Thread: 55t press

Originally Posted by uninformed

Thanks Brian. There is no problem getting Taps and dies in ANY of the MANY sizes and thread types: BSW BSF BA UNC UNF MF MC etc..

Go to your local engineering supplier and ask for non standard taps and dies. They won't recognise them, or tell you they don't exist, and damn certain they will not have stock. Go and ask for British Standard Cycle thread or Admiralty Fine, or British Standard Conduit. you can guarantee there is no one on staff who was born when BSF & BSC were last in use.

You will pay much less if you buy them from me. Best prices in Australia. I specialise in rare, obsolete, hard to find, no longer available, and "don't exist" taps and dies. Ask me for a quote.

I also stock BSC (Cycle Thread) 26 tpi and 20 tpi series.

For BA taps, dies, and fasteners, call Bruce Gardner in Melbourne, B.S.F. Bolts, 0408 056 255. Bruce even has LH BA, and is a good source for BSW, BSF, BSC, uns, unef fasteners.

Don't be afraid of buying box lots of fasteners from o'seas via internet. It is odds on that a box will be cheaper than a small hardware store pack.

To attach your 75 x 12 FB to the 100 x 16 FB I would not die in a ditch over M6 x 0.75 or M6 x 1.0.

Going back to the forces on the upright, at the bolt holes/pins that will hold the table the tear out forces on the bottom side of the hole will be pushing downwards. That might be where you were going with the forces when the press was in use.

Originally Posted by slug_burner

Going back to the forces on the upright, at the bolt holes/pins that will hold the table the tear out forces on the bottom side of the hole will be pushing downwards. That might be where you were going with the forces when the press was in use.

I wish I could say yes, but I don't have that much of a grasp on this stuff. Just learning along the way.

The steel structures code in use now (ASA4100) is based on Limit State design. The old code (before 1990) was based on Working Stress. The world started changing design of steel structures to Limit State in the late 80's because it was realised that working stress design produced some members that were too conservative (wasted $$$$).

Limit States involved much research to determine the limit of the various members/components and the codes are more complex. The most designed for limit states are Strength and Serviceability (e.g. excessive deflection).

For other uses apart from steel structures, (e.g. cranes until the crane code was revised to use AS4100, and machinery) a new working stress code was introduced (I can't remember the AS number). For this press, either code would be acceptable.

The load capacity of members is affected by their slenderness ratio (length / radius of gyration). For example (from memory) 100 x 100 x 6 EA (equal angle) has a greater tension load capacity than 75 x 75 x 10 EA even though the later has a larger cross sectional area, because the radii of gyration of the 100 x 100 x 6 EA are greater. I wouldn't be surprised if the Strength Limit State of 100 x 100 x 6 EA has a tension load capacity close to 100 x 16 FB (100 x 100 x 8 EA would be greater). See pic below for properties of 100 x 16 FB which shows rx is 4.62 mm. (edit) it should be no surprise that circular hollow sections have the greatest radius of gyration for their cross sectional area, which is why they perform best for compression and tensile members - although joints are difficult they are widely used in large structures such as sports stadiums (end edit).

Now ignoring bolt (or pin) holes, 303 kN / 1600 mm^2 = 190 MPa is OK (minimum yield stress is 300 MPa) for the ties providing the slenderness ratio is satisfactory – i.e. if the height of the part in tension is not too great. However we would also have to prevent bending at the attachment of the PFC's due to twisting (torsion) in the PFC (see my earlier post about this which seems to have been overlooked).

If the 75 x 10 FB was effectively attached to the 100 x 16 FB such as to reduce the slenderness ratio in the thin direction of the 100 x 16 FB it could increase the tension capacity. This could also be achieved by effective bolting (or welding) spacers between the pair of uprights at reasonable vertical spacings (reduce effective L to increase L/r ratio).

If the 75 x 10 FB was attached to the 100 x 16 FB to create an angle section it would reduce the increase the radii of gyration, increase resistance to bending, could provide torsional restraint to the ends of the PFC, add area to more than account for the loss due to holes.

