DE675149C - Grinding bodies, in particular grinding wheels - Google Patents

Description

1939

ISSUED ON
2. IMAl 1939

REICH PATENT OFFICE

PATENT LETTERING

CLASS 39 b GROUP 22

N38155 IVcl39b

It is known that in the case of abrasive tools with an organic bond (hard rubber or resin) to add finely divided fillers to the binder, on the one hand to stretch it, on the other hand to influence the strength and hardness of the grinding wheel.

According to the invention, a finely powdered insoluble fluoride, e.g. B. Fluorcalcium, Apatite or especially cryolite is used as a filler. This is a considerable increase the grinding performance achieved in relation to the wear and tear of the grinding tool. aside from that the grinding tools become less sensitive to temperature fluctuations and more resistant against mechanical loads, which z. B. is important for the very thin cutting discs.

Particularly good results have been achieved with cryolite as a filler. With him, the ratio of the material removal from the workpiece and the wear of the grinding wheel has improved _{by 75 to 95 ° / 0 compared to conventional fillers such as flint, feldspar, corundum and talc, according to available test results.}

Depending on the amount of filler added, of course, the properties of the abrasive articles different. You can therefore determine the properties by appropriately dimensioning the additive affect the grinding wheel. Using larger amounts will result in a larger one Insensitivity to grinding heat achieved. You can use up to 40 percent by volume of cryolite, based on the binder, go, but it has been found that «a lot is beneficial in the case of a rubber bond between 20 and 40 percent by volume and in the case of a resin bond between 15 and 25 percent by volume of the binder is used to achieve the better sanding properties of To achieve cast plaster disks. The lower limit is expediently not less than 5 percent by volume.

Instead of the natural cryolite (Na ₃ -AlF ₃ or 3 NaF-AlF ₃ ), which is in a colorless to snow-white crystalline form with a spec. Weight of 2.90 to 3.00 and a Mohs hardness of about 2.5 occurs and certain impurities, such as. B. contains some Mn ₂ O ₃ , MgO, vanadic and phosphoric acid, synthetic cryolite can also be used.

In practice, the filler is added to the binder and the mixture to the abrasive grains added.

_; example 1

In the manufacture of a rubber bonded grinding wheel, finely divided cryolite with a grain size roughly corresponding to a sieve with 2500 meshes on the cm ² or of even greater fineness with rubber, sulfur and abrasive grains, e.g. B. silicon carbide or corundum, mixed in the following proportions:

Abrasive grains 75.7 percent by weight

smoked raw rubber 6.2 -

Sulfur 3.1

Cryolite 15.0

100.0 percent by weight.

After fine grinding, ie up to a grain size corresponding to 2500 meshes per cm ² , the cryolite can be mixed with the rubber and the other constituents in the usual way. The smoked raw rubber and the abrasive grains of the desired size, sulfur flowers and cryolite in powder or flour form are mixed by working them between mixing rollers, with

to the raw rubber sheet is repeatedly folded and passed through the rollers, while the other ingredients are added in weighed amounts at desired intervals until the mixture is intimate and uniform. The mass is then in Sheets of the desired thickness rolled out, e.g. B. by passing between calender rolls. This is followed by "cutting to the desired size and shape. The resulting The object is vulcanized in a vulcanizing mold under heat and pressure.

Example 2

A resin bonded grinding wheel should contain roughly:

Abrasive grits 86.6 percent by weight

Phenolic resin. .... 9.5 -

Cryolite (2500 mesh
per cm ² or finer) 3.9 -

100.0 percent by weight.

The cryolite powder is first intimately in the dry state with 7.6 parts by weight of a Phenolic resin powder mixed. The remaining 1.9 parts by weight of the Phenolic resin added in liquid form to moisten the grain surfaces. The mixture cryolite and resin powder are then added to the resin-coated abrasive grains, and the whole mass is carefully mixed until a uniform mixture of the ingredients is reached. A desired amount of this mixture is then poured into a mold pressed and exposed to the usual temperature conditions under which the binder hardened.

You can also first of all the abrasive grains with the aid of an adhesive, such as Glue, shellac, liquid rubber or liquid synthetic resin, with a coating of Provided cryolite and the so coated grains the powdery rubber or Add resin binder, optionally mixed with the rest of the cryolite.

Claims (1)

Claim: Abrasive bodies, in particular grinding discs, consisting of abrasive grains, an organic one Binder and not exceeding 40 percent by volume of the binder finely divided inorganic filler, characterized in that the finely divided Filler made of a finely powdered insoluble fluoride, in particular cryolite, consists. Serum. BOOKED IN HAY TIEtcnsDitUCKEKEi