(help) Alignment Table Size??

[anthonymaietta]

I am looking to upgrade my alignment table setup and I see one locally at a very good price.

Its 36" x 24" x 6" solid granite. Is this big enough?

What size tables do you guys have?

Thanks,
Tony

[Dave Kirk]

I use a 30" x 36" plate and let the rear end of the frame hang off the plate. I then use a 3/4" piece of square drill rod, 3' long, that I lay on the plate and let it hang off and reference the driveside rear drop to it. Very simple and super accurate. I think it would still work very if it was the size you are talking about.

Dave

[Archibald]

I am looking to upgrade my alignment table setup and I see one locally at a very good price.

Its 36" x 24" x 6" solid granite. Is this big enough?

What size tables do you guys have?

Thanks,
Tony

IMO, too small. If you had it already, I'd say go for it, but since you're shopping, get at least a 3' x 4'. Granite works, I've used one since I started, but a blanchard or Mattison ground iron/steel table is a lot easier to tool up for.

[anthonymaietta]

This may be a really dumb question, but how thick do you need it? Slabs of remnant granite are eveywhere from countertop makers. Can 1" thick granite be ground flat and used?

[Craig Ryan]

I have a 24"x36" cast iron table and it gets the job done. I will probably stick with it for space savings. You have lots of space, right?

[Archibald]

This may be a really dumb question, but how thick do you need it? Slabs of remnant granite are eveywhere from countertop makers. Can 1" thick granite be ground flat and used?

The key word in "Alignment Table" is alignment. If you just want to QA frames, any documented flat surface will work. If you want to align, then you need something that can withstand the resulting forces and buck up your tooling. 1" would probably be fine for a steel/iron table if it had appropriate webbing underneath. For granite? NFW.

[EnginCycles]

Don,
Tony might not understand that there is a huge difference between a cast iron surface plate and a steel slab of metal. I had a steel 1" table that was blanchard ground and it had a hook in the very far corner that was .015" off. Not something that would have much effect because it was not a datum point that would be used but still bugged me. It did not have webbing welded underneath but from what I understand that still won't solve the issue. Cast iron as you know is not prone to moving and will hold its tolerance after being ground. My current table is 3'x5' and is 8" deep with ground sides and webbing underneath. It is mounted on an insane table with like 20 set pins for leveling (which is funny because I doubt it has the ability to twist) and 2 locating pins for keeping it from shifting. I had it re-ground for like $250 locally and they said it was under .001" for flat. The ground sides are really handy for random fixturing. Magnetic drill press is much easier than dealing with the effort involved in putting holes in the granite IMO. Or get a t-slot ot platen table like Dave is using.

My $.02

-Drew

[steve garro]

I have the big Bringheli & I can bolt on a 29er touring bike with a 25" TT & 18.5" CS's & nothing hangs off the edges. - Garro.

[Eric Estlund]

I have a 1.5" steel 3'x4' plate, and wouldn't want to go any smaller. It's not iron, and might not be as stable as a cast iron tooling plate, but it's way more accurate then tubes are straight. If I was building rocket ships I might want it flatter, but no issues building bikes on it.

It's about the max size I feel comfortable moving on my own, also a plus.


In this part of the world there are not a lot of used tooling plates- Eugene never had industry. Freighting something in turned a lot of the mid west / East coast good deals into prohibitively expensive ones. I had this plate purchased, drilled and ground in Portland for less then the steel cost in Eugene-

[zank]

Tony, for reference, the table at my shop is 4'x3'. I like it because I have my fork alignment block mounted to it as well.

I went with a grade A (6" thick) granite plate because it was nearly free. The hammer drill and carbide tipped bits that I borrowed cut through it like butter. They pop up on Craigslist and eBay regularly for cheap. Most let them go if you're willing to get it out of their shop.

[zank]

Tony, for reference, the table at my shop is 4'x3'. I like it because I have my fork alignment block mounted to it as well.

I went with a grade A (6" thick) granite plate because it was nearly free. The hammer drill and carbide tipped bits that I borrowed cut through it like butter. They pop up on Craigslist and eBay regularly for cheap. Most let them go if you're willing to get it out of their shop.

[Archibald]

Don,
Tony might not understand that there is a huge difference between a cast iron surface plate and a steel slab of metal. I had a steel 1" table that was blanchard ground and it had a hook in the very far corner that was .015" off. Not something that would have much effect because it was not a datum point that would be used but still bugged me. It did not have webbing welded underneath but from what I understand that still won't solve the issue. Richard's M&L table is that design and had a hook after time. Cast iron as you know is not prone to moving and will hold its tolerance after being ground. My current table is 3'x5' and is 8" deep with ground sides and webbing underneath. It is mounted on an insane table with like 20 set pins for leveling (which is funny because I doubt it has the ability to twist) and 2 locating pins for keeping it from shifting. I had it re-ground for like $250 locally and they said it was under .001" for flat. The ground sides are really handy for random fixturing. Magnetic drill press is much easier than dealing with the effort involved in putting holes in the granite IMO. Or get a t-slot ot platen table like Dave is using.

My $.02

-Drew

First & foremost, the key is to know what you're starting with. All you know about any old used steel or cast iron table you buy is that it's old & used. The material it's made out of tells you nothing about how flat it is. The same is true for used/old granite surface plates. It's the documenting and calibration of the surface that is important. Any surface that a builder buys to use as an alignment table needs to be documented regularly.

