The meaning of the GD&T symbol is: “a positional tolerance of 0.2 is applicable to the hole when it is at the maximum material condition (MMC)”. A rule of design for assembly (DFA) is to avoid tight tolerances. If slip fits are only for aligning tight geometry, should we redesign the parts for looser tolerances? Sometimes, especially in machinery design, you can’t have the loose tolerances which would be ideal—a head bolting onto an engine block needs to be exactly there. T-slotted extrusions in six different configurations, from 1″ by 1″ up to 2″x4″. These come standard in 240” lengths. 15 Series T-slotted extrusions in 12 different configurations, from 1.5″ by 1.5″ up to 3″ by 6″. The true position of the longitudinal center of the slot (center of the geometrical theoretical geometry). By the way, the location of the slot is not defined in the direction of the 50 basic, the position tolerance you show doesn't control that. The width tolerance of T-slots on the t-slotted cast iron floor plates is H12 and could also be H7 or H8 on request. Usually T-slots parallel to the longitudinal direction are offered, but also T-slots tilting to the longitudinal direction can be offered on request.
If you are designing a ramp for a dog to get onto and off from the couch or a bed, you may use plastic sections with slots to snap the sections together.
A slot in a plastic molded part may have draft. This complicates how it should be dimensioned. Below is a best practice for how to dimension slots with draft.
The figure below shows our slot. Not only does it have draft, but it also has fillets and rounds.
We start with the goal of locating the the slot with a tolerance of position. Recall that a tolerance of position must be applied to a feature of size. That's easy if the slot has no draft. But our slot has draft. So we cannot define the entire slot as a feature of size. We need to pick a specific place in our slot to define as our feature of size. The top and bottom of the slot are not good places to define a feature of size because the top and bottom have corners that may or may not be sharp. This is why we go down a basic distance, a basic 10 in this case, from the top of the slot. This is where we will define our feature of size. Our size dimension says that at exactly 10 down from datum [A], the size must be 20 +/- 0.2.
Having established a feature of size, we can locate our feature of size with a tolerance of position. Our tolerance of position says that the center of our feature of size must fall within a 0.5 wide tolerance zone while holding the part on datum feature [A], and pushing it against datum features [B] and [C]. The slot is oriented to datums [A] and [B] and located to datum [C].
Everything we have looked at so far is specifically 10 mm away from datum [A]. Now we need to define the rest of the walls. We use a profile of a surface with a 0.1 wide tolerance zone. The profile of a surface does not locate the walls. They are located by the tolerance of position and the size tolerance. The profile of a surface controls the orientation and form. The profile tolerance zone will float within the size tolerance zone, and the profile tolerance zone will be exactly 99.5 degrees to datum [A] and exactly perpendicular to datum [B].
Finally we control the location, orientation, and form of the bottom of the slot with a profile of a surface that has a 0.5 wide tolerance zone. The tolerance zone is located and oriented to datum [A].
The profile tolerance zones can float within the size tolerance zones. Each profile tolerance zone is independent of the other one. Each profile tolerance zone is two parallel planes 0.1 apart, exactly 99.5 degrees from [A] and exactly perpendicular to [B].
Our T-slotted cast iron floor plates have been supplied for years to overseas customers in the USA, Europe, the Middle East, South Asia etc.. Their high quality is guaranteed and prices are always under your economic budgets. Our T-slotted cast iron floor plates are always custom made to meet application requirements in various industries such as equipment/motor/gearbox/pump/compressor tests, boring mill bed plates etc..Meanwhile, we are capable of arranging international transportation by GP / OT containers or flat racks to deliver them to any seaport in the world.
Generally, our T-slotted cast iron / steel floor plates are used as rigid and precision bases in engineering industries for benchmarking, layout, precision measurement, assembly work, mounting jobs for precision machining operations such as drilling, milling and boring, etc.. They are also used as test beds to support engines, motors, compressors, pumps, valves, large machines, transmissions or other large industrial machines.
Upon your special requirements, we will present drawings indiciating the detailed designs as our technical proposals for your evaluations. These t-slotted cast iron / steel floor plates are always customized to generally any sizes conforming to the constraints of the site receiving the plates in your workshops.
Features of our T-slotted cast iron floor plates:
- Material is high-strength, high-density and close grained gray cast iron available at Grade of GG-20, GG-25 or GG-30 are to be chosen to manufacture the t-slotted cast iron floor plates. Other materials such as nodular cast iron or cast steel can also be used on request;
- The ribbed & cored structure offers the premium rigidity and strength for the t-slotted cast iron floor plates. The solid structure can also be offered as per your request.
- Hardness for GG-25 gray cast iron made t-slotted floor plates is in the range of HB170-240. The surface flatness accuracy on the top surface of the t-slotted cast iron floor plates is available as being Grade I, II or III as per DIN 876 Standarad. The higher flatness accuracy can be obtained by hand scrapping upon your request. Surface roughness on the t-slotted cast iron floor plates is usually Ra 3.2 μm obtained by adopting the CNC high-speed milling process. Lower roughness such as Ra 1.6 μm can also be achieved by grinding process on your request;
- The width tolerance of T-slots on the t-slotted cast iron floor plates is H12 and could also be H7 or H8 on request. Usually T-slots parallel to the longitudinal direction are offered, but also T-slots tilting to the longitudinal direction can be offered on request. You can also request for both longitudinal and cross t-slots on these t-slotted cast iron floor plates;
- Cored and ribbed construction, twice annealing heat treatments at a temperature in the range of 600-700° C (the 1st annealing is done right after casting, the 2nd annealing is done right after the rough machining on the plate) and the following aging treatment are implemented on these t-slotted cast iron floor plates to relieve the stress to the minimum, ensure high stability and maintain its accuracy free from distortion;
- Connecting grooves on all sides of the t-slotted cast iron floor plates can be provided on request to joint together the pieces of plates into a large plate area;
- Leveling and anchoring pads are supplied with the plates. Vibration absorbing spring mounts can alsot be provided on request;
- Size of each piece of t-slotted cast iron floor plates is available in a range from 1000x1000 mm to 10000x4000 mm. Other sizes can be made on requests.
T Slot Tolerances
4000x2000x300mm T-slotted cast iron machine bed for a CNC gantry drilling machine, supplied to a customer in the USA.
3000x3000x200mm T-slotted cast iron floor plates supplied to a very large motor company in the USA.
5000x2000x300mm T-slotted cast iron floor plate supplied to a customer in Germany.
T Slots Tolerance
3000x1500x300mm T-slotted cast iron floor plates supplied to a customer in the USA, for electromotors repairing.
5000x200x300mm T-slotted plate is being installed in an energy service company in Singapore.
3000x1500x300mm T-slotted cast iron floor plates, 10 sets, with tilting T-slots supplied to a customer in the USA.
3000x3000x180mm T-slotted cast iron floor plates are packed on a 20' Flat Rack, ready to be delivered to Oakland seaport, USA.
Large bed plate area combined with many pieces of t-slotted cast iron floor plates, supplied to a customer in France.