IMHO small bolts are a waste of time and of little use for either of the above. Given Serg is going to use (and not scrap) these FB sections, then I would advise welding them together. The rule of thumb for size of fillet welds on each side of corner 'L' or Tee joints is 2/3 thickness of thinnest member i.e. 10 x 2 / 3 = 6.7 mm. Call that 6 mm, which is often used as the largest FW for a single run. My gut feel is that for this case 5 mm would be OK with staggered intermittent fillet welds, say weld 50 and miss 50 (or even 75), and easier for Serg than a continuous 6 mm FW.

For the table pins, look at the pic of table 31 below for a guide to pin size. The shear capacity (AS4100, strength limit state) of an M24, class 8.8 bolt with threads excluded from the shear plane is 186 kN (column 4). Now look across to the 2nd column from right and the bearing capacity of hole for a M24 bolt through the 8 mm thick web of the 250 PFC exceeds the bolt shear capacity. So for the 303 kN load, 2 pins, diameter 24 mm and shear strength equivalent to class 8.8 bolts (4140 or better) would be sufficient. Note 2 pins at each end of the table, not total.

Again, thanks John,

as we said when we spoke, I have gone about this backwards....design first, materials list then build. What happend was I changed my design as I started to gather material as the obvious actually became obvious....bloody heavy!

I did not miss your point on the PFC's twisting. At this stage the PFC's at head will be bolted toe in with bolted endplates. This means that they are bolted to the Flat bar uprights and bolted to each other. I also was thinking/copying Daves idea of having the ram mounting plate "lock" in the top and bottom flanges of the PFC's



The table PFC's will be bolted to flat bar via custom made pin bolts AND utlising crush tubes between PFC's. Table PFC's will be toe out.



I wont be duplicating his ram mount exactly, but using his concept of locking in PFC (if it is thought to be a good idea)



Dont get me wrong, I can and do like to weld. I have a kemppi 250a GMAW. I have access to 3 phase WIA GMAW and a Structural Steel fab shop. But for my way of thinking at this stage, the less welding the better. Meaning less weld distortion to deal with and the press will break down into more individual parts for moving etc.

John, while welding the 2 flat bars together to form an angle, may be the logical and better way to do it, (after using angle bar instead) would even bolting them togther with M6 at 50mm centers achieve nothing? And in this situation, am I still guided by the egde distance rule? (ie am I stuck with M6 going into the 16 or could it be larger)

mounting to feet/ground (note the 100x10o shs is bolted to the concrete floor)




cheers
Serg

Originally Posted by uninformed

...
John, while welding the 2 flat bars together to form an angle, may be the logical and better way to do it, (after using angle bar instead) would even bolting them togther with M6 at 50mm centers achieve nothing? And in this situation, am I still guided by the egde distance rule? (ie am I stuck with M6 going into the 16 or could it be larger)

...

I can't deny they won't do anything, it will provide some stiffening in the weak direction, but will not transform 2 flats into an angle with anything like the properties achieved if welded.

IMHO you could get away with M8 screws in the edge of the 100 x 16 FB. Though still not what I would do - I have my thoughts on what is easier, quicker, stronger, etc.

Im guessing you mean ditch the flat bar and use 100x100x10/12 angle? I am listening to what you have to say John and taking it on board. Unfortunately I have already spent $$$ on the Flat and doubt i would ever use it otherwise....

Im happy to make up more boltable cross ties. If this is a better way to use the 100x16 on its own.

I hope to hear your thoughts on the head beam set up and ram mounting. Again If I have to tie the PFCs is bolting an option?

I am away for 3 days so will ponder more.

Give the intermittent (stitch/skip weld) a try. It is a good way to limit distortion by reducing the heat build up. I'd say you would be doing well to distort 16mm FB. Set it up, tack weld it in a few places, then start extending your weld from the tacks. If you work from either end and one stitch on each side of the 75 x 12 FB you will not cause enough distortion to worry you.



I suspect that you might make it easier if you bring the 75 x 12 FB in from the edge then you will not have to worry about having to prepare the outside corner for welding.

The thing will still be able to be disassembled, you will just have an angle or Tee like angle to transport instead of just FB. I think that the welding route will be quicker than drill and tap.