you I have a B'port riser that you can buy for $300. I also have never heard of a Bridgeport mill refered to as a Bridgy except on this newsgroup. I have been using and around machine tools since the mid-'60s so I guess I have 40+ years machining experience and I have owned, used and looked at a lot of B'ports. In fact I sold a three digit serial number J-head B'port with a BH designation, not BJ, today. The oldest J-head I had ever seen. I guess you can call a Bridgeport anything you like but most folks won't recognize the " Bridgy" moniker. Leigh@MarMachine

Reply to
Leigh Knudson

I suppose you could simulate the behavior of an iron casting with aluminum and lead, though I'm not sure why you'd want to.

It is, often in conjunction with polymer concrete.

Ned Simmons

Reply to
Ned Simmons

It seems to be mostly a UK-based word pattern, as I've seen it a lot more on the modeleng-l, which has a lot more UK members.

Enjoy, DoN.

Reply to
DoN. Nichols

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:-)

Ah. But that's not steel alone, as CI is alone in most lathes.

Tim

-- "I've got more trophies than Wayne Gretsky and the Pope combined!" - Homer Simpson Website @

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Reply to
Tim Williams

I think Bridgy sounds like a term of endearment.

Reply to
Tony

Ahhh.

I don't know that it's never been done, I'd be willing to bet it has. But the combination of steel and concrete has been quite successful. BTW, the polymer concrete is not cheap. I priced 800# about a year ago, it was almost $1/pound.

Ned Simmosn

Reply to
Ned Simmons

Reply to
David Billington

Ouch! Why not normal stuff? Shrinkage? Unstable?

Tim

-- "I've got more trophies than Wayne Gretsky and the Pope combined!" - Homer Simpson Website @

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Reply to
Tim Williams

The epoxy concrete I was looking at - Zanite - is intended to be used as a structural material rather than simply for vibration dampening or stiffening a steel frame, so may not be the most economical stuff in this context. Typically steel plates or threaded inserts are cast into the Zanite as attachment points, but the concrete carries the loads. The online information was limited, but there's some here...

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A search on "Phillycast" or "Philadelphia Resins" should turn up some other products.

Ned Simmons

Reply to
Ned Simmons

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