smontanaro 

That's 0.01mm. What dimensions on the bike frame require the closest tolerances?

BigPoser

All of them, at least to me they would be. So yeah, that'd work for my tastes. Thanks.

duanedr 

Yes, very much good enough. I'd guess that's identical to the table I have.

Nessism

I'd go for the granite. Seems a no brainer if you are settled and not planning to move around for a while.

guy153

The position of the rear dropouts is the most critical, in particular the angle of the axle. If one dropout is 1mm above the other, the tyre will be off by about 5mm up at the SS bridge, and if one is 1mm in front of the other, you'll have about 5mm of error at the CS bridge. The good news is that the rear triangle is the easiest to correct if you need to.

Also important is that the HT and ST are parallel. I've found this (fortunately) tends not to move much during welding, probably because of the bigger diameters on the tubes so with a few tacks and judicious weld sequence you're OK.

calstar 

Way beyond good enough. You're not building to NASA spec, I'd be very, very surprised if even the best pro builders consistently work to that spec. The well used phrase "chasing your own tail" comes to mind. I'm guessing it weighs 800+lbs, curious to know the shipping cost, still appears to be a good price relative to other options.

regards, Brian

Doug Fattic 

A bit of European and American frame building history can help explain alignment tolerances. In the 60's most framebuilders in the UK worked for low wages for whosever name was on the down tube. They made only a few dollars (less than a £) getting paid piecemeal for 1 frame (which usually took them less than a day). These were typically sold to the working class who also didn't make much money. When I went to learn at Ellis Briggs in Yorkshire in 1975, I was a high school teacher with a master's degree in education whose salary at the time was around $8,000 a year. I was surprised how much more money I made than others in the bike industry. The Hetchins I bought in 1969 cost 25£ (about $70) and by the time I went to Briggs, inflation had increased the price of frames to around $125. In this environment there wasn't extra money for expensive tooling (although there were exceptions).

Few adult Americans rode bicycles after the war and before the bike boom of 1970 when suddenly "10 speed" bicycles became popular. This new interest is what opened up the market for frames to be built here in the States. This market was completely different than in Europe. Middle class Americans wanting to buy good bicycles had more money and were willing to pay for a higher quality product. And for us young guys just starting out we had to demonstrate that our quality was higher or potential customers would buy a much more famous European frame. This was an era when Bicycling and Bike World magazines spent quite a bit of time writing about and examining custom frames. The expected standard was being raised. Over many years I’ve repainted many classic era steel frames and it was quite common for them to be out of alignment a lot. The exception were the Japanese frames which were usually spot on.

The New England Cycling Academy (NECA) developed a system to align cleats (late 70’s?). This was when they were nailed to the bottom of a shoe and before clipless and floating cleats were invented. They discovered that they were unable to properly position cleats if steel frames were not properly aligned. This brings me to the point that the #1 priority of frame alignment is so a seat tube is exactly 90º to the bottom bracket threads. If it isn’t when ridden, the seat will go straight vertical and the crooked BB will put the pedals at an angle that will potentially bother knees. What the Academy did to solve this common problem was come out with a beam type frame alignment system. Once the frame was square then cleats could be properly positioned. It is also an illustration that there would have been no market for an alignment system if the majority of frames would have been better made. Good framebuilders would not want to be embarrassed with the need for their frames to be aligned unless they were crashed. This check on our alignment work kept us within standard. I’m surprised their alignment system doesn’t come up for sale more often since frame shops no longer need them in the age of carbon frames.

There is no reason that a builder today can’t hold alignment tolerances tighter than 1mm.As already mentioned, the back end has to be even more precise because any error is magnified out my the tire.If one isn’t then their standard is too low and they need to figure out how to improve.

ksisler

Consider hitting up a counter-top supplier; A piece of 3 CM thick stone, either silica or granite can typically be had for $24->30 per square foot + about $20 to have them drill a hole where you need it. Tell them to make sure it is very flat, which it typically is. But take along a steel meter stick and a flashlight to slide along the surface in all directions to check flatness. If you set the stone down on your work stand/table it is a bed of silicone and just let it settle overnight, you should be ok, but recheck it again in the morning with the meter stick and flashlight. Hope that helps.

unterhausen

the place we bought our countertop has a pile of smaller stone out back that they sell at a discount.