As far as steel vs cast iron, it's really a difference in how they're prepared. Cast iron is certainly dimensionally stable, but steel is also very dimensionally stable; plenty stable enough for an alignment table as long as it's supported correctly. For a steel table that's webbed, they're generally stress relieved before being machined and ground as those two activities relieve internal stresses and will cause warping, the same as it does in cast iron that hasn't been aged and stress relieved. Plus steel has twice the MoE of cast iron so you need less of it to be as stiff (and yes, improperly supported, your 3'x5'x8" table will & can twist which is why they go to all the trouble to make sure it is). Blanchard grinding a plain steel plate on one side that has not already been stress relieved and machined is a waste of time & money since it will be affected both by the grinding itself and any legs/whatever that are attached to it after the fact. A properly made webbed steel steel table that's been stress relieved, machined, and then kissed with a Blanchard grinder & documented will be plenty accurate enough as an alignment table and it's a no brainer to tool them up. Tables like the M&L and Bike Machinery's are typically done this way. I don't know how the Bringheli's are made but folks seem happy enough with them.

[steve garro]

what are people making bikes out of, I-beam? I think that if you need to gank on a OX plat or spirit tube enought to distort 1" of Fe. then you will get poor results. all I do on mine is check process & then tack as needed to pull the frame. - Garro.

[EnginCycles]

First & foremost, the key is to know what you're starting with. All you know about any old used steel or cast iron table you buy is that it's old & used. The material it's made out of tells you nothing about how flat it is. The same is true for used/old granite surface plates. It's the documenting and calibration of the surface that is important. Any surface that a builder buys to use as an alignment table needs to be documented regularly.

As far as steel vs cast iron, it's really a difference in how they're prepared. Cast iron is certainly dimensionally stable, but steel is also very dimensionally stable; plenty stable enough for an alignment table as long as it's supported correctly. For a steel table that's webbed, they're generally stress relieved before being machined and ground as those two activities relieve internal stresses and will cause warping, the same as it does in cast iron that hasn't been aged and stress relieved. Plus steel has twice the MoE of cast iron so you need less of it to be as stiff (and yes, improperly supported, your 3'x5'x8" table will & can twist which is why they go to all the trouble to make sure it is). Blanchard grinding a plain steel plate on one side that has not already been stress relieved and machined is a waste of time & money since it will be affected both by the grinding itself and any legs/whatever that are attached to it after the fact. A properly made webbed steel steel table that's been stress relieved, machined, and then kissed with a Blanchard grinder & documented will be plenty accurate enough as an alignment table and it's a no brainer to tool them up. Tables like the M&L and Bike Machinery's are typically done this way. I don't know how the Bringheli's are made but folks seem happy enough with them.

The Bringheli is not stress relieved from what I gather and has chip board underneath that I think is attempting to make a cushion of some sort that is not pulling it if the stand is not as level as the top. It is bolted at all four corners through the board to the stand. I think it is more than good enough for making bikes but Tony is in an area that will have lots of stuff pop up. The very reason I had mine re-ground was I wanted to have a known starting point. They kissed the bottom, flipped it and took off .025" and left a few minimal marks that are below usable surface. I wanted a known datum and that is why I had it re-ground. No matter what the table I would have it ground before using it just so you have a known starting point.

-Drew

[anthonymaietta]

Drew is right, we live in a gold mine of old stuff like this. There are so many used machinery places around its not funny; and it becomes even less funny when you realize why there are so many.

I appreciate all the insights here. There are some pretty reasonable 3 x 4 x 6" slabs around. I haven't seen one steel/cast iron inspection/surface plate available yet.

[EnginCycles]

what are people making bikes out of, I-beam? I think that if you need to gank on a OX plat or spirit tube enought to distort 1" of Fe. then you will get poor results. all I do on mine is check process & then tack as needed to pull the frame. - Garro.

Steve,
The table is not moving from use it is moving from just the metal settling and shifting over time. For example and please don't get the wrong idea but your table is very prone to this issue because you have the table cantilevered off a smaller base. The outside area that is not supported will eventually sag and not be flat anymore, it is not avoidable with that design. It would need webbing welded so the outside edges have support before getting it ground.

Make sense?

-Drew
ps- my table is really an inspection table that gets used for the occasional rear end shifting. My head tube assembly that I use for the mounting point is not bolted to the table it is just ground on the top and bottom and heavy enough to rest on the table and remain flat.

[steve garro]

Steve,
The table is not moving from use it is moving from just the metal settling and shifting over time. For example and please don't get the wrong idea but your table is very prone to this issue because you have the table cantilevered off a smaller base. The outside area that is not supported will eventually sag and not be flat anymore, it is not avoidable with that design. It would need webbing welded so the outside edges have support before getting it ground.

Make sense?

-Drew
ps- my table is really an inspection table that gets used for the occasional rear end shifting. My head tube assembly that I use for the mounting point is not bolted to the table it is just ground on the top and bottom and heavy enough to rest on the table and remain flat.

I seriously doubt i will live long enough for it to be an issue. one of the jokes when boating the Grand Canyon: "watch out! it's all falling down!!" - Garro.

[EnginCycles]

Same as the Rockies. They say the Poconos were at one point as high as the Rockies. Man is that hard to believe.

[steve garro]

Same as the Rockies. They say the Poconos were at one point as high as the Rockies. Man is that hard to believe.

at one time the Appalachians we on par with the Himalaya. however, geological time also includes right now. what timeline do you think a 1.25" slab of Fe. sags? I doubt i have 20yrs left in me. - Garro.

[Archibald]

Steve,
The outside area that is not supported will eventually sag and not be flat anymore, it is not avoidable with that design. It would need webbing welded so the outside edges have support before getting it ground.

Make sense?

-Drew
.

You're talking about creep here. A 1" thick steel plate hanging a foot off a support is not going to creep enough to make a difference in Steve's lifetime unless he starts putting a torch to it. If it's flat after grinding it will stay flat outside of wear or trauma or significant temperature variations and temps are the reason why granite has replaced iron for surface plates.