bark_eater 

Well the cart got before the horse again... I "picked up" the 16x35 cnc milling table last week. I called ahead to find out how much it weighed. I was told around 300 pounds. When we skitched it off the fork lift into the back of my mini van the shocks just kept going down. I restrained it as best as i could with blocking and the seat belts but the 100 miles home felt a bit sketchy. The ahead of the horse part was in full effect when i got it home as i havent walled in the space where its going to live yet, so i ended updoing a van to suv transfer in the dark wearing a head lamp. It didnt help that the table is on rubber pads, so i had to lever it up enough to get some card board under the pads and then find a spot in the suv to get braced enough to pull it across a couple planks. Now ive got to build the shop to put it in and build a table to hold it. The shop floor is elevated so the finished table hight will end up being 3 feet up from where it will start in the suv trunk. I think I'll be renting an engine hoist at that point.

calstar 

Congrats, lets see a pic.

bark_eater 

calstar 

Nice, you got a good deal. Very beefy, 5-6" thick?

bark_eater 

I dont think I paid more than twice scrap value. Last year I saw a couple big mills with tables larger than this go through the scrap yard, but couldn't make the connection of why I needed to pull one of the tables. Might have spent less money for more but the sketch and hassle factor would have been way higher.

P.S. WAG with math puts it at 500lbs so maybe 25% over local scrap prices and only a 1 hour detour to get it. I dont count the hour I spent pokeing around a huge building filled with machinery.

duanedr 

I think that will be very nice. Plenty of weight to put pressure on it if you need to and easy to swap in other fixtures like a fork alignment system or stem fixture etc.

unterhausen

that came off of a crazy big machine. Looks really useful

bark_eater 

I guess I'll be working towards a set up like this:

unterhausen

I like that axle height gauge setup

bark_eater 

I'm going to have to make something to to work with 120 124 and 126 mm spacing, for the frames I want to check. For the seatpost deflection support bar, I would probably use a heavy aluminum extrusion. Now that I have a 35" reference surface I can go through my scrap pile and see whats flat enough. I like the idea of a beam that rotates off the top of the bb post with a drop down feeler. Same idea as a derailleur hanger gauge. At this point i only have a the Var BB faceing tool that relies on a cone on the opposite side of the shell, so I'm not sure how absolute a measurement I could get with out a proper faceing tool to prep the shell.

Andrew R Stewart 

"At this point i only have a the Var BB faceing tool that relies on a cone on the opposite side of the shell, so I'm not sure how absolute a measurement I could get with out a proper faceing tool to prep the shell."
So, do you or don't you have the far facing tool? (IIRC it can also be piloted with the BB taps still in the shell.) It should do a good enough facing job to use the shell face for a reference. Of course there's differing methods and opinions in how one uses the BB shell face during the build and aligning steps.

"I like the idea of a beam that rotates off the top of the bb post with a drop down feeler. Same idea as a derailleur hanger gauge."
I would discourage this. Why induce more gravity into the system? Why measure between two relatively flexible beams when only one (the frame) has to be part of the system. Used height gages are so easily found on Craig's List or Ebay and are made to do this kind of stuff, the future accessories you can add to a height gage add to it's long term value. Andy

bark_eater 

I have a VAR 380 that supposedly can be used with out a tap in the opposing threads. I'm not entirely convinced.

Andrew R Stewart 

Well with the non cutter side's pilot backwards no doubt the facing would be questionable I never liked the slide in pilots as they have more slop within the shell then a threaded in pilot guide does. Before Park began to produce frame prep tooling there was, in the US, pretty much only Campy (and the Silva/Cobra clones) and Var. I invested in Campy (loaned my boss the $925 to buy the shop a Campy kit then bought it from him a year later for $800). Only a few years later I concluded that I should have gone with Var as they had a wider cutters size range. Since then my opinion has softened, a bit. Still you now have the foundation in the Var brand so finding a Var BB tap set seems to me to be the next investment.

It was at the 19709 Eisentraut building course that I experienced Var cutters for the first time. leaving the taps in the BB shell and then facing using them as the pilots was a cool eye opening. Andy

calstar 

From above in this thread:

Your Blanchard ground steel plate will droop over time and will no longer be accurate.​​​​​​

What is the source of steel plate "droop" information? It implies that a steel plate will slowly deform under its own weight, I googled this and found nothing(not surprising). Lacking empirical data this remains a classic "old wives tale".

unterhausen

they are cast iron, so probably have some distortion even after aging and flattening. I don't think cast iron creeps at room temperature. I'm too lazy to read the literature, but people have tested cast iron creep at room temperature.

Tdotbikes

I'm not smart enough to understand the calculations but if you google "steel plate deflection" or "steel plate sag" you will find a ton of engineering data. You only have to look under a commercially made cast iron surface plate to see the amount of support underneath it.